Cleveland Clinic Design Standards MECHANICAL SYSTEMS DESIGN GUIDELINES HVAC AIR DISTRIBUTION PART I - GENERAL 1.1 SUMMARY

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1 PART I - GENERAL 1.1 SUMMARY A. This section addresses the general requirements for air handling distribution systems, including air handlers, ductwork, ductwork accessories, terminal units, air devices, and stairwell pressurization systems (if applicable to the project). B. Related Sections Metal Ducts Air Duct Accessories Axial HVAC Fans Centrifugal HVAC Fans HVAC Power Ventilators Air Curtains HVAC Gravity Ventilators Particulate Air Filtration High-Efficiency Particulate Filtration Breechings, Chimneys, and Stacks Modular Indoor Central-Station Air-Handling Units Packaged, Outdoor, Central-Station Air-Handling Units Computer-Room Air-Conditioners 1.2 REQUIREMENTS A. Air handling unit selection and performance shall comply with the latest ANSI/ASHRAE/IESNA B. The quality and quantity of outside air must meet the latest ASHRAE Standard 62.1, the latest Guidelines For Design and Construction of Hospitals and Outpatient Facilitates (FGI) which includes ANSI/ASHRAE/ASHE Standard 170 requirements and must also maintain the building pressurization reasonable positive (such as 5 to 15 percent net positive pressurization (outside air - exhaust air)/total supply air]) depending on the building envelope design/construction. Tighter buildings are eligible for less net pressurization, Architect and Engineer to work together to determine the correct pressurization for the building. Please note that if a building is connected to an adjacent building via skyway or tunnel the pressure relationship between the two buildings should be reviewed and discussed. C. Air change rates, temperature and humidity shall comply at a minimum with the latest Guidelines For Design and Construction of Hospitals and Outpatient Facilitates (FGI) which includes ANSI/ASHRAE/ASHE Standard 170. Use local mechanical code for all areas not defined in FGI. For energy conservation, spaces allowed to have unoccupied setpoints shall have the sequence of operations written for automated setback, owner adjustable. D. Mechanical rooms must be large enough to allow for air handling unit coil pull space and full space service clearance around the unit for filter replacement to accommodate both major and Page 1

2 minor repairs. A minimum clearance of 4 feet must be planned around the unit. The sides of the units shall be provided with enough space for coil pull along the entire length of the unit. Indicate the designated coil pull and maintenance clearance space on the Drawings. E. Each air handling unit fan shall be provided with a variable frequency drive (VFD). VFD s shall include either a by-pass switch or be configured in a manner that failure of one VFD does not disable the entire air handling unit. Fan motor shall be high efficiency. Control shall be by the duct static design pressure setpoint. F. Air handling unit fans shall have an efficiency rating where the ratio of the fan system power to the supply fan airflow rate (main fan) of each HVAC system at design conditions shall not exceed the allowable fan system power indicated in the latest ASHRAE Standard Fans shall be selected so that they are capable of meeting the design CFM at a max 60 Hz at normal operation. Normal operation shall be no greater than 80% of the max wheel RPM. G. Fan arrays are preferred to use on air handling units and energy recovery units (ERU s). H. Access doors (or panels) on the air handling unit sections shall always open against the positive side of the door and shall not be blocked by internal filter casings or internal equipment components. Micro switches or safety switch interlocks need to be provided at access doors or panels on UV sections to protect maintenance personnel from possible injuries. Windows shall be located 5 above finished floor. I. Coordinate location of wall-mounted room temperature sensors with furniture and equipment, so that sensor locations do not conflict with tall items of furniture/equipment. J. Each cooling coil shall not exceed 8 rows and 10 fins per inch. K. Design two (2) coils in a series arrangement if the cooling coil capacity requirement exceeds the capability of an 8-row, 10 FPI coil. Chilled water shall be piped in series through both coils and a 42 access section shall be provided between the two equally sized coils. Chilled water velocity through the coil tubes should be 8 fps maximum. (The minimum ARI Standard 410 rating condition for water velocity through a coil is 1.0 fps). L. Maximum cooling coil discharge face velocity shall not exceed 400 fpm. Heating coil discharge face velocity shall not exceed 800 fpm. Coils shall be selected to allow for an additional margin of 20 percent cooling capacity for future renovations. M. Coil connections 2½ and larger must include bolted flange spools and be arranged to allow the coils to be pulled and installed without having to remove the control valves. 