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Question DetailsAsked on 8/15/2017

Attic-fan-blades-stopped-working-today-Thermostat-motor-replaced-60-days-ago-work-pro

The blades spin freely when thermostat turned up to shut off fan but when turned down to turn on the blades start to turn then freeze up and are stiff to turn with assistance. In response to a previous answer the fan was turned on to run and then off repeatedly with final adjustment of set screw 6 days after it had almost continually run. It has ran almost every day for 60 days. we live where it is 100+ for about 2 months. I replaced three of these motors in last 2 months after having them 10 + yr without an issue and just decided to replace with new.

I tried to rate the company that responded with a thumbs up but my ipad recognized it as a thumbs down and I do not know how to change it. I also was trying to respond to them but do not know how. I can not find a help section for this issue or customer service to change it.......

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Thnaks for the thumbs up - and to keep the give and take for a given question in the same "thread" - either responding backk to an answer or adding more info or photos or such, just use the Answer This Question yellow button which is below your original question, as if youy were answering your own question.


If fan blades are not turning AND motor is not turning either, then motor is the problem. Only if the motor shaft is spinning but blades are not then the fan blade unit is loose on the shaft.


OK - with it free wheeling (full revolutions with no problem) when not under power the motor is burned out if it starts to turn under own power then freezes up and does not spin up to speed - sounds like a shorted armature. With a polarized motor (rarity in this circumstance) I guess it could be the wires are swapped, but that would also mean it starts to turn in wrong direction initially. Not a bearing problem because it would not turn freely at any time if that were the case. 


This all assumes that when it kicks on the motor is not twisting in the housing so that the fan blades are hitting the cage or such - like because of a loose mounting.


Sounds to me like, if you rule out the blades touching anything as it starts to wind up, two possibilities:


1) if a large fan - say probably 1/2 horse or more, meaning probably 24-36" or larger fan blade - it MIGHT have a starting capacitor on it to help it get started - typically looks like a rounded hood or shield on the outside of the motor with the lead wires going into it. If the capacitor is weak or shot, the motor will start slowly or sometimes not turn at all - but normally those come on the new motor so unless old one was used that is not likely the problem UNLESS overheating is the issue, as in 2) below.


2) as you say, 100 degree days can mean 120-160 in the attic, so it is possible the motor and/or starting capacitor (if you have one) is either not rated for that hot an environment, or is not continuous run rated, meaning it is a general use replacement motor rather than a fan motor - or it is just a junk brand.


Barring a problem with starting capacitor or the fan hitting the cage, I would say you need a different brand motor and capacitor - a top-brand name, high temperature service rated minimum Class B insulation and preferably Class F if available at reasonable price (which would likely make it last 10-40 times longer), and rated for rough service - though of course of appropriatemotor RPM's for the fan.


Common names with good reputations include GE of course, also Dayton and Broan. Nutone and AO Smith are two other brands that do fairly well, but I have found they tend to have bearing problems in high dust environments, so be careful if that is your case.


To tell you the truth,  I would take the old motor to an electric motor distributor and explain that you have changed out 3 times in 2 months and want a long-life motor for the application. The difference in cose, assuming existing fan is about 2-3 feet in diameter, is likely about $150-200 versus $60-90 for the one you have been getting - so maybe one service call charge difference but you should, with a rough service high-temp rated motor, get more like 10-20 years service than a few hundred hours.


Of course, make sure they know you want the same frame so it mounts identically - typically you will have to move the old mounting bracket to the new motor so don't let them take the old motor for recycling unless they do that for you there.


PS - for that application, should probably be permanently lubricated bearings rather than oill pad type - do not last quite as long, but what are the chances you will go up there every start of season to reoil the pads ?

Answered 1 year ago by LCD




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