AAF -HermanNelson Classroom Unit Ventilators

Transcription

1 Catalog AAF -HermanNelson Classroom Unit Ventilators Models AVS, AVB, AVV and AVR Floor Units Models AHF, AHB, AHV and AHR Ceiling Units C: UV-1-230E

2 Table of Contents The AAF -HermanNelson Advantage Innovative Sets Us Apart... 4 Unit Ventilators Built To Last... 5 Extra Strength... 5 Rugged Exterior... 5 Easy Maintenance Good... 6 Motor Location... 7 Comfort You Can Count On GentleFlo Delivery... 8 MicroTech Comfort Control... 9 Temperature And Humidity Control Draw-thru Face And Bypass Capacity Control Outdoor Air For Free Cooling Tailored For Adaptability And Good Looks Built-in Flexibility Extra Adaptability Addressing Window Down Drafts Matching Window Sills Outdoor Air Capability Room Exhaust Capability Matching Storage Accessories Expansive Coil Offering Overview Take Control Of Energy Expenditures. 18 Why Classrooms Overheat Systems DraftStop System Finned Radiation System Part Load Variable Air Demand-Controlled Ventilation (DCV) 22 Active Dehumidification Control (ADC). 23 Temperature Controls Ideal For Today s Schools Temperature Control And ASHRAE Control Cycle Typical Temperature Control Components Direct Digital Control (DDC) Background MicroTech Direct Digital Control (DDC) Operating Functions MicroTech Components Basic Unit Components Status/Diagnostic Capability Split System DX Operation Face And Bypass Sequence Of Operation Modulating Sequence Of Operation Field Installed Temperature Controls By Others ASHRAE Cycle II Required Control Sequence DX Low Temperature Limit End-Of-Cycle (EOC) Operation Water Coil Low Temperature Limit (Freezestat) Face And Bypass Damper Control s Control s DX Split System DX Split System s System Installation Typical System Wiring and Piping Outdoor Air Wall Structures Ventimatic Shutter Assembly Floor Units Arrangements Ceiling Units Duct System Arrangements Floor Units AV Available Combinations Ceiling Units AH Available Combinations Coil Combinations Quick Coil Procedure Procedure Example Hot Water Heating Capacity Correction Factor For Hot Water Heating Hot Water/Steam Heating Electric Heating Capacities Chilled Water Capacities CFM CFM CFM CFM CFM (Ceiling Only) Direct Expansion Cooling Coils Face And Bypass End-Of-Cycle 143 Modulating Steam s Floor AV Units Deep Floor AV Units Deep Floor AV Unit Coil Connections Heating Only Cooling only Heat/Cool Reheat Condensate Drain Ceiling AH Unit Air Arrangements Discharge Air Arrangements Inlet Air Arrangements Arrangement AU Arrangement AJ Arrangement AT Arrangement AH Arrangement BD Ceiling AH Unit Coil Combinations and Connections Heating Only Cooling Only Heat/Cool Reheat Condensate Drain End Panels and Enclosure s Wall Intake Louver And Grille Ventimatic Shutter Accessories Sink and Bubbler Cabinet Filler Sections and Utility Compartment Shelf Storage Cabinet with Painted Metal Tops Shelf Storage Cabinet with Laminate Tops Finned Tube Radiation Cabinet Wiring Diagrams Typical Power Wiring Diagram Typical MicroTech Control Wiring Diagram Typical Wiring Diagrams Typical Wall Sensor Diagrams AAF -HermanNelson The information in this catalog supersedes and replaces previous catalogs/bulletins with regard to AAF-HermanNelson unit ventilators. Illustrations cover the general appearance of AAF-HermanNelson unit ventilators at the time of publication. AAF-HermanNelson reserves the right to make changes in design specifications and construction Catalog any time UV-1-230E without notice. / AFF Page -HermanNelson 2 / (3/01) and MicroTech are registered trademarks of AAF-McQuay Inc. Windows is a registered trademark AAF of -HermanNelson Microsoft corporation.

3 The AAF -HermanNelson Advantage Quality Counts Take A Closer Look At The Best Unit Ventilator Ever Built... For Over 80 Years! Model AH (Ceiling) AAF-HermanNelson Units Optimize Comfort And Minimize Costs. Model AV (Floor) If you re looking for an economical, energy-efficient, and versatile solution to your heating and cooling requirements, AAF-HermanNelson Unit Ventilator systems can adapt to virtually any setting. That s why our unit ventilators have become the system of choice for schools. Since Herman Nelson received the original patents in 1917, unit ventilators have proven to be one of the most reliable energy-efficient systems available for maintaining proper ventilation and precise temperature control in the classroom. Because we know that a comfortable classroom environment creates a better climate for learning, we ve continually adapted our systems to address the changing requirements of modern school buildings. AAF-HermanNelson Unit Ventilator systems have an economical first cost and an economical life-cycle cost. The Model AV Floor and Model AH Ceiling Unit Ventilators were designed to provide optimal comfort levels with minimal energy consumption. This is made possible by state-of-the-art controls and superior outside air capabilities, which allow the unit to supply free cooling a large percentage of the time. Both the Model AV and Model AH are available with factory-furnished, fully automatic controls. These controls adjust quickly to compensate for changes in activity and occupancy so the proper learning environment can be maintained. Model AV Floor Unit The vertical floor unit, Model AV, utilizes chilled water or refrigerant for cooling, and hot water, steam or electric heat for heating. Refrigerant cooling is accomplished by using a remote condensing unit piped to the internal refrigerant coil. Model AV can also be supplied as a heating/ventilating-only unit, using either hot water, steam or electric heat; or a cooling/ventilating-only unit using chilled water or refrigerant cooling; or with heating/cooling/ventilation. Model AV is just right for new construction and retrofit applications. With the Model AV, older buildings with baseboard radiant heat or some other form of hydronic heating system can be easily adapted to work efficiently with the unit ventilator. Additionally, chilled-water or refrigerant cooling can be added, making the unit a heating and cooling unit that provides year-round comfort. All floor units come with a built-in drain pan so that heating-only units can be readily converted to heating-cooling units at a later date. Model AH Ceiling Unit The horizontal ceiling-mounted unit ventilator, Model AH, provides chilled-water or refrigerant cooling and hydronic or electric heating. Like the Model AV, it can also be supplied for heating/ ventilating-only, cooling/ventilating-only, heating/cooling/ventilating, or with the option of adding cooling at a later date. Model AH is designed for rooms where floor space is at a premium. It can be installed with a variety of exposures, including completely exposed, partially or fully recessed, or completely concealed. Responding To Your Needs Solid construction, reliability, and innovation have remained the cornerstones of our product development. We recognize the requirements of schools are constantly changing and remain committed to helping you prepare for the future. Whatever your application, there is a AAF- HermanNelson unit ventilator for you. AAF -HermanNelson Catalog UV-1-230E / Page 3 / (3/01)

4 Innovative Sets Us Apart Superior And Engineering And A Firm Commitment To Quality Result In Outstanding Performance...For Years To Come. Welded One-piece Chassis offers superior strength, durability, and vibration reduction. Large Fan Wheel with aerodynamically shaped blades moves air more quietly. Fan Housing utilizes logarithmic expansion for quieter operation. Advanced Heat Transfer Coil provides extra capacity. Integral Drain Pan, standard on all units, permits future cooling on heating-only units. Unique Draw-thru provides uniform air distribution across the coil to deliver even discharge air temperature. Face And Bypass Damper provides superior dehumidification and reduces the chance of coil freeze-up. Two Hinged Top Access Doors provide easy access to motor and end bearing. Special tamper-resistant fasteners deter unauthorized access. Fan Motor Location provides for easy removal and maintenance. Placing motor out of the air stream (and away from the heating coil) reduces heat exposure to prolong life. Three Sectionalized Front Access Panels provide easy access to unit interior. All panels can easily be removed by a single person and front side panels can be removed while unit is running. Special tamper-resistant fasteners deter unauthorized access. Sturdy Cabinet Construction includes hidden reinforcement, a non-glare textured surface, and a tough, scuff- and mar-resistant finish to make the top sturdy enough to support maintenance personnel. Single Full-length Air Filter is efficient and easy to replace. All air delivered to classroom is filtered. Indoor Room Air Damper blocks unwanted gusts of outdoor air on windy days. Its nylon bearings are quiet and maintenance free. Insulated Double-wall Outdoor Air Damper seals tight without twisting. Sampling Chamber provided on each unit for unit-mounted room sensor provides accurate sensing of room temperature. MicroTech Digital Direct Control uses time-proven algorithms to provide superior comfort control. It can function either as a standalone or networked control. UL/ c UL Listed. Rated in accordance with ARI 840. Catalog UV-1-230E / Page 4 / (3/01) AAF -HermanNelson

5 Unit Ventilators Built To Last Superior And Solid Construction Makes The AAF -HermanNelson Unit Ventilator The Best UV On The Market. The AAF-HermanNelson Unit Ventilator is truly engineered and manufactured using industrial design concepts to resist abuse over the years. Our solid construction promotes continued alignment and structural strength. They can remain as strong and rigidly assembled decades after they are installed. Extra Strength Promotes Long Life AAF-HermanNelson s exclusive unitized welded frame (Figures 5-1 and 5-2) is far superior to the fastener-type construction (Figure 5-3) used by other manufacturers. Loosened fasteners can allow vibration, rattles and sagging panels. With reinforced welded construction, there are no fasteners (screws or bolts) to come loose. Full-length Strong Channels Fan Partitions One-piece, Heavygauge, Full-length Kick Plate Strong, Formed, Vertical End Back Bracing with Built-in Access Knockouts Reinforced Top Support Figure 5-1. AAF-HermanNelson Welded Chassis Built-in Pipe Tunnel Extra-strength Pipe Tunnel One-piece End Frame Motor Mount The unique benefits of the welded-frame corrosionresistant galvanized-steel foundation, combined with AAF-HermanNelson s extra-strength steel bar grilles and heavy-gauge metal cabinet panels, provides trouble-free operation and long life. Metalforming techniques add rigidity for superior strength. The extra-strength pipe tunnel stiffens the structure while adding aerodynamic air flow within the unit. Hidden reinforcement provides additional built-in support for the top panel as well as better support for the fan assembly. This reinforced surface is strong enough to support maintenance personnel without fear of damaging the top. Rugged Exterior Withstands The Test Of Time Institutional quality cabinets offer durability and good looks. The superior finish fosters long-lasting beauty, as well as resistance to abuse and corrosion. We apply the very highest standards at every step of the finishing process to reinforce a lasting high quality finish. Figure 5-2. AAF-HermanNelson s Welded Construction High-quality furniture steel is carefully inspected before painting. Scratches and marks that might show through the finish are removed. After fabrication, the metal undergoes a fivestage cleaning and phosphatizing process to remove cutting oils and forming compounds, and prepare the surface for painting. This provides a good bonding surface and reduces the possibility of peeling or corrosion. A specially formulated environmentally friendly thermosetting urethane powder is applied electrostatically to the exterior panels. This film is then oven-cured to provide correct chemical cross-linking, which gives maximum scuff- and mar-resistance. The top of floor units is finished with a textured, non-glare and scuff-resistant, charcoal bronze electrostatic paint. Figure 5-3. Competitor s Fastener-type Construction End and front panels are available in a pleasing array of architectural colors. The Oxford brown steel kickplate is coated and baked with a thermosetting urethane powder paint to blend with floor moldings and provide years of service. Ceiling units are finished with an off-white, baked thermosetting urethane on all exterior panels and bar stock steel discharge grille, which blends well with most ceilings. Finally, each unit is painstakingly inspected before boxing, then encapsulated in a clear plastic bag to prevent chafing, surrounded by an extra heavy duty cardboard box, and secured to a skid permitting damage free shipment. We know the next inspector is the customer and we want you to be satisfied. AAF -HermanNelson Catalog UV-1-230E / Page 5 / (3/01)

6 Easy Maintenance Good Makes Routine Maintenance Quick And Easy. AAF -HermanNelson Unit Ventilators are designed to provide a safer and easier access for maintenance and service personnel. Our units have several access panels and doors that allow direct access to the motor, fan housings, bearings, filter, and temperature controls. This allows for easier maintenance that typically can be handled by a single person. Tamper-resistant Access Front panels and top access doors are held in place by tamper-resistant fasteners using positive positioning fasteners, which are quickly removed or opened with the proper tool but deter unauthorized access to the unit s interior (Figure 6-1). Removable Discharge Grille Tamper-resistant Fasteners Discharge Grille Mounting Bracket(s) Discharge Screen Center Front Access Panel Figure 6-1. Easily Accessible With Tamper-resistant Fasteners Tamper-resistant Fasteners Tamper-resistant Fasteners Sectionalized Access Panels And Doors All floor units have three separate front panels, sized for easy handling by a single person. This feature allows easy, targeted access to the component that needs servicing (Figure 6-1). Two 12"-wide front panels (Figure 6-2), conveniently located at each end of the unit, provide access to piping, temperature control components and the fan High-Medium-Low-Off switch. Unlike units that have full-length front panels, these smaller front panels can be removed without disturbing the normal operation of the unit. The short center front panel (Figure 6-1) provides access to the filter and discharge grille. Figure 6-2. Left Front Access Panel Top Access Doors Fan Shaft Bearing 12" Left Front Access Panel Motor Hinged top access doors allow easy access into the end compartments to facilitate convenient servicing of the motor and shaft bearing (Figures 6-2 and 6-3). Single-filter With AAF-HermanNelson s single-filter design, filter changeout takes only seconds. Change only one filter instead of several. One-piece filter design directs the mixture of outdoor air and room air through a single unit filter. This eliminates the possibility of uneven dust loading, common to units with separate filters for room air and outdoor air or units that restrict air through the filter by a metal partition between the return air and outside air. Because there are no gaps between indoor and outdoor air, the single-filter design also increases filter life so filter maintenance is less often. 12" Left Front Access Panel Structural Frame Figure 6-4. Renewable Media Filter Filter Figure 6-3. Filter Access 12" Right Front Access Panel Renewable Media (Single-use And Permanent Wire Mesh Filters Also Available.) Catalog UV-1-230E / Page 6 / (3/01) AAF -HermanNelson

