Mid-Efficiency Boilers and Furnaces Heating and Related Equipment Discuss Mid-Efficiency Boilers and Furnaces in the The Building Operations and Operators Lounge forums; Most mid-efficiency boilers and furnaces are essentially conventional units (although a few have a secondary heat exchanger) with some modifications to reduce off cycle losses. A motorized vent damper may ...

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Most mid-efficiency boilers and furnaces are essentially conventional units (although a few have a secondary heat exchanger) with some modifications to reduce off cycle losses. A motorized vent damper may be used in the exhaust pipe to prevent heat from escaping up the chimney when the system is shut down. Alternatively, the system includes an induced draft fan in the exhaust pipe which only operates when the system is on. Continuous pilots are replaced with spark ignited pilots. Their seasonal efficiency is not much lower than their operating efficiency. Therefore, most have a seasonal efficiency in the eighty percent range. These systems require annual maintenance, like any other.