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Old 08-09-2020, 11:25 AM   #1
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fan relay getting hot


I have a Bard oil furnace and Goodman 2.5 ton a/c and the fan relay gets hot, too hot to touch. I have replaced the entire fan center as one of the terminals burnt. I have checked the blower motor and it is pulling 12 amps. The fan center is a 120/24v,40va relay so 12 amps should be fine. It gets shot in both heat and a/c mode.
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Old 08-09-2020, 12:00 PM   #2
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Re: fan relay getting hot


12 amps seems pretty high. What is the amp rating of the motor?
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Old 08-09-2020, 12:09 PM   #3
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Re: fan relay getting hot


Check the 24 volts from the transformer.

If the relay is getting low voltage on G then the internal coil may get hot.

You should get 24 volts from G to C when the AC is on.

12 amps on a motor sounds high also but that won't heat the relay up.

Check the voltage to the furnace also. You should be getting between 110-120 volts. If it is low then the 24 volt transformer side will be low also.
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Old 08-09-2020, 12:28 PM   #4
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Re: fan relay getting hot


Quote:
Originally Posted by elishaman View Post
It gets shot in both heat and a/c mode.

24V Coil not in play in heat mode?
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Old 08-09-2020, 12:48 PM   #5
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Re: fan relay getting hot


It is a oil furnace and if the temp sensor for the heating is in the 24 volt circuit it could be.

I would have to see the wiring diagram.

Most newer furnaces don't use the old school 120 volt bi-metal controls.

It could have a normally open and closed circuit interlocked for heating and cooling.
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Old 08-09-2020, 12:57 PM   #6
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I am getting 25.3 vac from G to C with a/c running
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Old 08-09-2020, 12:58 PM   #7
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The blower motor is drawing 6.9 amps.
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Old 08-09-2020, 01:01 PM   #8
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118 volts ac at the fan center connections
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Old 08-09-2020, 01:06 PM   #9
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It gets hot in both heat and cool modes
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Old 08-09-2020, 01:07 PM   #10
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wiring schematic is in above post
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Old 08-09-2020, 03:00 PM   #11
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Re: fan relay getting hot


Hi, what is the FLA of the motor, check the motor name plate, does that motor spin freely?
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Old 08-09-2020, 04:01 PM   #12
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Can not gain access to the plate on motor. Yes it does spin free
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Old 08-10-2020, 12:56 PM   #13
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Re: fan relay getting hot


I'd test the capacitor on that motor just for laughs. That's a bit too much current for what is probably a 1/3 hp motor.

It's a bit of a stretch to blame that for the contactor coil heating up but stranger things have happened. I suspect the entire contactor may be heating up beyond normal spec.... the contacts may have developed an abnormally high resistance. You may have both of those problems to deal with... fortunately they're both cheap parts and easy to get.
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Old 08-10-2020, 02:22 PM   #14
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It ie a 1/3 ,hp motor. Rated at 6.7 amps
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Old 08-11-2020, 09:14 AM   #15
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Re: fan relay getting hot


Close enough in that case. I'd now replace the contactor and expect that would be the fix or at least get one on hand since you have been warned.

It may take out the control transformer or some other control element so I'd get it out of there right away.
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