7 Easy Maintenance (Continued) Filters are included in all units. AAF - HermanNelson single-use filters are standard on all but electric heat units, which come with permanent wire mesh filters. Permanent wire mesh and renewable media (Figure 6-4) filters are available for non-electric heat units, in lieu of singleuse filters. Single-use filters feature Amerglas media. They are designed to be used once and discarded. Permanent filters are metal filters that may be removed for cleaning and reused numerous times. Renewable media filters (Figure 6-4) consist of a heavy painted metal structural frame and renewable Amerglas media Figure 7-1. Ceiling Access Retainer Chains Ceiling Access Retainer Chains All ceiling units (model AH) are equipped with retainer chains to facilitate reduced access panel movement during opening as well as ease of maintenance. This feature enables one person to service the unit instead of a crew. Ceiling End Panels End panels ship installed on ceiling units for a clean, exposed finish. Four tamper-resistant fasteners with exterior access guard against tampering while providing easy access to the interior for authorized personnel. 10 Angle Figure 7-2. Discharge Grille Removable Bar Discharge Grille Facilitates cleaning of fans and fan housings. (Figure 7-2 and 6-1) The steel grille is made from extra strength bar stock promoting long life. A built-in 10 angle provides proper air throw to blanket the room for proper air circulation and comfort. Figure 7-3. Standard Energyefficient NEMA Fan Motor Motor Location Simplifies Access And Maintenance AAF-HermanNelson Unit Ventilator 115/60/1 NEMA motors offer low operating current and wattage. This can result in savings up to hundreds of dollars per year. The reliable permanent, split-capacitor (PSC) fan motor (Figure 7-3) features automatic reset, thermal-overload protection and has no brushes, contacts or centrifugal starting switches the most common cause of motor failure. In addition, the motor has a built-in decoupled isolation system to reduce transmission of vibrations for quieter operation. Even permanently lubricated motors are supplied with recommended lubrication charts calling for lubrication every five or ten years. We recommend that maintenance instructions of the motor manufacturer be closely followed. The large-diameter hollow fan shaft provides quiet economical performance. Easy Motor Removal Unlike many UVs, the motor is separate from the fan assembly and located out of the airstream at the end of the fan shaft away from the hot coil for easier maintenance and removal. Locat- Partition End Bearing End Compartment Fans PSC Decoupled Isolation Standard Molex Plug Figure 7-4. AAF-HermanNelson Air Stream Coupling Drive shaft solidly anchored and supported on both ends with motor located out of the air stream ing the motor away from the coil (Figure 7-4) has the added benefit of extending motor life. Our direct-coupled motor and self-aligning motor mount facilitate motor changeout. The motor comes with a molex plug that fits all sizes, which further simplifies removal. Multi-tap Transformer The auto-transformer (Figure 7-5) provides multiple fan motor speed control through the speed switch. The motor is independent of supply voltage, which allows stocking of one motor (school district-wide) for various voltage applications. Figure 7-5. Multi-tap Transformer Long-life Bearings The floor unit rotating element has only one large, self-aligning, sleeve-type end bearing (Figure 7-6) and two motor bearings for smoother operation. The location of the bearing at the end of the shaft (out of the airstream) (Figure 7-4) makes for easy access and convenience, should this become necessary. Figure 7-6. Long-life Bearings Oilable sleeve bearings on floor units are located on fan motor and fan shaft end bearings for quietness and long life out of the air stream. Maintenance-free permanently lubricated bearing are standard on ceiling units (Figure 7-6). Nylon damper bearings foster quiet, maintenance-free operation of room air, outdoor air, and face and bypass dampers. Motor Partition End Compartment AAF -HermanNelson Catalog UV-1-230E / Page 7 / (3/01)

8 Comfort You Can Count On Continuous Comfort With Our GentleFlo Delivery The AAF -HermanNelson Unit Ventilator air delivery system is engineered and manufactured to deliver quiet, continuous comfort. Engineering developed and applied leading-edge aerodynamic technology to create a unit that is much quieter. You will appreciate the difference. GentleFlo Delivery incorporates advances in Air- Moving Technology. The entire air-moving system is designed for a softer, quieter operation. Offset Aerodynamic Blades Figure 8-1. Large Fan Wheel Fan wheel is large, wide, and rotates at a low speed to reduce fan sound levels (Figure 8-1). The impact-resistant balanced fan wheel provides consistent performance. The large fan shaft of ground and polished steel operates reliably, well below its critical speed. Expanded Discharge Air Opening Figure 8-3. Quiet And Comfortable Equals An Excellent Learning Environment. Fan wheel blade shape moves the air efficiently (Figure 8-4). Offset aerodynamic blades (Figure 8-1) and balanced precise dimensions reduce the noise associated with turbulence and result in lower sound levels (Figure 8-2). Fan housing design incorporates the latest logarithmic expansion technology for smoother, quieter air flow. (Figure 8-2) The large fan housing allows the air to expand logarithmically after it leaves the fan. This feature works with the fan s slow-speed design to promote quieter operation. Large, expanded discharge opening (Figure 8-2) minimizes air resistance, lowering sound. Modular fan construction contributes to equal outlet velocities to promote quiet operation. Fan wheels, motor and shaft are pre-balanced, factory balanced after assembly, and factory tested for stable, quiet operation. GentleFlo Delivery is a combination of cuttingedge technologies; delivering gentler, quieter operation with smoother air-moving performance. Precision Tolerances Aerodynamically Tuned Fan Blades Fan Housing Incorporates Logarithmic Expansion Technology Figure 8-2. Wheel And Fan Housing AAF-HermanNelson Fan Wheel Blade Shows Minimized Flow And Pressure Turbulence Resulting In Lower Sound Levels. Figure 8-4. Flow And Pressure Test Results Of Fan Blade Typical Of Older, Smaller Wheel s Showing Flow And Pressure Turbulence Catalog UV-1-230E / Page 8 / (3/01) AAF -HermanNelson

9 Comfort You Can Count On (Continued) MicroTech Offers Precise Comfort Control The Direct Digital Control (DDC) package known as MicroTech has been designed to provide sophisticated temperature control of AAF - HermanNelson Unit Ventilators. The MicroTech package can function as a stand-alone controller (Figure 9-1), as part of a MicroTech system (Figure 9-2) or as part of a third-party Building Automation System (BAS) through Open Protocol (Figure 9-3). Figure 9-1. MicroTech Stand-alone Architecture Local Master Panel Unit Ventilator Unit Ventilator Network Master Panel Air Cooled Chiller Unit Ventilator Remote Monitoring Sequence Panel Integration Panel Open Protocol Master Unit Ventilator Air Cooled Chiller Level 1 Controller MicroTech Level 2 Controllers MicroTech Level 3 Controller MicroTech Figure 9-2. MicroTech Network Systems Architecture Open-protocol Partner Level 1 Controller MicroTech Level 2 Controllers MicroTech Figure 9-3. MicroTech Open-Protocol Architecture MicroTech System Capabilities MicroTech systems (Figure 9-2) and third-party Building Automation Systems (BAS) (Figure 9-3) can directly read and write data, e.g., new setpoints, to MicroTech controllers through network communications and Open Protocol respectively. Unit Ventilator MicroTech Controls All Direct Digital Controls (DDC) are factory installed and tested. Communication types include Stand Alone, Master/Slave, and Network. DDC promotes correct precise sequence of operation. (See s section.) The UV software that ships installed is for Stand Alone operation. Master/Slave and Network Software are field downloaded. UV Controls ASHRAE Cycle II Operation is factory programmed. A room temperature sensor controls heating, ventilation and cooling functions. Discharge Air control can override room temperature control to prevent discharge air from dropping below its low setpoint. ASHRAE Cycle II defines the basic operation of the Outdoor Air Damper, Economizer Functions, and the Discharge Air Temperature Control. Time Proven Algorithms MicroTech uses Change and Step & Wait algorithms, which work together in a two-stage process to maintain room temperature control with no overshoot. The Change algorithm changes the actuator (damper or valve) setpoint, in response to deviation of room temperature from its setpoint. The step & wait algorithm causes the actuator (damper or valve) to open or close to maintain the change algorithm calculated position setpoint. The step part is the amount of time the actuator is driven either open or closed, and wait is the amount of time the actuator holds its position. step & wait periods vary and are dependent on amount of actuator position setpoint offset. The step & wait algorithm thus prevents overshooting and provides better comfort control. Economizer Operation Economizer operation is facilitated by the outdoor air damper, which automatically adjusts above minimum outdoor air to provide free-cooling when outdoor air temperature allows for it. Other control sequences available include: 1. Part Load Variable Air Feature The Part Load Variable Air Feature uses Face and Bypass control for dehumidification, and PI Loop to calculate percent load. It automatically adjusts indoor fan speed based upon room load and the room temperature algorithm. By basing indoor fan speed upon room load, it provides higher latent cooling capabilities and quieter operation during non-peak load periods. The room temperature algorithm determines the speed of the fan. Fan speed varies according to the face damper position. It also provides for built-in step and wait delays. Based on fan speed, the part load variable air feature adjusts the outdoor air damper minimum position to bring in the same or constant amount of outdoor air. (See s section.) Figure 9-4. CO 2 Sensor 2. CO 2 Demand Controlled Ventilation Capability The MicroTech controller also has a built in demand controlled ventilation (DCV) algorithm that can make sure the system provides exactly the right amount of outside air. CO 2 is an excellent measure of occupancy. The more people the more CO 2 produced. The AAF-HermanNelson Unit Ventilator enables ventilation compliance at all times using the input from a CO 2 controller (Figure 9-4) to modulate the outside air damper based on actual occupancy versus a fixed design level. With this ASHRAE accepted control method, energy use is minimized as only the required amount of outside air is introduced to promote good indoor air quality. Humidity levels are improved. Ventilation is optimized, while providing energy savings versus a fixed ventilation strategy. The CO 2 Sensor is either Wall Mounted or Factory Mounted in the unit (See pages 22 and 23). Figure 9-5. Humidity Sensor 3. Active Dehumidification Units (Reheat) During excessive humidity conditions the Humidity Sensor (Figure 9-5) controls the Unit to continue cooling. Wet heat or electric heat then reheats discharge air. This removes excessive room moisture. During acceptable room humidity levels the Unit Reheat Function is disabled. The Humidity Sensor is either Unit Mounted or Remote Wall Mounted. (See page 23.) AAF -HermanNelson Catalog UV-1-230E / Page 9 / (3/01)

10 Comfort You Can Count On (Continued) Better Temperature And Humidity Control Face and bypass damper control coupled with draw-thru unit construction offers maximum dehumidification and optimal temperature control. On the AAF -HermanNelson draw-thru unit ventilator, the fans are located above the heating/ cooling coil, which permits separation of the indoor and outdoor air streams until it is optimal to mix the air streams. With a draw-thru design (Figure 10-1) and during most part-load conditions, the majority of the humid outdoor air passes through the cold coil (coil surface below the dew point), where the moisture is removed, and the previously treated, less humid room air bypasses the coil, providing maximum condensate removal. Consequently, humid outdoor air is not bypassed around the coil until the amount of air going through the coil is less than the amount of outdoor air that is entering the unit. On the other hand, with blow-thru construction (Figure 10-2), the amount of humid outdoor air that is bypassed around the coil at part-load conditions is directly proportional to the percentage of the total air stream that is being bypassed since the air is mixed in the fan. The tables below compare the composition of the air streams through the coil and air streams bypassing the coil at various bypass air percentages for draw-thru and blow-thru unit ventilators using 450 cfm of outdoor air. At both 0% bypass air and maximum bypass air no difference exists in the composition of the air streams when comparing draw-thru versus blow-thru units. However, at all other bypass air percentages (part load), significant differences are evident in the room air and outdoor air compositions of the two unit types. For instance, examine the 1500 cfm draw-thru unit (Table 10-1) against the 1500 cfm blow-thru (Table 10-2) unit at 70% bypass air. At this point, the draw-thru unit still has all of the outdoor air going through the coil, while the blow-thru unit is bypassing 315 cfm (70%) of outdoor air directly into the classroom while only 135 cfm (30%) of outdoor air is going through the coil. This illustrates that the most effective way of maintaining an acceptable humidity level with a chilled-water unit ventilator system is to use a face and bypass damper controlled draw-thru unit. AAF-HermanNelson Table cfm Draw-thru Unit % Bypass Air Total Unit cfm Bypass Air Stream (cfm) Coil Air Stream (cfm) Total From From Total From From Bypass Room Outdoors Coil Room Outdoors Increased Dehumidification Face and Bypass Damper Room Air Figure AAF-HermanNelson Outdoor Air Competitor s Table cfm Blow-thru Unit % Bypass Air Total Unit cfm Bypass Air Stream (cfm) Coil Air Stream (cfm) Total From From Total From From Bypass Room Outdoors Coil Room Outdoors Reduced Dehumidification Room Air Filter R.A./O.A. Divider Outdoor Air Figure Competitor s Blow-thru Catalog UV-1-230E / Page 10 / (3/01) AAF -HermanNelson

