A two-parameter linear model relating a boiler's fuel consumption to its thermal load is applied to the performance evaluation of heating boilers. The model is based on the conventional "economy line" steady-state representation of time-averaged boiler operation. Physical interpretations of the parameters are clarified and related to feasible in-situ diagnostic measurements. Data from field tests are presented to illustrate the model development. An application of the method is discussed for two boilers in a 60-unit, steam-heated apartment building. Boiler characteristics inferred by applying the model with simple diagnostic measurements are compared to results obtained by direct load and flow instrumentation. Parameters estimated from such short-term diagnostic tests plus annual fuel consumption may then be used to determine the seasonal performance of the boiler. It is concluded that applying a steady-state model is a practical means of using feasible on-site diagnostic tests to obtain a characterisation of boiler performance over working loads.

KEYWORDS: fuel consumption, boilers, models, calculating, site testing, comparing, steady state, measuring, energy consumption, data, flats, housing, flowmeters.