Replace condenser fan motor

[wambat]

I am curious as to how you would replace a defective fan motor on a 2 ton 8 year old straight air conditioner when there is no information avialible on the motor. Replaceing the unit is not an option and mfg out of business.

[GXMPLX]

Trial and error!

Ancient technique.

[monkey spanners]

You could take the old motor to your wholesalers and see if they have a similar one, or fit one that is the same size, possibly with a new blade from another manufactures range of units of a similar size, or take the old motor to a motor rewind shop and get it fixed.

Jon

[wambat]

If you can determine the CFM of the condenser then can you figure out how to get a replacement motor. ;)

[US Iceman]

If you can determine the CFM of the condenser then can you figure out how to get a replacement motor.


Now where is the fun it that?

Another way is to measure the blade pitch and diameter and look at some fan curves for various RPM's as a reality check for your method also.

Two guesses that get the same approximate answer are pretty good at eliminating doubt.

[wambat]

The fun is in the "how do I find the cfm" so your the technition on a hot roof and the customer is in desperate need of cool air. What's your stragity?
Of course you can always punt

[fowlie]

why not get the motor rewinded sometimes can be a bit pricey but can get you out of a tight spot also these guys a quite good at finding out the make/model of the motor just by looking at it

[wambat]

why not get the motor rewinded sometimes can be a bit pricey but can get you out of a tight spot also these guys a quite good at finding out the make/model of the motor just by looking at it

That's an option but I was just curious if others had a solution like what i was thinking of. US Iceman has one possible solution.

[McGuiver]

Typicly, a 2 ton unit will have 1/4 hp 1075 rpm motor. Some mfgs use a 1/4 hp 850 rpm like York. On rare occasion they will go either way by putting in a 1/3 or 1/5 hp motor, so check the capacitor, typicly you would see a 5 mfd cap on a 1/3 and a lower mfd like a 3 on a 1/5. But a 5 would be on a 1/4 as wel. What I did in the field was just put in a 1/3, 1075, and new cap, verified the amp draw that it wasn't over amping and called it quits. The customer gets their air conditioning back, you get to the next job and everybody is happy. No time wasted. Hope this helps.

[round_the_rack]

Is there no dataplate anywhere on the unit? Not even a model & serial number sticker? (Have you checked the compressor and the bottom perimeter of the housing for an oem sticker?) What is the make?

McGuiver's recommendation makes the most sense to me, especially since it's an orphaned eight-year-old condenser. I mean... just how critical is this system?

by

[US Iceman]

I think the purpose of this exercise is to show you you some different ways to determine information, when you lack the labels and tags which we assume are required to find the correct parts.

wambat... please feel free to jump in here if I misspoke.;)

[Magoo]

Check out the overload / current protection device, that will target the max amps before destruction, check blade diameter, work backwards so to speak. If blade looks like meaty bites of air then is slow speed, fine angle and lotz of flat blades, then high speed.
magoo

[wambat]

I think the purpose of this exercise is to show you you some different ways to determine information, when you lack the labels and tags which we assume are required to find the correct parts.

wambat... please feel free to jump in here if I misspoke.;)

That's correct :)

[EmCoastHVACR]

It's no big deal -- I do it all the time, and I'm a PE.

You can get generic fractional HP motors that will fit any application.

The main thing to remember is to disconnect the lead on the dual capacitor and wire in a 5 mfd cap on the new motor.

So easy a caveman can do it (or a PE engineeer like me :D)