DE-93-01-2 -- Seasonal Efficiency and Off-Cycle Flue Loss Measurements of Two Boilers PDF

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 throughout 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.

KEYWORDS: comparing, efficiency, measuring, boilers, hot water boilers, flats, models, steam boilers, central heating, controls, friction loss, flues, pressure drop, heating season, cyclic, heat loss, temperature, calculating, burners, outdoor temperature.