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Effect of Short Cycling and Fan Delay on the Efficiency of a Modified Residential Heat Pump



W. J. Mulroy


The object of this study was to detennine if the use of a cycling controller would improve the efficiency of a residential air conditioner or heat pump. Cyclic tests were perfonned on a capillary tube heat pump in three configurations: as manufactured, as modified to simulate a non-bleed expansion valve unit by operation of a valve in the liquid line, and as modified to simulate an air conditioner by elimination of the accumulator. The two modifications, the liquid line valve installation and accumulator removal, were found to greatly improve the cyclic perfonnance to about equal levels; however, some cyclic losses remained. It was concluded that any control strategy that resulted in shortened on-cycle run times would reduce cyclic efficiency for all designs tested. It was further concluded, based in part on the work of others, that fan delay is an undesirable control strategy for units that have the indoor air handler and coil installed within the conditioned space.
ASHRAE Transactions
No. Part 1


heat pumps, air conditioning, fans, valvs, test facilities, data analysis


Mulroy, W. (1986), Effect of Short Cycling and Fan Delay on the Efficiency of a Modified Residential Heat Pump, ASHRAE Transactions, [online], (Accessed May 30, 2024)


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Created January 1, 1986, Updated February 19, 2017