Experiences with Secondary Loop Systems

1
Experiences with Secondary Loop Systems

• Cynthia Gage
• US Environmental Protection Agency
• Office of Research and Development
• Acknowledgments
• Karolin Engsten, Jenny Lindh - Royal Institute of
  Technology
• David De Boer South Coast Air Quality
  Management District

ASHRAE February 6, 2005
2
Outline

• Data from the U.S.
• Direct expansion (DX)
• Comparative data from Sweden study
• DX and secondary loops (indirect)
• Experiences of supermarket chains in North
  America
• Medium temp secondary loop

3
Data from Southern California

• Biannual reporting of CFC and HCFC usage in
  facilities containing gt 22.7 kg
• In 2000 and 2001, 233 grocery stores responded
  representing about 1200 refrigeration systems
• Single condensing units and centralized direct
  expansion (DX) systems
• Charge size, refrigerant type, and refrigerant
  usage reported
• 5 of reported systems contained HFCs
• Average emission rate of 8-9.

4
Percentage of Systems with No Usage
5
Average Annual Emission Rates
6
Systems Requiring Refrigerant Both Years
7
Swedish Supermarkets

• Study of about 450 stores in six regions of
  Sweden (excluded hypermarkets)
• Yearly data from 1996 to 2003
• Factors investigated
• Refrigerant type
• Store and system charge sizes
• Refrigerant leak rate
• Two companion studies using smaller subset
• Comparison between high and low leakers
• Location of leaks

8
Refrigerant charge (kg) per system

• Stores have phased-out of CFCs and HCFCs. (In
  2003 only 4 are R22.)
• High leakage stores
• Average leakage 43.4 of charge/yr
• 1 to 2 DX systems per store
• Low leakage stores
• Average leakage lt2 of charge/yr
• 5 to 6 indirect (secondary loop) systems per store

9
Other Conclusions (Swedish study)

• Estimated average leak rate in Sweden 10 of
  charge/yr
• 40-50 of stores had no leaks
• 20 of stores account for 70-80 of total losses
• No significant differences in sites for
  refrigerant leakage in DX and indirect systems
• 50 of existing stores are indirect
• New installations are either partially or fully
  indirect
• Secondary to cases and secondary to condenser

10
North America Chain A

• Comparison of selected DX and SL stores
• Net maintenance expenses 12 lower for SL stores
• Refrigerant use 88 lower for SL stores
• Cost savings of 26 due to higher cost of HFCs
• For secondary fluid usage
• 80 of stores required some fluid recharge
• Glycol stores had significantly fewer fluid leaks
  compared to brine stores

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North America Chain B

• Less than 20 stores
• First installation was in a remodel 5 years ago
• 35 have secondary loop on medium temp
• One refrigerant leak due to compressor vibration
• Small drips on secondary fluid side
• Added less than 50 gallons total
• Financial impact
• Capital cost about 10 higher
• Installation costs about 10 higher attributed
  to lack of experience in installation
• Significantly fewer service calls for both system
  and cases

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North America Chain C

• Operates about 1000 stores
• 5 years experience of secondary loop on medium
• 5 of stores are secondary
• Compared to a DX medium temp
• 60-70 reduction in initial refrigerant charge
• 75 reduction in refrigerant losses
• Charge is better contained, and charge size is
  smaller
• Financial impacts
• Capital costs are higher, but dropping
• 40-50 savings in maintenance costs
• Set it and forget it

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Summary Observations

• Favorable ratings for secondary loops
• Two chains reported better product quality
• Less shrinkage higher coil operating temp
• Longer shelf life even temp distribution
• Bottom line
• Most continue to install secondary loop for
  medium temp
• Working to reduce initial cost
• Secondary on low temp?
• Concerns about gasket and corrosion problems with
  brines
• Some beginning to experiment