Physical Plant Complex

Transcription

1 Continuous Commissioning Report For the Physical Plant Complex Building #1156 Submitted to: Utilities Energy Office Physical Plant Department Texas A&M University Prepared by: Energy Systems Laboratory 8/25/2006

2 Executive Summary The building assessed in this report is the Physical Plant Complex (also known as the Plant Administration Building). It is a two-story building consisting of offices and shops located on the west campus at Texas A&M University. The HVAC system is a combination of a dual duct, dual fan VAV air handling unit and three single duct constant volume air handling units, as well as one direct expansion (DX) cooled air handling unit. A combination of DDC and pneumatic controls systems operate the equipment. Two Continuous Commissioning measures were implemented: 1) setting the minimum outside air intake correctly for the Built up Unit; and 2) implementing a boiler entering water temperature set point reset schedule with outside air temperature. Several measures were proposed that have yet to be implemented, including: 1) implement optimized start/stop function for the Built up Unit, with fan speed limited to 80% and outside air dampers closed; 2) schedule static pressure reset to vary with fan speed for SF1 (cold deck) on the Built up Unit; 3) implement economizer mode for the Built up Unit; 4) schedule SF2 (hot deck) on the Built up Unit to shut off when outside air temperature exceeds 73 F; 5) provide dehumidification and economizing functionality for AHU 2, as well as proper building pressurization control and scheduling; 6) provide improved control to AHU 1 by decoupling the valves, programming for dehumidification as needed, and tuning the valve PID loop properly; 7) use DX coil for cooling on AHU 1 when the Built up Unit and AHU 2 are not running so that the chillers and pumps can cycle off; 8) program the chillers to cycle as needed based on chilled water return temp, and program all four chilled water pumps to shut off at night when not needed; and 9) install air pressure sensing switch on Built up Unit and AHU 2, and link to associated exhaust fans to shut the fans off when the units are off. The comfort issues identified in the building will be resolved by the measures proposed. Some of these issues have already begun to be addressed, such as those involving the shop area pressurization. The proposed measures, particularly those that will allow improved control of AHUs 1 and 2, will aid in improving comfort in the areas served by these units. Additionally, it was recommended that as the existing chillers and boiler near the end of their life expectancies, a retrofit of the chilled water and hot water systems be considered, and that chilled water and hot water be obtained from the west campus central plant rather than from local equipment. A retrofit of the building lighting from T-12 lamps to T-8 lamps is also suggested.

3 Acknowledgements The Continuous Commissioning (CC ) process detailed in this report was a collaborative effort among the Energy Office, Area Maintenance, and the Energy Systems Laboratory at Texas A&M University. Many persons from each entity are responsible for the work done in the building, from the field and comfort measurements and CC measures determination, to the maintenance and controls items implemented. This document is designed to serve as a deliverable from the Energy Systems Laboratory to the Energy Office, and primarily details the CC activities and measures in which the Energy Systems Laboratory has been involved. For information concerning the Office of Energy Management, please contact Homer L. Bruner, Jr. at (979) The lead CC investigator for this building was Cory Toole. For additional information regarding the information in this report or the overall Continuous Commissioning program at the Energy Systems Laboratory, please contact Song Deng at (979) i

4 Table of Contents I. Introduction...1 II. Facility Information... 1 A. General Building Description... 1 B. HVAC & Lighting System Description... 2 III. Continuous Commissioning Activities... 4 A. Existing Building Conditions (Pre-CC) Existing HVAC Conditions Existing Comfort/Indoor Air Quality Conditions B. Continuous Commissioning Measures Implemented Measures Proposed Measures IV. Requested Action V. Building Comfort Improvements VI. Retrofit Recommendations VII. Conclusions Appendices ii

5 List of Figures and Tables Figure 1. Physical Plant Complex... 1 Figure 2. Physical Plant Complex location... 2 Figure 3. Flowchart of proposed programming modifications for fan SF Figure 4. Flowchart of proposed programming modifications for AHU Figure 5. Proposed programming flowchart for AHU Figure 6. Proposed programming flowchart for the chilled water system Table 1. Building pumping information Table 2. HVAC system airflow design information Table 3. Summary of implemented CC measures in building Table 4. Summary of proposed CC measures that have not yet been implemented iii

6 I. Introduction Since 1997, more than 80 TAMU - College Station buildings have been commissioned, resulting in energy savings to the university of millions of dollars. For the fiscal year 2006, 25 buildings (totaling 2.5 million square feet) have been identified to be commissioned, of which the Physical Plant Complex is the sixteenth. This building was identified as a prime candidate for Continuous Commissioning due to its high energy cost per square foot, and because it had not been commissioned previously. Commissioning began in June 2006 and was completed in August II. Facility Information A. General Building Description Figure 1. Physical Plant Complex. 1

