... 25 tons of coal-fired boilers, 1 ton to 20 tons of gas boilers, oil-fired boilers, biomass boilers, steam boilers, hot water boilers ... ,net boiler efficiency in a variety of furnace it will not leak into the cold air to the flue gas side, due ... tail heating surface the boiler to leak into the cold air, reduce and reduce heat loss, and secondly, due to thermalcombined ...