Continuous Commissioning Report

Transcription

1 ontinuous ommissioning Report For the G. Rollie White oliseum Building #453 Submitted to: Utilities Energy Office Physical Plant Department Texas A&M University Prepared by: Energy Systems Laboratory June 1, 2006

2 Executive Summary The G. Rollie White oliseum is assessed in this report. It is a two-story building with a 60-foot high coliseum located on the main campus at Texas A&M University. It has three types of HVA systems. The offices and classrooms are served by five single zone heating/cooling units with pneumatic controls. Individual offices and classrooms are served by four-pipe fan coil units (FUs). Twelve of the 39 units have wall or unit mounted thermostats that control both chilled water and heating water valves. The remaining units have only chilled water valve mounted thermostats and most of them do not work. The volleyball arena area is served by 13 cooling/heating units with mixed TE and pneumatic controls. Between January and February 2006, ontinuous ommissioning 1 ( ) process was conducted in this building. The following measures were recommended: Reset the zone temperature set-point under event mode to 70 F (implemented). Blank off the chilled water bypass piping on AHU 1 and 2 (implemented). Implement a wider heating/cooling dead band setting for AHU 1-13 (Arena area) when in non-event mode. Implement optimized P controls in chilled water pump and heating hot water pump control programs. It is also estimated that recommended measures would result in an additional $8,286 per year savings. It is strongly recommended that these measures be implemented so that the maximum amount of savings can be achieved. Additionally, it is recommended that the following retrofit recommendations be considered for further building improvement: onvert 27 old style fan coils to allow thermostat and two valve control (or install complete newer, more efficient fan coil units). Install VFD controls on the fan coil units chilled and heating water pumps. onvert AHU A through E to DD control. Retrofit existing lighting with more efficient ones Install interior insulating windows. If all the retrofit recommendations are implemented the estimated potential savings will be $46,600. The total cost is approximately $241,960. The simple payback is about five years. Two main comfort issues were identified in the building. The first is seasonal overcooling and over-heating in offices and classrooms. The second is cold temperatures in the arena area during sporting events. The root causes of the office and classroom discomfort appears to be single pane casement windows and fan coil units in disrepair. 1 ontinuous ommissioning and are registered trademarks of the Texas Engineering Experiment Station (TEES), the Texas A&M University System, ollege Station, Texas.

3 Interior insulating windows and working fan coil units with temperature control could resolve this problem. The over cooling in the arena area can be improved by adjusting the event temperature set point. Beside the and retrofit recommendations, the following maintenance issues that affected the building s energy consumption were identified: The grills and coils of all the AHUs were dirty. Outside Air and Return Air dampers of AHU 4 through 13 were not operable. Some of the outside air fans and dampers of AHU A through E were not functional. The thermostats of AHU A through E were out of calibration. The above maintenance issues were resolved during the period with the exception of the third item. Some ordered parts have not yet been installed. Data analysis from the Data Analysis and Savings alculation Task will reveal in the near future the overall savings achieved from in the building.

4 Acknowledgements The ontinuous ommissioning ( ) 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 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 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 investigator for this building was Larry Thompson. For additional information regarding the information in this report or the overall program at the Energy Systems Laboratory, please contact Song Deng at (979)

5 Table of ontents 1. Introduction Facility Information General Building Description HVA System Description ontinuous ommissioning Activities Existing Building onditions (Pre- ) Existing HVA onditions Existing omfort onditions Deferred Maintenance ontinuous ommissioning Measures Requested Actions Building omfort Improvements Savings Analysis Retrofit Recommendations onclusions Appendices List of Figures Figure 1 G. Rollie White oliseum... 1 Figure 2 G. Rollie White oliseum location... 2 Figure 3 Whole building energy consumptions time series plot... 5 Figure 4 HW and HHW consumptions VS outside air temperature... 6 List of Tables Table 1 HVA system airflow design information... 3 Table 2 Design Specifications of Fan oil Units... 3 Table 3 G. Rollie White oliseum pumping information... 4 Table 4 Summary of recommended measures... 8 Table 5 Summary of proposed retrofit measures Table 6 Field measurement of building primary loops Table 7 Zone 1 Arena units HW loop readings Table 8 Zone 2 Office/corridor HW loop readings Table 9 Zone 3 Fan coil unit HW loop readings... 16

