Capacitor: Can a 5MFD replace a 3MFD?

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Old 06-28-14, 08:47 AM
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Capacitor: Can a 5MFD replace a 3MFD?

This is a typical 'condensor fan not spinning' issue, so I'll try not to bore you with too many details...but here's the Reader's Digest version of the issue:

(HEIL NAC030AKC3 - spec's show a 35+3/370 capacitor)

Fan stopped running last summer, and (thanks to this forum and you knowledgeable experts) I determined it was the capacitor. Local HVAC supply house didn't have a 35+3...but stated a 35+5 was an acceptable replacement. Not knowing any better, I took it. Seemed to work fine for the rest of the season.

Yesterday, wife calls me at work, saying it's not working again. Asked her to lower the t'stat and tell me if she could hear the outside unit turn on - she says "no." (Obviously, she was inside, so not sure specifically what the condensor was/wasn't doing). I thought it was odd that the capacitor would crap out after only 1 season, but, seemed like the most-likely culprit, so I stopped at the HVAC supply house on the way home. Again, no 35+3 in stock, but was again told a '5' was fine.

Got home late. I knew I should have powered it up to see just what it did first, but it was getting dark, so I just swapped out the capacitor. Had wife lower t'stat and watched unit to see what happened:

Contactor pulls in, compressor starts, and fan starts nice and strong. However...after about 5-10 seconds, the fan slows and 'buzzing' noise increases - possibly the compressor straining? Fan eventually comes to a stop.

From the other threads I've read, I'm wondering if the fan motor is failing (although it initially started nice and strong). Which (finally) leads to my question:

- Could using a 5MFD instead of 3 have caused the motor to fail?

- Or...is something else going on (contactor losing 'contact')?

As always, your input is GREATLY appreciated.

Wally
 
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Old 06-28-14, 09:00 AM
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The 5 MFD can be used in a emergency, till you get the 3MFD.
 
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Old 06-28-14, 09:54 AM
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Thanx skaggs!

Just not in a big hurry to replace a $200 motor. Yes...I'm cheap.

Wally
 
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Old 06-28-14, 09:57 AM
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Some motors are very particular that they have the proper cap connected. You can also use a separate 3mfd cap if need be.
 
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Old 06-28-14, 10:13 AM
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There was another thread from a couple of days ago. The fan side of the replacement capacitor the guy got (dual cap) was 10 mfd instead of 5mfd (original). The fan would turn on and run for a short time (30 minutes as I recall) and then turn off (motor was overheating). After the guy got the correct capacitor (5 mfd) the fan worked normally and he reported that it ran for 2 hours without a problem. So, it's possible that the wrong value is causing the motor to overheat. What you'll probably have to do is to buy a single 3 mfd cap and use it in place of the 5 mfd cap in the dual capacitor.
 
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Old 06-28-14, 10:44 AM
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Thanx PJ and Bob! That's probably the thread I was reading that lead me to this theory.

I think step 1. will be to get the meter out and do some checking...see if I'm getting 240V on both sides of the contactor (just to rule out a bad contactor); and test the capacitor (although I'll bet it tests OK).

Then I'll try to get a single 3MFD cap...question: Do I just run a 'jumper' between the C(ommon) terminals?
 
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Old 06-28-14, 10:52 AM
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Yes, jumper the C terminal from your dual cap to one side of your new cap and connect the start wire from your fan motor to the remaining terminal on the new cap.
 
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Old 06-28-14, 11:19 AM
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Got it. Obviously won't have an update on this till Monday when I can get a new cap. I'll try to remember to get back here with the results.

Many thanx! to all!!!!!

Wally
 
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Old 06-30-14, 11:26 AM
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Well, that didn't work.

Now (using a 3mfd cap) - the compressor starts, but the fan doesn't even spin - not even with a "push".

What do ya think? New motor? (I found one local for $129).

Help!!!!
 
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Old 06-30-14, 03:17 PM
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If you are getting the correct voltage, everything is correctly wired and the cap is good...Sounds like it is time for a new motor.

Is the replacement motor that you found the small funny looking clamshell motor that you probably have now?

Some ICP condenser models also have the bolt holes for a conventional frame condenser fan motor.
 
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Old 06-30-14, 04:18 PM
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Thanx Houston! I had suspected it was the motor, guess now it's time to find out.

I've been dealing with my local United Refrigeration supply house. I know they're a pretty big outfit, and seem fairly knowledgeable (although, they're one of the places that told me a 35+5 would work in place of a 35+3...oh well).

I gave him my HEIL (ICP) model # NAC030AKC3) and the motor part # I found (1088235) - and he looked it up in their catalog from there. Honestly, I was running out the door with my 3uf cap in hand, so I didn't have him pull the motor off the shelf, so I don't know what it'll look like. From what I've Googled, it seems US Motors is the predominant manufacturer of replacement motors, so I imagine it's one of there's...probably like this:

ICP Central Air Condenser Fan Motor 1088235 Order now for same day shipping. 365 day return policy. RepairClinic.com

I'm fairly certain it's a 42Y frame - but I'll make sure it will fit first.

I was just happy they had a decent price (compared to what I've seen elsewhere).

I'll go pick it up tomorrow morning, so I should be back here with an update in the afternoon sometime.

I will, however, be checking this thread throughout the night, if anyone has any additional input - greatly appreciated as always.

Wish me luck!

Wally
 
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Old 06-30-14, 05:51 PM
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I think I have that same funny little motor on my ICP condenser.
 
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Old 06-30-14, 06:51 PM
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Lol! Any chance you could bring it over tomorrow?
 
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Old 07-01-14, 09:13 AM
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Success!!

Installed new motor (took all of about 15 minutes). Spun right up, and (I think) is a little quieter than the old one. Cooling has begun. Ahhhhhhhh.......

Houston: as I suspected, the replacement is a US Motors (made in China...go figure). It looks identical to the OEM (made by Emerson).

I have the 35+5 cap in place, with the fan running off the 3/370 piggy-backed to it. Which I guess brings us back to my original question:

I guess a 35+5 can replace a 35+3....but ONLY until a 3uf can be located. I have no way of knowing for sure, but I'm suspecting running a 5uf last year into this year probably hastened the old motors demise.

I'm still DEFINITELY not a pro, but I think if anyone has a "compressor runs, but fan doesn't", I'd probably NOT recommend a whole new dual-run cap, especially, if they can't get the EXACT correct specs.

Rather, I'd suggest just getting a single run - in the correct MFD/voltage - and putting that in. It's cheaper, possibly easier to find, and you're not getting more than you need. Oh well, just my .02.

Thanx again to ALL for your help!

Wally
 
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