Field Measurements of Air Conditioners with and without TXVs

Robert J. Mowris, Anne Blankenship, and Ean Jones, Robert Mowris & Associates

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Abstract

This paper summarizes field measurements of 4,168 air conditioners with and without TXVs. Approximately 72 percent of the air conditioners had improper refrigerant charge and 44 percent had improper airflow. Average energy savings for correcting RCA are 12.6 ± 2.3 percent. The paper provides detailed EER measurements and the relative efficiency improvement for sixteen TXV and forty-nine non-TXV air conditioners. EER measurements of air conditioners with improper RCA indicate a relative efficiency gain of 21 ± 7 percent for TXV and a gain of 17.1 ± 2.8 percent for non-TXV air conditioners. The difference in efficiency gain between TXV and non-TXV air conditioners is 3.9 ± 0.3 percent at the 90 percent confidence level. The uncertainty associated with field measurements of capacity and EER was evaluated using the propagation of error technique and the overall uncertainty error is ± 4.4 percent. The paper indicates proper RCA is much more effective than a TXV in terms of delivering rated efficiency performance, especially if TXV sensing bulbs are improperly attached to the vapor line or are not insulated. The paper describes an easy-to-use method to verify RCA using PDA software or automated voice telephony. The paper should be of value to anyone interested in reducing peak air conditioning demand.