The ABC's of Heating - Modulating Gas Furnaces

Over the last decade or so gas furnace technology has advanced considerably, with AFUE efficiency ratings now exceeding 95 percent. Many furnaces manufactured in the 1990s had efficiency ratings in the 60 percent range. One of the main reasons for this dramatic increase in efficiency is modulating gas furnace technology.

Traditional single or two-stage furnaces operate at fixed rates and will often exceed the preset temperature before shutting off, resulting in wide temperature swings. A modulating furnace is able to adjust it's gas input, inducer speed, and blower airflow to operate at 1 percent increments from 35 to 100 percent, providing more accurate control over temperature. While it may run more often, it can do so at a lower rate than a two-stage furnace.

The advantages of modulating furnaces include increased comfort, reduced operating costs and quieter operation. With a two-stage furnace you may notice a change in temperature right before your furnace turns on and right after the furnaces shuts off. With a modulating gas furnace, the temperature change will be imperceptible.

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