6 1. Introduction is a process by which the performance and energy efficiency of existing buildings are improved through the implementation of measures generally not involving major building retrofits. The Energy Systems Lab, which trademarked this process, has been under contract with the Physical Plant at Texas A&M University since 1997 to systematically commission the campus buildings as requested. During this time period, more than 70 buildings have been commissioned resulting in energy savings of millions of dollars to the university. For the year 2006, 21 buildings (totaling 2.3 million square feet) have been identified to be commissioned, of which the G. Rollie White oliseum is the eighth. This building was identified as a prime candidate for due to its high energy cost per square foot and frequent comfort problems in offices and the arena. ommissioning began in January 2006 and was completed in March. 2. Facility Information 2.1. General Building Description The G. Rollie White oliseum, pictured in Figure 1, was constructed in 1955 and is located adjacent to Kyle Field, the Memorial Student enter, and the Koldus Building (see Figure 2). It is home to the Health and Kinesiology Department and part of the Athletics Department. The building contains offices, classrooms, and an arena. Figure 1 G. Rollie White oliseum 1

7 Figure 2 G. Rollie White oliseum location The building has two floors for a total area of 86,000 square feet. It is generally occupied during classroom hours, hosts approximately 25 volleyball games per season, and has additional special events on occasion HVA System Description The building underwent a major renovation in 1966 to install HVA and fan coil units. This remodel provided the building with a total design supply flow at 180,945 cfm, of which 44,398 cfm is outside air. The 1966 total design exhaust flow from the building is 950 cfm, and is achieved with three exhaust fans. The maximum supply flow and outside air flow only occurs when all 13 Arena units are operating (Event Mode). There are three types of HVA systems serving different areas in this building. Table 1 and Table 2 give an overview of the units comprising the building HVA system, with their design information. The volleyball arena area is served by 13 cooling/heating units with mixed TE and pneumatic controls. The offices and classrooms are served by five single zone cooling/heating units with Johnson pneumatic thermostats and control valves. Individual offices and classrooms are served by 38 four-pipe fan coil units. Twelve of the fan coil units have thermostats, heating valves, and cooling valves (eight of them have unit-mounted thermostats and the other four have Siemens wall mounted thermostats). The remaining 26 of the fan coil units have wild heating coils and unit manufacturer three-way pneumatic controls with thermostat operators. System diagrams of AHUs and FUs are listed in Appendix A. The chilled water system in the building consists of three loops serving the three types of HVA systems. Each loop has its own pump and flow control valve. The two larger pumps have variable frequency drives controlled by the Energy Management ontrol System (EMS). The third pump that serves the fan coil units is fixed speed. The flow control valves are pneumatically operated under digital control to maintain individual loop differential pressures ( P) and are reset based on the Outside Air Temperature (OAT). All of the loops operate without bypass piping. 2

8 The Arena loop P set point is reset ( Tabled ) based on the OAT. The Arena loop pump is started and stopped based on the average opening of the chilled water control valves on the operating AHU s. The Office loop P set-point is reset ( Tabled ) based on the OAT. The Office loop pump is started and stopped based on the differential pressure versus set point. The Fan oil loop has a fixed speed pump which is started and stopped based on the outside air temperature. A summary of the building pumping system information is shown in Table 3. Unit Table 1 HVA system airflow design information Supply Air Outside Air Flow Service Flow (FM) (FM) AHU A 2 nd Floor Offices & lassrooms 5,400 2,700 AHU B 2 nd Floor Offices 5,470 2,845 AHU 1 st Floor Offices & lassrooms 5,420 2,625 AHU D 1 st Floor Offices & Locker Rooms 4,655 2,328 AHU E 1 st Floor Offices 6,000 3,000 AHU 1 Arena 10,000 0 AHU 2 Arena 10,000 0 AHU 3 Arena 10,000 0 AHU 4 Arena 13,000 3,090 AHU 5 Arena 13,000 3,090 AHU 6 Arena 13,000 3,090 AHU 7 Arena 13,000 3,090 AHU 8 Arena 13,000 3,090 AHU 9 Arena 13,000 3,090 AHU 10 Arena 13,000 3,090 AHU 11 Arena 13,000 3,090 AHU 12 Arena 13,000 3,090 AHU 13 Arena 13,000 3,090 Table 2 Design Specifications of Fan oil Units Type Horsepower ooling Heating GPM GPM FM Quantity 1 1/ / / / / / / /

