Modeled and measured effects of compressor downsizing in an existing air conditioner/heat pump in the cooling mode
It is not uncommon to find oversized central air conditioners in residences. HVAC contractors sometimes oversize central air conditioners for one reason or another--some to the point that they may be 100% larger than needed to meet the load. Retrofit measures done to improve house envelope and distribution system efficiency also contribute to HVAC oversizing, as they reduce house heating and cooling loads. Proper sizing of an air conditioner or heat pump allows more efficient operation and provides a more comfortable environment than a highly oversized unit. Another factor that lowers operating efficiency is an improper refrigerant charge. Field inspections have revealed that about half of the units checked were not properly charged. An option available to homeowners with oversized air conditioners is to replace the existing compressor with a smaller, more efficient compressor, rather than purchasing a new, smaller unit. Such a retrofit may be economically justified, especially during a compressor failure, provided the oversizing of the existing unit is not too great. A used, 15-year old, single-package heat pump with a capillary tube expansion device on the indoor coil was purchased and tested in a set of environmental chambers to determine its cooling performance at various conditions. The system was also modeled to estimate its existing performance, and that with two different types of retrofitted state-of-the-art (SOA) efficient compressors with about 30% less capacity than the original compressor. This reduced the overall system cooling capacity by about 25%. Modeling estimated that the retrofit would increase system EER at 95 F by 30%, SEER by 34%, and reduce power demand by 39% compared to the existing unit. Reduced cycling losses account for the higher increase in SEER.
- Research Organization:
- Oak Ridge National Lab., TN (United States)
- Sponsoring Organization:
- USDOE, Washington, DC (United States)
- DOE Contract Number:
- AC05-96OR22464
- OSTI ID:
- 238524
- Report Number(s):
- CONF-960606--2; ON: DE96008683
- Country of Publication:
- United States
- Language:
- English
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