a/c compressor trips circuit breaker


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Old 09-06-09, 09:53 AM
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Unhappy a/c compressor trips circuit breaker

I have been dealing with this issue for a couple of years now. My old compressor would trip the circuit breaker from time to time. Replaced the entire a/c system last year, including the compressor and now have a Goodman compressor. Thought that would take care of the problem but the new compressor does the same thing. Tried replacing the circuit breaker thinking it was just old. Did not work. Had an electrician come out and the electrical is fine. He says the compressor is drawing 70 amps when it starts up and that is causing the breaker to trip (the circuit is a 20amp breaker which is appropriate for the compressor he says). Electrician even ran new wires for us just in case. Electrician says we need a run capacitor installed on the compressor. Had the a/c guy come out, he says there is already a run capacitor and he installed a hard start kit, which did not help and he has no idea what else to do.

VERY frustrated- this doesn't happen every day but quite frequently especially during the day when it's hot out. My husband says it seems to happen only when the thermostat gets put down 2 degrees or more-- if we put it down only 1 degree, it kicks on fine, then can lower it further once it's running. However, I'm not sure if his theory is right and am concerned there's a bigger problem here.

Any ideas as to what else can be done? I need a second opinion I think because my a/c guy seems stumped.
 
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Old 09-06-09, 07:51 PM
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Does the voltage drop at startup? Is a minimum time of 3 minutes allowed between startups?
 
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Old 09-07-09, 07:44 AM
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Thanks for the reply--

After startup, the voltage drops back down to normal... there is at least 3 minutes between startups.
 
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Old 09-07-09, 11:47 AM
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You said a service tech looked at the system.I would think he put gauges on the unit to check the pressures?If not he should.If you have been having this sense install it could be overcharged,in which case he would need to reclaim refrigerant.
 
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Old 09-08-09, 01:57 AM
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Cool blowing circuit breakers

I use to have a large Carrier window a/c, that was a big hunk of junk. It used to blow the breakers a lot - and my electrician found the same thing, that it was drawing a huge draw on start up, then using much less when it was running.

Carrier did not stand behind their warranty well, but they did have a "hard start package" which was for this problem - I find myself thinking maybe this is the case with your unit?

Also, I believe there are air conditioner circuit breakers, which are supposed to be more slow blow than standard - most people don't use them however. Maybe this would help?
 
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Old 09-08-09, 01:03 PM
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My husband says it seems to happen only when the thermostat gets put down 2 degrees or more-- if we put it down only 1 degree, it kicks on fine, then can lower it further once it's running.
Just a shot in the dark here, but I've seen it before. Sometimes a cheap mechanical or mercury thermostat will double start. In other words, the connection is made, but immediately broken and then made again (all within a time frame of less then a second). Listen to the outside unit during start-up. If you hear a double click, this may be your problem.

Hard start kits are great but not the two wire PTC style. PTC's need time to recycle. Therefore, a 3 wire hard start (potential relay with start capacitor) is best.
 
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Old 09-08-09, 02:54 PM
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Originally Posted by appledude
Also, I believe there are air conditioner circuit breakers, which are supposed to be more slow blow than standard - most people don't use them however. Maybe this would help?
You are referring to HCAR-rated breakers. In the mid-1980s, UL changed things: all 240-V ckt breakers manufacturerd since then meet the the old HCAR standards. If the existing breaker were older than about 20 years and not HCAR rated, it might be worthwhile to replace it (but he said he replaced the breaker already).

He said his electrician confirmed that a 20-A ckt (and breaker) was correct for the compressor. This can be confirmed by inspecting the nameplate on the compressor unit.

If somehow there is too much voltage drop in the feeder ckt to the compressor, that will increase load amps and cause the fan and compressor motors to accelerate more slowly, possibly causing tripping. Check all the connections or splices from the panel through the manual switch mounted near the compressor, and the contactor.

Does he have aluminum wiring by any chance?
Doug
 
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Old 09-08-09, 03:31 PM
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Originally Posted by jim-connor
Just a shot in the dark here, but I've seen it before. Sometimes a cheap mechanical or mercury thermostat will double start. In other words, the connection is made, but immediately broken and then made again (all within a time frame of less then a second). Listen to the outside unit during start-up. If you hear a double click, this may be your problem.
This sounds like a plausible theory to me. Does the breaker trip only when the thermostat is turned down manually to a cooler setting or also when the thermostat automatically calls for cooling (without touching the setting)? If the trip only happens when you're manually resetting the thermostat to a cooler temp, then I think that would confirm the theory.

If the thermostat is old, I would replace it with a Honeywell (or other reliable brand-name) solid-state, digital thermostat (no mercury, no mechanical contacts, either of which can "bounce," causing multiple contacts).

Besides listening for the compressor contactor to make more than one "click" at turn on, you could try this: with the AC not running, turn the thermostat to "system off," turn down the thermostat enough to call for cooling, then turn the switch to "A/C on." If the problem doesn't occur using this turn-on procedure, that would point to the thermostat's contacts.

(Of course, don't restart the A/C within a few minutes after turning it off - the high head pressure can result in ckt breaker tripping. Newer digital thermostats may incorporate such an automatic delay.)
Doug
 
 

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