Project Report


Commercial High Efficiency Air Conditioners:
Savings Persistence

Prepared for: 1999 International Energy Program Evaluation Conference
Report dated: August 15, 1999
Prepared by Proctor Engineering Group
Contributor: John Proctor, P.E., Rob De Kieffer

Abstract

Proctor Engineering Group established a time series estimate for condenser and evaporator coil fouling rates for commercial air conditioning units. This was derived from available research. Laboratory testing was used to modify the estimated fouling rates and establish a profile for coil fouling. Both high efficiency and standard efficiency coils were tested in a controlled laboratory environment and subjected to continuous fouling. The efficiency of the air conditioner was monitored at various intervals to document the effects of coil fouling on efficiency.

The units were tested to determine the efficiency impact of the fouling. Efficiency measurements were made at various steps during the testing. Tests were run to establish the baseline efficiency, efficiency with the evaporator fouled, and with both the evaporator coil and the condenser coil fouled. The coils were then removed and the standard efficiency coils installed. The proper measured charge was reinstalled and the testing repeated.

The data collected provided a profile for each set of coils: the efficiency at a baseline and the efficiency with the various amounts of coil blockage. The results from these tests were compared to other research conducted on the effects of air flow reduction on air conditioning systems.

The results of the testing showed that the high efficiency coils start with and maintain a higher efficiency than standard efficiency coils. The slower degradation rate will increase the life of the equipment and use less energy over the operational lifetime. The study also suggested changes in the servicing requirements of the systems.

Executive Summary

This report presents the results of research conducted on the performance of commercial direct expansion air conditioners (Comm. DX AC). It was one of the measures evaluated in the larger DSM effort. The larger study, Persistence 3A: An Assessment of Technical Degradation Factors: Commercial Air Conditioners and Energy Management Systems (Persistence 3A), sponsored by the California DSM Measurement Advisory Committee (CADMAC) Persistence Subcommittee, is the third project to examine the relative technical degradation of demand side management (DSM) measures compared to standard efficiency equipment.

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