Is this common for filters to be the cause of the blower motor to catch on fire, or is it more likely that a bearing got overheated? I really doubt that the furnace filter caused the motor to catch on fire, although neglecting your furnace 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.
Furnace blower 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 HVAC 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, furnace blower motor 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 is 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. The 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 of oil-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 overheating.
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 furnace blower motor over heating caused by the problems listed above.