7 Figure 2. Physical Plant Complex location. The Physical Plant Complex, pictured above in Figure 1, was constructed in 1987 and is located on the West Campus of Texas A&M (see Figure 2 above). It is home to the Physical Plant department, and consists primarily of offices and shops, with the office portion being fully conditioned and the shop portion with heating only. It is generally occupied on weekdays during the day, with the Radio Room area being occupied continuously. The Physical Plant Building has a total gross area of 70,600 square feet. Of this area, 39,900 square feet is fully conditioned space and 30,700 square feet is heating only space. The conditioned part of the building consists mainly of offices while the heating only part of the building is shops/work space. The building has three air handling units (AHUs) that are remotely controlled, two that are locally controlled with direct expansion (DX) cooling, 20 exhaust fans, 30 ventilation fans, one relief fan, 28 hanging unitary heaters, four chilled water pumps, and one hot water pump. This building has two chillers (80 tons capacity each) and a boiler (1.9 MMBTU/hr capacity), which allow the building to be independent of the campus chilled and heating water loops. Three of the air handling units, the chilled water pumps, and the hot water pump are DDC controlled. The exhaust and ventilation fans are manually controlled, the unitary heaters are pneumatically controlled, and the chillers and boiler temperatures are locally controlled. B. HVAC & Lighting System Description The chilled water system in the building utilizes two 2 hp, 91.5 GPM building supply pumps, and two 1.5 hp, 120 GPM dedicated chiller return pumps. The pumps are constant speed, but are DDC controlled on and off by needed flow and chilled water supply temperature, and the bypass valve is DDC controlled to maintain loop differential pressure. The piping system is constant speed flow with bypass. The heating water system utilizes one 5 hp, 200 GPM pump. The piping system is a constant speed flow with three-way control valves on the coils. A summary of the building pumping 2

8 information is shown below in Table 1. Table 1. Building pumping information. CW System P-2 & P-3 CW System P-4 & P-5 HW System P-1 Number of pumps Pump control source Apogee Apogee Apogee Pump speed control Constant Constant Constant Pump speed control method Bldg Valve control method ne ne ne Control valve type DDC DDC DP Nameplate GPM Nameplate Head (ft) Nameplate HP DP The originally designed HVAC system in the building consists of three air handling units. The controls system is a combination of DDC and pneumatic. The total design supply flow in the building is 53,200 cfm, of which 5,500 cfm is outside air. The total design exhaust flow from conditioned spaces of the building is 11,480 cfm, and is achieved with three exhaust fans and one relief fan. Table 2 gives an overview of the units comprising the designed building HVAC system, with their design information. Table 2. HVAC system airflow design information. Building Name: Physical Plant Complex Total Area: 70,600 ft 2 Unit Function Service Supply cfm Outside Air cfm Fan hp te AHU-1 Supply Radio Room AHU-2 Supply Shop Offices Built up Unit Supply Administration Cooling SF-1 Administration Heating SF-2 RF-3 Relief EF-2 Exhaust Restrooms EF-4 Exhaust Break room watt EF-5 Exhaust Break room watt 3

9 The lighting system in the building is comprised primarily of T-12 lamps on all floors. The building contains a total of 365 three-bulb fixtures and 14 two-bulb fixtures. A total of 14 incandescent bulbs are used for accent lighting in foyers. III. Continuous Commissioning Activities A. Existing Building Conditions (Pre-CC) 1. Existing HVAC Conditions The conditions found in the building at the time commissioning began related to the HVAC system are categorized by group and summarized below. Air Handling Units AHU 1 AHU 1 is a couple controlled unit with a DX cooling coil followed by a chilled water cooling coil followed by a heating coil, and serves the Radio Room area. The DX coil was designed to provide backup cooling to the unit in case of problems with chilled water. The unit was found to have had some significant modifications made to its control before commissioning took place. It was discovered while investigating the unit that the couple control had been removed from the valves. The chilled water valve was hooked to main air to remain open at all times, while the hot water valve continued to be controlled. The outside air intake duct for this unit had been blocked off with a fibrous material to prevent any intake. These actions were apparently taken due to complaints of high humidity levels in the Radio Room. While the actions taken did serve to help limit the rise of humidity in the Radio Room, other problems were created. It was observed that the hot water valve control response was slower than desired. When space temperature fell below set point, the valve would open to provide reheat, but the space temperature would then rise above set point. At this point, the DX unit, which was programmed to come on when the space temperature exceeded set point by 0.9 degrees or more and turn off when space temperature fell 0.9 degrees or more below set point, would cycle on. However, due to the slow response of the hot water valve, it would not fully close, causing the DX coil and the hot water coil to fight one another. The result was a tremendous amount of simultaneous heating and cooling. When the DX unit would finally shut off, the hot water valve would still be open, and discharge air temperature from the unit would be in the high 70s or low 80s. This would soon cause space temperature to rise, and the DX unit would cycle back on. In talking with the Radio Room occupants, complaints were received that the space 4

