Diving Into Electric Furnaces- Its elementary!

Submitted by DonHester on Tue, 04/07/2015 - 09:56.

Diving Into Electric Furnaces- Its elementary! Wenatchee Home Inspection Services

I am amazed how often I find electric furnaces with an element or two not working. Quite often the home occupant does not even know because warm air is still blowing out of the registers.

Heating Elements (10kw)

The beauty of electric furnaces is that they are pretty straight forward. During a home inspection I can test the element leads to see if they are coming on using a clamp on amp meter. Typically I will see around 20 amps per element.

By using the clamp on meter I will check to see if each element is energizing which they should after a minute or two. After running the furnace for a little while with the meter I can evaluate whether a specific element energizes and starts to heat up or never comes on.

element not energizing

One of the main culprits for an element not energizing is the sequencer. The sequencers for the electric furnace are designed to turn on and off the heating elements in a series of delays so they all do not come on at the same time causing a surge of current that could trip the breaker.

typical sequencer

Sequencer Function

Typically a sequencer depending on model will come on in a few seconds to about a minute and a half. These sequencers rely on a heat relay which is a heater coil and a bimetal switch. The coil heats the bimetal which causes it to flex and create a contact and allow power to the elements. Most modern sequencers are 24v, though you may have an older furnace with 120 or 240 volts but those are not that common anymore, at least here.

The other big issue I find during the inspection is burned up wires which I see these quite often. This is most commonly caused by a poor connections but corrosion, vibration and that thing that never stops... Age, can also show their ill effects on the wiring. Sometimes repairs have been made and the wrong wire was used, these wires are high temperature rated to handle the environment they are in.

Another possible problem is that the heating element has failed or has the high temperature limit switch or fuse has failed. Often this failure will be related to the air filter, not changing the air filter which will reduce airflow and cause the elements to overheat. Repeated overheating will cause these switches to fail.

The furnace air filter is one of the most important maintenance item in your forced air system. If the filter becomes clogged, the entire system has to work harder and run longer to deliver heat. You should replace or clean your air filter monthly during the heating season.

By doing this simple test during a home inspection I am able to give my clients a little more information about this system and is a good reminder that annual servicing should be performed.

“An investment in knowledge pays the best interest.”

Benjamin Franklin

NCW Home Inspections, LLC is a Licensed Washington State Home Inspection service located in Wenatchee Washington serving Chelan County, Douglas County, Kittitas County, Okanogan County and Grant County Washington and the cities of Wenatchee, Leavenworth, Cashmere, Oroville, Cle Elum, East Wenatchee, Quincy and many more…

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www.ncwhomeinspections.com 509-670-9572

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Diving Into Electric Furnaces- Its elementary!