Condenser fan motor replacement

Problems related to residential installations.

Condenser fan motor replacement

Postby dalami » Mon Aug 08, 2011 2:34 pm

Hi!

I'm a new to this fun stuff. Looks like my condenser fan has failed - need a replacement. The condenser is a Comfortmaker 10, the stock motor is an Emerson K48HXFCM-3726 - nameplate says 208-230v, 1/5hp, 1075 rpm, frame 42Y. The Emerson seems quite pricey - I've found a few alternatives from AO Smith from a local distributor I was considering.

I've seen comments before that going with a higher hp or rpm motor will cause problems - and I don't understand that. I would think having a higher hp motor that can handle turning the fan at higher speeds would result in superior cooling. What am I missing?
dalami
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- Condenser fan motor replacement

Postby heatseeker » Tue Aug 09, 2011 8:20 am

ao smith motors are a good replacement. The unit is designed for a specific rpm condenser so if you get a faster or slower fan it will throw off the ratio of temperatures. Im not an engineer so that is the best way I can explain it. Also you can go up a little in hp however too much will cause the motor to overheat once again due to the design of the condensing unit.
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- Condenser fan motor replacement

Postby Freon » Tue Aug 09, 2011 10:54 am

Two things you need to be cautious about. First is the run capacitor for the new fan motor. You may have a dual capacitor now (one "can" for both the compressor and fan motors... there will be 3 terminals on one end usually) and the fan capacitance in the existing dual capacitor may not match what your new motor calls for. So you may need a run capacitor for the new motor. Be sure the new motor has the exact run capacitor called for by the manufacturer.

Second, if you are reusing the fan blades, you need to have the same direction of rotation and RPM for the new motor. Motors are matched to a given fan blade pitch to create a set air flow through the condenser (cfm). If you have a higher rpm motor and the old fan blade, you will move more air through the coondenser (that is good), however moving more air means the motor is doing more work and therefore has a good chance of overheating. So match the RPMs to be safe.

Last question... how do you know the motor is bad and not possibly the run capacitor? Maybe a trip to a motor shop for a quick test would be wise.
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- Condenser fan motor replacement

Postby aircooledtx » Tue Aug 09, 2011 12:17 pm

dalami -
> Hi!
>
> I'm a new to this fun stuff. Looks like my condenser fan has failed - need
> a replacement. The condenser is a Comfortmaker 10, the stock motor is an
> Emerson K48HXFCM-3726 - nameplate says 208-230v, 1/5hp, 1075 rpm, frame
> 42Y. The Emerson seems quite pricey - I've found a few alternatives from
> AO Smith from a local distributor I was considering.
>
> I've seen comments before that going with a higher hp or rpm motor will
> cause problems - and I don't understand that. I would think having a
> higher hp motor that can handle turning the fan at higher speeds would
> result in superior cooling. What am I missing?


Better stay with what was designed for that unit, 1/5hp 1075 rpm/230 vlt.Be sure that run capacitor is replaced w/ motor.Check rotation too..
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- Condenser fan motor replacement

Postby nomadpeo » Wed Aug 10, 2011 6:49 am

the 42y frame is not universal either. sometimes the body diameter and length is a consideration. one more note in addition to all the other good advice you are getting - make a note of the relative position of the fan blade height. a slight change up or down can change performance.
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