The potential for conserving energy and thereby reducing energy costs associated with commercial refrigeration systems will vary with each application. The followng information on energy savings estimates is provided by Arizona Public Service (APS), Arizona's largest and oldest electricity utility. Commercial refrigeration contractors can use this information, and the energy savings estmates, when counseling store customers to improve system efficiencies.
High-efficiency evaporator fan motors. These small fans are typically less than one-tenth horsepower. A grocery store can have hundreds of them, so their energy consumption can be significant. Specifying high-efficiency motors for evaporator fans is almost always a good investment, and they can also be implemented on a retrofit basis. Energy savings are estimated to be about 2% of refrigeration system electricity use for reach-in freezers, 7% for reach-in refrigerators, 8% for grocery store display cases, 5% for ice machines, 14% for vending machines, and 29% for beverage merchandisers.1
High-efficiency condenser fan motors. Specifying high-efficiency motors on condenser fans is also a good idea. System energy savings estimates are in the 3% to 5% range. High-efficiency compressor systems. Energy savings potential for high-efficiency compressors are estimated to be 6% for ice machines, 9% for vending machines and beverage merchandisers, 12% for reach-in refrigerators, and 16% for reach-in freezers.
Floating head pressure controls. Floating head pressure controls allow compressor head pressures to vary with outdoor conditions. This saves energy dollars and helps refrigeration equipment to last longer. Floating head pressure controls are often standard features on new systems; however, they can be retrofitted as well. Estimated savings range from 3% to 10% for grocery store systems.
Liquid pressure amplifiers. Liquid pressure amplifiers are small refrigerant pumps that raise liquid line pressure to increase system efficiency. For systems with air-cooled condensers, the lower the outdoor air temperature, the greater the efficiency gain. Energy savings can be up to 20%.2
Anti-sweat heater controls. Anti-sweat heaters are electric heaters installed in virtually all low temperature and many medium temperature display cases to keep their external surfaces free of condensation during high humidity conditions. Typically they are on all the time. Anti-sweat heater controls sense store humidity conditions and turn the heaters off when they are not needed. Energy savings estimates range from about six percent for grocery store display cases to 14% for reach-in freezers and 20% for reach-in refrigerators.
Defrost controls. Energy-efficient defrost systems improve the operation of the defrost cycle. The most effective controls are called demand controls. These controls initiate defrosting in a variety of ways such as measuring the temperature or pressure drop across the evaporator, measuring frost accumulation and sensing humidity. All of these methods, if used properly, are more effective than using a simple timer clock to initiate defrosting. Energy savings estimates range from about 1% to 6% of refrigeration system energy use.
Evaporative condensers. Most refrigeration systems use air-cooled condensers to expel heat. Evaporative condensers use a wetted filter to cool ambient air as it enters the condenser, increasing its ability to reject heat. Energy savings estimates range from about 3% to 9% for grocery store refrigeration systems.
Ambient subcooling. Ambient subcooling involves the use of an oversized condenser or an additional heat exchanger to subcool liquid refrigerant. Savings estimates range from about 1% for grocery store systems to about 9% for walk-in coolers.
Mechanical subcooling. Mechanical subcooling is an effective method of cooling liquid refrigerant below its saturation pressure in order to increase system capacity and improve efficiency. Energy savings are estimated to be as much as 25% for grocery store refrigeration systems.
Heat recovery. Heat recovery systems use heat removed from display cases to heat water. The amount of water that can be heated will depend on the situation. However, a 7.5 hp compressor can supply close to 100%of the hot water requirements in a medium-sized grocery store all year long.3
Energy efficient case lighting. T-8 fluorescent lamps and electronic ballasts are often used in new energy-efficient cases and can be retrofitted in existing cases as well. These high efficiency fixtures reduce lighting energy use and reduce the cooling load on the compressor. Energy savings potential is estimated to be about 10% for beverage merchandisers.
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Add doors to display cases. Glass doors on open multi-deck display cases can reduce compressor energy costs, reduce cold air spillage and increase store comfort conditions. Often, doors can be added to existing cases as a retrofit. Savings are estimated to be as high as 50%, and paybacks will typically be in the range of one to two years for retrofits.4
However, installing doors can cause the compressor system to be oversized, so always encourage your supermarket customers to seek your assistance with retrofits.
Energy efficient reach-in refrigerators. Equipment with the EPA's Energy Star® logo uses at least 30% less energy than required by federal government standards. Side-by-side refrigerator/freezers use significantly more energy than those with the freezer above the refrigerator. Use the Energy Guide label on new refrigerators to select the most efficient model.
Operating and maintenance efficiency measures. Operating and maintenance practices can significantly improve refrigeration system efficiency. Clean cooling coils several times a year. Make sure outdoor coils are shaded from the sun and have good air circulation around them. Make sure the doors on freezers, refrigerators, and display cases seal tightly, and repair any damaged door seals.
1. Energy Savings Potential for Commercial Refrigeration Equipment, U.S. DOE, 1996.
2. HY-SAVE Inc.
3. The Commercial Refrigerator Manufacturers Association's "Recommended Guidelines for Retail Food Store Design", 1/79.
4. Energy savings data in this paragraph taken from PG&E Application Note No. 53-43-82, 1982.
Information provided by APS, Arizona's largest and longest-serving electricity utility. APS serves more than 1.1 million customers in 11 of the state’s 15 counties. With headquarters in Phoenix, APS is the principal subsidiary of Pinnacle West Capital Corp. Used by permission.
Service Tip:
System Clean-up After Motor Burn
Q: What type of filter drier is recommended for cleaning a system after a compressor motor burnout?
A: After a burn, both the liquid and suction line cores (if provided) should be replaced with special "burnout blocks." These cores have an "HH" in their model nomenclatures. The system is then operated with these cores in place until the refrigerant and oil are clean and free of acids. Once this condition is attained, the liquid core must be replaced with a standard type core (UK48 or H48). The suction core should also be replaced with an F-48 filter.
Copyright 2008 Emerson Climate Technologies, Inc. All rights reserved. Used by permission.