Run capacitor size


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Old 11-16-13, 06:31 AM
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Run capacitor size

I have an old Water Furnace gepthermal heat pump. I need to replace the run capacitor but the cap that is in the unit is rusted and I cannot read the label to see the value. It is a 3 ton unit. Can someone help me estimate what size cap I need for a 3 ton comptessor? Is there a rule oh thumb to get me in the right ball park?
 
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Old 11-16-13, 06:45 AM
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The fan motor or compressor that your capacitor serves may have the required cap size listed on it.

Some websites list the parts list for different units if you know the model number of the geothermal unit.

I once had a customer bring me a piece of white chalk that helped me read a rusty cap label.
 
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Old 11-16-13, 10:57 AM
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Thanks for the suggestion. I had to get down on my belly on the cold cement floor and try to see the compressor and lo and behold a corroded crimp connector not making contact that I could not see before. That was the problem. Thanks for sending me in the right direction.
That run cap still looks very bad, but seems to work for now. I still don't know if there is a way to find the correct value if you don't have access to a service manual for a 30 year old unit that refuses to die. I guess I coud try to measure it with a meter but I don't think the one that is in there is original because it is a dual cap and geothermal heat pumps, of course, do not have fans. Thanks for the help.
 
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Old 11-16-13, 11:03 AM
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I would still measure it and write the reading in the service panel with a marker.
Caps fail and that one is workin now.
(Of course I have 5 or 6 meters that can measure microfarad and wouldn't need to buy one for this test)
 
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Old 11-17-13, 04:39 AM
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In order to measure the MFD rating you need a meter that is designed to read capacitance.
The manufacturer of the heat pump is where you would get the correct rating for your unit.
If that isn't available the compressor manufacturer will have a rating that may not be exactly what came with the unit but would but would not overheat the windings by being too large.

If you can read the compressor tag and give us the make and all the other numbers we may be able to find it.
A clear photo of the compressor and a clear macro photo of the tag would do it.
 
 

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