a/c tripping circuit breaker

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68chstiger

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Dec 20, 2009
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The a/c on my travel trailer will occasionally trip the breaker when it starts up. It will cycle on and off normally and then in the middle of the night when the thermostat call for the a/c to come back on it trips the breaker. I replaced the run capacitor but it still does it every once in a while. It is a 30 amp system.. Any suggestions would be greatly appreciated.
 
What else is drawing power when it happens? Your converter can draw quite a bit of juice when it's charging batteries. Is your water heater LPG or electric? (or a hybrid?)

When the AC is running, does it work well? Could you have a fan shaft that's hanging up, causing some extra draw to get started?

We need a bit more info to help troubleshoot.
Age of coach and AC unit
Make/model of AC unit

I'm sure there's other stuff that will help...but I'm having a senior moment...:p
 
Two other sources of AC power load are the hot water heater, if powered by shore power 120vac  and not by propane, and the refrigerator (if in auto mode where it uses an electrical heating element instead of propane. As Air conditions age, the compressor may draw more current at startup. Combine that with any other load that maybe on at the same time as the AC tries to start then the breaker may trip.
Don't rule out a degraded circuit breaker. It too can become weak and trip at a lower current than it's rating.
 
Often, a faulty starting capacitor on the compressor can cause the breaker to blow. If you rule out the simple items, you may consider this.
 
Is a starting capacitor the same s a run capacitor? The unit is 2 years old and is only used 4 to 5 times a year. It is always hooked up to shore power, the refrigerator is on 110 but I use propone for the water heater. How do I test to see if circuit breaker is bad? Thanks for the replies
 
Probably easist and cheapest to just replace the breaker if it's in question. Never hurts to have a spare anyway.

Ernie
 
Are you tripping the a/c circuit breaker or the main 30A breaker, either on the RV or the power pedestal? If its the a/c circuit breaker that trips, none of the other loads in the RV are relevant, cause that breaker is dedicated to the a/c. It should be a 20A breaker unless the a/c is under 13,500 btus (some are 11,000 or even 7000). What brand and model of a/c is it?  Tough to make guesses without at east a few facts...

What is the voltage of the power source? The amp draw of an a/c increases as the voltage goes down, so the a/c is more likely to trip the breaker at 105v than at 120v. Get a voltmeter or Kill-o-watt and check it out.

The start capacitor has a "run device' associated with it, to take the capacitor out of the circuit once the compressor is up to speed.
 
What is the purpose of a "Start" capacitor on an electric motor?

Answer. An electric motor that uses such a device actually has two windings, one is the operational (run) winding and the other is for starting,, IF both windings are "in phase" however the motor does not know which way to turn and may well not turn at all  I will add to this later.

Capacitors obey the law of ELI the ICE man.. ELI is an inductor (ELectronic symbol L) and ICE is a Capacitor (Symbol C) so in an capacitor E (Voltage) Leads I (Current) and thus the start winding powers up a fraction of a second BEHING the main winging,, this sets up movement of the magnetic field that actually turns the shaft and in the direction of interest... SO it starts, (With gusto since both windings are now workign together) and when it gets up to speed a simple centrifical switch opens and says goodby to ELI the ICE man and the motor runs normally.

(OK ELI in the story.. The windings of the motor are INDUCTORS of course)

Small motors such as clock motors do not use a start cap. They use a 'Check lever" if the motor starts in the wrong direction it hits a stop (ratchet like device) that stalls it, since it can not restart in the wrong direction it reverses and runs properly.

Microwave turntable motors. .;Does not matter which way it turns so sometimes you will see it clockwise, sometimes anti-clockwise..  That's why.
 
I replaced the breaker and it seemed to fix the problem. Has been running smoothly since. Thanks for all the advice
 
I am having a similar problem on a Coleman 13,500 worked fine shut the ac off and all the lights off in camper unplugged camper from my 4600 peak and 3800 running watt generator when to town for 5 hrs or so got back started generator plugged in camper and let run a min then turned the ac on and it almost stalled my generator ac was blowing real weak and could not tell if the compressor kicked on because it tripped the breaker in a30-60 secs so I thought it was the generator took it back and got a new one from tractor supply ( champion brand ) and it did the same thing if I set it to just fan high or low it runs fine just no ac everything else works in the camper I bought this camper used 5 months ago and use it at the camp on generator only if used it once on shore power and never have had a issue anyone know what it could be
 
James,
Could you please use periods and comma's between sentences? It would make it so much easier to read and understand what you're attempting to relay to us. Thanks.
 
James.. Since yours boggs down soon as you fire her up I'd guess that Start Cap everyone mentioned above.. They come in two flavors for most A/C's. one is a "Standard" and the other is called a "Hard Start" Slight difference in the value is all.. The hard start may also be called a "Soft Start" (Anything other than a Normal or Standard Start) because it "Softens" the starting inrush current a bit.

I would see if there is a Hard Start cap for your A/C and try it.. See if that fixes the problem.

Another thing you can do is hook to shore power (if it's enough) and meter the thing, though most meters do not respond fast enough to see starting current less you are very lucky.
 
This is what most rv ac units use for a starting device, basically, it bypasses the capacitor on the start winding for a fraction of a second         
http://i.ebayimg.com/00/s/MTIwMFgxNjAw/z/UzEAAOxyaTxRQ6~j/$T2eC16RHJIQE9qUHsjyKBRQ6+jfs!g~~60_35.JPG

there are 2 wire and 3 wire hard start kits, the difference being that the 2 wire kits have to cool off for about 60 seconds before they will allow the start capacitor back in the ckt. The 3 wire units require no time before restart  http://www.supco.com/images/pdfs/AC%20Hardstarts%20Booklet.pdf
 
Sorry about the no periods,etc. I was on my phone typing it.
Anyhow thanks for the advise,I do know when I pulled the cover off there was 2 caps. One had 3 wires on it, red, blue,brown ( I do believe ) the other had 2 wires both brown. They was both side by side held in with the same hold down strap. And it don't trip the break as soon as I turn it one, it takes a min or so. I was gunna replace both caps but I was reading somewhere that the caps don't really go bad, so I didn't know if I would be wasting my money. But I guess if I buy new ones and it don't fix it and I need a new unit I'll have spares. Thanks a lot guys if anyone else has had this problem or got a suggestion feel free to let me know thanks again
 
You said it takes a minute or so to trip the breaker. During that time is the compressor groaning as if is struggling, or not running at all? And what breaker resets, the air conditioner's?


Mike
 
It's hard to hear if the compressor is even coming on, between the generator noise and the noise from the ac. Although the air coming out of the vents seems cold just not blowing hard due to the generator being bogged down. And yes it just tripps the ac breaker.

As I said before it was working just fine before I had to run to the store. And I shut the ac off, and unplugged the camper from the generator. I leave the generator in the bed of my truck, it's to heavy to get in and out by myself. And don't wanna leave it there, since it is just a weekend place with no gate, fence nor shed to lock stuff up in.

Idk if it was maybe the sun beating on the black rv cord but once the ac started messing up and I just unplugged the camper from the generator. The cord seemed a little warm. Maybe caused from the ac pulling so much power trying to start. I don't recall it ever feeling warm before. And I could of been over reacting since the ac was messing up.
 
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