9 Table 3 G. Rollie White oliseum pumping system information HW System HHW System Zone Arena Office Fan oil Arena Office Fan oil Speed control VFD VFD onstant onstant onstant onstant DP reset Speed control Bldg Valve control Piping system Reset from OAT Modulate to maintain DP set point Modulate to maintain DP set point Two-way without bypass Reset from OAT Modulate to maintain DP set point Modulate to maintain DP set point Two-way without bypass None None None None Fixed Fixed Fixed Fixed Reset from DP Two-way without bypass From Pump Start/Stop Two-way without From Pump Start/Stop Three-way without bypass From Pump Start/Stop Two-way without bypass type bypass GPM HP RPM The lighting system in the building is comprised of T12 lamps in offices and classrooms. 150W incandescent bulbs are used in the sports storage area under the arena seating. There are 149 individual 300W incandescent bulbs in the sports seating area. 3. ontinuous ommissioning Activities 3.1. Existing Building onditions (Pre- ) The existing building retains many of the features from the 1955 design and 1966 modification. The building was last commissioned in At the present time, the Athletic Department is contemplating replacing the building with new facilities in the near future. onsequently, the decision was made to correct the significant deficiencies and identify other opportunities. 4

10 70 7, HW 6,000 HW and HHW onsumption (MMBtu/Day) HHW ELE 5,000 4,000 3,000 2,000 ELE onsumption (KWH/Day) 10 1,000 0 Jul-05 Aug-05 Sep-05 Oct-05 Nov-05 Dec-05 Jan-06 Feb-06 Mar-06 Apr-06 May-06 Jun-06 Month Figure 3 Whole building energy consumptions time series plot The building HW, HHW and ELE consumption data have been obtained from Energy Management Office. Figure 3 is a time series plot of the building energy consumption during the time period from 8/1/2005 to 5/25/2006. The HW consumption is indicative of both weather related loadings and special events. In event mode, the existing control scheme can utilize all 13 units in the arena area if required to maintain comfort in the arena. The chilled water design consumption for these units is 1,195gpm at 13 F T. The HHW consumption is indicative of primarily weather related loadings. The ELE consumption shows a typical pattern for a building with some baseline activities and some scheduled special activities. After the opening of Reed Arena, G. Rollie White has housed fewer special events. However, it is still used for Big 12 Volleyball, some special events related to conferences, and for summer camps. - 5

11 HW HHW HW and HHW onsumption (Btu/Day-Ft 2 ) TOA ( F) Figure 4 HW and HHW consumptions VS outside air temperature Figure 4 is a scatter plot of the building HW and HHW consumptions over the outside air temperature. It can also be identified from the HW consumption pattern that the nonevent mode and the event mode. In event mode, the building HW consumption can be as high as 780 Btu/Day-Ft 2 and in non-event mode. The HW consumption can be as high as 340 Btu/Day-Ft Existing HVA onditions Arena AHUs The arena section of the building has 13 air handling units. Three AHUs in the center of the arena ceiling are 100% recirculation units. The rest of ten are equipped with outside air inlet. However, none of their outside air dampers was functional at the beginning of the investigation. The arena area tested negative. All units were designed and installed with three-way valves on the HW side. On two of the recirculation units, the HW bypass piping has not been valved off. The loop flow control valve also leaks. These factors allow HW to circulate and create a low T on that loop. In turn, this low T adversely affects the T for the whole building (See Table 6 and Table 7 in Appendix B). Additionally, on all thirteen units in the arena, the return air grills, filters, cooling coils, and heating coils were dirty when the study started. This adversely 6

