Refrigeration

Commercial refrigeration systems account for a large percentage of a facility's total energy consumption, especially in supermarkets, restaurants and cafeterias. The total energy used depends primarily upon the "produce" load, the distribution or "parasitic" load, and the seasonal efficiency of the compressor. The following are several energy-saving opportunities.

Set Usage Guidelines

The following sample usage guidelines can help you save energy.

1. Use night covers over cold products. Be careful to avoid compressor damage or frost build-up on products.

2. When not in use, turn off refrigeration for cutting rooms, prep rooms, and some display fixtures, such as meat cases. Put appropriate food products in coolers, where possible.

3. Keep return grilles of fixtures clear of stacked products.

4. Automatically shut off all prep rooms at night and weekends. Set up for automatic startup when required.

5. For multi-shelf fixtures, follow manufacturers' recommendations for shelf position and size to prevent increased refrigeration loads.

6. Avoid setting pressure and temperature controls any lower than necessary.

7. Keep products below clearly marked load lines. An over-loaded display case increases energy use by as much as 10 to 20% for each fixture.

8. Repack product displays and keep them below load lines throughout the day.

9. Do not permit refrigerated products to stand in the aisles, on docks, or any place where they will warm up and create an additional refrigeration load when placed in fixtures. Reduce the volume of items requiring cold storage.

10. Consider reducing or eliminating internal shelf lights.

11. Consider unloading meat and produce displays and then shutting off refrigeration at night and weekends. Set a timer to automatically turn off at closing and on in the morning.

12. Where possible, construct a tight partition or hang a heavy drape from roof to floor between sales and storage area. Maintain storage areas at 60°F or lower in winter, to prevent interchange of air.

Improving Operations and Maintenance

With good O&M practices, you can save energy. Here are some energy-saving tips:

1. Clean display fixtures and cooler coils regularly.

2. Replace worn refrigeration seals.

3. Check all electrical circuits for power leak to ground. A leak to the ground may be small enough to go undetected for years with substantial accumulated loss of energy.

4. Check all systems for correct refrigerant charge to avoid excessive compressor operation. Shortages usually will show up when low ambient air conditions exist.

5. Check all fixtures of multi-shelf low temperature equipment for inoperative fan motors.

6. If refrigeration load is decreased, as by lighting, use reductions or case cleaning, recheck temperature pressure control settings to avoid freezing of products or short cycling of compressors. Enforce closed door rules when case is not in use, even for short periods of time.

7. Most storage coolers are well insulated and have little difficulty at night maintaining temperatures when there is little traffic. Depending on the merchandise, the thermostat might be set to 45-50°. You might even be able to turn the unit off at night if 50°F could be tolerated for a few hours.

8. Redirect outlets that are discharging into refrigerated fixtures.

9. Minimize head pressure by increasing air supply over the condenser to increase compressor capacities and reduce energy use.

10. Clean condenser coils regularly. Maintain lowest head pressure at which the commercial refrigeration system can operate without short-cycling or impairing expansion valve and coil efficiency.

11. In cool months, set heat pressures with controls. Adjust hold back valves to control condenser surface to lowest possible head pressure. Set fan cycling with small differential and low cut-in point. Where more than one fan is used, consider cycling one or more fans.

12. To prevent pressure drop and loss of compressor capacity, avoid using suction line controls.

13. It may be possible to insulate the suction and liquid lines together to increase efficiency, except where not recommended.

14. On forced defrost systems (electric or hot gas), use a defrost-terminating thermostat on each fixture to avoid over-defrosting individual fixtures. Bring the compressor back on as soon as all fixtures are satisfied.

15. Consider demand frost for all types of defrost systems. The number of defrosts is normally set up for the most adverse store conditions which occur in a year. These conditions usually exist for only short periods of the year. Demand defrost compensates for these periods by causing fixtures to defrost only when required. Consult the fixture manufacturer before specifying demand defrost.

16. For systems where produce is required at 32 °F or above, use time defrost rather than an added heat source. With existing equipment, disconnect the heater and rest the controls. Energy will be saved because the compressor does not operate and no electricity is used for defrost heaters.

17. Consider separate wiring circuits for anti-condensate heaters. These heaters operate 24x7x365, and are big energy users. Heaters are only required when humidity is high. Be aware, however, that most existing installations have fan and anti-condensate heaters on the same circuit. Do not turn off the fan. Consider eliminating incandescent lighting over top display meat cases.

18. Where possible, provide staged cooling controls. Consider replacing one large compressor and coil with two or more circuits. Where possible, consider removal of hot gas bypass capacity control.