Plugged Filter - Motor Damage?

desol

Ok you guys,

Will a plugged filter hurt the furnace motor. If so, why?

I've been having some discussions about this will fellow techs and interested to see what you guys say.

D.

flashheatingand

I wouldn't just condemn a motor just because the filter was clogged, but if left unattended, it will cause the motor to overheat, which in the long haul will shorten the life. Why?

desol

Ok. So will it overheat from overamping...or because of no airflow?

Tech at work denies overamping...as amps 'increase' with MORE air(load)...not less(clogged filter). He also denies it overheating from lack of air, which i believe will happen with a clogged filter.

flashheatingand

Way I was explained by a guy from ao smith is: The air also cools down the motor. As a result, the motor windings will overheat if air flow is too low. Thats why its important to clean a motor. The dust will close up those "breathing" holes on the ,motor frame.

A motor should be able to run something like 25,000 hours.

NickTech

the centrifical wheel on the blower carries the load, air, and the motors work is reflected in amps. if the airflow is obstructed for any reason, ie. dirty filter etc, then there will be less air for the wheel to move. this will result in less work for the motor to do reflecting in a lower amp draw. inversly, if the blower door is removed from an AHU, the resistance of the duct work is bypassed allowing for more than normal the amount of air to go over the blower wheel resulting in more load/work for the motor causing a higher amp draw.
blower motors are refered to as air-over motors which require a certain amount of air passing over the motor to cool it off. hindering the airflow while long cycling can result in overheating of the motor.

desol

Thanks guys. That's exactly what i thought. A clogged filter will not allow the motor to cool, causing damage.

flashheatingand

If left unattended. If it aint busted, don't fix it.

mics_54

a clogged filter in a duct system does not keep a motor driving a squirrel cage blower from circulating air through the motor. Most of the blowers I've seen in ventilation systems are driven by motors that are outside of the vent duct anyway. Closing off the inlet of a blower will in fact cause the amperage to decrease because the motor load decreases. Try it and see.

A second thought...If the vent system is clogged the system will probably run for longer periods and more often trying to satisfy the demand...this would likely shorten longevity(years of service) of its componants in general although not shorten a componants given lifespan. (hours of operation)

NickTech

what?!
i don't think he's talking about a ventilator, but he mentions a furnace motor, which is a direct drive assembly. meaning the blower hub is mounted directly to the motor shaft. the air being drawn throught the return goes over the motor to cool it off.
your responses are contradicting, in the first paragraph your disputing our responses that it will over heat on the long cycle, then the second paragraph completely agrees with it. not sure what you want to say.

mics_54

Your eyeball is disturbing.

NickTech

yeah it annoys me too, gotta get a new one.