12 affects the building energy performance. This cleaning and filter replacement significantly improves air flow through these units and heat transfer through the coils. Maintaining a clean system will provide better athlete and spectator comfort in the arena. Office and orridor AHUs The office and corridor HW loop has a VFD on the pump and a flow control valve. However, the present scheduling of their operating points permits more pressure on the system than is needed under low load conditions. This creates a low T on this loop. See Table 8 in Appendix B for additional details. The five office and corridor AHUs had no operating outside air systems. The return air grills, filters, cooling coils, and heating coils were dirty. The controlling thermostats were out of calibration. The separate outside air fan and dampers had some bad bearings, missing belts, and bad damper operators. lassroom and Office Units The original design included an uncontrolled ( wild ) heating loop and a unit mounted three-way valve with a built in thermostat to adjust the temperature. Few, if any, of the units are fully functional which allows for frequent simultaneous heating and cooling. Approximately 70% of classroom and office fan coil units had significant operating deficiencies. These deficiencies include heating and/or chilled water piping crimped closed, chilled water control valves that no longer operate, and blower motors that don t operate or operate only on one speed (See Table 9 in Appendix B) Existing omfort onditions The comfort issues in this building include: old and/or hot offices and classrooms. Arena being over cooled when the system was placed in event mode. ondensation on the volleyball floor during high dew point conditions Deferred Maintenance During the process, the following major deferred maintenance issues that closely related to the building energy consumption performances have been observed: The grills and coils of all the AHUs were dirty. This adversely affects AHU air flow rate and coil heat transfer efficiency. 7

13 Outside Air and Return Air dampers of AHU 4 through 13 were not operable. Some of the outside air fans and dampers of AHU A through E were not functional. The thermostats of AHU A through E were out of calibration and potentially cause discomfort in the area they serve. The above deferred maintenance issues have been informed to Area Maintenance, Energy Management Office and Athletic Departments. Majority of the above maintenance issues was found to be resolved during a field follow up work after the work was completed ontinuous ommissioning Measures Several measures were proposed. Some have been implemented but others have not yet been implemented for various reasons. Table 4 is a summary of these measures with a rough estimation of how much each measure would save if implemented. Their implementation will complete this phase of for this building, and will correct the remaining problems with building performance. Table 4 Summary of recommended measures Estimated Estimated Estimated Measure Purpose Annual Payback ost Savings (years) Reset event mode set Improve spectator comfort. $964 $0 0.0 point to 70 F. Blank off HW bypass piping Open arena area dead band to 69 F 77 F. Reduce P set point on Arena HW pump. Reduce P set point on orridor HW pump. Reduce HW flow $1, Reduce the heating and cooling during low occupancy and unoccupied hours. $1,412 $ To reduce over pumping. $2,300 $ To reduce over pumping. $2,110 $ The first recommended measure is to change the Arena area Event Mode temperature set point to 70 F. During non-athletic events the set point could be raised to 72 F. Raising the set point will improve athlete and spectator comfort during athletic events and occupant comfort during non-athletic events. The second recommended measure is to blank off HW bypass piping on AHUs 1 through 3. HW flows through this piping at all times and is not used. It lowers the T for the loop and for the building. This measure has been implemented and only needs insulation installed to complete it. The third recommended measure is to open the Arena area non-event dead band. It will allow the temperature in this area to drift (within limits) and not consume any cooling or heating energy when it is unoccupied or lightly occupied. This will reduce energy 8

14 consumption when the area is not in Event mode. This is a new recommendation which can easily be implemented with building proctor approval. The fourth recommended measure is to reduce the P set point for the Arena HW pump control. The proposed range is 5 to 9 psig (versus the old range of 8 to 12 psig). This measure will maintain adequate pumping for the non-event mode and will not affect the Event mode operation. The fifth recommended measure is to reduce the P set point for the orridor HW pump control. The proposed range is 3 to 14 psig (versus the old range of 5 to 17 psig). This measure will maintain adequate pumping for the corridor and office areas. 4. Requested Actions In order to maximize the performance of the building and its potential energy savings, it is requested that a number of maintenance and controls issues be addressed in the building as soon as possible. Some of the issues that need to be resolved for the building to operate as efficiently as possible include: 1. omplete the repair/replacement of the outside air fan and damper sections for AHU A through E. 2. Repair/replace AHU 8 damper operator as it hangs at mid-stroke 3. onnect AHU 11 damper linkage 4. Repair/replace AHU 12 damper operator to retract fully 5. alibrate the HW return pressure sensor located on loop serving orridor area 6. alibrate the HW return pressure sensor located on loop serving fan coil units 7. alibrate the primary HHW supply and return temperature sensors 8. Blank off the HW bypass piping on AHU 1 and AHU 2 9. Finish the installation of the individual HHW loop temperature and pressure sensors and connect them to the Apogee system 10. Install HW and HHW control valves on the fan coil units plus a thermostat or install new fan coil units complete with controls 11. Update the P set point schedule of the HW pump serving Arena area 12. Update the P set point schedule of the HW pump serving Office/orridor area 9

