vav-ahu variable static pressure control and constant ... · pdf filevav-ahu variable static...

© 2007 Matrix Controls Pte Ltd

VAV-AHU Variable Static Pressure Control

And Constant Static Pressure Control

Comparison Test Report

Version 1.0

VAV-AHU Variable Static Pressure Test Report Version 1.0

Matrix Controls Pte Ltd i

Revision History

Version Description Prepared by Date Version 1.0 Create this report base on 4 weeks testing data Fan Jinsong 17 Nov. 2007


Matrix Controls Pte Ltd ii

Contents

1 DESCRIPTION....................................................................................................1

2 TESTING DATA AND TREND GRAPHIC.....................................................2 2.1 Supply Air Fan Power Consumption Comparison.........................................2 2.2 AHU Trend Graphic Summary......................................................................3 2.3 VAV Boxes Trend Graphic ...........................................................................5

3 CONCLUSIONS ..................................................................................................9

4 REFERENCE:....................................................................................................10 4.1 AHU Trend Graphic ....................................................................................10

4.1.1 Constant Static Pressure Control ..............................................10 4.1.2 Variable Static Pressure Control ...............................................25

4.2 Ambient Air Temperature Trend Graphic ...................................................37

Tables Table 1 Testing AHU.....................................................................................................1 Table 2 AHU-3-2-2 Supply Air Fan Power Consumption Comparison........................2 Table 3 Summary of AHU Trend Graphic ....................................................................3 Table 4 Summary of AHU Trend Graphic (Cont') ........................................................4 Table 5 VAV-3-2-2-1 ~7 Space Temperature Trend Graphic.......................................5 Table 6 VAV-3-2-2-1 ~7 Space Temperature Trend Graphic (Cont’) ..........................6 Table 7 VAV-3-2-2-8 ~10 Space Temperature Trend Graphic.....................................7 Table 8 VAV-3-2-2-8 ~10 Space Temperature Trend Graphic (Cont’) ........................8 Table 9 Ambient Air Temperature Trend ....................................................................37 Table 10 Ambient Air Temperature Trend (Cont') ......................................................38


Matrix Controls Pte Ltd 1

1 Description In VAV-AHU system the most energy efficiency control logic for supply air fan speed control is variable static pressure control strategy that modulates fan speed to fulfill total airflow demand from all serving VAV terminal boxes. This comparison testing report shows how much fan power energy can be saved comparing with traditional constant static pressure control.

Table 1 Testing AHU

AHU AHU-3-2-2

Location 2nd floor of Li Ka Shing Library in Singapore Management University (SMU)

Controller Matrix Controls LonWorks® Variable Pressure Regulator DDC UVP0000L

Communication Network LonWorks Network. Terminal Quantity 10 VAV boxes

AHU Configuration Static Pressure set point: 150Pascal Supply Air Temperature Set point: 14°C Constant Static Pressure Control: 17 Oct. 2007 ~ 31 Oct. 2007, 15 days Testing Date Variable Static Pressure Control: 2 Nov. 2007 ~ 13 Nov. 2007, 12 days

Testing location is shown in picture below. Red block is the location of testing AHU-3-2-2, and blue dots are the location of 10 VAV boxes severed by AHU-3-2-2. This area is at north side of building. In sunny afternoon, sunlight will shine in this area through windows. Cooling demand will be significantly changes with time throughout the day, and differes day-by-day.