2 and smaller connections may be union connections. Provide strainers on inlet of the coils. Provide a pressure and temperature gauge downstream of the cooling coil control valve. Control valve to be on discharge side of coil. N. Electronic filters are not acceptable. O. The maximum shaft speed on any fan or pump shall be 2000 rpm. P. Self tension adjusters are not acceptable. Page 2

3 Q. All lab exhaust fans shall be provided with protective corrosion resistant coating. R. Variable-pitch and variable-inlet fans are not acceptable. S. VAV boxes shall be located outside of patient occupied spaces for ease for ease of maintenance. T. Stairwell Pressurization Fans: 1. The IBC lists physical building height criteria, for determining when stairwell pressurization fan system is required. 2. The stairwell pressurization system shall meet or exceed latest edition of NFPA requirements. 3. On buildings over 7 stories should be evaluated for two fans for pressurization of each building exit stairwell. One fan shall be located at the top of the stairwell and the other fan shall be located near the bottom of stairwell. 4. The fan shall be variable volume using a VFD and shall maintain positive static pressure in each stairwell. The differential pressure across the stairwell access door shall not exceed the maximum opening force as specified in the latest edition of NFPA 92A. U. Ductwork 1. Low pressure ductwork is defined as ductwork subjected to velocities of 1600 fpm or less, and operating pressure of 2 inches w.g. or less, positive or negative. 2. Low-pressure ductwork required for the project shall include the following: a. Air-conditioning supply air systems downstream of terminal units and fan coil units. b. Outside air intake plenums. 3. Volume dampers shall be provided at all individual, low-pressure take-offs. Low pressure take-offs shall be bellmouth or 45 degree boot tap. 4. Medium and high-pressure ductwork is defined as ductwork subject to operating pressures in excess of 2 inches w.g., positive or negative and up to 6 inches w.g. positive or negative. 5. Types of medium and high-pressure ductwork include the following: a. Air conditioning supply air systems from air handling unit discharge to terminal units. b. Exhaust distribution systems. 6. Construct elbows with radius of not less than 1-1/2 times width of duct on centerline. Comply with SMACNA Standards. Use smooth radius elbows where feasible. 7. Transform duct sizes gradually, not exceeding 20 degrees divergence and 30 degrees convergence. Comply with SMACNA Standards. 8. Ductwork Sizing: The following criteria will be utilized for sizing ductwork for the various systems: a. Medium pressure supply ductwork upstream of air terminal units will be sized for a maximum pressure drop of 0.15 inches of water per 100 feet of ductwork for ducts carrying up to 12,000 CFM. For ductwork over 12,000 CFM, sizing will be based on maintaining a maximum velocity of less than 2,000 feet per minute (fpm). (Low pressure ductwork may be utilized in lieu of medium pressure duct for energy conservation and sustainability). b. Low pressure supply ductwork between the terminal unit and grille/diffuser of air terminal (Supply Air, Return Air or Exhaust Air) will be sized for a maximum Page 3

4 pressure drop of 0.08 inches of water per 100 feet of ductwork for ducts carrying up to 8,000 CFM. For ductwork over 8,000 CFM, sizing will be based on maintaining a maximum velocity of less than 1,500 feet per minute. c. Transfer openings and return air sound boots shall be sized for 500 fpm at the air handler mechanical room wall and 300 fpm at all other locations. 9. Low-pressure ductwork will be utilized between the terminal unit and grille/diffuser to transport supply air to the space and return/exhaust air from space. 10. Flexible runs of ductwork to air devices are not to exceed five (5) feet in length with no kinks or crimps in the branch. Flexible duct to terminal units shall not exceed one (1) foot. 11. All seams shall be sealed to ensure the minimum allowable leakage rate. 12. Non-metal rigid ductwork shall not be used except fiberglass underground. 