15 5. Building omfort Improvements One of the primary objectives of is to improve occupant comfort levels in buildings. As noted, some of the major comfort issues that this building experienced before commissioning were cold/hot offices and classrooms and spectator discomfort during events in the coliseum. The cold/hot offices and classrooms have been addressed to the degree possible by work done on AHUs A through E. The controlling thermostats have been calibrated which improves response to changing conditions. Spectator comfort has been addressed by improving the operation of the 13 AHUs in the Arena area. Return grills and coils have been cleaned and filters changed which improved air flow and makes better use of the chilled water and heating water. Outside air and return air dampers are now operating and adjusted for shut-off. The Event Mode space temperature set point is now 72 F, which will improve comfort. These improvements were accomplished by a cooperative effort of the Energy Office, AM3, and the staff from Energy Systems Lab. 6. Savings Analysis At this point in the commissioning process, post- data is unavailable and thus savings cannot be determined. These values will be given at a later date by the ESL data analysis group. 7. Retrofit Recommendations Retrofit Measure Install two way valves on the old Fan oil Units. Install VFD controls on the Fan oil Unit HW and HHW pumps. Upgrade AHU A-E to DD ontrol. Table 5 Summary of proposed retrofit measures Estimated Purpose Annual Savings To better meet actual space needs and reduce simultaneous usage. If two way valves are installed then pump speed must match the load. Improve scheduling and reset capability. Estimated ost Simple Payback $14,768 $27, $759 $10, $6,000 1 $22, Upgrade to T8 from current T12 tubes. More efficient lighting. $14,900 1 $131, Replace watt Equal lighting at lower energy incandescent bulbs with usage. compact fluorescents. $55 2 $ Replace watt Equal (or better) lighting at incandescent bulbs with lower energy usage. compact fluorescents. $5,695 $5, Install interior insulating Reduce air leakage to/from the windows. outside. $4,482 $45, Note: 1 - Per ERIA 8/15/05 10

16 2 - Excludes reduced labor from longer life 3 - Excludes labor cost 4 - Includes one time charge for adapter Table 5 summarizes several retrofit options to improve occupant comfort and reduce energy consumption. The summary gives a rough estimation of the savings and cost for each measure. The first proposed measure is to install thermostatically controlled two-way valves on both the cooling coils and heating coils in the old-style fan coil units. At present the heating coils are uncontrolled and few (or none) of the cooling coil valves are operating. This measure will match the classroom or office space heating or cooling to what is required to meet university mandated comfort levels. When this issue is addressed, consideration should be given to replacing the entire FU with a new one if adequate funding is available. The second proposed measure is to install VFD controls on chilled water and heating hot water pumps serving fan coil units. These are presently fixed speed pumps suitable for uncontrolled loops or loops with three-way valves. If the fourth measure is implemented then loop flow/pressure control of some sort will be needed. The most energy efficient method is VFD control of the pumps. This will reduce pump energy consumption to only that needed to satisfy the coils calling for cooling or heating. This measure has not yet been implemented pending installation of two-way valves on the Fan oil Units. The third proposed measure is to upgrade the controls on AHUs A through E to DD controls. Implementing this measure will allow scheduling these units to run only when needed and allow reset of control point to better match capacity to requirements. This measure was first proposed in the August 15, 2005, ERIA Report. The fourth proposed measure is to convert the existing fluorescent lighting fixtures from T12 to T8 tubes and fixtures. This measure will maintain adequate lighting levels while reducing electrical power consumption. It was first proposed in the August 15, 2005, ERIA Report. The fifth proposed measure is to replace 14 existing 150-watt incandescent light bulbs in the storage areas under the seating with 40-watt fluorescent compact, screw-in tubes. These compact devices provide equivalent light output with much lower input. They have a much longer service life than incandescent bulbs, too. Replacing the 150 watt devices will reduce electric power consumption and replacement labor cost for these areas in the building. The sixth proposed measure is to replace 149 existing mogul base 300-watt incandescent light bulbs in the oliseum seating area with 85-watt compact, screw-in fluorescent tubes. These compact devices provide equivalent light output with much lower power input. They have a much longer service life than incandescent bulbs, too. This measure will result in a well-lighted seating area with lower power consumption and lower labor costs. 11

