A/C problem, need help ASAP

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Makes sense.

Does not seem to be the case for me (the contactor is energized).

That could be. I did a few more measurements. I will post a summary soon.

That's correct, I saw a diagram (and posted it).

Sure.
I am afraid that it is the case, as well (see my UPDATE #2 that I am about to post).
i
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On 3 Aug 2006 04:00:15 GMT, snipped-for-privacy@d-and-d.com (DoN. Nichols) wrote:

Funny, most 3 phase units I've seen have high starting torque. Some units have shutoff solenoids, and start under headpresure, even after long off-periods.
But since this is crossposted to alt.home.repair, I can see why the presumption is made, since you likely only deal with residential units.
--
-john
wide-open at throttle dot info
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    Well ... I've observed a failure from a power glitch in an industrial unit (out where I worked before I retired). I was sitting out in my car relaxing at lunchtime, and I heard a loud whooshing sound, and saw a dense white cloud billowing out of the room which had the air conditioner compressors, along with other HVAC stuff for the building.
    It turns out that it blew a hole in the compressor's crankcase. It apparently tried to start with liquid in at least one cylinder, and the three phase motor *did* have plenty of starting torque -- too much in terms of the health of the multi-cylinder compressor.
    Luckly, there were two other units in the same room which did survive, so we were not baked out of the building until repairs could be performed.

    Well ... I'm the one you quoted, and I was posting from rec.crafts.metalworking instead. Still not as an expert on refrigeration systems, but with a bit of mechanical knowledge at least.
    And -- if this system had had an electronic time delay on the restart as my home system does, it would have survived, and would not dumped a large quantity of whatever refrigerant it happened to use. This was before the changing regulations forced us to abandon the Halon (another CFC) fire control system in our large computer room and replace it with dry-pipe water fire extinguishers.
    Enjoy,         DoN.
--
Email: < snipped-for-privacy@d-and-d.com> | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
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Ignoramus2645 writes:

Values should be on the old capacitor.

Common terminal. The can is (unless defective) isolated.
One of your terminals may be shorted to the (grounded) can, thus causing your circuit breaker overload.
Costs about $10 or $20 at http://www.grainger.com/ to get a replacement. Also all over eBay.
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On Thu, 03 Aug 2006 03:18:25 GMT, Ignoramus2645

If there is a short in the cap, that's one place there won't be any visible sparking and maybe nothing visible.

It says what it is on the can. If not, I guess a diagram, and if not, maybe the AC supply house knows. If you know the value you want you might get it cheaper at an electronics supply house, but they might not even sell one that big. Never tried.

Probably.
I doubt it.
If it's the cap, you may have gotten off cheap. Good for you.

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mm writes:

AC electrolytic capacitors of this type are not sold by electronics distribution.
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Richard J Kinch wrote:

Um, no.
http://www.alliedelec.com/Catalog/Indices/IndexHandler2.asp?n 40270&MID35452&DESC=Motor+Run+%2F+Start&IND=T&DEPTH=2&LVL
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Jim Stewart writes:

I should have said, "typically". You won't find them at Mouser or Digi- Key.
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Your name says it all!!! Call a pro. Muff

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This is symptomatic of a bad compressor. Try testing the motor leads for a dead short (to each other and ground). There are start and run leads. You may need a HVAC guy to replace your compressor and recharge the system.
Tony

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Good idea, I will check motor leads for leaks to ground. (the main motor leads should read a very low resistance to one another).
i

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Um, no, that could not be the case. If I disconnect the cap's fat blue lead and let the cap hang in the air, the breaker does not blow, the blower runs, and the compressor hums (I am sure that it does not run).
It is very likely the cap.
i

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most likely you will need a new compressor from DIDO

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Yep, that is indeed the case. I will get a whole new system.
i

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