Blower fan motor overheating in Carrier HVAC

DCLVJanuary 9, 2012

Saturday morning I awoke to the smell of overheated wiring. After searching the house for the source of the smell, I determined the problem lay with the heater. Later, I opened the unit and found a piece of insulation had fallen on top of the blower fan housing, which I surmised had restricted air flow and had caused the motor to overheat. I used Liquid Nails to re-affix the insulation, and tested the unit again, and found the odor persisted. My hypothesis was the motor had heated beyond the breaking point and would need to be replaced. Today, I took the fan housing and motor to an electric motor repair shop, where they replaced the Emerson 1/3 hp motor with an Emerson 1/2 hp motor. They provided a new two pole capacitor, to replace the 3 pole that was part of the assembly. I eventually rewired the assembly using the original capacitor. After re-installing the housing, fan, and new motor, I successfully started the furnace. After running it for a few minutes, I began to smell hot wiring again. I ran the unit long enough to heat the house from 60 to 72 degrees, then turned the unit off, as the smell had grown strong enough to give me a slight headache. The smell was in some ways a little different, not as acrid as the original odor. I thought it might be a "breaking in" smell. I haven't run the unit since about 4 this afternoon.

Perhaps there may be someone who could give me some advice about what might be causing the new motor to overheat. Any comment or additional questions are welcomed.

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You state the original motor overheated when the insulation fell on the housing. Are you sure about this? I would think the motor would no longer operate if the internal mechanism became so hot to give off a strong smell.

Are you sure the new motor is overheating? Does it feel very hot when you touch the housing? You stated you have changed the motor from a 1/3 HP to 1/2 HP. Have you set the air flow so that it is the same as the 1/3 HP motor?

The smell may be coming from something unrelated to the motor. If the smell is giving you a headache then you should have a professional inspect the heat exchanger. You may have a more seious problem.

    Bookmark   January 10, 2012 at 8:09AM
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Why would you replace the new capacitor with the old one?
Are you sure the old capacitor is the same value and is good?
This can affect the operation of the new motor.

As previously stated, you should have a professional repair your system. What's your life worth? What's your house worth should your fire insurance deny a claim because you tried to fix your heating system yourself?


    Bookmark   January 10, 2012 at 9:30AM
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Sounds as if something ....possibly relative to the original insulation falling off, has made it's way to your heat exchanger. Especially in that you begin to smell it after a few minutes and it does not smell as "acrid" as at first. Whatever it is is slowly deteriorating, as in ... burning up. Remove the blower housing or possibly a side or rear panel of the furnace and look around. you'll probably find it.

    Bookmark   January 14, 2012 at 1:18AM
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