Electric furnace not hot enough

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I'm having a strange problem with heat output from my Coleman Evcon EB15B. The short version is that it is only putting out about 80-degree air. I've checked the volts to all heater coils, as well as ohms through them. Upon initially turning on, it will put out 100-degree air, but will drop back to 80-degrees after a minute or so. Could it be the sequencer?
Any ideas would be greatly appreciated.

Lilly

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If it runs does it heat the home? Electric heat does not get as hot a propane/oil heat so do not base you temperature discharge on a comparison basis. if all the heaters are working you are getting the maximum amount of heat the unit is capable of producing.

If you have a amprobe you can take the current draw (not voltage) of each heater to make sure they are all working.

hvac1000

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It does run, but last night the outside temperature was about 25 degrees, and the heater was running all the time and only kept the temperature inside at 68. The thermostat was set on 70. I have plans to check the amp draw on all legs of each heating element tonight, but I do not think any of the elements are bad, considering I know that it CAN put out 20-degree hotter air than it is now.

Lilly

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Check the elements. If they are good but not getting hot it is possible that the heat sequencer is defective. But before you condem the sequencer I would follow the voltage trail and make sure that no other safety device (limit control) is stopping the power on the way to the heaters. Remember you need 220 volts on each element. 110 volts on each side of the element and 220 volts across the element.

hvac1000

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Would it be possible for you to describe how to check the limit switches on this particular model? I had thought of that, too, but I'm not sure exactly how to check them as they don't resemble limit switches that I'm used to seeing.

Lilly

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Check the limit switches for continuity. test one at at time. Remove wires and remember where you removed them from. Next check for continuity thru the limit to see if it is open or closed. They stop the flow of current when they are open. This is or limit switches.

hvac1000

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IF you can get to the sequencer with enough room for testing voltage and feel comfortable doing so, test across M1/M2, M3/M4 and M5/M6 after waiting 2 minutes from call of heat by t-stat.

You should read 0 vac across all 3 sets and it should remain that way for a few minutes as home warms up.

You may have a set of contacts dropping out early, thus losing one or more elements.

Robert

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And I'm guessing that if I DO have a set of contacts dropping out early, I can assume that the sequencer is bad?

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Yes the sequencer does control the elements.

Robert

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Thanks for all the help!! I found that there was no amp draw through the leg going from the sequencer to the bottom heater coil.

Lilly

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Well, I replaced the sequencer, but I'm still having the same problem. I still occasionally don't have any amp draw through to the bottom element. Sometimes it works sometimes it doesn't. Any other ideas?

Lilly

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When it does not work and has zero amp draw, immediately test across Sequencer M5/M6 for 240vac.

Then test across both ends of bottom element for 240vac.

IF M5/M6 reads 0vac and the element reads 240vac, it's most likely a bad element.

If you get any readings other than this, it's a power/wiring problem.

Thanks,
Robert

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I have tested across M5/M6 and have 0 vac; the element also has 0 vac at the same time.

Lilly

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Turn t-stat to OFF.

Then test across M5/M6 for 240vac .

IF you read 240vac, continue.

Turn t-stat to call for Heat.

Test across H3/H4 . Test for 24-28vac.

IF you read 24-28vac, continue.

Test across M5/M6 for 240vac.

IF you read 0vac, continue.

Test across the element terminals for 240vac.

BEFORE doing these, check and be sure ALL wires are connected tight and secure.

Check sequencer, element and limit connections.


Thanks,
Robert

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FYI: All the electric was fine. The problem was: There was not enough airflow through the A-coil and the thermal limiter on the lower element was overheating. Thanks.

Lilly