The Three Types of Electronic Ignition Furnaces

 

There Are Three Types of Gas Furnaces:

Warm Air Furnace,

Induced Draft Furnace

Condensing Furnace

Warm Air Furnace

The warm air furnace has the lowest efficieny rating (AFUE) of these 3 types of furnace. Furnaces made prior to 1992 commonly have AFUE ratings below the minimum of 78% with some old furnaces having AFUEs in the 55% to 65% range. These old low efficieny rated furnaces are equipped with a standing pilot light.

 

Mid to high efficiency furnaces having AFUEs of 80% to 97% are equipped with electronic ignition systems and are either induced draft furnaces with AFUEs of 78% to 82% or condensing furnaces with AFUEs of 90% to 97%.

 

Mid Efficiency Induced Draft Fan Furnace

Induced draft furnaces have an electronic ignition, of either the intermittent pilot or hot surface ignition (HSI) type instead of using a pilot light. An induced draft furnace uses a small fan to pull combustion gasses into the flue. By using electronic controls, electronic ignition and induced draft the efficiency of the furnace is increased to the range of 78% to 82% AFUE.

 

High Efficiency Condensing Furnace

The condensing furnace has a second heat exchanger by means of which hot flue gasses have heat removed, and the water vapor condenses to liquid water. This means that the furnace extracts much more heat from the combustion of fuel. The flue gases are cool enough that they can be vented to the outdoors by means of a plastic pipe. The water formed from condensation is drained to a floor drain. Condensing furnaces use hot surface ignition and are of high efficiency rating with AFUEs of 90% to 97%.

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