10 temperature would fluctuate significantly throughout the day. Aside from the slow response of the hot water valve, it was also discovered that the hot water temperature was being maintained around 120 F by the boiler. The boiler and hot water pump were required to run solely to supply AHU 1, even though outside air temperatures commonly exceeded 90 F. An experiment was conducted wherein the outside air temperature, space temperature, discharge temperature, hot water valve control, and DX cycling were trended over a period of nearly two weeks. The obstruction in the outside air duct was removed before this trending began. During the first week, the unit was allowed to operate as normal. Then, at the beginning of the second week, the boiler water temperature set point was lowered to 80 F to observe the effects on the variables mentioned. It was found that during the first week the DX unit cycled on and off almost continuously. After the hot water temperature was lowered, the unit cycled on only once or twice during the week period. Had the hot water been valved off completely, or if the control valve PID loop had been tuned effectively, it is believed that the DX unit would not ever have needed to come on. This is in accordance with the design for the DX unit, as a backup in case chilled water became unavailable for a period. AHU 2 AHU 2 is also a couple controlled unit, but with a heating coil followed by a cooling coil. It serves conditioned portions of the shop building (including the hallway and a few offices), and has full economizing capability. The situation observed with AHU 2 at the onset of commissioning was very different than what had been designed for the unit. The supply fan and relief fan were both found to be operating in Hand. The temperature sensor previously controlling the unit was no longer present, and the control to the valves had been circumvented so that the valves were both connected to direct main air, with the normally closed chilled water valve remaining fully open all the time and the normally open hot water valve remaining fully closed all the time. This was the summer operation for the unit. According to the building mechanic, during winter operation couple control was restored to the unit and the valves were allowed to control. However, a note on Apogee claimed that the return air temperature sensor was the control point for valve operation, even though it was discovered that the return air temperature sensor was actually installed in the outside air duct, and was not an indicator of space temperature at all. The outside air damper was found to be commanded fully closed by the program at all times, and was mechanically linked to the return air damper, which remained fully open all the time. The linkage between the two dampers was worn and ineffective, so that even if the program had been set to control properly, it would have been very difficult to obtain the desired damper positions with any degree of accuracy. Despite the lack of outside air intake, the relief fan was being run to help cool the shop area outside the mechanical room, which was designed as an unconditioned space. This created negative pressures in the building. Infiltration was found to be occurring through nearly every shop door and through the main entrances. Additionally, holes above the ceiling not present by design were discovered, which allowed unconditioned outside air from an 5

11 atrium area to mix with the return air and to enter the conditioned space. Ventilation fans for the shops that were designed to draw air from the atrium area above the shops and blow it through the shops had been reversed so that they would suck air from the shops and blow it to the atrium area, due to complaints that hot air was blowing down on the workers in the shops throughout the day. This did not create problems as long as the shop bay doors were open and outside air could be drawn in from that direction. However, when the shop bay doors were closed and the ventilation fans were on, air would be sucked under the hallway doors and into the shops. This also would not be a major problem if the hallway shop doors were closed. But it was observed on several occasions that the Utilities shop door was propped open with the shop bay doors closed so that conditioned air from the hallway would be sucked into the shop. Internal conditioned offices in this area also often had their doors propped open in an attempt to condition the shop space. This, along with the relief fan running with the outside air dampers closed, caused negative pressurization in the hallway. Any time an entrance door or shop door was opened, which happened very frequently, a rush of unconditioned air would enter the hallway area. The spring ranges on the valves were also found to overlap considerably. The hot water valve had a range of 4-10 psi (normally open), and the chilled water valve had a range of 5-14 psi (normally closed). Had the valves been receiving control air, a significant amount of simultaneous heating and cooling would have occurred. It was also noted that the freeze protection sensor for the unit was located in front of the return air intake for the unit, rather than in the mixed air stream. This essentially rendered the sensor useless. Built Up Unit Compared to the two units already mentioned, the Built Up Unit was operating closer to design. However, some problems were discovered. Like the other two units mentioned, the Built Up Unit also was not receiving outside air through its intake dampers. Part of this was a programming error. The program commanded the minimum outside air dampers to close whenever outside air temperature exceeded return air temperature. But the other issue was that even when commanded to open, the dampers would not open. It was discovered that the pressure signal going to the minimum dampers when they were commanded open was being regulated to 6 psi. The dampers were difficult to move anyway, and needed to be lubricated and freed up, so the low pressure would not move them at all. The economizing dampers were also found to be stuck shut and could not be moved. The hot deck fan, SF2, was found to be running at the time commissioning began, even though outside air temperatures exceeded 90 F. It was discovered that the programming that had originally commanded the fan off when outside air temperature exceeded 73 F had been commented out, requiring the fan to run at all temperatures. Shortly after 6

