1967 York GM48-25A condenser doesn't list RPM

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1967 York GM48-25A condenser doesn't list RPM

Postby mrwombat » Wed Oct 17, 2012 9:09 pm

My mom bought a house one year ago and this summer the A/C ran poorly, no more than 10* drop from ambient, leading to high electric bills and "random" shut offs near the end of the summer. She paid for techs to come out that told her everything inside was "new and fine" so the high pressure cutoff switch must be going out and needs to be replaced. Come to find out when I looked at the unit, the motor is a rescue motor rated 1/3HP, 220V, 4.1FLA, and 1075RPM. It has been seizing or slowing down more and more frequently, causing the high pressure switch to trip. Reset of the switch had been all that was necessary before but now the motor won't run at all. The plate on the unit specifies the original motor as 1/3HP, 220V, 2.7FLA but does not specify the RPM. The rescue motor was rated at 40*, which I presume lead to its quick demise in a position above the condenser coils pulling hot air over it. Not In southern Arizona with 40*+ ambient for weeks at a time.
I want to replace the motor but cannot find info on a unit of this model. I've been told it's a 4 Ton unit and I know the house is around 2500 square feet, nearly half as a basement. The only other info I have is that there only appears to be a run cap in the setup, no start. Can anyone one tell me what motor I need to properly replace the original?

Thanks,
Brett
mrwombat
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- 1967 York GM48-25A condenser doesn't list RPM

Postby Freon » Fri Oct 19, 2012 7:32 pm

It has been seizing or slowing down more and more frequently...

Replace the run capacitor. It may be a dual, 3 terminals. Buy an identical capacitor. Pull the main disconnect to the condenser then after 5 minutes replace it... label the wires.
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- 1967 York GM48-25A condenser doesn't list RPM

Postby mrwombat » Fri Oct 19, 2012 8:08 pm

Thanks for your reply, Freon. While the capacitor has been tested for shorts and doesn't show any visual signs of death, I will consider this for a temporary solution as I feel the motor may not have the necessary RPM and I would like to replace the motor anyhow. At this point, when command for cooling is sent, the motor hums violently and binds or spins very slowly (a round 10 RPM) and gives resistance when trying to assist the spinning. It won't even run ten minutes before seizing as it had last weekend. Is there a way I can find out or calculate the CFM demand of this condenser? The coils measure 31"x37"x about 6" and the opening for the for is 24". I am considering replacement of the entire condenser but I would prefer to just replace the motor/cap as there have been several opinions on the unit being in great shape. Aside from the fan not spinning, of course. The unit did not seem to provide enough of a drop from ambient this summer and last spring, even with lower ambients and the fan spinning at full speed.
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- 1967 York GM48-25A condenser doesn't list RPM

Postby Freon » Sun Oct 21, 2012 5:42 pm

If there is the resistance to spinning the fan blade by hand, as you describe, then you have bad bearings and need the motor repaired or replaced. You might try running oil down the motor shaft into the bearings but that's a temporary fix.
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