CH-81-09-1 -- Determination of Annual Efficiency of Vented Heaters Equipped with Thermally Activated Vent Dampers

Part-load space heater efficiency requires the determination of five flue losses. These are latent heat loss (L_L), on-period sensible heat loss (L_S,ON), on-period infiltration loss (L_I,ON), off-period sensible heat loss (LS,OFF) and off-period infiltration loss (L_I,OFF).

We determined: -- Which of the part-load losses can be adequately measured using the current DOE procedure? -- Which part load losses cannot be measured using the DOE procedure? -- Seasonal efficiencies for three vented heaters using the current and a modified procedure.

All stack losses associated with the calculation of part-load utilization efficiency (nu) were reviewed in the development of a test method for heaters equipped with the thermally-activated vent damper. Annual fuel utilization efficiency and associated energy savings were determined for two thermal vent dampers tested with three types of gas-fueled heaters which operate in either the cycling mode or in the modulating fuel input mode.

Test results showed energy savings from 1 to 9% depending on the type of heater as well as the type of damper used.