11 Comfort You Can Count On (Continued) Draw-thru Provides Even Discharge Temperatures And Better Humidity Control Air Flow Shaded Coil Figure Draw-thru With Even Air Distribution The AAF -HermanNelson Draw-Thru principle sets the AAF-HermanNelson Unit Ventilator apart from most competitive models. With this system, fans draw air through the entire heat transfer element (Figure 11-1), rather than blowing it through highly concentrated areas of the coil element. AAF-HermanNelson s draw-thru design is more effective because: (1) Draw-thru design provides uniform discharge air temperatures. (2) Draw-thru fans allow complete, even, heat transfer over the entire face area of the coil for more efficient unit ventilator operation. Draw-thru vs. Blow-thru With AAF-HermanNelson s draw-thru construction, situations requiring less than full cooling can be controlled with accuracy. The face and bypass damper directs the humid outdoor air through the cooling coil and allows the low humidity room air to bypass the coil. In addition, in a draw-thru design the air is drawn evenly through the entire coil fostering even temperature across the coil and maximizing coil surface utilized for dehumidification. Blow-thru designs cannot provide comfort like this. With blow-thru designs, the humid outside air is pre-mixed with the room air before it can go through the coil. Dehumidification occurs only to the portion of the air that is directed through the cooling coil. The air that bypasses the coil is largely humid outdoor air, resulting in unconditioned air being bypassed and creating poor comfort conditions. With a blow-thru design the positive pressure of the fan discharge can create areas across the coil of varying temperatures and airflow. In addition, Blow-thru face and bypass damper construction picks up heat by wiping the coil creating overheating conditions. Also the sound in a blow-thru design will vary based upon the position of the face and bypass damper. Face And Bypass Offers Infinite Capacity Control The AAF-HermanNelson face and bypass damper control units utilize standard unit ventilator cycles of temperature control and can allow maximum outdoor air into the room for cooling. The face and bypass damper can be positioned to: 1. Direct all the air through the heating or cooling coil (Figure 11-2). Face and Bypass Damper Room Air Damper Coil Outdoor Air Damper Figure % Room Air 2. Direct all the air to bypass the heating or cooling coil. (Figure 11-3) Room Air Damper Room Air Outdoor Air Damper Outdoor Air Figure Full Economizer Operation With 100% Outdoor Air 3. Direct a portion of the air through the coils and allow a portion to bypass the coils (Figure 11-4). Face and Bypass Damper Room Air Outdoor Air Figure Portion Of Air Through Coil And Bypassed Notice natural bypassing of treated room air AAF-HermanNelson s modulating controller automatically adjusts the damper so that maximum energy efficiency and maximum comfort are achieved. Face and bypass damper control (Figure 11-5) eliminates the frequent problem of incorrectly sized modulating control valves. Improperly sized control valves often result in twoposition valve cycling, resulting in poor comfort (temperature and humidity) control and valve wear. Metal Formed For Extra Rigidity Flexible Air Seal Wool Mohair End Seal Figure Face And Bypass Damper Face And Bypass Damper The AAF-HermanNelson modulating face and bypass damper assembly has twist free reinforced aluminum construction for durability. Aluminum is used because it is lightweight and noncorrosive, resulting in low torque and easy movement. The end seals are wool mohair and the long closing edges of the damper use a cushion formed of woven glass fabric-coated silicone rubber. This seal is free from deterioration and retains its memory for a tight seal. Nylon damper bearings foster quiet, maintenancefree operation of the face and bypass damper. AAF -HermanNelson Catalog UV-1-230E / Page 11 / (3/01)

12 Comfort You Can Count On (Continued) Maximum Dehumidification The design of the AAF -HermanNelson face and bypass damper control has been carefully engineered to provide maximum dehumidification at all times. Constant water flow through the coil is maintained to keep the surface temperature at, or below, the dew point. Directing all the air through the cooling coil may result in short cycling or an over-cooled condition. Directing all the air around the coil may result in overheating and no dehumidification. AAF-HermanNelson s sophisticated DDC controls monitor room conditions and modulate the face and bypass damper to obtain maximum dehumidification and optimal temperature control. Ease Of System Balancing With a face and bypass damper, the water in the system is constantly circulating, which maintains a desirable head pressure to the pumps. With fluctuating head pressure eliminated, balancing the system can enable the correct quantity of water in all circuits. Increased Coil Freeze Protection With face and bypass damper control, there is no change in the flow of water through the coil. Coils that have a constant flow of hot water cannot freeze. Additionally, the AAF-HermanNelson assembly has a double-walled insulated outdoor damper with an encapsulated insulation and wool mohair seals to prevent unwanted cold air from entering the unit. This cold-weather air-tight construction further decreases the chance of coil freezeup, if waterflow is inadvertently interrupted. Furthermore, a low-temperature Freezestat (Figure 12-1), factory installed on all hydronic units, significantly reduces the chance of coil freeze-up. Its wave-like configuration senses multiple locations by blanketing the leaving air side of the coil to react to possible freezing conditions. Coil Freezestat Figure Freezestat Delivering Outdoor Air For Free Cooling It is well recognized that cooling, not heating, is the main thermal problem in school classrooms. The typical classroom is cooled by outdoor air over half the time, even in cold climates. It is therefore essential that unit ventilators efficiently deliver outdoor air when classroom conditions call for free or economizer cooling. With AAF-HermanNelson Unit Ventilators, you can have outdoor air whenever it is needed. Room Air Damper Room Air Outdoor Air Figure Full Economizer Operation With 100% Outdoor Air Cold Weather Outdoor Air Damper The standard AAF-HermanNelson outdoor air damper is made of galvanized steel to inhibit corrosion, with double-wall welded construction for rigidity, and encapsulated insulation (Figure 12-2). The outdoor damper has additional insulation on the exterior of the outdoor air damper blade and on the outdoor air entry portion of the unit. Turned-metal Damper Blade Turned-metal Damper Stop Wool Mohair End Seal Additional Insulation Wool Mohair End Seal Room Air Damper Full-length Wool Mohair Damper Seal Figure Turned-metal Seal Dampers on AAF-HermanNelson Unit Ventilators use the turned-metal principle on the long closing edges (Figure 12-3), which provides positive sealing by embedding into wool mohair (no metal to metal contact). This superior design prevents outdoor air from entering (Figure 12-4). There are no plastic gaskets to become brittle with time, sag with heat or age, or require a difficult slot fit to seal. Turned Metal Full-length Wool Mohair Seal Wool Mohair End Seal Figure Cold Weather Outdoor Air Damper Room Air Balanced Damper The AAF-HermanNelson room air damper design is free floating and prevents intermittent gusts of cold air from blowing directly into the classroom on windy days (Figure 12-5). It is constructed of aluminum with built-in rigidity. The metal forming technique resists twisting and incorporates a full-length counter weight for easy rotation. Figure Room Air Damper Insulated Doublewall Construction Additional Insulation Turned Metal Full-length Wool Mohair Seal Gust of Wind The simple principle of an area exposed to a force is used to prevent gusts of cold air. The larger area closes the damper. The return air damper uses turned-metal sealing concepts with a mohair seal. Both the room air and outdoor air dampers have nylon damper bearings to foster quiet, maintenance-free operation. Catalog UV-1-230E / Page 12 / (3/01) AAF -HermanNelson

13 Tailored For Adaptability And Good Looks Built-in Flexibility AAF -HermanNelson unit ventilators have many standard features with flexible options that make them just right for retrofit applications and well suited for new-construction. It is this attention to detail and understanding of school applications that make AAF-HermanNelson units the product of choice. Add Cooling At A Later Date All units (heating-only, cooling-only, heating/ cooling) come with an insulated, galvanized-steel drain pan. (Figure 13-1) The drain pan is insulated on the bottom to help prevent condensate formation. Some manufacturers eliminate the drain pan on heating-only units. Because we recognize that some schools may wish to add cooling at a later date, we include a built-in drain pan on heating-only units as standard. Figure Insulated, Galvanized Steel Drain Pan Reversible Drain Connection The insulated drain pan has drain connections at both ends. One drain is shipped open. This can be reversed in the field. Ceiling Unit Drain Connection Center-line located 5" above unit bottom for proper drainage. Leg Levelers Figure Adjustable Leg Levelers Adjustable Leg Levelers Front adjustable leg levelers on floor units compensate for floor irregularities. (Figure 13-2) Built-in Pipe Tunnel Built-in pipe tunnel on floor units allows field crossover of hot-water or chilled-water piping, electrical or refrigeration tubing (Figure 13-3). Room Air Damper Room Air Wire Race Outdoor Air Figure Built-in Pipe Tunnel And Wire Race Protective Metal Wire Race Built-in metal wire race for extra protection that runs from one end of the unit to the other so wires are not exposed to unit air (Figure 13-3). Auto Transformer Auto transformer provides multi-speed fan motor speed control through speed switch. Motor is independent of supply voltage to unit. Easy Fit-up To Shelving Easy fit up to shelving cabinets is realized by a welded slot in the floor unit top front rail, which receives a spline from cabinet shelving (Figure 13-4). Unit Ventilator Front Alignment Bar Built-in Pipe Tunnel Outdoor Air Damper Shelving Cabinet Figure Fit-up Shelving Reversible Bar Discharge Grille Reversible bar discharge grille s optimum 10 up (standard) or 10 down vertical deflection on ceiling units provides architecturally pleasing appearance. Standard on 30" units. Optional accessory on 36" units. Figure Double Deflection Discharge Grille Adjustable Double Deflection Discharge Grilles Ceiling units with front (36" unit) and bottom (40" unit) discharge are available with four-way double deflection discharge grilles (Figure 13-5) so that air distribution patterns may be adjusted on the job to meet room requirements. Both the horizontal front vanes and vertical rear Exposed Soffit Partially Recessed Concealed Figure Ceiling Unit Ventilators vanes of the double deflection discharge grilles are adjustable to provide both side deflection and upward or downward deflection. Finished Appearance Ceiling unit ventilators can be mounted in an exposed position, in a soffit, partially recessed, fully recessed, or concealed (Figure 13-6). For partially- and fully-recessed units, recess flanges (Figure 13-7) are a standard accessory to provide a finished appearance to help finish off the ceiling and provide a break to isolate the unit from the ceiling. Recess Flange Figure Recess Flange Return Air Static Balancer Return air static balancer is used whenever the outdoor air static pressure is 1 8" greater than return air static pressure (ceiling model only). In applications where significant external static pressures are encountered due to outside air duct work, the return air static balancer may be used to balance air flow between outdoor air and return air. A balancer is included in the return air plenum of the unit that may be manually set so that the room air fan motor is not subject to overload conditions as the outdoor air/return air damper travels during the normal cycle. Accurate Response To Room Temperature Change A sampling chamber is provided on each unit for housing the unit-mounted temperature sensor whenever the unit mounted temperature sensor is provided with MicroTech controls. A representative sample of room air is continuously drawn into the sampling chamber when the fan is running, to provide an accurate response to room temperature changes. AAF -HermanNelson Catalog UV-1-230E / Page 13 / (3/01)

14 Tailored For Adaptability And Good Looks (Continued) Extra Adaptability 1 End Panels 1 End Panels finish off stand-alone floor units. They are individually wrapped in plastic and boxed to prevent damage during construction. Figure End Panels 6 End Panels 6 End Panels with kick plates can be used to add extra space for piping with stand-alone floor units (Figure 14-1). They are individually wrapped in plastic and boxed to prevent damage during construction. Take The Chill Out Of Window Down Drafts AAF -HermanNelson DraftStop TM is designed to minimize cold window downdrafts. Downdrafts can be generated in classrooms with relatively large windows during prolonged periods of cold outside temperatures. For comfort during such conditions, some form of downdraft protection should be provided. The AAF-HermanNelson DraftStop System is one of the best systems available to address the downdraft problem. Our unique DraftStop System intercepts falling cold air at the window sill level and recirculates it back to the unit ventilator. It then enters the unit s air stream through the room air damper and becomes part of the normal air circulation pattern. This is accomplished by blocking the return air grille at the front of the unit ventilator to cause the return air to be drawn in through the ends of the unit. Sub-base Available To Match Window Sills Or Existing Cabinets AAF-HermanNelson unit. Sub-bases (Figure 14-2) are available in five different heights: 1, 2, 4, 6, or 12 with or depths. Their Oxford brown baked thermal setting urethane powder paint matches the unit s bottom section and withstands cleaning of floors. In addition, the unit s leg levelers can be used to level the entire unit/ sub-base assembly, compensating for uneven floors. The AAF-HermanNelson sub-base can also be used to raise the outside air opening above floor level to reduce blockage of outside louvers and reduce louver soiling from rain splash. Figure Sub-base Functional Unobtrusive Outdoor Air Capability With today s increased emphasis on outdoor air for ventilation and proper indoor air quality, AAF- HermanNelson louvers are especially important. They allow outdoor air to be drawn in while blending with the building architecture. The AAF-HermanNelson Louver is constructed with heavy blades in a rugged frame. Both louvers and frames are made of heavy-gauge aluminum, which is available either painted or unpainted. For painted louvers and grilles a specially formulated environmentally friendly thermosetting urethane powder is applied electrostatically and baked for long lasting beauty as well as resistance to corrosion. The paint is then oven cured to provide correct chemical cross-linking, which provides years of service. The alloy used for louvers and grilles, AQ 5005, is suitable for color anodizing by others. Louvers can be supplied with or without a flange. The optional flange can be used for a panel wall finish. The unflanged louver is Louver Flange Sub-base used for recessing into the building masonry wall. Louvers are sized to match the unit outside air opening to maximize outdoor air. Drainage is located in the exterior side of the frame. All aluminum construction is standard, with a decorative grille optional. The 1 2 -square mesh bird screen (Figure 14-3) located on the leaving air side prevents birds and other small animals from entering. The strong aluminum mesh is designed to minimize air pressure drops, unlike expanded metal. Horizontal And Vertical Blade Louvers Horizontal blade construction turns the air to keep moisture from entering. The bottom weep holes drain moisture to the outside (Figure 14-4). Vertical-blade multiple-break configuration provides positive water impingement and entrapment. The bottom lip drains moisture to outside (Figure 14-5). Weep Holes Figure Horizontal Blade Louver Lip Drains Figure Vertical Blade Louver Grille AAF-HermanNelson decorative intake grilles are available in heavy-gauge aluminum. The square holes are designed to match the blades of the AAF- HermanNelson louver, maximizing the air opening. The grilles come in either painted or unpainted AQ 5005 aluminum with holes for mounting to building exteriors (Figure 14-6). AAF-HermanNelson sub-bases are used to provide additional height to the floor unit ventilator. This allows the unit to match the window sill or existing cabinets heights. Prior to 1968, unit ventilators came in 28, 30, and 34 heights. The industry standardized on the 30 height of the Bird Screen Figure Bird Screen On All Louvers (Indoor View) Weep Holes Figure Outdoor Grille Catalog UV-1-230E / Page 14 / (3/01) AAF -HermanNelson

