How An Electric Furnace Works (A Simple Guide)

How does an electric furnace work? Or, how does a Coleman electric furnace work? They all work basically the same. There is nothing too complicated about most electric furnaces.

A thermostat controls a sequencer in the furnace. The sequencer has switches that close to turn on power to the elements. The sequencer also can turn on the fan to blow air over the elements and send warm air through the duct work and out the registers.

An electric furnace is just like a hair dryer. Inside the round neck end of the hair dryer is an element that heats up when you turn it on. The fan comes on at the same time and blows air over the element and heat comes out.

Have you ever had a hair dryer that the filter on the end where the air goes in, gets plugged with lint like stuff and the dryer doesn’t blow warm air anymore? That’s because the hair dyer has a limit. A limit is a heat sensitive switch that opens up and turns off the element to keep the hair dryer from catching fire.

Electric furnace are no different than that hair dryer. The controls are a little bigger and so is the amount of heat they can produce.

The essential parts of an electric furnace are:

  • Breakers or Fused Disconnect
  • 24 Volt Transformer
  • Sequencer
  • Limits
  • Elements
  • Blower
  • Blower relay

Pretty much a big hair dryer, right?

This was a pretty nasty furnace, huh? It was a very much neglected electric furnace. But it contains all the basic parts.

The blower motor is mounted on a bracket to the blower housing.

Inside the blower housing is a squirrel cage blower. Yes, the kind you see in cartoons with squirrels running around inside.

When the motor spins it pulls air in and blows it down and over the elements below.

Electric furnaces such as this can be mounted to duct work in any direction. They can blow down, up, or horizontal.

Some inquisitive, researching persons have asked “how does a Coleman electric furnace work?” and I’d have to say just like a Goodman, Trane electric furnace or any other brand. Electric furnaces are most all basically the same.

Some electric furnaces use different styles of sequencers or convert the ac voltage to dc. No result in increased efficiency.

One is not more efficient than the other. You put one penny’s worth of electricity in and you will get one penny’s worth of heat out.

A heat pump can be more efficient if added to an electric furnace where a refrigeration system heats your home during moderately cold weather and the electric furnace is backup heat during severely cold weather.

What Does A 24 Volt Transformer Do?

A transformer in an electric furnace does just that, it transforms 120 volts or 240 volts down to a more manageable voltage of 24 volts. Inside the control panel in an electric furnace are all the relays and switches that turn stuff on or off.

Having a lower voltage makes these controls easier to wire and safer to work on, especially when running thermostat wire to central locations in a home. Thermostat wire is usually 18 gauge wire versus 14, 12, and 10 gauge wire for most circuits in a residence.

The larger the number the smaller the wire.

If you ever need to change out a 24 volt transformer be sure to purchase a fused transformer.

I prefer and carry in my service truck an auto reset transformer. Trouble shooting shorted circuits is a lot more fun when all you have to do is reset the transformer rather that replace a fuse.

What Is An Electric Furnace Sequencer?

Also an appropriate name for a part. The sequencer, is powered by the 24 volt thermostat when the thermostat makes a call to heat and in turn the elements come on in sequence.

This is just one example of what a sequencer looks like. They take on several shapes and forms but they all do the same thing, turn on the elements gradually so the load on the electric panel is not all at once but a little bit at a time.

Electric Furnace Limit Switch

You can find more that one limit switch in most any furnace. The reason is for safety. When fan motors quit or filters get neglected and plugged up then limit switches come into play and shut things down.

Electric Furnace Elements

Just like that element you can see looking down the throat of your hair dryer these curly wires get hot when electricity flows through them.

Heater section removed from an electric furnace
The inner workings of an electric furnace

Now that you have been introduced to the basic parts and operation of an electric furnace you can sort of put all these parts together as in the image above.

All you have to do is add the blower wheel and motor. The result when installed into a cabinet like the image at the top of this post, is an electric furnace.

Chad Peterson

Chad Peterson is a veteran of the HVAC industry since 1977. "I like to explain heating and air conditioning problems in a way the average home owner can understand. "

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