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Different Capscitor for replacement motor

1K views 8 replies 5 participants last post by  JJboy 
#1 · (Edited)
Ok, I've been out of the DIY arena for a while so I need some help.

I've replaced the condenser fan motor on a residential HVAC unit and the new motor uses a 7.5 µF run capacitor just like this one:


The replacement motor only has three wires: (AS DID THE ORIGINAL)

Black - I assume goes to the power on the circuit board (like the old one)

Brown -
Orange -

The old setup used a start/run capacitor rated at 40/5µF (the three terminal cylinder type) which powered both the fan and compressor motors. I know I can't just use this for the new motor as it is rated for 7.5µF.

So, here are the questions:

1. Do I just add the new 7.5µf run capacitor? And how should it be wired up?

OR...

2. Do I buy a new start/run capacitor (three terminal cylinder type) rated at 40/7.5µF? Will the higher µF rating damage the compressor motor? ...since the original is 5µF

Please advise.....it's hot.


Also, sorry for the misspelled title.....Capascitor?
 
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#3 ·
First of all thank you for the reply.

I don't want to over complicate things but....

the original three wire config., which is similar to your "DUAL CAP" illustration had the BLK going to a circuit board and not directly to the contactor. Is this irrelevant since the BLK ultimately ends up at the contactor T1 even if there is a circuit board in between?

So, the new setup would be like your 3 WIRE diagram. The only wire I would have to add would be a RED wire from T2 to the new run capacitor, thereby eliminating the the DUAL CAP from the fan motor circuit......

Did I get that right?

Also, putting in a higher rated µF DUAL CAP will or won't harm the motors rated for lower µF?

Again, thanks for the help.
 
#7 ·
Thank you all for taking time to respond.

When I read further about Capacitor sizing I did find warnings about improper sizing.

If the capacitor has a lower µF rating the motor will not start/run and if it has a higher µF rating then evil magnetic forces will be unleashed that can cause the fabric of space-time to unravel and ultimately destroy the universe.....or it makes the motor fail prematurely.....one of those two.

So, I went back to Grainger and got the original run capacitor back along with a handy diagram that is similar to the 3 WIRE diagram that Houston204 provided.

Thank you all again.
 
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