15 Tailored For Adaptability And Good Looks (Continued) Simple Room Exhaust Capability Ventimatic TM Shutter The Ventimatic shutter is a continuously variable, gravity-actuated room exhaust vent that operates in direct response to positive static air pressure (Figure 15-1 and 15-2). Unlike other non-powered vents, it opens at extremely low positive pressure (0.005"). Outdoor air introduced by the unit ventilator must leave the room in some way. In some states, exhaust vents are required by law or code to accomplish this. The Ventimatic shutter is a more economical solution to the problem. The operation of the Ventimatic shutter is inherently silent. The shutter flaps are made of temperature-resistant glass fabric impregnated with silicone rubber for flexibility and long life. This fabric retains its original properties down to -50 F. The Ventimatic shutter s ability to exhaust only the amount of air required results in considerable energy savings. In the heating mode, the unit ventilator brings in the minimum percent of outside Exhaust Room Air Ventimatic Shutter Louver Figure Ventimatic Shutter With Louver air required. The Ventimatic shutter, in turn, exhausts the minimum amount. In cooling mode, the unit ventilator brings in outdoor air for full natural cooling when conditions allow; the Ventimatic shutter responds by exhausting an equal amount. Figure Ventimatic Shutter Front Matching Storage Accessories Available To Meet Your Needs Figure Sink And Bubbler Cabinet With Stainless Steel Top Alignment Slot Storage cabinets are designed to complement the AAF -HermanNelson classroom Unit Ventilator and provide adequate storage. Heavy gauge steel finished with environmentally friendly thermosetting urethane powder electrostatically applied and oven-cured in a pleasing array of matching architectural colors. The one-piece stainless steel top has stainless steel bowl(s), a raised front lip, and formed back and end splashboards. Comes with chrome fittings, a choice of single or double bowl and optional door locks to conceal storage and piping. Adjustable kickplates with leg levelers are standard on all units and functional accessories. European cabinet design has adjustable leg levellers on each corner that adjust to compensate for variations in the floor. When the sink and bubbler model with adapter back is furnished, the adapter back has a charcoal textured finish. Shelving cabinet tops are furnished with a textured, non-glare and scuff-resistant charcoal bronze electrostatic paint. Optional laminate tops are available. Also available for field-supplied and installed countertops. Adjustable kickplates with leg levelers are standard on all units and functional accessories. European cabinet design has adjustable leg levellers on each corner that adjust to compensate for variations in the floor. Adjustable height metal shelves for flexible storage space. Shelf adjusted without tools by repositioning the four concealed shelf holding clips. Optional easy sliding door with bottom glide track for good alignment. Bottom glide track prevents door bottom intrusion into the storage space. Optional door locks. Door pulls added for convenience and finished appearance. Front alignment bars fit into welded notches permitting alignment of storage accessories with the Unit Ventilator. Unit Ventilator Adjustable Kick Plate And Leg Levelers Front Alignment Bar Shelving Cabinet Figure Shelf Cabinets AAF -HermanNelson Catalog UV-1-230E / Page 15 / (3/01)

16 Tailored For Adaptability And Good Looks (Continued) Expansive Coil Offering AAF -HermanNelson offers a complete and flexible coil selection. All coils are located safely beneath the fans and designed for draw-thru air flow to provide maximum efficiency of heat transfer. All water, steam and direct expansion coils are constructed of aluminum fins with a formed integral spacing collar, mechanically bonded to the seamless copper tubes by expansion of the tubes after assembly. Fins are rippled or embossed for strength and increased heat transfer surface. Coils and unit are ARI capacity rated. Quality Coil The coil design (Figure 16-1) relies on advanced heat transfer to provide extra cooling capacity for today s increased ventilation requirements. Tuned internal water flow and balanced header design with additional surface area in the air stream increases heat transfer to satisfy the increased need for dehumidification. Figure Typical Coil Air Vent And Drain A manual air vent and drain is provided on all hydronic coils. The vent allows air to be purged from the coil during field start-up or during maintenance. The manual air vent is located on the top of the coil header of all floor (AV) hydronic coils. (Figure 16-2) Ceiling (AH) unit hydronic coils come with auto air vents. Air Vent Drain Figure Manual Air Vent And Drain Plug The manual drain plug (Figure 16-2) is located at the bottom of the coil header of hydronic coils. Others may not provide drainage of coils. With AAF-HermanNelson unit ventilators, the extensive choice of coil combinations means that room conditions can be met using almost any cooling or heating source. Maximize Heat Transfer Heat transfer is maximized (promoting comfort and reducing operating costs) by ensuring that all coils have their own individual unshared fin surfaces. Some manufacturers use a continuous fin surface sacrificing proper heat transfer. An air break between coils in all AAF-HermanNelson units is used to enhance decoupling of heat transfer surfaces, providing full capacity output, comfort and reduced operating costs. Electric Coils With a draw-thru design electric coils are directly exposed to the air stream and come with a builtin dead front switch to de-energize the coil when the center front panel is removed. A unit mounted disconnect switch is included. A continuous electric sensory element for high temperature is not required because the air is drawn smoothly and evenly across the coils, prolonging life. A blowthru design uses cal rods inserted into the tube of a fin tube coil that results in reduced heat transfer. The constant movement of the electric heating cal rod within the tube shortens life. Steam Distributing Coils Steam distribution coils allows even distribution of steam and even discharge air temperature. Vacuum Breaker The vacuum breaker relieves the vacuum in the steam coil to allow drainage of condensate from the coil. This eliminates water hammer and greatly reduces the possibility of coil freeze-up. Standard Capacity High Capacity 2 Row 3 Row 4 Row 5 Row U D E F Figure Hot/Chilled Water Coil 2-Pipe System Standard Capacity High Capacity 2 Row 3 Row 4 Row 5 Row V S W Y Figure Chilled Water Coil 4-Pipe System Catalog UV-1-230E / Page 16 / (3/01) AAF -HermanNelson

17 Tailored For Adaptability And Good Looks (Continued) 1 Row 2 Row 3 Row Figure Hot Water Coil Thermal Expansion Bulb Equalizing Tube 3 Row G Figure DX Coil Close-up of factory installed TEV (Thermal Expansion ) suction line and equalizing tube Staging Connector Dead Front Switch Electric Heat Disconnect Figure Electric Heat Control Panel 1 Row 2 Row Row 2 Row Steam Coil Opposite End Connections Figure Steam Coil With Opposite End Connections With factory supplied pressure equalizing and check valve assembly Low Heat High Heat Figure Electric Resistance Heating Coil AAF -HermanNelson Catalog UV-1-230E / Page 17 / (3/01)

18 Overview Take Control Of Energy Expenditures Schools consume more than 10% of the total energy expended in the United States for comfort heating and cooling of buildings. As energy costs increase, educators are placed in a difficult position caught between rising costs and irate taxpayers and the requirements to raise educational standards. Fortunately, the technology and the system (i.e. the unit ventilator) exists to enable schools to take control of their energy expenditures while providing a comfortable environment for learning. Energy use in schools is actually determined more by hours of operation and system selectivity than by building design. Most of the school heating costs are accounted for by unoccupied spaces. Because lights, computers and students give off considerable heat, occupied spaces require little supplemental heat. In fact, the removal of heat is usually required in occupied classrooms when outside temperatures are moderately cold (i.e.: F). However, all cooling energy is typically required during occupied periods. The AAF - HermanNelson Unit Ventilator is designed to deliver natural air or free cooling (economizer operation) directly into the classroom, reducing energy usage and lowering operating costs. Central systems (i.e. all air types using rooftops or air handlers) waste energy by bringing in outside air, heating and cooling the air and delivering it to unoccupied spaces. Contrast this waste to the unit ventilator located in each classroom. The unit ventilator can be turned on when needed, cycled off during unoccupied periods, bring free natural air cooling directly into the space, and provide individual classroom control and comfort. In addition, each unit ventilator has its own air-moving device (fan and motor), which uses about as much energy as two 100-watt light bulbs. Contrast this with the energy consumed by the large horsepower motors (20hp-plus) of central air systems, which pump supply air and return air to a central source from unoccupied or occupied classrooms, and then exhaust the air. Ideally a school should be able to turn on heating, cooling, and ventilating equipment only when it is needed and use free economizer cooling to keep each classroom at a comfortable temperature. Unit ventilator systems provide this kind of energyefficient, cost-effective incremental operation. Room Heat Loss, BTU/HR. 60,000 50,000 40,000 30,000 20,000 10, A B C D Why Classrooms Overheat ROOM HEAT LOSS LINES Outside Air Temperature, F. Figure Heat Gain vs. Heat Loss Overheated classrooms occur every day in schools in every area of the country. When you consider the consequences of an overheated classroom, the problem is obvious to all who have been even remotely associated with schools. The most serious result of an overheated classroom is its detrimental effect on students ability to concentrate and learn. Research has determined that the ability to learn and retain knowledge decreases rapidly as the temperature exceeds recommended classroom temperatures. Overheated rooms also represent wasted fuel, resulting in excessive operating costs. This is a needless waste of school operating funds. Correcting an overheating problem in an existing building is very difficult and expensive. It calls for redesign and alteration of the heating and ventilating system, necessitating considerable renovation. This potential problem should be recognized, understood and planned for when heating and ventilating systems are designed for new and existing buildings. Temperature On Room Heat Loss Line Above Which Cooling Is Always Required } 10,000 BTU/HR. Possible Heat Gain From Sun Direct And Reflected 8,500 BTU/HR. } Heat Gain From Lights 7,800 BTU/HR. } Heat Gain From Students Note: Figure 18-1 shows the Room Heat Loss and Uncontrolled Heat Gains plotted to show reason for overheating of school classrooms. During occupied day, classroom is more likely to require cooling than heating in very cold weather. Schools Have Special Needs Schools have unique heating and ventilating needs, in large part because of their variable occupancy and usage patterns. Fewer cubic feet of space is provided per student in a school building than any other type of commercial or public building. School classrooms are typically occupied six hours a day, five days a week for only three-fourths of the year, with time out for vacations. All in all, this represents approximately 15% of the hours in a year that a classroom is occupied. To understand the overheating problem in schools, one must first realize that the excess heat that causes the classroom to become too warm comes from what is commonly termed uncontrolled heat sources. To gain some perspective on how this affects heating and cooling decisions, let s take a look at a typical classroom in the northern section of the midwestern United States. Let s suppose we have a classroom that is 24 by 38 feet long with 10- foot ceilings and 100 square feet of window area along the outside wall. At an outside temperature of 0 F and a desired room temperature of 72 F, let s assume the normal amount of heat loss from the room to the outside is 55,000 BTUs per hour. Catalog UV-1-230E / Page 18 / (3/01) AAF -HermanNelson

