off cycling is one source of efficiency loss in single-speed air conditioners and heat pumps. The primary accepted method of estimating cycling losses is through a degradation coefficient that was developed by the National Institute of Standards and Technology. A single-time-constant model was developed that could be used to predict the cycling losses for single-speed air conditioners and heat pumps. Results from the model were compared with previously reported data. The model estimated the major trends in the part-load factor and cooling load factor reported by previous investigators. The degradation factor was found to have a minimum fraction on-time near 0.5 when the cycling rate was held constant. Careful analysis of data from previous investigators indicated comparable trends. Combining a simple thermostat model with the single-time-constant model resulted in a nearly linear relationship between the part-load factor and the cooling load factor (i.e., constant degradation coefficient). The cycling characteristics of the thermostat were found to affect the value of the degradation coefficient.

WORDS: performance, efficiency, unit air conditioners, heat pumps, speed, calculating, cyclic, comparing, cooling load, factors, part load, thermostats, properties, air conditioning