Seasonal Efficiency and Off-Cycle Flue Loss Measurements of Two Boilers

In situ input/output measurements were performed on a hot water and a steam boiler, both of which are used in apartment building central heating systems. Measurements on the hot water boiler were made with two distinct control schemes: (1) constant boiler temperature and (2)variation of the boiler temperature with an outdoor reset control. The measured part-load efficiency curves of these boilers are presented along with a comparison of various boiler models. The models were used to estimate the seasonal efficiency of the two boilers and to estimate the magnitude and variations in off-cycle energy loss rate. In particular, the dependence of off-cycle loss rate on outside temperature was studied. Direct measurement of the rate of energy loss through the flue of the steam boiler during burner off periods was conducted through the heating season. These results were also studied to examine the dependence of off-cycle flue losses on outside temperature, cycling rate, and other boiler operating parameters.

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Seasonal Efficiency and Off-Cycle Flue Loss Measurements of Two Boilers