19 Overview (Continued) As the outside temperature changes, so does the amount of heat that the room loses. This is represented in Figure 18-1 by the line marked, Room Heat Loss Line A, which ranges from 55,000 BTUs per hour at 0 F outside air temperature to 0 BTUs at 70 F. Obviously, if the heating system were the only source of heat in the classroom, the problem would be simple. The room thermostat would cause the heating system to supply exactly the amount of heat required to maintain the room at the room thermostat temperature setting. In reality, however, the introduction of excess heat from a variety of uncontrolled source makes the problem considerably more complex. Heat From Students Body heat generated by students in a classroom is one of the three primary sources of uncontrolled heat. In a typical classroom of 30 students, the amount of heat given off at all times will vary according to factors such as age, activity, gender, etc. A conservative estimate is 260 BTUs per hour per pupil. Multiply this by 30 and you get a total of 7,800 BTUs per hour added to the room by the students alone. This excess heat is noted in Figure 18-1 as Heat Gain from Students. Heat Gain From Lights Heat emitted by the lighting system constitutes a second uncontrolled heat source. Artificial lighting is needed in most classrooms even during daylight hours to prevent unbalanced lighting and eye strain. A typical classroom requires approximately 2,500 watts of supplemental lighting to provide properly balanced lighting. Fluorescent lights add heat to the room at the rate of 3.4 BTU per watt per hour or a total of 8,500 BTU per hour. This extra heat is represented in Figure 18-1 as Heat Gain from Lights. Add the heat gain from lighting to the 7,800 BTUs introduced by student body heat and we now have an extra 16,300 BTU/HR being introduced into the classroom by uncontrolled sources. This heat gain remains constant regardless of the outdoor air temperature. Solar Heat Gain The sun is a third source of heat and, because it is neither positive nor constant, calculating its contribution to the overall heat gain is difficult. Solar heat gain can be the worst offender of the three in classrooms with large windows. Indirect or reflected solar radiation is substantial even on cloudy days, even in rooms with north exposure, as a result of what is termed skyshine. To get an idea of the potential effect of the sun, let s assume that the solar heat gain in our hypothetical classroom will peak at 240 BTU/HR per square foot of glass area. If we then assume a glass area of 100 square feet and at least 100 BTU/HR per square foot of glass for solar heat gain, we can calculate a very conservative estimate of 10,000 BTU/HR heat gain through windows. If we add this to the heat from the lights and body heat, total heat gain adds up to 26,300 BTU/HR from sources other than the heating and ventilating system. This is indicated in Figure 18-1 by the top horizontal line, which intersects Room Heat Loss Line A at approximately 37 F. This is a reasonable estimate of the maximum uncontrolled heat gain that can be received in the typical classroom from these common heat sources. The Analysis From Figure 18-1 it is evident that at an outside temperature of 48 F or higher, the heat given off by 30 students and classroom lighting is sufficient to cause overheating, requiring the heating and ventilating system to provide some form of cooling at all times. This is true even if the classroom was occupied at night when solar heat gain is not a factor. But, since classrooms are occupied during the day, solar addition provides heat in varying amounts even in classrooms with north exposures. Consequently, the heating and ventilating system in our typical classroom must provide cooling at all times when the outdoor temperature is above 48 F, and at any time during colder weather when the solar heat gain exceeds room heat loss. If we assume an average winter temperature of approximately 33 F in the region where our typical classroom is located we know that half of the time, both night and day, the outside temperature will be above 33 F. However, since it is generally warmer during the day, when school is in session, the heating and ventilating system will be required to provide cooling for this classroom during much of the time that the room is occupied. In this example, we ve assumed that our classroom had a room heat loss of 55,000 BTU/HR at a design outdoor air temperature of 0 F (Room Heat Loss Line A ). Bear in mind, however, that the recent trend in energy-saving building design often results in rooms with lower room heat loss, as indicated by Room Heat Loss Lines B, C and D. At 0 F design outdoor air temperature, Room B has a room heat loss of 45,000 BTU/ HR, Room C has a room heat loss of 35,000 BTU/HR, and Room D has a room heat loss of 25,000 BTU/HR. Note the lowering of the temperature above which cooling will always be required as the room heat loss decreases. We ve noted that cooling is always required in Classroom A when outdoor air temperatures exceed 48 F. In Classroom B we see that cooling is always required when outdoor temperatures exceed 44 F. In Classroom C cooling is always required when outdoor temperatures exceed 36 F. In Classroom D cooling is always required at an outside temperature of 23 F or higher. Lowering room heat loss means that classroom D requires cooling most of the time that the room is occupied. Now that we understand the reason for classrooms overheating, the solution is simple. The heating and ventilating system must provide cooling to take care of the heat given off in the classroom by uncontrolled heat sources. Cooling of the Classroom The AAF -HermanNelson Unit Ventilator has become a standard for heating and ventilating systems in schools because it provides the solution to this very problem. The unit ventilator cools as well as heats. During the heating season the outdoor air temperature is nearly always below the desired room temperature. It stands to reason then that the outside air should be used to provide the cooling necessary to keep classrooms down to thermostat temperature. The classroom unit ventilator does just that. By incorporating an automatically controlled outdoor air damper, a variable quantity of outdoor air is introduced in the classroom, metered exactly to prevent overheating. This automatically controlled damper is capable of bringing in outside air as needed to prevent classroom overheating. Since our problem is more one of cooling than of heating, it is evident that more than just the room heat loss must be determined to design a good heating and ventilating system. The cooling requirements should be assessed as well, and the free-cooling capacity of the equipment specified along with the heating capacity required. If this is done, the optimum learning temperature can be maintained in each classroom. AAF -HermanNelson Catalog UV-1-230E / Page 19 / (3/01)

20 Systems DraftStop System/ Window Down Draft Protection Falling Cold Air from Window Figure DraftStop System Over the years the unit ventilator system has proven to be the most effective system in maintaining excellent comfort conditions in classrooms. This is still true today. Cold window down drafts are a common problem in classrooms with relatively large windows, particularly during prolonged periods of cold outside temperatures. The AAF -HermanNelson DraftStop System is designed to address this problem. Because down-draft conditions cause discomfort to the room s occupants, some form of down-draft protection should be provided. Window down-draft protection is recommended for classrooms where the following conditions exist: 1. Window area exceeds 40% of the total outside wall area. 2. Single-pane glass is used. 3. Outside temperatures are below 35 F for a significant portion of the occupied period. The need for window down-draft protection will not always be so clear cut. Where uncertainty exists, a further check can be made by calculating the window heat loss at an outdoor temperature of 35 F. If estimated window heat loss exceeds 250 BTUH/FT, window down-draft protection is recommended. If estimated window heat loss is less than 250 BTUH/FT, the need for downdraft protection is marginal but should not be arbitrarily dismissed. The DraftStop system can be employed even in those marginal applications to assure the occupants comfort without the material installation and operating cost penalty associated with auxiliary radiation. How DraftStop Works Morning Warm-up (Figure 20-2) During this period, no outdoor air is admitted. The cold air from the windows flows into the DraftStop slot and is drawn toward the unit ventilator. This air enters the unit through the room air damper, passes through the heating element and is discharged into the room. Unit Discharge Unit Ventilator Down-drafts Optional Ventimatic Exhaust Figure Morning Warm-up Normal Operation (Figure 20-3) During much of the day, the unit ventilator circulates a mixture of outdoor air and room air, proportioned to maintain thermal comfort in the classroom. The return air continues to be drawn off the windows, providing the DraftStop action. We now see the impact of the optional Ventimatic TM gravity exhaust. The Ventimatic shutter concealed behind the cabinets allows air to be expelled to the outdoors. This prevents excessive room pressurization, which would interfere with the ventilation cooling capability of the unit. This exhaust action also enhances the DraftStop effect since the air to be exhausted is forced into the DraftStop slot at sill level. Outdoor Air Unit Discharge Unit Ventilator Down-drafts Figure Normal Operation, Minimum % Outdoor Air Optional Ventimatic Exhaust Maximum Ventilation Cooling (Figure 20-4) During these periods, the unit ventilator will operate with the outdoor air damper fully open. In this mode, there will be little or no return air to the unit and little or no DraftStop action. The unit ventilator will not operate at maximum ventilation cooling when the outdoor temperature is low enough to create cold window downdraft conditions. Therefore, the lack of DraftStop action is of no consequence. The optional Ventimatic exhaust continues to provide an effective means of relieving the room of excess pressure. Outdoor Air Unit Discharge Unit Ventilator Down-drafts Figure Maximum Ventilation Cooling Optional Ventimatic Exhaust Catalog UV-1-230E / Page 20 / (3/01) AAF -HermanNelson

21 Systems (Continued) Unit Nom. CFM High DraftStop Wall Enclosure Minimum Length (Ft.) Each Side Consult Table 21-1 for recommended minimum and maximum DraftStop grille lengths. Note that the maximum lengths are based on maintaining optimum velocity through the DraftStop grille. If the maximum lengths are exceeded the system will remain operational; however, the efficiency will be correspondingly reduced. DraftStop Enclosures DraftStop wall enclosure or DraftStop cabinets are fitted to the ends of the unit ventilator so that there is a continuous elongated return air grille located beneath the windows. These cabinets have a built-in 3" or " cavity between the rear of the cabinet and the wall, which forms the return air path to the unit ventilator. Cool air from the windows is drawn into the plenum before it is allowed to reach the occupants. Either a steel bar-type inlet grille or a stamped inlet grille is fitted to the rear of the cabinet, flush with the cabinet top. In applications where cabinets are intended to be included as part of classroom equipment, the DraftStop feature can be added to the cabinets and unit ventilator at no increase in material cost over a standard cabinet installation without draft protection. The installation labor cost would be the same in either case. Both shelf-type cabinets (16 5 8" or " deep) and sink bubbler cabinets (21 7 8" deep) are available in the DraftStop configuration. Filler sections are available to complete the installation; however, they do not have inlet grilles and their use under windows should be held to a minimum Maximum Length (Ft.) Each Side High DraftStop Wall Enclosure or Storage Cabinets Minimum Length (Ft.) Each Side Table DraftStop TM Grille Length Maximum Length (Ft.) Each Side Wall enclosures are used to form the return air path to the unit ventilator when DraftStop cabinets are not used. The enclosures are available with stamped inlet grille or with an aluminum bar-type inlet grille. Enclosures can be 14", 20" or 24" high and are available in 1 through 8 lengths in 6" increments. Accessories such as wall trims and end caps are available to complete the installation. Normal measures should be followed concerning installation when using DraftStop enclosures or DraftStop cabinets. If the grille length limitations are adhered to and the DraftStop grille dampers are adjusted to achieve a uniform velocity in the 150 FPM to 500 FPM range, the system will be functional. Radiation elements can be installed behind storage cabinets or in separate wall hung enclosures. Finned Radiation System Finned radiation down-draft control is available for those who prefer it. Made of furniture-quality steel and designed to complement the unit ventilator styling, it is particularly appropriate for a building with very large expanses of window where the DraftStop system is not used, and for use in other parts of the building (Figure 21-1). Figure Typical Finned Radiation Enclosure (left) And Typical DraftStop Enclosure (right) There will be many periods during the heating season when window down-draft protection is required even though the unit ventilator is no longer adding heat to the space. In fact, the unit ventilator will most likely be attempting to cool the space with outside air due to the heating effect of the occupants, solar load and lights. This presents an obvious control dilemma when using radiation as window down-draft protection. Auxiliary radiation is normally controlled so that the radiation is turned off whenever the unit ventilator heating element is off (Figure 21-2). This control sequence is required to prevent the costly addition of heat that is not required by the space. It is used to prevent serious overheating problems that can occur if the radiation capacity exceeds the ventilation cooling capability of the unit. However, this is a compromise solution since cold window drafts can definitely exist even when no further heat is required in the room. In fact, a well-heated room can accentuate the draft problem due to the larger difference between room air and window draft temperatures. In order to conform to the above sequence, steam or hot-water radiation will require an additional field-installed control valve. (see MicroTech Controls page 26 for auxiliary heat control function and setup). A manually adjustable damper is located beneath each section of DraftStop grille. This damper is provided so that a uniform air velocity can be achieved throughout the entire length of the DraftStop grille. This simple adjustment is made once by the installer during the final stage of installation. Figure Typical Finned Radiation Piping AAF -HermanNelson Catalog UV-1-230E / Page 21 / (3/01)

22 Systems (Continued) Part Load Variable Air Control: Satisfies Requirements, Reduces Operating Costs bypass control, humidity in the space can be maintained in the 30% to 60% relative humidity comfort zone. The result is improved humidity control, a key concern in schools today. control systems are unable to do this consistently. lated movement/time the actuator is driven either open or closed. The wait is the amount of time the actuator holds its position. The system constantly samples to prevent overshooting for better comfort control. Satisfying School Requirements The AAF -HermanNelson Unit Ventilator offers a unique opportunity to combine the best features of a unit ventilator system for schools. Schools require: Easy to maintain systems Simple operation Even comfort Fresh outside air brought directly into the space for a good learning environment Low operating cost Low capital cost All these requirements are satisfied by AAF- HermanNelson 2-pipe Face and Bypass Unit Ventilators with part load variable air control. Using AAF-HermanNelson Unit Ventilators with a 2-pipe Face and Bypass System, central equipment can be sized smaller using building diversity. This results in a low capital-cost system. Further savings can be realized in renovations or new construction by piping. Piping installations use less space than duct systems. This is important in existing buildings and also in new construction when floor to floor heights can be reduced, saving on overall building costs. Better Learning Environment We invented unit ventilators in 1917 specifically to satisfy the school requirements for a durable unit that delivers fresh air right to the classroom. AAF-HermanNelson Unit Ventilators are located in each classroom so the outdoor air is drawn in through the building wall directly into the space, unlike central systems that deliver outdoor air indirectly. This promotes student attentiveness and a better learning environment. Humidity Control A draw-thru unit ventilator using face and bypass with a 2-pipe system provides superior humidity control and overall comfort. The coil is selected for cooling. With face and bypass, during mechanical cooling the coil is always dehumidifying due to water being pumped continuously to keep the coil surface below the dew point. With face and Economy In the 2-pipe system with the coil selected for cooling during the heating season extra coil heat transfer is available. Since the water is always being pumped with face and bypass, boiler water temperature can be modulated rather than fixed, reducing the hot water temperature to better match the heating load. This is an opportunity to reduce operating costs. By resetting the boiler hot water to 90 F and modulating upward to F for design conditions, boiler economy results in savings. Better room temperature control is available at low heating loads and the system can be quickly and easily changed over from heating to cooling or vice versa. Since conditions of full heating or full cooling are only achieved 1-2% of the time, savings are innumerable with today s fuzzy logic chillers that are air cooled, load rates at changeover of 100 F plus are limited and the chiller protected. And, McQuay chillers have this state-of-the-art system. Couple the cooling with today s high-efficiency condensing boilers (which can accept 45 F entering water without damage), the elimination of boiler circulating pumps, mixing valves and isolation valves considerable savings can be realized. Part Load Variable Air Control It all starts with the unique Part Load Variable Air Control system that is available on AAF- HermanNelson 2-pipe Face and Bypass Unit Ventilators with MicroTech DDC (4-pipe also available). The Part Load Variable Air feature uses PI loop algorithms to calculate room load, face and bypass control for dehumidification, and it automatically adjusts indoor fan speed based upon room load and the room temperature algorithm. By basing indoor fan speed upon room load, it provides higher latent cooling capabilities and quieter operation during non-peak load periods. The room temperature algorithm determines the speed of the fan. Fan speed varies according to the face damper position. The change algorithm changes the Direct Digital Control (DDC) damper actuator setpoint, responding to room load. The step & wait algorithm causes the actuator to open or close. The step is the calcu- With Part Load Variable Air, air delivery is based on the face damper position or the degree to which room load is being satisfied. When the face damper position is 0-15%, the unit ventilator runs on low speed. When the face damper is 15-30%, air is delivered at medium speed. For face damper positions greater than 30%, the fan runs on high speed to satisfy the room load. During the Part Load Variable Air operation, fresh air is maintained at the set minimum. The Part Load Variable Air control adjusts the outdoor air damper to bring in the same or a constant amount of fresh air to promote student comfort and attentiveness. Easy Maintenance The AAF-HermanNelson Part Load Variable Air Unit Ventilator 2-pipe face and bypass control heating/cooling system is easy to maintain. It has fewer moving parts: one pump, one motorized valve, two or three small modular condensing boilers, one or two air-cooled chillers, and, in each classroom, one outdoor air damper actuator, one face and bypass damper, and one fan. Simple periodic filter changing promotes filtered air in each classroom. The system can deliver the lowest utility cost and with AAF-HermanNelson Unit Ventilator s long, durable life, replacement/maintenance costs can be deferred. These low costs are desirable to taxpayers and school officials so limited resources can be used to support teaching. This unique Part Load Variable Air concept is the product and system schools need and expect for today s and future schools. It satisfies school requirements for a quality environment while addressing the need to contain costs. Demand-Controlled Ventilation (DCV) For Proper Air Control Using AAF-HermanNelson Unit Ventilators with built-in Demand Controlled Ventilation (DCV) enables the ventilation system in your classrooms provides the right amount of outdoor air. This saves money and energy by preventing costly over-ventilation. Catalog UV-1-230E / Page 22 / (3/01) AAF -HermanNelson

