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Old 06-26-2016, 10:19 AM   #1
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1972 29' Ambassador
Boynton Beach , Florida
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A/C keeps throwing breaker

Ack! My not-quite-two-year-old Dometic DUO THERM Brisk II RV Compact Air Conditioner 15000 BTU keeps intermittently throwing its 20A breaker. I've got a EMS-HW30C surge-dip protector in-line, and sometimes that drops out, which then kicks the A/C breaker when it restores the power. Also, typically when the A/C is turned on, the inverter kicks into invert mode for a minute, even though the trailer is still plugged in.

This happens mostly on hot days, rarely at home, more often in camp.

All this points to a huge power draw... I installed the hard-start kit, but little joy there. The A/C otherwise works fine, an R/V tech came out and pronounced it working well. Granted, all he did was stick a thermometer in it.

Is there some sort of super-capacitor that I can get? This is Florida in the summertime, I gotta get my system more reliable! Help this sweaty camper, please!

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Old 06-26-2016, 10:27 AM   #2
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20 amp for a 15000? Might be overloaded in hot weather. Is your home circuit 20 or 15 amp?

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Old 06-26-2016, 10:37 AM   #3
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2007 27' Classic FB
Ridgefield , Washington
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We had a similar problem in the past. When using the A/C, we put the hot water heater and fridge on LP. No popped circuit breaker on the A/C when we do this. Hope that helps.
John & Lisa
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Old 06-26-2016, 10:52 AM   #4
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Princeton , New Jersey
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The common reason is Low Voltage. Many campgrounds are not wire for the current day number of units using lots of power.

Memorial Day weekend we were in a campground with recently upgraded power, 50 amp. We had low voltage, 102 volts on a 30 amp breaker, and could not use the AC. Even those attempting to keep up are falling behind.
2004 Excursion 4x4
1991 34 ft. Excella +220,000 miles, new laminated flooring, new upholstery, new 3200 lbs axles

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Old 06-26-2016, 11:44 AM   #5
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1991 34' Excella
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For under $10, try replacing the 20A breaker with a new one. We had a similar problem with a '77 and the old breaker was simply worn out.
Hi Ho Silver RV! Vernon, Sarah, Mac the Border Collie -
A honkin' long 34' named AlumaTherapy
and a 26' '63 Overlander, Dolly
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Old 06-26-2016, 11:45 AM   #6
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2012 27' FB Eddie Bauer
Laguna Niguel , California
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Same thing with my Eddie Bauer 27ft. I cant run the A/C when the water heater is on electric power or POP Goes the breaker and if its real hot you my need to put the frig on propane too.
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Old 06-26-2016, 12:22 PM   #7
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Boynton Beach , Florida
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Now it's popping all of the time, here at home. Heat index is 100. It's plugged into a 30A circuit, the trailer all by itself. Fridge and inverter are running, but that's about it. Fridge is already cold. I can watch the voltage drop as the compressor struggles, until the surge/dip protector chops the circuit.

I'm beginning to think that I have a bad compressor. Fan part of the A/C works fine.
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Old 06-26-2016, 12:32 PM   #8
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1977 31' Sovereign
Lynnwood , Washington
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I presume your 15K AC is an upgrade from 13.5K, correct??

Granted, the 1.5K upgrade doesn't seem like much. But when push comes to shove, something's gotta give. In this case, your 20 amp breaker is working as intended.

As they say, "Lunch is never free."

Try replacing with a new 20 amp. Your original breaker may be old and tired.

BTW - You've gotta resist the temptation of installing a higher amperage breaker.

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Old 06-26-2016, 01:01 PM   #9
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1973 31' Sovereign
Middletown , California
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There is not much you can do if the problem is low voltage except try another source for the power. Maybe move to another space? Good idea about the breaker being old, or it could be making poor contact with the bus bar. Check to see if the breaker is pushed on all the way and feel it when AC is running normal and if it's very warm that could be the problem. Always a good idea to keep a volt meter handy to see what you've got coming in for volts. The service guy you called should have checked the volts and amps or if he was good he should own a watt meter. The manufacturers of AC's usually publish a table of watts used at specific temperatures of operation and that is vital info when having problems like this. The most difficult type of problem to fix is things like this which are working, but not quite good enough!
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Old 06-26-2016, 01:01 PM   #10
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Progressive Ind

Perhaps give a call to Progressive Industries. It sounds like the EMS is doing its job and protecting your equipment from low voltage.
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Old 06-26-2016, 02:17 PM   #11
2007 27' Safari FB SE
Milton , Georgia
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Some electrical things I would check-

Check the shore power cord to be sure the end plugged into the campsite power is not getting hot. Sometimes the molded plug can get a weak connection causing low voltage.

Tighten screw terminals at your breaker box, but make sure power is off to do this. They can loosen from vibration on the road.

There is a run capacitor for the AC fan. If it is weak, fan will still run but draw more current than usual. Capacitors degrade over time. Lightning spikes and excessive heat speed up decline.

Compressor has run cap too. Separate from start cap where you added hard start kit already.

The only supercapacitor I know to suggest is a good name brand like GE and a step higher voltage, like 440Vac. Higher voltage cap will last longer. Keep the same capacitance value. If a cap is cheap & weak to start with, it can fail early. Weak caps are very common HVAC failure causes.

If your low voltage protector system turns off power to AC unit, it needs to wait 5 minutes before restarting compressor to let pressure drop. If it is attempting to restart right away, that will surely blow breaker.

12vdc thermostat controls might need to be reset at same time as 120vac is switched off to insure 5 minute delay before compressor re-start.

Use a voltmeter to measure your voltage to make sure the low voltage protector is behaving properly. It could be nuisance tripping and need adjustment or repair.

If inverter has been running while power was off, it will draw down house batteries. When AC power is restored, the converter will momentarily draw a lot of ac power to recharge the batteries. This would occur at the same time as the compressor is attempting to start. Try to manually turn inverter off and other loads while trouble shooting this problem. It will reduce the number of things happening at once.

Hope, eventually, you can stay cool.

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Old 06-26-2016, 02:29 PM   #12
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If you ran the air on low voltage, twenty amp for a long time, the compresser may be toast.
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Old 06-26-2016, 02:39 PM   #13
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might want to have a real tech put an amp meter on compressor feed at roof !
note has 3 year war. sounds like compressor is going out and current repair is to replace a/c ( if still in war need to have checked at dometic warr station )
most rv dealers have dometic warr statis .
we don't recharge / replace charged system components anymore , thanks to epa/ snap protocol. if amp draw to comp exceeds spec or flutters is bad comp .
could from sound of it be bad time delay relay . I do know that dom. is having some problems . we have recently replaced 3 a/cs that were under warr 1 was for bad compressor 2 for loosing charge .
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Old 07-01-2016, 06:02 AM   #14
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Boynton Beach , Florida
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It looks like it was a bad compressor. I took the trailer into the good folks at Stomski Trailer in Lake Worth, FL. After much back and forth with Dometic (on Stomski's part), the entire upper unit is being replaced under warranty.

At least it happened one month before the warranty was due to expire!

Thanks to all for the suggestions! Now I get to wait on parts to arrive...

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