13. Indicate manual air volume balancing devices in supply, return, and exhaust mains, and branch mains. 14. All exterior supply and return ductwork shall be insulated double wall. 15. Lined ductwork is not acceptable on any new projects or equipment. V. Exhaust and Intake Louvers 1. Coordinate louver selection with architectural drawings. To allow for future expansion of the HVAC system ventilation requirements, the maximum design face velocity at the louver face must not exceed a free area face velocity of 800 fpm on intake louvers and 1200 fpm on relief or exhaust louvers. 2. All air intake louvers must include bird screen, and in some cases depending on the location and height of the air intake, the louvers may need to include removable screens with no smaller than ½ openings located on the leaving air side of the louver. This requirement also applies to spaces such as boiler rooms and diesel generator rooms, etc, where combustion air may be required. 3. Air intake locations shall be coordinated with the building general exhaust system, kitchen exhaust, plumbing vents, generator exhaust, grease traps, trash dumpsters, vehicle exhaust, etc., to avoid introduction of undesirable odors into the building, under all conditions. 4. The bottom of all outside ventilation air intakes for occupants shall be located as high as practical but not less than twelve (12) feet above ground. Intakes on top of buildings shall be located no less than 3 feet above roof level. Select outside air intake louvers for a maximum face velocity of 400 fpm using a free area of 50 percent. 5. Due to potential entrainment of contaminated air or odors into outside air intake louvers, AE to evaluate the need for a building study, to aid in finalizing the best locations for the ventilation air intake louvers. Ventilation air intakes for occupants shall not be located near potential locations where vehicles idle such as garage entrance and exits, loading docks, trash compactors or near LN2 and CO2 bulk storage tanks. W. Energy Recovery Units 1. The determination of energy recovery is based on the compliance of ASHRAE 90.1 or ASHRAE 62.1 or actual energy recovery needs. 2. Unless otherwise required to comply with applicable codes or standards, energy recovery components should be evaluated by considering equipment installed cost, equipment life, the time value of money, any utility avoided costs, and a simple payback of 5 years or less. Page 4

5 3. All the major parameters of an energy recovery system should be connected to the building automation system. 4. Refer to ASHRAE 170 for additional clarity. X. Patient Treatment Air Handling Units 1. Air handling systems shall be designed as single duct variable air volume (VAV) distribution systems with supply and return ducts. 2. Air handling units shall have a fan array system where if one fan goes off line the others can ramp up to cover a minimum 80% of the air flow. Multiple supply and return air fans or fan wall technology shall be incorporated in the unit design to achieve redundancy. 3. VAV terminals with reheat shall always provide at a minimum the required air change rates and critical pressure differentials with respect to adjoining spaces. 4. Air handlers shall be designed to accommodate the pressure drop from 12 charcoal filters based on Camfil Farr or AAF 24 x24 x12 filters. 5. Coil drain pans shall be 316 stainless steel. Coils shall be mounted at a height so that discharge of drain pan is located 12 minimum above finished floor. Drain pans shall be individually piped and trapped with a discharge of 3/4 minimum union connection. Cooling coil drain pan piping shall be copper. Cascading of drain pans is not allowed. 6. A cost benefit analysis should be performed to determine if a mixed air temperature air handling unit should be selected for 100% OA. 7. Each VAV air handler may include, but not be limited to the following components for air distribution systems: a. Inlet section. b. Return fan, centrifugal type. Fan speed is controlled by a VFD. c. Economizer section with air blender. d. Pre-filter section MERV 7 (30%) as rated by ASHRAE Standard e. Energy recovery pre-heat coil. f. Access section g. Steam or hot water preheat coil; copper tubes, aluminum fins; maximum 10 fins per inch; Integral face and bypass. Pre-heat coil discharge temperature sensor. h. Access section. i. Supply fan, centrifugal type (fan type may change due to fan array, review change with Cleveland Clinic). Fan speed is controlled by a VFD. j. Chilled water-cooling