23 Systems (Continued) How It Works The AAF -HermanNelson Unit Ventilator uses input from a CO 2 controller to ventilate the space based on actual occupancy instead of a fixed design occupancy. The CO 2 Demand Controlled Ventilation system monitors the amount of CO 2 produced by students and teachers so enough fresh outdoor air is introduced to maintain good air quality. The system is designed to achieve that a target ventilation rate (e.g., 15 cfm/person) is maintained based on actual occupancy. By using DCV to monitor the actual occupancy pattern in a room, the system can allow code-specific levels of outdoor air are delivered when needed. Unnecessary over-ventilation is avoided during periods of low or intermittent occupancy. This saves money by minimizing the conditioning of outdoor air. Instead of providing a fixed ventilation rate based on an assumed occupancy, this system automatically delivers the proper amount of outdoor air at the proper time. This means that you can be confident that your school is meeting ventilation standards for Indoor Air Quality and that your students are receiving adequate air to be attentive to instruction. At the same time, you are saving money in early morning hours, in between classes, or after hours when classrooms are heated and cooled but not always fully occupied. As Simple as a Thermostat Demand Controlled Ventilation is easy to apply. Simply mount the DCV CO 2 sensor near the remote MicroTech room sensor or use the unitmounted DCV CO 2 sensor and unit-mounted room temperature sensor. The system does the rest. If desired, the ventilation control setpoint can be adjusted through the MicroTech Controller. Acceptance By Codes And Standards ASHRAE Standard Ventilation for Indoor Air Quality recognizes CO 2 based DCV as a means of controlling ventilation based on occupancy. The ASHRAE standard has been referenced or adopted by most regional and local building codes. This standard references ventilation on a per person basis. Using CO 2 control will sometimes lower the absolute amount of outside air delivered into a room but will maintain the per person rate. For example, if a classroom is designed for 30 students, the ventilation rate is 450 cfm (30 students X 15 cfm/student). However, when there are only ten students in the classroom, the CO 2 control will adjust ventilation to 150 cfm (10 students X 15 cfm/student). A minimum base CO 2 Concentrations [ppm] :00 AM 1:00 AM 2:00 AM 3:00 AM 4:00 AM Daily CO 2 and Occupancy Level with Demand Controlled Ventilation Teacher Prep 5:00 AM CO 2 Concentrations And Occupancy Using CO 2 Proportional Control Strategy = Classroom Density = 30 people/1000 sq.ft. Proportional Control 200 ppm > OA Outside Air Ventilation Rate = 15 cfm/person CO 2 Upper setpoint = 965 ppm Figure Daily CO 2 And Occupancy Level With DCV ventilation rate (typically 20% of design levels) is provided when in the occupied mode. This provides outdoor air to offset any interior source contamination while allowing for proper space pressurization. Active Dehumidification Units (Reheat) In high-humidity applications in which valve control reheat units are used, the Active Dehumidification Control (ADC) sequence should be considered. During excessive humidity conditions, the Humidity Sensor controls the unit to continue cooling. Wet heat or electric heat then reheats discharge air, removing excessive moisture. During acceptable room humidity levels, the unit reheat function is disabled. The humidity sensor is either wall mounted or remote wall mounted. Dehumidification unit ventilators with ADC utilize the proper control management of a cooling coil with a post-conditioning reheat coil coupled with a humidity sensor. PI loop algorithms are designed to govern both classroom temperature and relative humidity. MicroTech algorithms minimize the amount of reheat needed to maintain relative humidity below a preset limit. Reheat is used only when required and in the most energy-efficient manner for this system type. 6:00 AM 7:00 AM 8:00 AM 9:00 AM 10:00 AM 11:00 AM Lunch Break 12:00 1:00 PM PM Time 2:00 PM CO2 Concentrations 3:00 PM 4:00 PM Percent of Max. Occupancy 5:00 PM 6:00 PM After Hours Use 7:00 PM 8:00 PM The MicroTech ADC sequence uses a humidity sensor, unlike others which use a humidistat. A humidistat is an open-close signal based on the level of relative humidity detected, which indicates whether the humidity is above or below a certain level. The MicroTech ADC humidity sensor issues a signal proportional to the classroom s humidity level. This enables a control sequence that manages both the temperature and the relative humidity. When the relative humidity exceeds a preset value, the modulating chilled-water valve opens fully to dehumidify the mixture of outdoor and return air entering the cooling coil. The reheat modulating water valve then opens to reheat the air leaving the cooling coil, as required to maintain the classroom setpoint. Active dehumidification starts when the indoor relative humidity exceeds the preset relative humidity upper setpoint and continues until the room humidity falls 5% below the endpoint. During active dehumidification, the economizer operation is disabled (and the outdoor air damper reset to its minimum position) unless the outdoor air temperature is below 55 F and maintained until dehumidification is completed. When the indoor humidity level is satisfied, the MicroTech control reverts to its normal sequences to satisfy the classroom temperature setpoint. 9:00 PM 10:00 PM 11:00 PM 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 0% Percent Maximum Occupancy AAF -HermanNelson Catalog UV-1-230E / Page 23 / (3/01)

24 Temperature Controls AAF -HermanNelson UVs: Ideal For Today s Schools IAQ Defined The issue of indoor air quality (IAQ), which has caused great concern for the health hazards posed in the home and at work, is no less a threat to students and faculty. For the past several years, efforts to reduce energy costs in new school buildings have seen the use of tighter construction, sealed windows and heavier insulation. While these construction techniques have helped reduce energy costs, tightly sealed buildings, or envelopes, when combined with increased use of recirculated air, have led to a condition known as sick building syndrome. In a poorly ventilated school building, fumes and vapors from plastics and other synthetics are often not properly exhausted, while mold, fungus, and bacteria are able to flourish. These conditions can cause various ailments, including nausea, smarting eyes, and coughing, as well as increased student absenteeism and diminished productivity. In fact, the American Society of Heating, Refrigeration and Air Conditioning Engineers (ASHRAE) now recommends 15 cfm of outdoor air per pupil, and no longer endorses the practice of little or no usage of outdoor air. AAF-HermanNelson Unit Ventilators Solve The IAQ Problem AAF-HermanNelson unit ventilators have been found to do a more thorough job of maintaining a healthful and productive classroom environment than other systems through the introduction of plenty of filtered fresh air directly into the classroom. This unique feature, which has always been a significant factor in reducing energy costs, is now more important than ever in the promotion of a healthful environment for learning. It should be kept in mind that a properly designed exhaust system is essential for avoiding indoor air quality problems. Simply put, if room air is not being exhausted in a prescribed fashion, fresh outside air cannot be introduced into the room. Likewise, an excessive amount of outside air will be admitted, wasting energy. The AAF-HermanNelson Ventimatic TM shutter (see page 15), a gravity-actuated room exhaust vent, solves both these problems. The Ventimatic shutter allows that the correct amount of outdoor air is brought into the room while maintaining a slight positive pressure in the room. This slight positive pressure, maintained during normal operation, can also help prevent the infiltration of undesirable gases into the classroom. Temperature Control And ASHRAE Control Cycle Control Impact How well a unit ventilator performs its intended function is governed largely by the performance of the automatic temperature controls. In order to achieve optimum unit ventilator operation, it is imperative that temperature controls be properly applied, installed, calibrated and maintained. ASHRAE Control Cycles-Heating Unit ventilators are normally controlled according to ASHRAE Control Cycle II. ASHRAE control cycles apply only to heating, heating and ventilating and free cooling operation. Cooling control is discussed in later paragraphs. ASHRAE Cycle II During warm-up, the outdoor air damper is closed. As the room temperature approaches the thermostat setting, the outdoor air damper opens to a predetermined minimum percentage of outside air. The heating coil capacity controller then modulates to maintain the thermostat setting. If the room temperature rises above the thermostat setting, the heating coil is turned off and the outdoor air damper opens beyond the minimum position to maintain the thermostat setting. Open Outdoor Air Damper Min. Closed Full Heat Heating Coil No Heat Room -2 F Temp. -1 F Set Point + 1 F Figure ASHRAE Cycle II +2 F ASHRAE Cycle II is a very economical sequence of control, since only the minimum amount of outdoor air is heated and free outdoor air natural cooling is available to offset the large internal heat gain associated with the dense occupancy of classrooms. EXAMPLE: For a 60 F entering air mixture temperature and 70 F room temperature, with 30 F outdoor air temperature, 25% outdoor air will produce the 60 F mixture air temperature. When the outdoor air temperature drops to 10 F, 12.5% outdoor air will produce the 60 F mixture air temperature. Night Setback Substantial fuel savings can be realized by operating the unit ventilator system at a reduced room setting at night and during other unoccupied periods, such as weekends and holidays. Units with steam or hot-water coils will provide convective heat during the setback period. If the space temperature falls below the setting of the unoccupied thermostat, the unit fans will be brought on to provide additional heat. Units with electric heat coils do not provide convective heat. The electric coil and the unit fans will be brought on to maintain the thermostat setting. Typical Temperature Control Components In general, unit ventilators require the following basic DDC electrical components in order to operate on any of the standard unit ventilator ASHRAE cycles of control. The control components listed in this section are for familiarization purposes only and should not be construed as a bill of material. Outdoor Air Damper Actuator This is a modulating device, under the control of the room and discharge sensors, which positions the outdoor air damper to admit the amount of outdoor air required at any given point in the control cycle. The room air damper is mechanically linked to the outdoor air damper, which permits the use of a single actuator. Electric actuators should be of the spring-return type so the outdoor air damper closes whenever the electric power supply to the unit is interrupted. Discharge Airstream Sensor This device overrides the room sensor and modulates the outdoor air damper toward the closed position when the unit discharge air falls to a potentially uncomfortable temperature. Catalog UV-1-230E / Page 24 / (3/01) AAF -HermanNelson

25 Temperature Controls (Continued) Capacity Controller For Heating Or Cooling Coils: a. Face and Bypass Damper Control This modulating damper actuator, under control of the room sensor, positions a face and bypass damper to control the amount of air that passes through or around the unit coil. b. Control This modulating valve, under control of the room sensor, regulates the flow of steam, hot water or chilled water through the unit coil. c. Electric Heat Step Controller This modulating step controller, under control of the room sensor, steps individual electric heating elements on and off as required. Staging relays are sometimes used in lieu of step controller. Contactors/Relays When unit ventilators containing electric heat are ordered without controls (controls by others) the contactors and relays used for staging the electric heat are not provided. This is because the number of stages varies based on the type and manufacturer of the control devices. It is not possible to pre-engineer contactors and relays for all these variables. The control contactor is responsible for making certain that the controls correctly control the unit s functions. Room Sensor A temperature-sensing device that modulates the intensity of a pneumatic or electric signal to the controlled components within the unit in order to maintain the comfort setting of the room sensor. Room sensors can be mounted on the wall or within the unit in a sampling chamber. Additional components may be required depending on the specific application. They include: Sampling Chamber This device is required whenever the room sensor is to be mounted within the unit ventilator rather than on the wall. The sampling chamber is located behind a series of holes in the unit front panel. The sensing element of the room sensor is positioned within the sampling chamber. The unit fans draw a representative sample of room air over the sensing element at a relatively high velocity, which is necessary for rapid control response. Sampling chambers are furnished with MicroTech controls. Low Temperature Protection A low temperature limit or freezestat senses the discharge air temperature off the hydronic coil. If the temperature drops below 38 F, the unit ventilator will shut down, closing the outdoor air damper and opening the heating valve. DX Cooling Control This sequence switch in the cooling control circuit energizes the condensing unit contactor on a call for mechanical cooling. DX Cooling Low Ambient Lockout Must be used on DX split systems to lockout the condensing unit when the outdoor air temperature is below 55. This device must be integrated into the control system so that the unit has full ventilation cooling capability during the lockout period. DX Low Temperature Limit Must be used on DX split system cooling units to de-energize the condensing unit (compressor) when the refrigerant falls below freezing. Direct Digital Control (DDC) Background Microprocessor-based Direct Digital Controls (DDC) are microprocessor-based devices that measure variables (inputs), process those variables with application programs and produce actions (outputs). They can be thought of as instruments that measure a controlled variable and respond by producing an output signal which is proportional to the difference between the set point and the control point. Inputs and Outputs (I/O) There are two types of Inputs and Outputs (I/O) Direct Digital Control (DDC) uses; binary or digital, and analog. Digital describes a signal with only two states (e.g., on and off ) or a device such as a compressor or a fan which is either on or off. Each state is constant over time. Analog describes a signal that has many values (e.g., 60, 61, 62, etc.) or a device such as a temperature sensor or a humidity sensor that reports many values. The values generally change over time. Floating point devices are digital devices that simulate analog devices by using positions that float based upon two digital signals. One signal is used to push the device open and the other to push the device closed. When both signals are off, the device remains in its last position. Some floating point devices, such as damper actuators or valve actuators that use two digital signals, are provided with springs that force them to a home position when power is lost, e.g., when an outdoor air damper is closed or a hot-water valve opened during loss of power. Protocols Similar to languages such as English or French that people use to communicate information, protocols are languages controllers use to communicate information. They are defined by a set of rules that govern data exchange between microprocessors and facilitate communications between controllers using the same protocol. Proprietary protocols are unique typically not shared, not exposed, not published and usually unable to be utilized by different Building Automation Systems (BAS) without specific information from the original manufacturer. Communications between different proprietary BAS is usually not possible without cooperative efforts toward translation. Open, proprietary protocols, such as the MicroTech protocol, have proprietary information published, usually under a license agreement, for others to use. Once the protocol is translated, certain types of information, such as monitoring and control points, are made available for use by participating third-party BAS. Other types of information, such as specific sequences of operation to protect equipment, remain inaccessible. Because they can create interfaces that use the proprietary protocol, participating BAS providers establish direct communications with controllers provided by the original manufacturer, which can be a cost effective means of exchanging information. Open, standard protocols have information published, usually without license, for others to use. Because this information is shared openly, anyone can use it to create native devices or to translate between it and proprietary devices in a system. Open, standard protocols are usually developed by committee or by independent companies, and are becoming widely used. They are evolving within the HVAC industry to facilitate interoperability between devices provided by different BAS manufacturers. In the same way a person speaking English to a person speaking French will require a language translator, mixing protocols, regardless of whether they are proprietary, open proprietary or open standard protocols, will require the use of a communications translator, or gateway. Electrical Communication Standards Many Direct Digital Control (DDC) devices communicate using standards from the Electronic Industries Association for serial communications such as EIA-485 (RS-485). ly, this provides communications networks with foot limitations. AAF -HermanNelson Catalog UV-1-230E / Page 25 / (3/01)