2 Testing Data and Trend Graphic

2.1 Supply Air Fan Power Consumption Comparison

Table 2 AHU-3-2-2 Supply Air Fan Power Consumption Comparison

S/N Date Start Time End Time Running

Hours

Daily Consumption

(KWH)

Total Consumption

(KWH)

Hourly Average (KWH)

Daily Average (KWH)

Daily Saving

(%)

Hourly Saving

(%) Constant Static Pressure Control (Ps= 150 pa)

1 17-Oct-2007 7:30 0:00 16.5 28 2 18-Oct-2007 7:30 0:00 16.5 31 3 19-Oct-2007 7:30 0:00 16.5 28 4 20-Oct-2007 8:30 17:00 8.5 18 5 21-Oct-2007 13:00 21:00 8.0 30 6 22-Oct-2007 6:30 0:00 17.5 37 7 23-Oct-2007 6:30 0:00 17.5 33 8 24-Oct-2007 6:30 0:00 17.5 30 9 25-Oct-2007 6:30 0:00 17.5 31

10 26-Oct-2007 6:30 0:00 17.5 34 11 27-Oct-2007 7:30 17:00 9.5 20 12 28-Oct-2007 13:00 21:00 8.0 26 13 29-Oct-2007 6:30 0:00 17.5 33 14 30-Oct-2007 6:30 0:00 17.5 30 15 31-Oct-2007 6:30 0:00 17.5 28 subtotal: 223.5

437 1.96 29.1

Variable Static Pressure Control 1 2-Nov-2007 7:30 0:00 17.5 17 2 3-Nov-2007 7:30 17:00 9.5 11 3 4-Nov-2007 13:00 21:00 8.0 18 4 5-Nov-2007 6:30 0:00 17.5 25 5 6-Nov-2007 6:30 0:00 17.5 20 6 7-Nov-2007 6:30 0:00 17.5 21 7 8-Nov-2007 6:30 0:00 17.5 10 8 9-Nov-2007 6:30 0:00 17.5 16 9 10-Nov-2007 7:30 17:00 9.5 9

10 11-Nov-2007 13:00 21:00 8.0 14 11 12-Nov-2007 6:30 0:00 17.5 19 12 13-Nov-2007 0:00 0:00 24.0 19

180 0.99 15.0

48.5% 49.3%

subtotal: 181.5 617



2.2 AHU Trend Graphic Summary

Refer to reference section to see detail trend graphic.

Table 3 Summary of AHU Trend Graphic

(Red: Static Pressure, Blue: Fan VSD Output, Brown: Power Rate)

22 Oct. 2007 29 Oct 2007

5 Nov 2007 12 Nov 2007

23 Oct 2007 30 Oct 2007

6 Nov 2007 13 Nov 2007

17 Oct 2007

24 Oct 2007 31 Oct. 2007

7 Nov 2007



Table 4 Summary of AHU Trend Graphic (Cont')

(Red: Static Pressure, Blue: Fan VSD Output, Brown: Power Rate) 18 Oct 2007

25 Oct 2007

8 Nov 2007

19 Oct 2007

26 Oct 2007 2 Nov 2007

9 Nov 2007

20 Oct 2007

27 Oct 2007 3 Nov 2007

10 Nov 2007

21 Oct 2007

28 Oct 2007 4 Nov 2007

11 Nov 2007



2.3 VAV Boxes Trend Graphic

Table 5 VAV-3-2-2-1 ~7 Space Temperature Trend Graphic

22 Oct. 2007 29 Oct 2007

5 Nov 2007 12 Nov 2007

23 Oct 2007 30 Oct 2007

6 Nov 2007 13 Nov 2007

17 Oct 2007

24 Oct 2007 31 Oct. 2007

7 Nov 2007



Table 6 VAV-3-2-2-1 ~7 Space Temperature Trend Graphic (Cont’)

18 Oct 2007

25 Oct 2007

8 Nov 2007

19 Oct 2007

26 Oct 2007 2 Nov 2007

9 Nov 2007

20 Oct 2007

27 Oct 2007 3 Nov 2007

10 Nov 2007

21 Oct 2007

28 Oct 2007 4 Nov 2007

11 Nov 2007



Table 7 VAV-3-2-2-8 ~10 Space Temperature Trend Graphic

22 Oct. 2007 29 Oct 2007

5 Nov 2007 12 Nov 2007

23 Oct 2007 30 Oct 2007

6 Nov 2007 13 Nov 2007

17 Oct 2007

24 Oct 2007 31 Oct. 2007

7 Nov 2007



Table 8 VAV-3-2-2-8 ~10 Space Temperature Trend Graphic (Cont’)

18 Oct 2007

25 Oct 2007

8 Nov 2007

19 Oct 2007

26 Oct 2007 2 Nov 2007

9 Nov 2007

20 Oct 2007

27 Oct 2007 3 Nov 2007

10 Nov 2007

21 Oct 2007

28 Oct 2007 4 Nov 2007

11 Nov 2007



3 Conclusions

1) Variable Static Pressure control can use least supply air fan energy to satisfy air-con space heat demand.