coil; copper tubes, aluminum fins; maximum 8 rows, maximum 10 fins per inch, desaturation coil (blow thru units only). Provide with flow taps. Provide freezestat on entering face of cooling coil). k. Properly spaced ultra violet germicidal irradiation (UVGI) lamps shall be located on the leaving air side of the cooling coil. Access section with micro switches on door to enable unit. l. Access section. m. Mist eliminator (blow thru units only). n. Access section. o. Final filter section shall comply with the latest Guidelines For Design and Construction of Hospitals and Outpatient Facilitates (FGI) which includes ANSI/ASHRAE/ASHE Standard 170. (Units serving operating rooms shall have HEPA filters) p. Access section. Page 5

6 q. Steam humidifier, should be located after the final filters or at a distant sufficient to be 100% evaporated prior to reaching the filter. r. Discharge section s. High static pressure and smoke detection shutdown control and reset capability. High static pressure reset shall be push button type with LED indicator light. Locate in a usable location. t. Instrument measurement taps for static pressure, temperature, etc. 8. Restrooms, janitors, and locker rooms in patient facilities are negative with respect to adjacent spaces and corridors, and they are connected to the building s general exhaust fan system. 9. Design patient rooms for care and recuperation at proper outside ventilation and recirculation air change rates. Patient restrooms are to be connected to the building s general exhaust fan system except for those located within an isolation room. 10. Design criteria, ventilation air rates and recirculation air rates for Intensive Care Rooms (ICUs) shall comply with the latest Guidelines For Design and Construction of Hospitals and Outpatient Facilitates (FGI) which includes ANSI/ASHRAE/ASHE Standard 170. Y. Airborne Infection Isolation Rooms: 1. Rooms must be designed as once-through ventilation systems served with dedicated redundant (N+1) exhaust air fan systems. The quantity of supply air to each isolation room, shall meet the required supply and exhaust air offset to maintain the room at a 0.02 negative pressure per Cleveland Clinic Negative Isolation Room Standard and also meet room total cooling and heating load requirements. The supply air VAV box shall modulate to maintain negative pressure in the isolation room. Provide differential pressure monitor with alarm points to building automation system. 2. The exhaust airflow rate from the isolation room shall meet the minimum required air change rate and modulate to maintain constant CFM offset exhaust airflow during all modes of system operation. The patient private restroom shall also be considered as part of the isolation room exhaust air requirement. The exhaust shall have a VAV box. 3. For each project, the total exhaust from all of the combined isolation rooms should be filtered with a bag-in and bag-out HEPA filter housing prior to being discharged to the environment by an exhaust fan with a discharge 10 feet minimum above roof level. Refer to the Isolation Room standard for the specific details on the exhaust fan system. 4. VFD control of fans to maintain duct static pressure as filters load up. Z. Patient Protective Environment (PE) Rooms: 1. Rooms must be designed at proper outside ventilation and recirculation air change rates, and maintained at the required minimum positive pressure with respect to the corridor and adjacent rooms or spaces per Cleveland Clinic requirements. Filter the supply air to PE rooms using MERV 17 HEPA filter ceiling modules. Provide differential pressure monitor with alarm points to building automation system. 2. The quantity of supply air to each PE room shall meet the required supply offset to maintain the room at a positive pressure with respect to adjacent spaces and the corridor and to also meet the room s cooling and heating load requirements. The supply air VAV box and the return air VAV box shall modulate to maintain positive pressure in the space to 0.01 positive. Page 6

