Understanding How a Variable-Speed Furnace Works

A variable speed furnace is an energy-saving comfort enhancer compared to the single-speed system you’re living with now. Back when electric motors had just two settings (on and off), the conventional furnace blower was your only option. Unfortunately, it used a lot of electricity—a major component of heating costs, even with a gas-fired furnace—incurred excessive wear and tear, and subjected the household to extreme temperature swings as the furnace constantly cycled between zero and 100 percent output. Today, electronically-commutated motors (ECM) operate across a wide range of speeds and air output, programmed to meet the heating requirements of the moment. In addition, these brushless DC motors consume a fraction of the electricity used by an old-school, single-speed blower.

How it Works

The pre-programmed controller in a variable speed blower starts at slow, silent RPM and gradually ramps blower output up to reach the thermostat setting. Once the indoor temperature is stabilized, the controller slows the blower to reduced output, just enough to maintain the desired thermostat setting to high accuracy as well as sustain healthy air circulation. A variable speed furnace runs almost nonstop, but often at an output of 60 percent or less.

Advantages of upgrading to a variable speed furnace include:

Energy Savings

The ECM technology in a variable speed system consumes as much as 65 percent less electricity than a conventional single-speed blower.

Comfort Consistency

Because a variable speed blower runs continuously, indoor temperatures vary as little as one degree plus or minus the thermostat setting. This accuracy eliminates annoying temperature swings common as a single-speed blower alternates between full-blast output and no output.

Better Air Quality

Your system air filter only works while air is circulating. If the blower cycles off, filtration ceases. Because a variable speed blower maintains nearly continuous circulation, filtration is non-stop and air quality is improved.

At Sobieski Services, Inc., our goal is to help our customers in Delaware, Pennsylvania, Maryland and New Jersey learn more about energy and home comfort issues – especially HVAC and plumbing issues – so that they can save money and live in healthier, more comfortable homes.

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