2) It saves 48% fan energy to use variable static pressure control compare with using constant static pressure control. Constant static pressure control wastes much energy maintaining static pressure.

3) Most energy consumption period is at first 2 to 3 hours after AHU operating. During this period system, energy is used mainly to remove the heat accumulated during AHU non-operation period. Rest of time, the energy is used to balance dynamic cooling demand. On 12 and 13 Nov 2007, the AHU operated continuously. Even if it operated 24 hours on 13 November the fan power consumption is still same as previous day on 12 Nov that only operated 17.5 hours. Although it only operated half the time of normal weekdays on Sunday, its power consumption is quite high. Air conditioned space accumulated much more heat during long non-operation time (around 20 hrs compare with 6.5 hours on weekdays) between Saturday and Sunday.

4) Matrix Controls Variable Static Pressure Regulator can remove accumulated heat efficiently using low power consumption.

5) Another advantage of using variable static pressure control is that there is no need to worry about pressure sensor installation location and static pressure set point selection. It’s not an easy task to select a proper location to install static pressure sensor and give a correct set point value during commission AHU. Normally the duct pressure sensor reading will always fluctuate heavily especially at high-pressure location or installed at incorrect location in duct. It will increase difficulties for controller to maintain pressure properly. If controller can’t process fluctuating static pressure reading properly, it will waste much energy to maintain pressure properly because of unstable control. We need not worry about these issues to use Matrix Controls Variable Static Pressure Regulator (VPR) controller. It is even possible to go without installing any static pressure sensor in the VAV AHU duct. VPR modulates supply air fan speed directly according to total airflow demand from all VAV boxes served by AHU.

6) Referring to the ambient air temperature trend data; heat gain in this area with large glass windows highly varies with outdoor ambient air temperature and sunlight. Variable static pressure controller can adapt to such situations dynamically and efficiently to lower energy consumption.

7) Possible energy saving per year: (refer to table 2) We note that this AHU operates 105 hrs on average every week (Weekdays 17.5 hrs x 5 + Saturday 9.5hrs + Sunday 8hrs) per week. Every hour saves 0.97KWH (=1.96-0.99). 52 weeks per year. Energy savings = 0.97 x 105 x 52 = 5296.2 KWH $ savings = 5296.2 x S$0.20 = S$1059.24 $ savings = 5296.2 x S$0.15 = S$ 794.43 At the lower tariff or $0.15 that SMU gets, and at a cost of $1260 per AHU, this AHU will earn back its VPR install cost in 1.586 years, slightly more than eighteen months. Larger AHU will likely earn back in close to one year or even less than a year.



4 Reference: 4.1 AHU Trend Graphic 4.1.1 Constant Static Pressure Control

(Red: Static Pressure, Blue: Fan VSD Output, Brown: Power Rate)