7 3. The exhaust airflow rate from the patient restroom shall be included in the required air change rate and to also maintain constant exhaust airflow during all modes of system operation. AA. General Operating Room (OR) Suites(including Orthopedic): 1. Operating room suites shall be served by an air handling system that is dedicated to serving only operating rooms and the surrounding spaces. 2. The operating room air handling unit low temperature cooling coil shall be tied into the low temperature chilled water loop where available. Verify tie in location and capacity with Cleveland Clinic during design development. 3. Suites must be designed at proper outside ventilation and recirculation air change rates, and maintained at the required minimum positive pressure with respect to the corridor and adjacent rooms or spaces per Cleveland Clinic requirements. Filter supply air to OR Suites using MERV 17 HEPA filters in air handling unit or in ceiling modules. The supply air VAV box and return air VAV box shall modulate to maintain 0.01 w.c. positive pressure in the space. Air valves may be used in lieu of VAV boxes. 4. The quantity of supply air to each OR Suite shall meet the required supply and return air offset to maintain the room at a positive pressure with respect to adjacent spaces and to also meet room total cooling and heating load requirements. 5. The exhaust airflow rate from the OR Suite shall meet the minimum required air change rate from FGI Guidelines 6. Air Change Rates for operating rooms shall at a minimum comply with the latest Guidelines For Design and Construction of Hospitals and Outpatient Facilitates (FGI) which includes ANSI/ASHRAE/ASHE Standard OR s shall be designed with equipment that will allow for unoccupied setbacks and an automated sequence of operations written for the setbacks. 8. Humidity requirements for each OR Suite shall be individually maintained using a steam distribution manifold installed in the supply duct downstream of the terminal unit reheat coil. Access panels are to be placed in hard ceilings to gain access to the humidifiers for maintenance purposes. 9. A cost benefit analysis should be performed to determine if new operating rooms should be designed with mechanical space directly above the operating rooms. The humidifiers and VAV boxes serving the operating rooms shall be located in the mechanical space above the operating rooms. BB. Imaging Procedure room: 1. Rooms must be designed at proper outside ventilation and recirculation air change rates of and maintained at the required minimum positive pressure with respect to the corridor and adjacent rooms or spaces per Cleveland Clinic requirements. Filtration shall meet the requirements of FGI guidelines (ASHRAE 170).. 2. The quantity of supply air to each Imaging procedure room shall meet the required supply and return air offset to maintain the room at a 0.01 positive pressure with respect to adjacent spaces and also to meet room total cooling and heating load requirements. 3. Humidity requirements for Imaging procedure room shall be maintained and the humidifier steam distribution manifold shall be installed downstream of the final filter at the discharge of the air handling unit. Page 7

8 CC. Spaces that require specific pressure offsets (Typically: OR, Procedure Rooms, PE, AII, Sterile Cleaning, etc.): 1. The rooms shall be sealed and a room integrity test needs to occur. 2. Room indicators shall be located in the spaces to verify proper ACH, temperature, humidity, and differential pressure. DD. Except for patient isolation rooms, which are totally exhausted, return air shall be ducted and shall be considered as a design standard for patient care, patient treatment, examination rooms, and protective environment rooms. EE. FF. Duct sections shall be made of stainless steel where steam humidifiers are placed, and stainless steel drain piping or tubing shall be placed at the bottom of the duct to prevent condensed steam from remaining inside the supply air duct. Duct humidifiers shall be provided with type 304 stainless steel for a minimum of 5 feet downstream of the humidifier. Designer to verify the absorption distance for each application and adjust the length of 304 stainless steel. GG. Laboratory fume hood exhaust shall be type 316 with welded joints. HH. Commercial dishwasher exhaust, steam sterilizer, and sterile washer exhaust shall be type 304 stainless steel with welded joints. II. Kitchen hood exhaust shall be 16 gauge black steel where concealed, and 18 gauge type 304 stainless steel, welded, grinded and polished to a No. 3 finish, where exposed. JJ. When secondary humidification is required in family health centers, steam generating canisters are acceptable. KK. Air handling units that are roof mounted shall be located on a structural steel platform or curb mounted with ease of maintenance designed into the unit. LL. New VAV system designs shall use heating hot water reheat coils. PART 2 - PRODUCTS 2.1 MANUFACTURERS: Refer to construction specifications for acceptable manufacturers. ***** Page 8