12 commissioning began, it was noted that the hot deck fan was manually turned off. The static pressure and discharge temperature set points for both fans were found to be on a reset schedule with outside air temperature. For the cold deck fan, SF1, the normal occupancy static pressure set point was scheduled to vary from 0.75 in. W.G. to 2.0 in. W.G. as outside air temperature varied from 50 F to 105 F, and the discharge air temperature set point was scheduled to vary from 57 F to 53 F as outside air temperature varied from 50 F to 105 F. During periods of minimal occupancy, the discharge air temperature set point schedule was the same, and the static pressure set point was scheduled to vary from 0.5 in. W.G. to 2.0 in. W.G. as outside air temperature varied from 50 F to 105 F. For the hot deck fan, the normal occupancy static pressure set point was scheduled to vary from 1.0 in. W.G. to 0.25 in. W.G. as outside air temperature varied from 40 F to 80 F, and the discharge air temperature set point was scheduled to vary from 100 F to 90 F to 75 F as outside air temperature varied from 40 F to 57 F to 75 F. During periods of minimal occupancy, the static pressure set point was scheduled to vary from 0.5 in. W.G. to 0.25 in. W.G. as outside air temperature varied from 50 F to 80 F, and the discharge air temperature set point was scheduled to vary from 90 F to 75 F as outside air temperature varied from 50 F to 75 F. The air handling unit was scheduled to shut down at 6:00 PM and come back on at 6:00 AM on weekdays. A somewhat serious maintenance issue was discovered while measuring airflow on this unit. It was observed that the cold deck duct that extended from the unit straight up to the second floor of the building was close to rusting completely off of the cold air chamber of the unit. The ultraviolet light illuminating this chamber allowed the many holes around where the duct was connected to the unit to be seen clearly. If left unfixed, serious issues could result from this problem, particularly if the duct were to rust completely off and fall through the chamber. AHU 1-3 The unit labeled AHU 1-3 was added at a time subsequent to the original construction of the building. It serves an area of offices in the shops portion of the complex that reportedly housed telecommunications personnel previously, but is currently vacant. The unit still runs, and four pneumatic thermostats control volume-only boxes in the ceiling. The unit has no outside air intake, and uses solely recirculated air from the space. It does use chilled water and hot water from the building chillers and boiler. Measurements on the unit were taken and are included in the Appendix. It is not known what the future usage of this space will be at the present time. Carrier Unit A Carrier unit was added in the recent past to the building to serve an office area 7

13 connected to the area served by AHU 1-3 in the shops area of the complex. The unit has a design cooling capacity of 10 tons, and has electric heat. The unit is constant speed, but has variable volume boxes controlled by electronic thermostats in the offices. A damper in the mechanical room on the main supply duct regulates the supply air pressure so that it does not become excessive. Measurements on this unit were taken and are included in the Appendix. This unit does not utilize chilled water from the chillers. Exhaust Fans At the time of commissioning, the exhaust fans in the main administration building (EF- 2, EF-3, and EF-6) were not running. While the spaces served by EF-3 had changed from design so that no exhaust was needed from these areas, the areas served by the other two fans were restrooms, janitor closets, and kitchens, and probably should have been running. This was reported to the building proctor and he passed the information to Area Maintenance so that an investigation could be performed and the fans could be repaired if needed. However, the fact that the fans were not running was actually better from a building pressurization standpoint, since the Built up Unit was scheduled to shut off at night. With the fans running and the unit shut down, negative pressurization would occur in the building, which could create humidity problems in the building during humid times of the year. The restroom exhaust for the shop area was found to run continuously, even though AHU 2 was supposed to be scheduled to shut off at night as well. Since the unit was in Hand and was running continuously, negative pressurization from the exhaust fans was not an issue, but if the unit was operating as it should in Auto, the same potential humidity problems could occur as with the main administration building. Chilled Water Loop Because of frequent problems in the past with chilled water in the building, the chilled water loop was found to be operating far from design at the time commissioning began. The control programming was supposed to cycle the building and chiller pumps on and off as needed, rotating the lead supply pump by day of the week, and rotating the lead chiller by load needs. The building cooling load was to determine when both supply pumps were needed and chilled water temperature was to determine when both chillers were needed. However, because of reports from the building mechanic that the pumps and chillers were not running when needed, all four chilled water pumps were running in Hand at all times at the time of commissioning. This meant that both chillers also ran continuously. Chiller 2 was found to have at least one defective unloader, and would not chill the water as effectively as Chiller 1. Two bypass lines were found on the chilled water loop. One was a building bypass, which has a control valve set to modulate in order to maintain loop differential pressure. Another very short bypass line was discovered on the loop that allowed supply water to 8