17 Oct 2007, Wed, Running 16.5Hrs, Power Consumption: 28KWH, Constant Static Pressure Control (Ps=150Pa)



18 Oct 2007, Thu, Running 16.5Hrs, Power Consumption: 31KWH, Constant Static Pressure Control (Ps=150Pa)



19 Oct 2007, Fri, Running 16.5Hrs, Power Consumption: 28KWH, Constant Static Pressure Control (Ps=150Pa)



20 Oct 2007, Sat, Running 8.0Hrs, Power Consumption: 18KWH, Constant Static Pressure Control (Ps=150Pa)



21 Oct 2007, Sun, Running 8.5Hr, Power Consumption: 30KWH, Constant Static Pressure Control (Ps=150Pa)



22 Oct 2007, Mon, Running 17.5Hr, Power Consumption: 37KWH, Constant Static Pressure Control (Ps=150Pa)



23 Oct 2007, Tue, Running 17.5Hr, Power Consumption: 33KWH, Constant Static Pressure Control (Ps=150Pa)



24 Oct 2007, Wed, Running 17.5Hr, Power Consumption: 30KWH, Constant Static Pressure Control (Ps=150Pa)



25 Oct 2007, Thu, Running 17.5Hr, Power Consumption: 31KWH, Constant Static Pressure Control (Ps=150Pa)



26 Oct 2007, Fri, Running 17.5Hr, Power Consumption: 34KWH, Constant Static Pressure Control (Ps=150Pa)



27 Oct 2007, Sat, Running 9.5Hr, Power Consumption: 20KWH, Constant Static Pressure Control (Ps=150Pa)



28 Oct 2007, Sun, Running 8.0Hr, Power Consumption: 26KWH, Constant Static Pressure Control (Ps=150Pa)



29 Oct 2007, Mon, Running 17.5Hr, Power Consumption: 33KWH, Constant Static Pressure Control (Ps=150Pa)



30 Oct 2007, Tue, Running 17.5Hr, Power Consumption: 30KWH, Constant Static Pressure Control (Ps=150Pa)



31 Oct 2007, Wed, Running 17.5Hr, Power Consumption: 28KWH, Constant Static Pressure Control (Ps=150Pa)



4.1.2 Variable Static Pressure Control (Red: Static Pressure, Blue: Fan VSD Output, Brown: Power Rate)

2 Nov 2007, Fri, Running 17.5Hr, Power Consumption: 17KWH, Variable Static Pressure Control



3 Nov 2007, Sat, Running 9.5Hr, Power Consumption: 11KWH, Variable Static Pressure Control



4 Nov 2007, Sun, Running 8.0Hr, Power Consumption: 18KWH, Variable Static Pressure Control



5 Nov 2007, Mon, Running 17.5Hr, Power Consumption: 25KWH, Variable Static Pressure Control



6 Nov 2007, Tue, Running 17.5Hr, Power Consumption: 20KWH, Variable Static Pressure Control



7 Nov 2007, Wed, Running 17.5Hr, Power Consumption: 21KWH, Variable Static Pressure Control



8 Nov 2007, Thu, Running 17.5Hr, Power Consumption: 10KWH, Variable Static Pressure Control



9 Nov 2007, Fri, Running 17.5Hr, Power Consumption: 16KWH, Variable Static Pressure Control



10 Nov 2007, Sat, Running 9.5Hr, Power Consumption: 9KWH, Variable Static Pressure Control



11 Nov 2007, Sun, Running 8.0Hr, Power Consumption: 14KWH, Variable Static Pressure Control



12 Nov 2007, Mon, Running 17.5Hr, Power Consumption: 19KWH, Variable Static Pressure Control



13 Nov 2007, Tue, Running 24.0Hr, Power Consumption: 19KWH, Variable Static Pressure Control



4.2 Ambient Air Temperature Trend Graphic

Table 9 Ambient Air Temperature Trend

22 Oct. 2007 29 Oct 2007

5 Nov 2007 12 Nov 2007

23 Oct 2007 30 Oct 2007

6 Nov 2007 13 Nov 2007

17 Oct 2007

24 Oct 2007 31 Oct. 2007

7 Nov 2007



Table 10 Ambient Air Temperature Trend (Cont')

18 Oct 2007

25 Oct 2007

8 Nov 2007

19 Oct 2007

26 Oct 2007 2 Nov 2007

9 Nov 2007

20 Oct 2007

27 Oct 2007 3 Nov 2007

10 Nov 2007

21 Oct 2007

28 Oct 2007 4 Nov 2007

11 Nov 2007

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