HA-2460 -- Measurement of Heating System Dynamics for Computation of Seasonal Efficiency

The steady state efficiency of gas fire residential furnaces is usually assumed to be about 75%. Another 5% credit is given for heat recovered from the jacket and flue pipe when the furnace is installed in the heated space. Thus the input and output capacities state on the furnace name plate normally have ratio of 0.8 A well adjusted oil burner can achieve equally high efficiency. However, residential heating loads seldom require the furnace to approach steady state conditions. Residential furnaces are normally controlled in an on/off mode. Concern for fuel conservation raised questions about, the applicability of the steady state furnace efficiency to describe the operating efficiency of the whole heating system, the average seasonal system efficiency, identification of the factors which influence season efficiency, and means to improve it.