14 flow directly back to the return line. This bypass line was necessary in order to decouple the plant loop from the building loop, since the chiller pumps have higher flow rates than the building pumps. This bypass line does not have a valve, and due to its proximity to one of the chiller pumps more than to the other, Chiller 2 was found to receive most if not all of the bypassed water to its return, causing the entering water temperature to Chiller 2 to be as much as 10 degrees colder than the entering water temperature to Chiller 1. Both chillers were also found to have bad flow switches, and would not shut off when their respective pumps were off. This caused one chiller to freeze up one morning when its pump was shut off for repair. This also meant the chillers could not be commanded off by the programming and would be another reason the pumps were left on in Hand. The chillers currently do not have the capability of having their temperature settings changed through Apogee. A manual switch controls the entering chilled water temperature. Chiller 1 had an entering water temperature setting of 55 F, and Chiller 2 had an entering water temperature setting of 50 F, probably to correct for the lower entering water temperature due to the short bypass line. Hot Water Loop The hot water loop appeared to be functioning as designed at the onset of commissioning. The hot water pump was designed to cycle on whenever heating was called for in any of the units. Because of the problems with valve control on AHU 1 already mentioned, this pump remained on at all times. Additionally, it was noted that the boiler was producing hot water temperatures in the 120 F range when outdoor air temperatures were in the 90s, which caused energy to be wasted. Terminal Boxes As noted, terminal boxes are present only in the main building portion of the complex served by the Built Up Unit. These boxes are pneumatically controlled dual duct boxes. It was discovered during the early stages of commissioning while conversing with the building mechanic that many of these terminal boxes had been modified significantly. Due to the scarcity of parts for the existing Krueger boxes, it was decided that the velocity controllers would be bypassed completely and taken out as they malfunctioned, and instead a reversing relay was installed. This occurred on several boxes. It was found on these boxes that simultaneous heating and cooling would occur whenever the thermostat was near its satisfied level. Other It was discovered several times following heavy rains in the area that a large amount of water would enter the mechanical room housing the Built up Unit and AHU 1. This water entered through a conduit line installed through which presumably wire would be 9

15 run in the future. Other drains in the mechanical room appeared to be stopped up, especially the drain under AHU 1, which compounded the problem. This standing water in the mechanical room presented a safety hazard due to electrical cords and computer equipment being in the water. Slippery conditions in the room were also common, as dust and dirt became mud. Another issue of concern that was discovered was that from time to time water was found in the pneumatic control lines throughout the building. This could be an indication that the compressor has a bad after-cooler. 2. Existing Comfort/Indoor Air Quality Conditions Two major comfort complaints surfaced at the beginning of commissioning. One was that the conditioned area for the shops served by AHU 2 was often too warm in the mornings when some of the workers arrived. As noted previously, a number of issues contributed to this, including the fact that occupants begin work in this building at or before 7:00 AM (as opposed to the 8:00 AM schedule in other areas). The end result was that the unit was left in Hand so that it would no longer shut off at night. The other major comfort complaint received was from the occupants in the Radio Room area. Those at the front of the area near the entrance from outside (and furthest from the thermostat) complained of being hot frequently. Temperatures were measured in this area to be as high as 79 F, even when the thermostat area was below 76 F. This was due to the significant additional heat load created from the equipment in this area, as well as the proximity of the door to the outside, which was opened frequently. Comfort complaints in the back area near the thermostat were of drastic swings in space temperature that occurred often. Although the trended data presented earlier for this area did not show a drastic change in temperature generally for the space, the original operation did cause a lot of fighting between the heating valve on AHU 1 and the DX coil in order to maintain space temperature. This was most likely the cause of the discomfort noted. B. Continuous Commissioning Measures 1. Implemented Measures Table 3. Summary of implemented CC measures in building. Category CC Measure Result AHUs Set minimum outside air correctly for Built Up Unit. Improved ventilation. HW Loop Implemented reset schedule for boiler entering water temperature set point with OA temperature. Natural gas savings. 10

16 To resolve the problems described in the previous section, two Continuous Commissioning measures have been implemented in the building, as noted in Table 3. The first measure implemented was to set the minimum outside air correctly for the Built up Unit. Both ESL technicians and Area Maintenance mechanics worked to allow the minimum outside air damper to operate freely. Once the damper was able to move well, the regulator was adjusted and outside air flow was measured to allow a proper amount of ventilation air into the building for occupants and to allow adequate building pressurization. A problem in the control programming still needs to be corrected, however, that will allow the minimum outside air damper to open at all times when the building is occupied. This is described further in the Proposed Measures section. The other measure to be implemented was a reset schedule on the boiler based on outside air temperature. The boiler temperature set point control is local, and is controlled by three dials on the boiler panel. One dial is for the entering water temperature, one dial is a reset ratio, and one is a throttling range. The entering water temperature set point at an outside air temperature of 70 F should be the value on the water temperature dial. The reset ratio then sets the amount of gain or loss of set point temperature based on the amount over or under the outside air temperature is from 70 F. The throttling range sets the degree span over which the full eight stages of the boiler are energized. The reset ratio implemented during commissioning was to vary the boiler entering water temperature from 110 F at a 70 F outside air temperature to 140 F at a 20 F outside air temperature. This corresponds to a reset ratio of 1.7, or one degree of water temperature rise for every 1.7 degrees of decrease in outside air temperature. When outside air temperature exceeds 70 F, the boiler water temperature is also reset at the 1.7 ratio. The 110 F set point was based on a recommendation in the boiler specifications to avoid condensation on the heat exchanger tubes. The upper limit of 140 F was set in an effort to prevent boiler leaving water temperature from exceeding 160 F, to avoid seal problems under extreme heat. In order to achieve the 110 F at 70 F outside temperature, however, the set point dial actually had to be set to 130 F, due to a calibration problem with the dial. The throttling span was set to 24 F, meaning that for every three degrees of water temperature under set point, another of the eight boiler stages would come on. 2. Proposed Measures Table 4. Summary of proposed CC measures that have not been implemented in the building. # Category CC Measure Purpose 1 AHUs Implement optimized start/stop function for the Built up Unit, with fan speed limited to 80% and OA dampers closed. Reduce fan power consumption. 11

