AC-83-01-2 -- Water-Heating Efficiency of Integrated Systems Designed for Space and Water Heating

This paper presents field test results on the water-heating performance of integrated systems under actual usage conditions. Field tests were performed at 24 residential sites over a two-year period. Water-heating data were taken for periods of exclusive hot water usage during the summer months in order to measure the water-heating efficiency. The integrated systems were installed side by side with the existing conventional water heaters, and performance was monitored for alternating weekly periods. Analysis of the data indicates that the noncondensing integrated systems produce hot water at an efficiency in the 49-54% range at 64.3 gal/day (243.4 L/day) usage, which is comparable to the performance of conventional water heaters. The corresponding efficiency of the condensing integrated system was 58%, which is comparable to the performance of energy-conserving water heaters.