26 Temperature Controls (Continued) MicroTech Direct Digital Controls (DDC) Direct Digital Control (DDC) System The MicroTech unit ventilator control on AAF - HermanNelson units is a complete Direct Digital Control (DDC) system. It provides comfortable classroom environments through configuration flexibility that allows the unit ventilator to be set up in any of several operating modes. Modes Of Operation Stand-Alone Operation When operating in stand-alone mode, the MicroTech unit ventilator controller performs complete room temperature and ventilation control. Occupied/Unoccupied Changeover Occupied/unoccupied changeover on stand-alone units can be accomplished manually by a unitmounted day/night switch, automatically by a unit-mounted day/night time clock or automatically by a remote-mounted time clock operating unitmounted day/night relays. If a school has more than one zone, a separate remote time clock regulates each zone. In this case, the remote-mounted time clock energizes or de-energizes an external (24- volt or 120-volt) control circuit which operates the unit-mounted day/night relays in that zone. The control circuit is de-energized during occupied cycles and energized during unoccupied cycles. Master/Slave Operation When operating in master/slave mode, the MicroTech unit ventilator control provides coordinated operation for up to 6 stand-alone units. Master/slave control is used in large spaces, such as school libraries, or where multiple in-room unit ventilators are operating together. The objective of master/slave control is to maintain a uniform temperature throughout the space. In master/slave mode, each slave unit ventilator has its own room air temperature sensor enabling it to maintain a common room heating or cooling setpoint dictated by the master unit ventilator. Communications between the master and its slaves is accomplished with RS-485, twisted-pair wiring. Master/slave operation is not intended to be used in place of network operation. Master Unit The master unit initiates communications and provides control inputs to the slaves that designate common room heating and cooling setpoints (occupied and unoccupied), minimum outdoor air damper position setpoint and operating mode (occupied, unoccupied, or tenant override). Slave Units Slave units do not initiate communications, but rather respond by acknowledging they have received control inputs from the master unit. Slaves operate independently as if in stand-alone mode, however, they ignore their own three on-board setpoint potentiometers. In the event communications between the master and a slave fail, the slave unit triggers an alarm, reverts to using its local potentiometers for setpoints and remains in its current operating mode until communications are restored. Occupied/Unoccupied Changeover A master/slave configuration requires only one day/night changeover device, as described previously under stand-alone operation, for the master unit only. Network Operation When operating in network mode, the MicroTech unit ventilator controller provides building operators the capability to perform advanced equipment monitoring and control from a central or remote location. Network mode provides capabilities such as heating and cooling setpoint adjustment, minimum outdoor air damper position, setpoint adjustment, ventilation lockout, a network changefilter indication for preventative maintenance, demand limiting, scheduling and occupied/unoccupied changeover through communications. In the event network communications fail, the unit ventilator remains operational using the last operating mode and setpoint information received over the network. Communications between the unit ventilators and other MicroTech system controllers is accomplished with RS-485 twisted-pair wiring. Communications between the MicroTech controllers and a MicroTech or other Building Automation System (BAS) is accomplished with RS-232 or RS-485 wiring. Operating Functions Regardless of the mode of operation selected (stand-alone, master/slave or network); the MicroTech unit ventilator control offers many advanced operational functions. Economizer Operation Economizer operation is facilitated by the outdoor air damper, which automatically adjusts above minimum outside air position to provide free cooling when the outdoor air temperature is appropriate. Exhaust Fan Operation An output signal, Exhaust Fan Control, can be used to operate a remote exhaust fan when the outdoor air damper opens. It provides a triac signal for use with a field-provided, pilot duty, 24- VAC relay and associated diode. The Exhaust Fan Control output signal defaults to an energized relay coil, which equals the exhaust fan being on. Exhaust Fan Interlock The Exhaust Fan Interlock (reset condition Outside Air Ventilation Lockout Control) provides external capability to fully open the outdoor air damper. A personal computer (PC) loaded with MicroTech Monitor for Windows software can be used to reconfigure the Ventilation Lockout input signal using a field-provided, pilot duty 24-VAC relay. When the input is energized the outdoor air damper will be fully opened. All safeties remain in effect to override this function for equipment protection. Auxiliary Heat Operation A triac output signal, Auxiliary Heat Control (reset condition Exhaust Fan Control), can be used to operate a normally open hot-water valve. A PC loaded with MicroTech Monitor for Windows software can be used to reconfigure the Exhaust Fan Output signal. The output signal is activated when the room temperature is less than the heating setpoint minus the auxiliary heat differential setpoint (default=2 F). This condition de-energizes a field-provided, pilot duty 24-VAC relay and the hot water valve is opened. A room temperature 1 F above the heating setpoint energizes the relay and the hot-water valve is closed. The auxiliary heat differential setpoint is adjustable. Ventilation Lockout An input signal, Outside Air Ventilation Lockout (default), provides external capability to fully close the outdoor air damper. A field-provided, pilot duty 24- VAC relay with normally open contacts is factory wired to the DI-1 input on the unit controller. The relay is field wired to a signal device capable of controlling a 24- VAC relay (115-VAC accessory relay coil available). When the relay is energized, the outdoor air damper is closed. Alternatively, in the network mode of operation, the Network Ventilation Lockout variable is used. Catalog UV-1-230E / Page 26 / (3/01) AAF -HermanNelson

27 J1 J2 J3 J R G S G S G S G S G S G S G S G S G S1 S0 COMMB COMM A DIGITAL INPUT IN 13 IN 12 IN 7 IN 6 IN 5 IN 4 IN 3 IN 2 IN 1. 0 J1 J2 J3 J4 J COOLING SETPOINT IS FACTORY SET 6 F ABOVE HEATING SETPOINT NETWORK ADDRESS % F F MINIMUM OA UNOCCUPIED HEATING SETPOINT POSITION OFFSET This devise complies with Part 15 of the FCC rules. Operation is subject to the following 2 conditions: (1) This device may not cause harmful interference. (2) This device must accept any interference received, including interference that may cause undesired operation. J6 J7 J8 J9 LED RELAY OUT AUX OUT STATUS POWER PWR G 0 H V 9 10 G 24V J6 J7 J8 STATUS POWER J C J5 Temperature Controls (Continued) Night Setback Control The MicroTech unit ventilator control offers night setback options to match the operation of the AAF - HermanNelson unit ventilator to building requirements. Occupied (day) is the normal, or default, mode of operation. During unoccupied mode the outdoor air damper is closed, night setback and setup room setpoints are maintained and the fan is engaged when either heating or cooling is required. The unit controller uses a single room air temperature sensor for both occupied (day) and unoccupied (night) control, which eliminates the requirement for a separate night-setback thermostat. Steam and hot-water unit ventilators provide convective heat during unoccupied operation but remain under the control of the room air temperature sensor to help prevent convective overheating. When convective heat is insufficient to maintain the unoccupied heating setpoint, the fan is engaged until the room air temperature exceeds the unoccupied heating setpoint. The outdoor air damper remains closed during unoccupied operation. Stand-Alone and Master/Slave Operation Units operating in stand-alone mode, and the master in master/slave applications, establish and maintain unoccupied (night) operation by closing the contacts of the DI-2 input on the unit controller. Alternatives for closing the contacts include fieldprovided, pilot duty 24-VAC relays (115-VAC relay accessory is available), manual day-night switches, time clocks and holiday switches, and pneumatic-electric (PE) switches or relays. Network Operation Units operating in network mode establish and maintain occupied (day) and unoccupied (night) operation according to a time schedule established for each unit. A PC loaded with MicroTech Monitor for Windows software or signals from third-party building automation systems (BAS) can be used to configure the time schedules. Control System Components Unit Ventilator Controller (UVC) The brain of the MicroTech DDC system in AAF- HermanNelson Classroom unit ventilators is the microprocessor-based model 325 unit ventilator controller (UVC). It is located in the left end compartment of the unit ventilator. The UVC (Figure 27-1) utilizes digital control algorithms to maintain adjustable heating, cooling and ventilation setpoints. It is factory-mounted, capable of standalone, master/slave or network operation, can interface with a personal computer (PC) running MicroTech 325 Controller File E Model 325 Part No Figure The MicroTech Unit Ventilator Controller (UVC) Model 325 MicroTech Monitor 2.0 for Windows software, or in network mode, with either Monitor or third-party front-end software. The UVC is pre-programmed with application software that provides heating and cooling control of the unit ventilator by sending outputs to actuators and auxiliary equipment in response to various inputs such as that from a unit or wall mounted room temperature sensor. The UVC supports 20 inputs (14 analog, 6 digital) and 10 outputs (8 binary electromechanical relays, 2 analog solid-state relays). Input and output connections are of the Insulated Displacement Connector (IDC) type. Heating and cooling setpoints, offset and the minimum outdoor air setpoint are adjustable by means of on-board potentiometers except in the network mode of operation where these potentiometers are disregarded. The UVC provides a visual means of fault detection through the use of on-board status LEDs and has self-diagnostic capability to provide reliability. Heating and Cooling Setpoints The UVC utilizes separate heating and cooling setpoints. This energy-saving feature permits onetime setting of the desired heating and cooling temperatures and eliminates the need to make seasonal thermostat adjustments. The room heating setpoint adjusts unoccupied heating setpoint. The unoccupied offset is the delta temperature between occupied (heating minus occupied setpoint). On units operating in stand-alone or master/slave (master unit) mode, the heating setpoint is determined by the room temperature adjustment potentiometer. On units operating in network mode, setpoints are adjusted using PC-based software and the temperature adjustment potentiometer is disregarded. The cooling setpoint is determined by adding a dead band to the heating setpoint, and is typically offset 6 F (default). Typical setpoint values for a heating/ cooling unit would be 70 F heating and, consequently, 76 F cooling. Thus, a room temperature below 70 F will cause heating to be initiated while ABCDEF HI ABCDEF LO a room temperature above 76 F will initiate mechanical cooling. When the room temperature is between 70 F and 76 F, the dead band, heating or mechanical cooling will not be permitted. Other than for the fan, no energy is expended during this mode. The room temperature can be held between 70 F and 76 F during a substantial portion of the school year by simply admitting more or less outdoor air to offset the high internal heat gains associated with school classrooms. Minimum Outdoor Air Setpoint On units operating in stand-alone or master/slave (master unit) mode, the minimum outdoor air potentiometer located on the UVC allows for the adjustment of the minimum outdoor air setpoint from 0-100%. On units operating in network mode, the factory setting is 20% (default), setpoints are adjusted using PC-based software and the minimum outdoor air potentiometer is disregarded. Actuators Actuators used on AAF-HermanNelson Classroom unit ventilators utilize floating-point control with position feedback for damper and valve modulation. The actuators are controlled using Change and Step-and-Wait control algorithms running in the UVC. The outdoor air damper is normally closed and the face-and-bypass damper is normally opento-face. Heating valves are normally open (includes 2-Pipe). Cooling valves are normally closed. Self-Calibration When power is restored or applied, damper and valve actuators calibrate full-open to full-close. The status (amber) LED blinks 3 seconds on, 3 seconds off, until calibration is complete. Figure Damper Actuator Damper Actuators Damper actuators are of the compact electric/hydraulic type (Figure 27-2) and are factory mounted, wired and adjusted. They implement floating-point control with position feedback. A digital output signal from the UVC controller moves the actuator in one direction, another digital output signal moves the actuator in the opposite direction. When both outputs are de-energized, the damper actuator holds AAF -HermanNelson Catalog UV-1-230E / Page 27 / (3/01)

