Electric furnace differential

Had two 1999 International Comfort Product electric furnaces that were putting out a 22 degree differential. One unit was 95/73 and the other unit was 98/76. I heard that electric furnaces should put out at least 100 degree temperatures and I have also heard that temperature differentials for electric furnaces should be between 20-50 degrees. Both units appeared to warm up the home. Any helpful thoughts would be helpful. Thanks.

I often write up electric furnaces for producing warm not hot air and advise this could indicate a failed element (or two). It can be tough during warmer times of year since it’s hard to tell just how hot the air is.

It was 46 degrees outside.

I get far less hung up on a number I read in a textbook and focus more on what I feel the day I am there. I picture myself sitting in this house and turning on the heat when I’m cold. Is there adequate heat being produced? Would I be happy with this in these circumstances if I lived here? Our clients don’t care about an optimal temperature differential. Did the air feel cooler than it should? If so, write it up.

Inspecting to a number or a chart or a code IMO is not what this biz is about.


15 degree F temperature rise per 5KW (element) for an electric furnace is the average.

Put away the text books, charts and gizmos… what did it feel like?

The benchmark per most (all?) SOPs is, “is a given system performing as intended?” There’s nothing about measuring temperature differentials or doing other “technically exhaustive” inspecting. We are there to determine if something is “working”. Being too focused on technical numbers, etc. gets our eyes off the ball.


I think Texas has some screwed up differential reporting criteria. I do not know about the rest of the country. NACHI’s SOP is even more vague.

I will report, in my opinion if the heating and cooling was not adequate for comfort. (I may use a tool or two to confirm my thoughts)


So, getting my amp meter out to check the heating elements is going beyond :smiling_imp:


Maybe just a tad bit. But you do you and I am sure someone will appreciate the effort! :+1:

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The temperature differential is based on the airflow through the heater coils.
You must determine “Bypass Factor”. And you did this how?

When an electric heater produces 3.412 Btu/watt, tell me how you measure Btu’s from a Delta-T?

Did you determine the heat bank capacity?
Did you measure Amps to determine Watts, and convert to Btu. Determining Watts requires you to measure voltage by the way.

Might this be beyond HI SOP?

How do you answer the Texas SOP? Report the Delta-T and shut your mouth, would me my SOP.