17 2 AHUs Schedule static pressure reset to vary with fan speed for SF1 on the Built up Unit. Allow fan to better track building load, electricity and CHW savings. 3 AHUs Implement economizer mode for the Built up Unit. Chilled water savings. 4 AHUs 5 AHUs 6 AHUs Schedule SF2 (hot deck) on the Built up Unit to shut off when OA temperature exceeds 73 F. Provide dehumidification and economizing functionality for AHU 2, as well as proper building pressurization control and scheduling. Provide improved control to AHU 1 by decoupling the valves, programming for dehumidification as needed, and tuning the valve PID loop properly. HW and electricity savings. Chilled water savings, improved comfort. Improved comfort, chilled water, hot water, and electricity savings. 7 AHUs/ Chillers Use DX coil for cooling on AHU 1 when the Built up Unit and AHU 2 are not running so that the chillers and pumps can cycle off. Electricity savings. 8 CHW Loop Program the chillers to cycle as needed based on CHW return temp, and program all four CHW pumps to shut off at night when not needed. Electricity savings. 9 Exhaust Fans Install air pressure sensing switch on Built up Unit and AHU 2, and link to associated exhaust fans to shut the fans off when the units are off. Electricity savings, improved building pressure control. Several Continuous Commissioning measures are proposed that for various reasons have not been implemented. Table 4 above is a summary of the Continuous Commissioning measures that have not been implemented in this building. Their implementation will complete this phase of Continuous Commissioning for this building and will correct the remaining problems with building performance. (Measures 1-3) The first three proposed measures to be implemented involve programming modifications to fan SF1 on the Built up Unit. Specifically, these modifications deal with optimal start/stop, improving economizer operation, and implementing a static pressure set point schedule based on building load. A flow chart of the proposed programming modifications is shown in Figure 4. 12

18 Occupied Mode? Close Min OA Damper and Economizer Damper Perform Optimal Start/Stop of fan with speed limited to 80% and OA dampers closed. Turn fan off unless maximum zone temperature exceeds night setback limit. Open Min OA Damper Set fan static pressure set point based on fan speed. Set cold deck temperature set point based on OA temperature. OA Enthalpy < 26 Btu/lb? Set Economizer Damper at 0 psi (fully closed). Modulate Economizer Damper to control Mixed Air Temperature to 2 degrees below cold deck set point. OA Temp <= (CD Temp S.P. - 2)? Modulate CHW valve to control cold deck temperature to set point. Close CHW valve. Figure 3. Flowchart of proposed programming modifications for fan SF1 on the Built up Unit. 13

19 The fan should be started with the optimal start stop function in order to have the space ready for occupancy by 7:30 AM on weekdays. During this startup period, the minimum outside air damper should remain closed, and the VFD speed should be limited to 80%, or 16 ma. This will use less fan power than allowing the unit to run at 100% during startup, even though it will take longer to get to temperature. After this startup period, the minimum outside air damper should be opened, and should remain open as long as SF1 is running. The static pressure set point should be reset based on fan speed. This will allow the fan to track actual building demand rather than strictly outside air temperature changes. The equation for this reset will allow the static pressure set point to vary from 0.75 in. W.G. to 2.0 in. W.G. as fan speed varies from 12 to 18.4 milliamps. The equation is given by: Static Set Point = ("ADMIN.SF1SPD" - 12)/( )*( ). Upper and lower limits of 2.0 and 0.75 in. W.G. respectively should be incorporated in the programming. These limits are the same as the upper and lower limits currently in place in the programming, and were verified by field testing of static pressure needs. But allowing the static pressure set point to vary with fan speed, tracking the building load, should either save energy or improve comfort in the building, or both. The cold deck temperature schedule can remain as it is currently in place, varying with outside air temperature. However, it is now recommended that the economizer function of the unit be made to operate. This can be done effectively by mapping a control point that mirrors the campus average outdoor air enthalpy. This point is then compared with an estimated return air enthalpy (assumed 26 Btu/lb, which would be close to a 70 F dry bulb, 50% relative humidity condition). If outside air enthalpy is less than the assumed return air enthalpy, the economizer damper should be commanded to modulate to try to maintain the mixed air temperature at two degrees below the cold deck temperature set point. This is because the mixed air temperature sensor and cold deck temperature sensors are on opposite sides of the fan, and it is estimated that two degrees will be picked up as the air flows through the fan. When outside air temperature is at least two degrees below cold deck set point, no chilled water should be needed, and the chilled water valve should be commanded closed to avoid damper and valve fighting. Some type of alarm system should also be implemented if the mixed air temperature falls to a point below around 40 F, so that the outside air dampers will close, the valve will fully open, and possibly the fan may even shut off. (Measure 4) The fourth proposed measure is to schedule fan SF2 (hot deck) on the Built up Unit to shut off when outside air temperature exceeds 73 F. This line was already in the programming but had been commented out. The fan is being manually turned off in the summer time, but this should not have to be the case. If it is found that 73 F is not the 14

