Central AC trips its breaker and main breaker!

My Trane 2 ton central AC has been flawless in the past 8 years. Last month had it checked out and tech added little freon, working just fine until yesterday afternoon. AC was running fine, then tripped its own 30 amp breaker AND the 100 amp main breaker...I reset and 30 seconds later it happened again. Waited a hour and reset breakers, everything running fine. AC cycles on and off like usual. After 5 hours of normal running both breakers trip again..I checked the tightness of all connectors in the breaker box and the outside disconnect and where they attach to the AC unit outside. Everything nice and snug, no corrosion, no smoke, no smell, no arc marks.
Just trying to get some idea what the problem might be, maybe a start or run capacitor on the compressor? Maybe the 20 year old breaker is dying? I will try to get a clamp on ampmeter to see how many amps the AC is drawing. I do have the AC company coming out to look at it tommorrow. Anything suggestions? I was going to post this in the HVAC group but if your not a pro, they do not want to answer.. THanks.
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Breakers trip for a reason. If both are going it sounds to me like you need a service call. If you have an amp meter by all means use it and check the compressor out. Starting current can be 6X of full load amps. It is possible that the breakers are weak, it happens but only when there is a lot of tripping. Of course one good fault could be the culprit. But your also resetting the 100 amp main. So your seeing a lot of current. That puts my remote troubleshooting viewer, back to the compressor. Sorry I do not have better news.
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Get the opinion of the HVAC company before proceeding. It sounds like there's a short to ground that's either high resistance or is intermittant. It's very difficult to give advice over the internet but the company checking the unit should be able to analyze the compressor/unit to see if it's causing the trip. As with many mechanical systems, there are many many possibilities.

Thank you for directing your questions here in the appropriate forum and most of all thank you for taking the time necessary to determine that this is the correct forum. :-)
- Robert
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You might want to try replacing the 30 amp breaker first before calling in the HVAC pro.

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Just keep resetting the breaker. Soon you will be calling an electrician......or the fire department........
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I read this, and...
All I can say is turn it off, leave it off, and wait until the AC company shows.
Your problem screams of a bad compressor, and if its tripping the main, you dont want to consider what it might be doing to the line from the breaker box to the unit in the meantime...
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You are probably right but I had a similar case and could not get anyone look at it for several days so I decided to take a chance and change the breaker and it turned out the HVAC was fine and it was a bad breaker. I asked all the HVAC guys and they told me changing the breaker would be a waste of my time. Guess I was lucky for once.

marks.
you
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AC man will be here in the AM to check it out. I did have access to a clamp on ampmeter and while running the AC pulled a steady 8 amps. Cycled on an off several times in two hours, then both breakers tripped again. Odd thing was the AC was not running or trying to startup...Wondering if the problem is at the power pole. My wires are rubbing against the metal guy wire to the ground and I guess the last power co tech just wrapped electrical tape around them for insulation, wonder if it has worn thru and when the wind blows makes contact and blows my breakers...Will have the power co out in the AM also!
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box
outside.
or
dying?
if
company
breaker
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replaced
was
when
Sure hope you bill them for the trip.
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HVAC man arrived right on time at 8am. He went to the outside unit took off the electrical cover hooked up his ampmeter and in 30 seconds if failed. Turned out it was the wire from the disconnect box to the AC unit itself, two wires were chafing from the vibration of the AC running. This occured over 20 years..BTW. We could see where a little water had gotten in and thats were the short was. Insulation was worn away and you could see where it was arcing..New heavy flexible stranded wires fixed it right up! Thanks for all the suggestions/help!
Rob
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was.
Very glad you got your problem resolved!
- Robert
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And now that you've tripped your main quite a number of times throughout this ordeal, it wouldn't hurt to get that puppy replaced...
I'm not saying nothin', I'm just sayin'...
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X-No-Archive: Yes
Art wrote:

The OP said its taking out both the branch and main breakers. The odds of both breakers failing simultaneously is low. A weak branch circuit braker might trip, but if the 100A main breaker is tripping along with it, something is seriously wrong.
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