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Can Neglecting Your Furnace Filter Cause The Blower Motor To Catch Fire?

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Nicole Asked:
I am a tenant living in a duplex and here recently the blower motor caught on fire. I use MERV 8 filters and have changed them every three months.

The HVAC technician that came out to the home said that the filter caused this blower to catch on fire. The issue I have is that it was not sucked into the blower but was still in the filter cabinet and moderately clean (with a little smoke damage).

Is this common for filters to be the cause of blowers to catch on fire or is it more likely that a bearing got overheated / was not lubricated? Remind you that these units have not been serviced for over three years. If you could give me your knowledge and information based off that I would appreciate it.

Hi Nicole,
You are correct in your analysis of what happened. I really doubt that your furnace filter caused the motor to catch on fire, although neglecting your filter can contribute to some of the factors that cause this to happen. That sort of thing is caused by overheating and a MERV 8 filter is not going to have enough impact on air flow to cause that to happen.



Motor overheating can be caused by several things like low voltage, high voltage, tight bearings, shorted windings in the motor and probably a couple of other things that don”t come to mind at the moment.

If you haven’t had the motor replaced yet, make sure the technician checks for proper supply voltage and other problems. I would really recommend a different contractor.

Some Common Causes of Blower Motors Over Heating

Although unlikely, blower motors do occasionally catch fire. As with any fire this is a dangerous situation and is one more reason HVAC equipment needs to be installed and maintained properly, by a qualified service technician.

  • Dirt collecting in and around the motor. – Over time dust can build up on the inside and outside of the motor and act as insulation. This reduces the amount of air passing through and around the motor and causes overheating. Inefficient filters can contribute to this problem.
  • Sustained low voltage or high voltage. – Motors are designed to operate within a certain voltage range. Improper voltage causes motors to overheat. The usual cause of low voltage is poor electrical connections. High voltage is a distribution problem.
  • Tight and worn motor bearings. – This is usually caused by a lack ofoil-motor lubrication. Not all bearings are designed to be lubricated, some are sealed and can’t be accessed for lubrication. Check your motor to see if there are oil ports on the ends of the motor. They can be difficult to access but if the motor is oiled it could potentially last years longer. When bearings become dry they wear and overheat.
  • Shorted motor windings will cause a motor to fail and can cause the motor to catch on fire, although, the motor will usually fail without catching on fire. Shorted motor windings are usually caused by weak winding insulation which is the result of over heating caused by the problems listed above.

Best,

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About the author: Don has been working in the HVAC industry for more than 25 years and shares his experience and knowledge on this site. If you find the information presented here helpful please share with your friends.

{ 1 comment… add one }

  • Jack Johnson

    This blog had a lot of great information about what can cause a blower motor to overheat. I will definitely use this great information the next time I have to get my furnace checked. Thanks for the great info.

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