20 ideal temperature for this shut down, this value can be raised to a higher point as needed. (Measure 5) The fifth proposed measure yet to be implemented involves AHU 2. Some work has been done already in the commissioning process to improve building pressurization in the hallway served by this unit. The holes above the ceiling where untreated outside air was being drawn into the space were temporarily plugged, and the outside air damper on AHU 2 was manually adjusted to be slightly open to allow 2,600 cfm of outside air to the space. However, as noted, the relief fan was being turned on by shop occupants in an attempt condition the shop (an unconditioned area), which still resulted in negative building pressure. Also, the Utilities Shop door was often left open to draw in conditioned hallway air. When either of these two events occurred, the building experienced negative pressurization. When neither of these occurred, the building experienced much better pressure control. This was tested, and besides improving pressure in the building, the temperature in the hallway dropped significantly, indicating the potential for much easier temperature control. The building mechanic was instrumental in getting a notice sent to building occupants that the relief fan was to remain in Auto, and that all shop hallway doors were to remain closed. However, these fixes have the potential to be temporary. It is recommended that a policy be clearly implemented that all doors between conditioned and unconditioned areas remain closed at all times except when in use and that the relief fan is not to be used to condition an unconditioned area, and that this policy be approved and enforced by building supervisors. If conditioning is needed in the shop areas, it should be provided in a better way, so that it does not negatively affect the rest of the building. The air handling unit control also needs considerable improvement. The supply and relief fans should be made to run in Auto at all times. During commissioning, the incorrectly labeled return air sensor was relabeled, and the space temperature sensor was apparently repaired, and is now located in the Area 7 shop offices. It is recommended that several digital temperature sensors be placed throughout the spaces served, so that an average space temperature can be used as the control point for the valves on the unit, and maximum and minimum space temperatures can be monitored. If this is not possible, the return air temperature could also be used as the control point if the space sensor is relocated to the return air duct. Since the return air enters through two separate ducts to the mechanical room, one of these would need to be chosen for the sensor location, and it is recommended that the duct coming in on the east side be used, since it picks up air from a larger area. In order for return air to be an effective control point, however, the holes mentioned that have been found above the ceiling need to be repaired, since currently they allow untreated outside air to mix with the return air, heating it considerably on warm days. It is recommended that the control for AHU 2 be modified to allow proper humidity 15

21 control, as well as effective economizer operation. For this to work, the ineffective linkage between the return air damper and the outside air damper should be corrected. Ideally, this would be done by replacing the current setup with two DDC controlled motorized actuators, one for each damper, that would be controlled from the same signal. If this is not possible, the current linkage should be repaired or replaced so that both dampers will operate as designed. During commissioning, Area Maintenance mechanics did lubricate the dampers, which improved operation, but did not completely fix the problem. The recommended control for the unit after these issues have been addressed is shown in a flowchart in Figure 5. Dehumidification Needed OA Dewpoint > 55 F? Dehumidification Needed n- Economizer function OA Enthalpy < 26 Btu/lb? Economizer function Set OA Damper to Minimum OA position. Set OA Damper to Minimum OA position. Control the OA Damper to maintain the valve position at 7 psi (both valves fully closed). Control the valves to maintain a 57 F discharge air set point. Control the valves to maintain the space temperature at its set point. Trigger alarm if Mixed Air Temperature falls in freezing range. The OA Damper should be commanded closed and both valves opened. Figure 4. Flowchart of proposed programming modifications for AHU 2. 16

22 For this programming to be effective, a point should be mapped to the control system that will mirror the campus average outside air dew point temperature and another that will mirror the campus average outside air enthalpy. When the outside air dew point temperature is higher than 55 F, dehumidification is recommended. For this scenario, the outside air damper should be commanded to minimum position, and the control for the valves should modulate to achieve a discharge air temperature set point of 57 F. It must be noted here that while this will prevent humidity problems in the space, it will remove temperature control capability for the unit, since no reheat coil is present. The spaces have the potential to fall well below their temperature set point under certain high humidity, moderate temperature conditions. It must be decided which problem is of greater importance: humidity control in the space or precise temperature control. Some trial and error may be needed to observe comfort conditions when humidity control is implemented. When the outside air dew point temperature is less than or equal to 55 F, no dehumidification is needed. When the outside air enthalpy is less than 26 Btu/lb (a conservative estimate for return air conditions), the economizer mode can be utilized. Because it is a couple controlled unit, the outside air damper should be modulated to try to maintain the valve air pressure at 8.5 psi, the condition at which both valves are fully closed. The spring ranges on the valves were adjusted during the commissioning process to give a 3 to 8 psi range on the hot water valve and a 9 to 16 psi range on the chilled water valve. However, it was found that the control signal sent from Apogee is not exactly calibrated to the actual pressures being sent. Therefore, in the programming the spring range for the hot water valve should be 2 to 7 psi, and for the chilled water valve it should be 7 to 13 psi. Thus, the outside air damper should be controlled to maintain a 7 psi signal to the valves. Meanwhile, the valves must control to maintain the space temperature at its set point (or the return air temperature at its set point, if the temperature sensor is relocated to the return air). A freeze protection alarm should be installed in the programming to fully close the outside air damper and open the hot water valve if freezing mixed air temperatures are detected. Otherwise, the outside air damper should not close past the minimum intake position for building pressurization reasons. The control to the relief fan should still be linked to the outside air and return air damper control, such that when this control exceeds 10 psi, the fan will come on. This unit can continue to be scheduled off at night and on the weekends, but should be optimized to start in time to have the space at set point by 6:30 AM. This should reduce complaints from occupants who arrive early. (Measures 6 and 7) The sixth and seventh proposed CC measures involve improving the control of AHU 1. It is recommended that another control point be added so that the chilled water and hot water valves can be decoupled. This will allow for dehumidification when it is needed, but will not require it when it is not. Links to the campus outside air dew point 17

