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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 7994
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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I am very confused. I have a Rheem RMB-030JBZ. Late last

Customer Question

I am very confused. I have a Rheem RMB-030JBZ. Late last summer the fan wouldn't start and I had a small independant contractor come out and look at it. He decided it was the capacitor. He didn't have the exact cap but had a universal cap. I said it was fine to use the universal and he did. I didn't notice any issues the rest of the season. It has be a very mild spring here in Colorado, but a few days ago we noticed the fan wasn't running again and it was buzzing. It seems that it was overheating. I called him out the next morning and of course the thing was running great but the motor was scalding to the touch. He couldn't source the parts locally and is extremely busy and I am extremely impatient.
I looked up the part numbers for the motor and sourced it at our local Grainger. Here's the rub the motor is a 5uf. But when I look up the part number for the capacitor based upon model it is a 3uf. The universal he installed is a 5uf.
My question is if I match the cap to the motor am I good?
Submitted: 1 year ago.
Category: HVAC
Expert:  Phil replied 1 year ago.
Hello, match the run capacitor to the new motor run capacitor requirement, that will be on the new motors name plate. So far it sounds like the new motor requires a 3uf, if that is that case buy a 2uf run capacitor for it. You should have a clamp around type amp meter, to put on the common lead to the motor to check its run amps. if it runs at or slightly below the motors rated FLA, full load amps, then its the right capacitor. Home depot and lows have them at $50 or so, Harbor freight has them $25.----------We are on the honor system here. Please remember to rate my service before you leave today. It is how I earn a living, and does not increase your charges. If you need anything else, just let me know. You can continue asking follow-up questions within your agreed on limit at no additional charge.
Customer: replied 1 year ago.
The motor that I bought require a 5uf this what came up as a cross at grainger from the Rheem number, what is odd is that the capacitor number crosses to a 3uf. Regardless of all of that, my question is if I match the cap to the new motor will I be okay?
Expert:  Phil replied 1 year ago.
Hello again, if you match the run capacitor to the motor is should be fine, I am at a total loss to explain why a 5uf capacitor cross matches to a 3 uf capacitor... there is a mistake somewhere.---------------We are on the honor system here. Please remember to rate my service before you leave today. It is how I earn a living, and does not increase your charges. If you need anything else, just let me know. You can continue asking follow-up questions within your agreed on limit at no additional cost.