Condenser fan motor speed

Need to replace my condenser fan motor in my heat pump. The current one is 1100 RPM. The Tech support at Grainger's recommended one that is 1075 RPM. Would this make a difference or harm the compressor due to the slightly slower rotation?
R
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not likely to do damage
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wrote:

If it fits and is otherwise the same, eg hp, outdoor rated, etc, then it's perfectly fine. I've seen that before, slight speed differences. I think it may just be a spec/measurement issue. It's only 4%.
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On Tue, 15 Jan 2013 11:08:23 -0800 (PST), "hr(bob) snipped-for-privacy@att.net"

Semantics 1100 rpm theoretical? 1075RPM actual, after slip would be my take on it. Actual syncronous RPM is LIKELY 1080 (1080/60). There is no number of poles that would give you either 1075 or 1100.
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On 1/15/2013 10:33 AM, Roanin wrote:

I have to wonder why you need to replace it? Did the motor freeze up, or is it vibrating wildly?
The reason I ask is we have owned our current place for 6 years. About 2 years after moving in, the fan on the heat pump froze up. I had noticed the fan and motor were vibrating some since we moved in and figured it had always done that and was really ok.
We had a local professional replace the motor. It still had the vibration, but ran really well. Last fall, the motor began to vibrate wildly and eventually stopped running, but was still free to turn.
We had a different company cone look at and the wires going to the motor had burned up. The bearings in the fan were destroyed and oil had leaked out.
The service man replaced the motor and commented on the vibration. should be NO vibration. I had removed a length of small round wooden dowel from the bottom of the case and showed the service man. I questioned him if someone running that stick into the fan could cause the out of balance vibration and he concurred and ordered up a new fan.
The old fan looked perfect, but I replaced the 4 bladed fan when the new one came in. No vibration at all. I examined the old fan and could see a place on the corner of one blade where the previous owner had straightened out a bent place. So the stick had actually hit a blade.
The old fan was still statically balanced, but because the curvature of the repaired blade was not the same as the other three blades, it was not dynamically balanced. There was either too much pitch or not enough. I could not tell by looking which it was.
So, in conclusion, you may need to also replace the fan as well as the motor.
Good luck, Paul
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Replacing it because it is squealing very loud after running for about 20 minutes. You bump it on the top and it quits for a second then starts again. No vibration.
R
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On 1/15/2013 1:59 PM, Roanin wrote:

bad bearings. eventually it will seize up, causing further damage. pull the fuse until you get it replaced.
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Or, dried out and needs oil.
Christopher A. Young Learn more about Jesus www.lds.org .
wrote in message
bad bearings. eventually it will seize up, causing further damage. pull the fuse until you get it replaced.
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Another perhaps less expensive option might be to have the motor rebuilt. Many motors nowadays can't be rebuilt, but it might be worth your while to look on that motor for information about it, and phone around to the electric motor rewinding businesses in your area to see what they say.
If you have a digital camera, you can e-mail a picture of it to the motor rebuilding shops, and they might be able to tell if they can rebuild it just from the picture.
I agree that a small difference in the fan speed won't affect or harm your heating system.
--
nestork


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if its a von weise motor, that company imploded. moved overseas.
parts order time near 2 years minimum order 3 grand or other insane amount, required prepaid.
how insane is that. grainger quit selling von weise motors when they made those changes.
the machines i service for a living used von weise motors, and the motor parts were affordable.
now its all new motors and has cost me big bucks, since the machines i service are mostly under maintence
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There is oil, made for such motors. Sometimes, the motors have oil ports.
Christopher A. Young Learn more about Jesus www.lds.org .
Replacing it because it is squealing very loud after running for about 20 minutes. You bump it on the top and it quits for a second then starts again. No vibration.
R
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On 1/15/2013 12:59 PM, Roanin wrote:

Sure sign one of the oil seals has failed and let the oil leak out. As was explained to me, the top and bottom bearings both have a small amount of oil in a reservoir protected by oil seals. With age and heat, the seals crack and let the oil escape.
If you look at the fan hub you will see oil and dirt. Be sure to clean this off so you can detect the oil leak next time! Also be sure the new motor turns in the correct direction. My service guy had it wrong and had to unbutton the fan screen and reverse two wires.
To the other posters, these motors are designed to be suspended vertically and have no way to replace seals and oil.
Paul
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I havn't seen anything like this, in the years I've worked on motors. I've seen bronze bearings, some with oil ports, and some not. The ones without oil ports can still be oiled, sometimes.
Christopher A. Young Learn more about Jesus www.lds.org .
Sure sign one of the oil seals has failed and let the oil leak out. As was explained to me, the top and bottom bearings both have a small amount of oil in a reservoir protected by oil seals. With age and heat, the seals crack and let the oil escape.
If you look at the fan hub you will see oil and dirt. Be sure to clean this off so you can detect the oil leak next time! Also be sure the new motor turns in the correct direction. My service guy had it wrong and had to unbutton the fan screen and reverse two wires.
To the other posters, these motors are designed to be suspended vertically and have no way to replace seals and oil.
Paul
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Agreed, you should try oiling it first.. Also even if the fan blade is fine, you may want to get anew one because it may be difficult to remove the exiting blade from the motor. Be sure to keep track to the direction of spin of the motor CW or CCW , the direction of spin the blade is designed for, the pitch of the blade and the HP rating of the motor. Also pay attention to the location of the blade how far on the shaft it is. I'm a DYI guy and successfully replaced the blade and motor on my heat pump. Just pay attention to the details. Another detail is the routing of the wires, they must be securely attached so they don,t droop over time and get clipped by the blade.
Mark
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A squirt of oil might make the motor last several more years. Can't hurt, at least to try. Agreed, get a new blade. Sometimes even if you can get the old bade off, it's not going to fit the new motor. And it may be out of balance. Being Mormon, I don't drink, and so don't get DYI trouble with the cops. UV resistant nylon tie straps are good, for wires. Clip the end off the wrap, so the end doesn't droop.
Christopher A. Young Learn more about Jesus www.lds.org .
Agreed, you should try oiling it first.. Also even if the fan blade is fine, you may want to get anew one because it may be difficult to remove the exiting blade from the motor. Be sure to keep track to the direction of spin of the motor CW or CCW , the direction of spin the blade is designed for, the pitch of the blade and the HP rating of the motor. Also pay attention to the location of the blade how far on the shaft it is. I'm a DYI guy and successfully replaced the blade and motor on my heat pump. Just pay attention to the details. Another detail is the routing of the wires, they must be securely attached so they don,t droop over time and get clipped by the blade.
Mark
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Should work, fine. Cost more than some oil for electric motors, though.
Christopher A. Young Learn more about Jesus www.lds.org .
Need to replace my condenser fan motor in my heat pump. The current one is 1100 RPM. The Tech support at Grainger's recommended one that is 1075 RPM. Would this make a difference or harm the compressor due to the slightly slower rotation?
R
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On 1/15/2013 12:33 PM, Roanin wrote:

I've run into this a lot when I did more service on AC units. 1075rpm is more of a standard speed in low speed fan motors which makes them less expensive than the 1100rpm motors. Check the price difference and you may find the 1075rpm is much less expensive than the 1100rpm replacement and will have negligible impact on performance. ^_^
TDD
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