28 Temperature Controls (Continued) its position. Damper actuators position the outdoor and room air dampers, and face and by-pass dampers (when furnished). On shutdown, the outdoor air damper will close and the face and bypass damper (when used) will return to the full-face position, allowing air through the coil. During loss of power, the outdoor air damper will spring-return to closed position and the face and bypass damper actuator will springreturn to full-face position. This combination protects the unit and prevents outdoor air from infiltrating the space when the unit ventilator is not in use. s actuators use floating point control with position feedback. A digital output signal from the UVC controller moves the actuator in one direction, another digital output signal moves the actuator in the opposite direction. When both outputs are de-energized, the valve actuator holds its position. actuators are shipped individually boxed. End-Of-Cycle s (Face And Bypass Control) For face and bypass damper control, the MicroTech DDC system requires an End-Of-Cycle (EOC) valve (Figure 28-1) for each hydronic coil. The EOC valve prevents simultaneous heating and cooling operation. It uses floating point control with position feedback. A digital output signal from the UVC controller moves the EOC valve in one direction, another digital output signal moves the EOC valve in the opposite direction. When both outputs are de-energized, the EOC valve holds its position. During loss of power, heating EOC valves springreturn to the open position and cooling EOC valves spring-return to the closed position. EOC valves ship individually boxed. Figure End-Of-Cycle Units with a face and bypass controlled steam coil require a 2-position, 2-way, EOC valve to shut off steam flow at the end of the heating cycle. Units with a face and bypass controlled hot-water coil that also have a separate cooling coil require a 2-position, 3-way, EOC valve to shut off the hot water flow at the end of the heating cycle. Hot-water-heat- ing-only and chilled/hot water (2-pipe) units that are face and bypass controlled can optionally have a 2-position, 3-way, EOC valve to shut off the hot water flow at the end of the heating cycle. When a hot water reset schedule is used, the EOC valve is not required. Any two-coil unit with a chilled water coil that is face and bypass controlled requires a 2- position, 3-way, EOC valve to shut off the chilledwater flow at the end of the cooling cycle. Figure Modulating Modulating s (Figure 28-2) Steam valves are 2-way, normally open, angle pattern that spring return to the open position during loss of power. Hot-water and chilled/ hot water (2-pipe) valves can be either 2-way or 3- way and are normally open to the coil. They spring return to the open position during loss of power. Chilled-water valves can be either 2-way or 3-way and are normally closed to the coil. They spring return to the closed position during loss of power. Care must be taken with modulating valves to ensure proper water flow. In freezing conditions, water flow must be maintained through the heating coil or a suitable freeze-prevention solution employed to prevent freeze-up. Similarly, the cooling coil should be drained or a suitable freeze-prevention solution employed. Room Air Temperature Sensors (Tenant Override) The MicroTech unit ventilator control system utilizes Negative Temperature Coefficient (NTC) thermistors for temperature sensing. Only one room air temperature sensor is required for both occupied and unoccupied control. A tenant override function allows the user to manually override unoccupied control for up to two hours. Tenant override, when initiated, operates in accordance with occupied control. Contact closure initiates unit ventilator operation for 120 minutes (default), however, the tenant override value can be adjusted with a personal computer (PC) running MicroTech Monitor 2.0 for Windows software, or in network mode, with either Monitor or third-party front-end software. Room air temperature sensors are available in either unit or wall mount configurations. LED Mode Indicator Tenant Override Switch Setpoint Adjustment Figure Wall Mounted Room Sensor Wall-Mounted Temperature Sensors Wall-mounted temperature sensors (Figure 28-3) provide electronic (thermistor) sensing of temperature at wall locations and include an LED (green) mode indicator. Options include a tenant override switch, a setpoint adjustment potentiometer (to offset the current control setpoint by ± 3 F), a communications port and a bi-metal thermometer. Wall-Mounted Sensor Location Locate the wall mounted sensor in the classroom but not in direct sunlight or directly in the unit ventilator air stream. Avoid mounting the sensor near drafts or dead spots behind doors or in corners, near concealed pipes or chimneys, or on outside walls (Figure 28-4). Exterior Wall Exterior Wall Exterior Wall Interior Wall Interior Wall Interior Wall Interior Wall Interior Wall Window Unit Ventilator Suggested Sensor Location (about 5 feet from floor) Figure Sensor Locations Unit-Mounted Temperature Sensors Unit-mounted room air temperature sensors (Figure 28-5) provide electronic (thermistor) sensing of temperature and are positioned in a sampling chamber located behind a grouped series of holes in the front panel of the unit ventilator. A unit-mounted tenant override switch is available. Unit Left End Compartment Room Air Temperature Sensor Figure Unit Mounted Temperature Sensor Catalog UV-1-230E / Page 28 / (3/01) AAF -HermanNelson

29 Temperature Controls (Continued) A representative sample of room air is continuously drawn across the unit-mounted room air temperature sensor in the sampling chamber by the unit ventilator fans during occupied operation. This provides excellent room air temperature sensing. Using a unit-mounted room air temperature sensor configuration can also eliminate the problem of determining an optimum location for a wall-mounted room air temperature sensor. System Products A MicroTech or third-party control system can be implemented to provide network support for AAF - HermanNelson classroom unit ventilators. MicroTech system controllers are used to construct a control network that ties the MicroTech unit ventilator controllers together and to provide a level of supervisory control constituting a unit ventilator system. Interaction with the unit ventilator controllers, or with the unit ventilator system, is provided by means of PC-based software, MicroTech Monitor 2.0 for Windows, or by a third-party Building Automation System (BAS) through Open Protocol. MicroTech System Controllers MicroTech system controllers are used to coordinate communications in a MicroTech network of unit ventilator controllers (i.e., a MicroTech unit ventilator system). These products are seldom used in an open system application because the thirdparty BAS would provide their functions. MicroTech Monitor 2.0 for Windows MicroTech Monitor 2.0 for Windows (Figure 29-1) is a PC-based software package that provides a high-level graphical user interface (GUI) to MicroTech unit controllers and system products. Monitor software can be used to commission, troubleshoot, monitor or control stand-alone or master/slave configured MicroTech unit ventilator controllers, or systems consisting of network configured MicroTech unit ventilators and MicroTech system controllers. and control, time scheduling and facsimile capability. A PC communications cable kit, including adapters for AMP, IDC, and Phoenix type connectors is required to connect the serial port (DB-9 or DB-25) of a personal computer to any MicroTech controller. MicroTech Open Protocol MicroTech Open Protocol allows third-party building automation system (BAS) companies to create an interface to MicroTech unit and system controllers. Every MicroTech unit and system controller contains a comprehensive set of monitor and control points that are available for system designers to use in meeting the requirements of specific applications. When an existing or specified BAS company is involved, an Open Protocol Site License allows the BAS company to use these monitor and control points in their system. Each BAS company determines the extent to which their interface takes advantage of the monitor and control points available in the MicroTech controllers. BAS companies who are Open Protocol partners with McQuay International can direct connect to any single AAF-HermanNelson classroom unit ventilator with a factory installed MicroTech unit ventilator controller. Multiple unit ventilators with factory installed MicroTech unit ventilator controllers can be connected as level-2 controllers directly to a MicroTech Open Protocol Master (OPM) panel. The OPM panel provides single point access to the unit ventilator system for the BAS. An Open Protocol Site License is required when access is provided to any MicroTech unit ventilator controller or series of unit ventilator and system controllers,. The license serves two purposes; (1) it grants permission to establish communications between the MicroTech controls and another BAS and (2) it is provided with MicroTech Monitor software that is used in the commissioning process to establish and verify communications between the MicroTech controllers and the BAS. Basic Unit Components High-Medium-Low-Off Motor Speed Switch This switch allows the user to select the fan speed. The off position de-energizes power to the fan motor and UVC. Electric Connection Box The electric connection box contains the motor speed switch, motor speed transformer and fusetron(s), when furnished. Wiring connections to the day/night relay and vent relay are made in this box. Refer to the unit wiring diagram for specifics. Right End Compartment Class 1 wiring required. Left End Compartment Class 2 wiring permitted. Unit Terminal Strips (Left End Compartment) Provides convenient connection points for the following: a. End of Cycle (factory required) b. Modulating steam or water control valve (factory required); c. Wall-mounted room sensor; d. Condensing unit control circuit (field wired by others). 5 Motor Figure MicroTech Monitor 2.0 Software for Windows Monitor runs on Windows 3.x or Windows 95/98 and utilizes the full set of Windows capabilities. include password protection, network diagnostics, trend and alarm logs, group monitoring 1 13 MicroTech UVC Room Temperature Adjust Terminal Strips Damper Actuators Sampling Chamber Time Clock Electrical Box Tenant Override Switch Motor Speed Switch Holiday Switch Figure Front View, Floor Model AV With Front Access Panels Removed (AH Ceiling Models Similar) 12 Right End Compartment Class 1 wiring required. Electric Heat Disconnect Switch Left End Compartment Class 2 wiring permitted. AAF -HermanNelson Catalog UV-1-230E / Page 29 / (3/01)

30 Temperature Controls (Continued) Accessories Daily and Holiday Operation Used with Stand-Alone or Master/Slave, the unitmounted time clock has a 24-hour dial with skip-aday feature and battery backup. The time clock utilizes the unit line voltage power supply. The remote mounted time clock can be furnished by others or by AAF -HermanNelson. The AAF-HermanNelson time clock is 120 volt, 24 hour with skip-a-day or 7-day and with or without reserve power. It can set daily start/stop times. Voltages available are 115v, 460v and 208/230v. The holiday switch places the unit into night setback operating mode. Figure Time Clock Time Clock This accessory device, field installed behind the right front access panel, automatically cycles the unit through occupied and unoccupied modes in accordance with a user-programmed time schedule. Programming instructions are included. Time clocks have battery backup, so they will not require resetting if electric power is interrupted. A time clock is not required with network units as this function is handled through the communications network. Holiday Switch This device is furnished with the time clock as an accessory. It permits manual changeover to unoccupied (night) control for extended or otherwise unscheduled periods. The switch must be manually returned to the normal (automatic control) position at the end of the holiday period for the unit to operate on the automatic temperature control sequence. This is not required with Network units as this function is handled through the communications network. Status/Diagnostic Capability AAF-HermanNelson MicroTech Control provides additional benefits of status and diagnostic capabilities for ease of service, if needed. Status Information Power LED The green power LED indicates the UVC has power. Status and Alarm Indication The yellow UVC status LED and Wall Mounted sensor green LED indicate whether the unit status is occupied, unoccupied or in tenant override, and any fault codes. LED Mode and Fault Indicator A yellow LED is on the UVC board and a green LED on the Wall Mounted room air temperature sensor. Both LEDs indicate the UVC status by flashing at predetermined intervals to indicate: occupied mode, unoccupied mode, tenant override mode and fault conditions. Steady lighted LED equals occupied mode. A flashing LED, on 1 2 second, off seconds equals unoccupied mode. Flashing on seconds, off 1 2 second indicates tenant override mode. The status LED indicates alarm mode conditions by flashing and blinking for: room temperature sensor, outdoor air damper position, discharge air temperature sensor, outdoor air temperature sensor, low leaving air temperature, heat valve position feedback, valve or face and bypass damper position feedback, high refrigerant pressure, low DX coil temperature, brownout, water-in temperature sensor and communication failure (Master/Slave only). Sensor Diagnostics The UVC monitors for sensor faults due to failed sensors and/or broken connections. Each sensor fault has a specific priority, alarm indication and a set of response actions. Hex Switches These switches determine the address of the unit. For Stand-Alone units, leave AV/AH at 01. For Stand-Alone split system DX units, the hex switches define the random start delay period (up to 63 seconds in one second intervals) so multiple units do not start at the same time. On Master/Slave and Network units the hex switches determine the controller s address as well as compressor delay. Split System DX Operation Remote Compressor Operation The UVC energizes a 24-volt control circuit to the remote condensing unit on a call for DX cooling. An outdoor air sensor provides input to the UVC to prevent condensing unit operation in cooling when the outdoor temperature is below 60 F. Brownout protection and short cycle protection is included in the software program. If the outdoor air temperature is below 64 F, the outdoor air damper will modulate for economizer cooling. When the outdoor air temperature is above 64 F, the outdoor air damper will be at the minimum setting. Indoor Low Leaving Compressor Temperature Protection With Split Systems (AV/AH with DX Coils) The DX coil low leaving temperature thermostat detects an indoor coil low leaving air temperature condition and an alarm is indicated and appropriate action occurs. Brownout Protection Split System For DX Units The UVC senses the line voltage of the phase used to power the 24-vac supply. If brownout failure occurs and/or line voltage drops by approximately 20% below unit s nameplate value, compressor operation stops and electric heat operation is stopped. Normal operation resumes when line voltage returns to approximately 90% or more of the unit s nameplate value. Adjustable Power-Up Delay or Random Start This prevents simultaneous compressor start-up at unit power up during unoccupied to occupied changeover, and brownout condition. The UVC hex switch setting determines the 1 to 63 second delay. Compressor Short Cycle Protection Short cycle protection prolongs compressor life. When the compressor is energized, it runs for at least 8 minutes before the temperature sequence can de-energize it. An alarm condition can override this. When the compressor is de-energized, it remains off for at least 3 minutes before the temperature sequence can energize. High Refrigerant Protection This protects the unit from destruction (required agency protection). If excessive refrigerant pressure is detected by the external pressure switch (provided by others on remote condensing unit), the compressor is de-energized immediately and an alarm is indicated. Low Ambient Lockout This prevents damaging unit due to freeze-up and prevents compressor operation in cooling when the outdoor air temperature is below 60 F. Catalog UV-1-230E / Page 30 / (3/01) AAF -HermanNelson