17 The last of the proposed measures is to install interior insulating windows. This measure will reduce air leakage to and from the outside. It will improve comfort conditions in a number of offices and classrooms. In addition, it will reduce energy consumption for heating and cooling in all of the affected spaces. 8. onclusions The G. Rollie White oliseum has been a part of the A&M system since Energy consumption concerns and comfort problems in the building made it a good candidate for. The process was performed in a period of three months. It is believed that the measures implemented to this time will save on energy costs and/or improve comfort in the building. If the proposed measures shown in Table 4 and Table 5 are implemented, it is estimated that over $55,000 per year can be saved, and the remaining comfort issues can be resolved. With the estimated total cost of $242,000, the simple payback is about five years. Better energy efficiency will occur in the building, as well as an increase in the productivity of occupants who will be more comfortable in their working environment. A number of issues have been identified that need to be addressed in order that the proposed measures be able to be implemented. It is highly recommended that the proposed measures be implemented to maximize energy savings and improve comfort levels in the building. In this way, the Texas A&M University campus can move forward in its quest for energy efficiency, and the process will have been beneficial in aiding in this endeavor. 12

18 9. Appendices Appendix A: AHUs and FUs Diagrams Filter Supply Air Fan RA R H Discharge Figure A - 1 System diagram of AHU 1-3 Fresh Air RA Damper Filter R H Supply Air Fan Discharge Figure A - 2 System diagram of AHU 4-13 Fresh Air with Damper and Fan RA Mechanical Room Plenum Filter R H Supply Air Fan Discharge Figure A - 3 System diagram of AHU A-E Filter Supply Air Fan RA H Discharge T Figure A - 4 System diagram of FUs (new style) 13

19 Appendix A: AHUs and FUs Diagrams (continued) Filter Supply Air Fan RA H Discharge Figure A - 5 System diagram of FUs (old style) 14

20 Appendix B: HW and HHW Pumping System Survey Data Date OAT ( F) Table 6 Field measurement of building primary loops hilled Water Heating Hot Water Supply Return Supply Return T Flow T Temp. Temp. Temp. Temp. ( F) (GPM) ( F) ( F) ( F) ( F) ( F) Flow (GPM) 1/5/ /5/ /6/ /6/ /9/ /9/ Pumps off NA 1/12/06 OPER /13/06 OPER /17/ /18/ /20/06 NA NA NA NA 2/1/ /1/ /6/ /6/ NA /7/ /7/ Average T ( F)= 3.87 Average T ( F)= Table 7 Zone 1 Arena units HW loop readings Date Temperature ( F) Pressure (psi) Valve Pump Supply Return T Supply Return P Pos. (%) Status 1/5/ OFF 1/5/ OFF 1/6/ OFF 1/9/ OFF 1/9/ OFF 1/12/ OFF 1/13/ OFF 1/17/ OFF 1/18/ OFF 1/20/ V 2/1/ V 2/1/ V 2/6/ V 2/6/ V 2/7/ V 2/7/ V 15

21 Appendix B: HW and HHW Pumping System Survey Data (continued) Table 8 Zone 2 Office/corridor HW loop readings Date Temperature ( F) Pressure (psi) Valve Pump Supply Return T Supply Return P Pos. (%) Status 1/5/ ON 1/5/ ON 1/6/ V 1/6/ V 1/9/ V 1/9/ V 1/12/ V 1/13/ V 1/17/ V 1/18/ ON 1/20/ V 2/1/ V 2/1/ V 2/6/ V 2/6/ V 2/7/ V 2/7/ V Table 9 Zone 3 Fan coil unit HW loop readings Date Temperature ( F) Pressure (psi) Valve Pump Supply Return T Supply Return P Pos. (%) Status 1/5/ ON 1/5/ ON 1/6/ ON 1/6/ ON 1/9/ ON 1/9/ OFF 1/12/ OFF 1/13/ OFF 1/17/ OFF 1/18/ ON 1/20/ OFF 2/1/ ON 2/1/ ON 2/6/ ON 2/6/ ON 2/7/ ON 2/7/ ON 16