23 temperature and outside air enthalpy are also needed for this programming. The proposed programming for the unit is summarized in a flowchart in Figure 6. Are any of the other units on? Set CHW valve to 8 psi (fully closed). OA Dewpoint > 55 F? Dehumidification Needed Dehumidification Needed Dehumidification Needed OA Dewpoint <= 55 F? Set CHW valve to control space temp. Calculate total cooling capacity needed to sufficiently dehumidify based on estimated mixed air enthalpy (11% OA, h_ra = 28, h_sa_needed = 23.2) Turn on DX unit. Capacity needed > CHW coil capacity? Set HW valve to control space temperature with a heating deadband. Set CHW valve to maximum of needed value for humidity control and space temp. Turn on DX unit. Set CHW valve to make up needed capacity or to control space temp., whichever value is higher. Set HW valve to control space temperature with a heating deadband. Set HW valve to control space temperature with a heating deadband. Space temp >= (set point + 1.5)? Space temp <= (set point - 1.5)? Turn on DX unit. Turn off DX unit. Figure 5. Proposed programming flowchart for AHU 1. The unit is scheduled to run continuously, since it serves the Radio Room. However, the other two Apogee controlled units receiving chilled water from the chillers are generally scheduled to shut down at night, and AHU 1-3, though not able to be programmed to shut 18

24 down, has no occupancy and uses return air only, meaning essentially that a chiller has to run each night solely to provide chilled water to AHU 1. The proposed programming will force the chilled water valve closed on AHU 1 when the other units are off, and will use the DX coil to provide cooling. This will allow the chillers and chilled water pumps to shut down during this time. When dehumidification is needed, the DX unit will run continuously and the hot water valve will control to a heating dead band (somewhere in the neighborhood of 5 degrees below the cooling space temperature set point). If dehumidification is not needed, the DX unit will cycle on when the space temperature reaches 1.5 degrees above set point, and will turn off when the space temperature falls 1.5 degrees below the cooling set point. These values can be adjusted as needed for maximum comfort and efficiency. During normal operation, however, with the other units running and the chillers running, AHU 1 will rely principally on the chilled water coil for its cooling, and the DX coil will only be used to makeup needed capacity for dehumidification or space temperature control during periods of very high load or when a problem with chilled water temperature occurs. Two separate paths are followed, one involving dehumidification and one where dehumidification is not needed. When dehumidification is needed during normal operation, a calculation must be performed to estimate how much cooling is needed. Since no temperature sensors exist for the unit other than the space temperature, some assumptions must be made, and the control must be based on coil capacities. Field measurements during peak cooling load conditions revealed that the current cooling capacity of the chilled water coil, with a chilled water temperature of 45.7 F, is approximately 7 Btu/lb. The capacity of the DX coil at peak cooling load conditions was found to be approximately 10 Btu/lb. The combined capacity of both coils was measured to be approximately 12 Btu/lb. Outside air flow to the unit was measured at approximately 11 percent of total flow, and the average return air enthalpy over a two week trended period was found to be approximately 28 Btu/lb. It is assumed that for proper humidity control, the air should be cooled to an enthalpy condition of 23.2 Btu/lb, which corresponds to 55 degrees and fully saturated. Using these assumptions, the cooling capacity needed for humidity control can be estimated as follows: Cooling capacity needed (Btu/lb) = 0.11 * (Outside Air Enthalpy 28) As noted earlier, the outside air enthalpy is a mirrored point mapped to the campus value. Once the capacity is determined, it is compared with the capacities of the coils. If 7 Btu/lb or less is needed, the chilled water coil alone takes care of the cooling. The valve command is from a table statement that will give a linear range of psi commands to the valve from fully closed to fully open that corresponds to 0 to 7 Btu/lb of capacity. The command to the valve will be that which corresponds to the needed cooling capacity. Although in reality the capacity and valve range would not be linear, this is a simplified control method that will be reasonably close. If the valve command is not enough to satisfy the space temperature, the command will be increased. Any reheat needed to satisfy the heating space temperature set point is provided by the hot water coil. If space 19