Floating Head Pressure for Refrigeration Single Compressor Systems

1. Floating Head Pressure for Refrigeration Single Compressor Systems Michele Friedrich, PE – Sr. Engineer Dustin Bailey – Engineer PECI 11/2/2010

2. Acknowledgements We would like to thank the following for their support: Avista Utilities Bonneville Power Administration Puget Sound Energy RTF refrigeration subcommittee

3. Purpose Approval for new deemed measures for floating head pressure on refrigeration single compressor systems

4. Agenda Proposed Measures Technology Overview Calculation Methodology Cost Effective Useful Life Market Potential Program Specifications Program Summary

5. Proposed Measures Measure Application Energy Savings (kWh/yr-HP) EUL (yr) Measure Cost ($/HP ) Benefit Cost Ratio Floating head Pressure Single- Med Temp Condensing Unit 757 15 307.51 2.6 Floating head Pressure Single- Low Temp Condensing Unit 855 15 270.76 3.4 Floating head Pressure Single- Med Temp Remote Condenser 473 15 206.73 2.4 Floating head Pressure Single- Low Temp Remote Condenser 685 15 157.34 4.6

6. Technology Overview Current measure for FHP on multi-plex systems excludes single compressors. Two types of Single Compressor systems: Condensing Units (~85-90%) & Remote Condensers. Allows condenser to operate at a lower temp. and pressure depending on ambient conditions. Lower condenser temperature = less compressor work due to lower compression ratio.

7. Head Pressure Control

8. Technology Overview Refrigeration System Diagram

9. Technology Overview This measure requires using adjustable head pressure control valve which is adjusted to equivalent pressure of 70F saturation. Replaces fixed valve set at 180 psig by factory (~94.3F for R22). Expansion valve is retrofitted to balanced port valve or a device is installed to supplement refrigerant feed at lower condensing pressures.

10. Calculation Methodology • eQUEST model • Set at “typical” specifications for convenience store refrigeration system. • Condensing Unit modeled as 1 compressor and 1 condenser with fan ON when compressor is ON. Min Condensing P set by flood-back control valve (head pressure control valve). • Remote Condenser modeled as 4 compressors and 4 fans that are controlled to come ON staged with Outside Air Temperature (OAT). Minimum Condensing P set by flood-back control valve (head pressure control valve).

11. Calculation Methodology • eQUEST model • Conduct sensitivity analysis for each type of Single Compressor system: Condensing Unit and Remote Condenser. • Condensing Unit highest sensitivity to Compressor efficiency and Compressor/condenser over-sizing (split into LT and MT before sensitivity analysis). • Remote Condenser highest sensitivity to condenser set point and suction temperature.

12. Calculation Methodology Presented to RTF refrigeration subcommittee for direction and input. Condensing Set Point: fixed head pressure control valve set at factory to 180 psig +/- 5 psig. For R22 this is 94.3oF +/- 1.8oF. Assume that there are as many at – 5 psig as at +5 psig. Suction Temperature: Split into LT and MT measures Compressor/Condenser over sizing: used refrigeration schedules for single compressor systems to find median value of compressor and condenser over sizing

13. Calculation Methodology Weighted for compressor motor efficiency for Condensing units by weighting by motor size (efficiency a function of size for 0.5 HP to 7.5 HP). Motor size from GrocerSmart database audits in PNW for single compressor systems. Weighted for climate zone (different savings for east vs. west side of cascades) using store population in GrocerSmart in PNW. Remote Condenser picked 1 HP fans (0.5 HP fans are quieter, 1.5 HP fans are cheaper: designers pick in between.) Picked # fans per condenser from catalogue after condenser size was found. Refrigeration schedule review median value for # fans was 3.5.

14. Cost • $164.64 per evaporator • Balance Port Valve and labor • $585.55 per condenser • Adjustable head pressure valve, filter drier, bypass valve and labor. • Unknown extended life on compressor from lower operating hours. *Cost data from Grainger, Sporlan and HVAC/R wholesaler

15. Effective Useful Life 15 years Same as FHP on Multiplex. Equipment life = 15 years.

16. Market Potential 100% penetration of PNW GrocerSmart audited stores with Single Compressors = 1.8 aMW

17. Program Specifications • Install adjustable head pressure control valve (flood-back control valve) to lower minimum condensing head pressure. Field calibrated to pressure equivalent of 70 F saturated temperature or lower using NIST certified calibration of +/- 5 PSIpressure gauge or transducer. • Measure applicable only to refrigeration systems having single compressor systems of 1 HP motor or larger either in condensing unit or in remote condenser. • Must install either balanced-port valve or EEV that is sized to meet the load requirement at 70 degree condensing temperature, if not currently installed, or install device to supplement refrigerant feed to each evaporator attached to condenser that is reducing head pressure.

18. Summary

19. Summary

20. Summary

21. Proposed Measures Measure Application Energy Savings (kWh/yr-HP) EUL (yr) Measure Cost ($/HP ) Benefit Cost Ratio Floating head Pressure Single- Med Temp Condensing Unit 757 15 307.51 2.6 Floating head Pressure Single- Low Temp Condensing Unit 855 15 270.76 3.4 Floating head Pressure Single- Med Temp Remote Condenser 473 15 206.73 2.4 Floating head Pressure Single- Low Temp Remote Condenser 685 15 157.34 4.6