AC circuit breaker keeps tripping

[iwejun]

I have a Parallax converter in my Sandpiper when I get to campsite I turn on Ac and all works well,sometimes for hours at a time. Sooner or later though the a/c breaker trips about halfway and I have to reset it. Talked to guy at United RV in FW and he said the 30/20 breaker, 30 being Main are too close and the breakers warm up enough to trip the a/c when a load is put to it. My a/c is thermostatically controlled. His recomendation is to put a fan to blow on the breakers and he sees this all the time. Does this make sense or do I need to replace the breaker? I just came back from camping for a week and am going out for 3 more too soon to get it to a dealer to sit on their lot until they get time to check it out. Any ideas? TYIA

[LeeChristianson]

Wow, that sounds like a Mickey Mouse fix to a problem that shouldn't happen in the first place. Maybe have the breaker replaced first. You might have a weak/faulty one. Is it possible the A/C unit's drawing too many amps? Have you had that unit checked for proper draw?

[SmokeyWren]

I have the same problem, but only when I really need the Air conditioner - when ambient temp is over about 95º F.

Mine's at the RV dealer right now. It's probably caused by one of three things:

1) The 20-amp circuit breaker is defective and breaking when there is less than 20 amps load. And my dealer's tech said that's common when the breaker is facing the sun and gets hot from direct sun. But my breaker is inside the coach, so direct sun is not the problem. I doubt that a fan blowing directly on the breaker would help keep it cooler

I agree that silly design with the 30-amp main and the 20-amp A/C circuit in the same wrapper is really dumb. So I suspect the breaker is my problem.

2) The A/C is defective and drawing more than 20 amps under some conditions. But the dealer checked ou the A/C last year and said it was fine.

3) The power source is less than about 108 volts when it enters the breaker box. Caused by too-long, too-small extension cord, or perhaps by a generator that doesn't put out enough watts to handle the load. But my generator is a 4,500-watt Honda, so I doubt that's the problem. And the breaker breaks when tied into shore power in my garage, as well as when using the generator, and I don't use an extension cord, so I don't think that's my problem.

[drcampbell]

Does “too close” refer to physical proximity or to the amperage ratings? A 20-Amp branch breaker installed downstream of a 30-Amp main breaker is not within the recommended 2:1 minimum ratio for proper fuse coordination. But if I read this right, it’s not the main breaker that’s tripping, it’s the branch breaker?

A correctly-installed and correctly-operating circuit breaker should not dissipate more than a trifling amount of heat. If a breaker’s more than one or two degrees warmer than its surroundings, there’s something wrong with it – usually a high-resistance connection from worn-out, dirty or corroded contacts, a worn-out spring holding the contacts closed or loose/dirty/corroded connections. Cleaning and tightening connections often works wonders for electrical apparatus.

Putting a fan on the breakers is absolutely the wrong thing to do. If you do have a heat problem, a fan might keep things running but you’ll just postpone fixing the real problem, which will only get worse if ignored. Whoever told you to do that, don’t put a lot of faith in his advice.

Of course, the first question is whether it’s a nuisance trip or a genuine one. So first, put an ammeter on the breaker that’s tripping and see how much current is actually being drawn. And don’t just make a quick, one-time measurement but leave the ammeter in place all day to see what the current is during the hottest part of the day and after it’s been running for several hours. If you’re pulling more than 20 Amps through the breaker, it’s not a breaker problem.

Also look for short-cycling. If the thermostat turns off the AC compressor, then turns it back on too soon, before the refrigerant pressures have had a chance to equalize, the compressor will be starting under a much heavier load than expected and the starting current will be much higher than expected. Once a compressor’s off, it should stay off for at least two or three minutes.

[mdmasters]

I would also check to see if their is anything else tie to the A/C breaker. It would not be the first time somebody cut some corners.

[iwejun]

"Too close" means that they are sandwiched side by side with no gap. They do feel warmer than the outside air, mine are located inside away from fridge and other heat producers. Yea, the fan is Mickey Mouse and this particular unit (04') sat on the lot for the better length of a year in the upper north, thus the good deal I received for it in Oct. 05. I'll replace the 30/20 breaker and see if that will fix it. A/C doesn't seem to cycle quickly, and that was my first thought about head pressure being too high on restart. At least this next trip is up to the RV campground where I bought the trailer in the first place, maybe I'll get it fixed on site from the dealer when I get up there. Another thing is that my fan continues to circulate air, but the cooling stops.

[ritschner]

I had the same issue with my last fifth-wheel when it was brand new. It would trip the circuit breaker for the AC occasionally. Since I had a spare breaker lying arround, I decided to pulled the panel cover to swap the breakers out. That is when I noticed the wire from the breaker to the AC was just stuck in the breaker loosely. It turns out someone had forgot to tighten the set screw on the wire going out from the breaker to the AC. After tightening the set screw I never had another problem.

[Bob C.]

You lost me with the fan continues to run & but the cooling stops.
Both of those items are run thru the breaker that controls the A/C. So,if the breaker is tripping the A/C should completly shut off.
As previously mentioned, do an amp draw check on the A/C circuit also check the voltage at the breaker. 100 volts = excessive amp draw & tripped breaker.
Whoever thought up the "cool the breaker with a fan" should turn their tools in.

[Down South]

As mentioned above (You lost me with the fan continues to run & but the cooling stops.) The fan and compressor should be controlled by the same breaker as a unit. So I'm confused too now.
As also mentioned above, check the connections. A loose connection will cause the breaker to heat up.
I've had the same problem myself but mine was an easy fix. The fellow that owned the trailer before me had rewired a few things and had hooked the AC up to a 15 amp breaker instead of a 20 amp. After looking at the data tag on the unit, seeing what the normal amp draw should and my handy amp probe I discovered the unit was pulling the right amps but was just a little much for the 15 amp breaker. Actually he had hooked the hot water heater up to the 20 amp when it should have been on the 15 amp.
A bad breaker will cause this problem too. The real test would be as mentioned above. Use an amp meter to determine exactly how many amps you are pulling. Take the cowling off the unit and look at the data plate and see what it should be pulling and work from there. If the load is close to 20 amp but not exceeding 20 then a new breaker might be in store. If the load is over 20 amps and the unit data tag shows a normal amp draw of let’s say 15 amps them you have a problem with the unit. Also check the connections at the unit. Usually they will just be wire nutted together in a junction box at the unit. Wire size from the unit to the breaker panel can be a problem too but I would figure the factory would have installed the right size wire.

[drcampbell]

[ QUOTE ]
You lost me with the fan continues to run & but the cooling stops. ...

[/ QUOTE ]

I think that was a response to the question about short cycling. It's difficult to tell what the compressor's doing when the fan runs all the time and masks the compressor noise.