Wrong Run Cap Size - Sufficient?


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Old 05-11-13, 05:12 PM
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Wrong Run Cap Size - Sufficient?

Hi,

I have a 10ACB-24 Lennox condensing unit, and the run dual capacitor went out. I wasn't sure of the unit when I purchased a 35/5 440 VAC dual cap, and I installed it today. Works great. I did some more digging, and I should have installed a 30/5 370. What are the implications if I leave it alone? Should I bother ordering the right cap?
 
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Old 05-11-13, 05:30 PM
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Voltage...as long as it's higher is no problem. Normally they say 10% on the cap mfd specs...but I'm not sure if higher will hurt.

Lets see what the Pro's say...
 
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Old 05-11-13, 05:40 PM
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IIRC plus or minus 5% on the mfd ,good for the higher vac,I wold replace would draw higher amps with 30mfd. Oh you put in a 35 sorry and it needed a 30.Still would change I'll shut up now.
 
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Old 05-11-13, 06:21 PM
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The 30 mfd section of the capacitor is for compressor starting.
A slightly higher mfd rating will cause the start current to be slightly higher.
When a capacitor only is used for compressor starting there is current flowing to the start winding whenever the compressor runs.

It is possible over the long term the higher amps on the start windings could ave a negative effect.
It is possible to research your specific compressor model number as in some applications a 35 mfd cap might be used but it would take a lot of digging.

Safest bet is to get the right one.
 
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Old 05-11-13, 06:53 PM
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Thanks GregH!

So the 440 is no big deal right?

I dug up the specs online for my unit, and that's how I found out it needed to be a 30/5. But that doesn't mean the compressor that is there is the same one as when it was installed...

There is also a booster attached also, maybe a bandaid to the older cap I just replaced?
 
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Old 05-12-13, 02:44 AM
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Oh, ok.
If the specs call for a 30 mfd then you are good to go.
The voltage rating really means the "minimum voltage.....Higher can actually be better.

The booster could possibly be installed when there was a starting problem but I will install one when replacing a capacitor to reduce the chance of a call back.
 
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Old 05-12-13, 06:56 PM
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If the unit calls for a 30/5 and you put in a 35/5 then it is not ok. You need the called for MFD of 30/5. Voltage of 370 or 440 is ok in your case.
 
 

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