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Old 05-28-2018, 09:56 AM   #1
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AC unit on 20 AMP breaker !!!

I removed my AC unit last week after doing some checks, I had turned of the breaker but still got bitten while up on the roof. So turned all off and disconnected the shore power, to make sure when removing the unit I did not get bitten again.
Well I have discovered that the AC is running off a 20 AMP breaker. Surely this is wrong, I would have thought it was on a 30 AMP breaker !!!!!!
Am I loosing it, or have I discovered an installation error ?
Cheers,
James.
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Old 05-28-2018, 10:06 AM   #2
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Year, model of Ac unit and AS?
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Old 05-28-2018, 10:18 AM   #3
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The old one is a Dometic 13,500 btu. My new unit is the same replacement that Airstream is installing a Dometic Penguin 2 rated at 15,000 btu.
Well I just checked the installation instructions and all of the units run on a 20 amp breaker.
I believe I will call both Dometic and Airstream tomorrow morning and talk about the advantages of plugging the new unit into a 30 AMP breaker. I will have to find out what is pulling off each breaker to be sure it is doable. I must admit the old unit was sluggish on getting the compressor going, sounded like it needed more snap.....
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Old 05-28-2018, 10:25 AM   #4
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I would make a list of the advantages and disadvantages of using a 30a breaker, and post them here before you call Dometic or Airstream.
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Old 05-28-2018, 10:34 AM   #5
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Quote:
Originally Posted by jmpgino View Post
I believe I will call both Dometic and Airstream tomorrow morning and talk about the advantages of plugging the new unit into a 30 AMP breaker. I will have to find out what is pulling off each breaker to be sure it is doable. I must admit the old unit was sluggish on getting the compressor going, sounded like it needed more snap.....
30 amp breaker is just the main. AC is 20.

A 30 amp breaker will not impact how a compressor starts. There won’t be ‘more’ current going to it. The compressor pulls what it needs. If the breaker is not tripping, the compressor is getting adequate power.

So your new unit runs fine? You’re done!
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Old 05-28-2018, 10:44 AM   #6
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I just walked out and checked my trailer to be sure. The AC is wired to a 20 amp breaker and that is the way it came from the factory. But my AC is probably smaller that the one you are putting in. My AC does not blow the 20 amp breaker so it is fine. The microwave does blow the breaker sometimes so I know the breaker works. There is a 30 amp breaker in the box but I suspect it is the main cutoff rather than an individual circuit. I know when I switch the 30 off everything AC in the trailer seems to go out.

One thing about you situation. If you upsize to a 30 amp breaker for the AC you will need adequately sized wiring in the trailer for 30 amp service. I doubt if you have that now.

My opinion, and it is just an opinion, is that if the unit is sized to run on 20 amps going to a 30 amp circuit will buy you nothing. The breaker does not limit power to a circuit. It just shuts it down when it is over loaded. My guess is that the sluggish operation probably is more from low voltage situations.

I like the Easy Start. If you are putting in a new AC anyway adding the Easy Start while you have it down would make it start a lot easier and smoother and less likely to kick the breaker out.

Actually you may have another issue. If the 30 amp breaker was off in the trailer I do not think there should have been power to the AC.
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Old 05-28-2018, 10:48 AM   #7
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If the new AC calls for a 20 amp breaker you would be creating a dangerous condition by using a 30 amp breaker. If the new unit is actually drawing 30 amps for some reason, something is wrong!

Follow the mfg. instructions and don’t overthink this.

Avoid analysis paralysis.



PS ditto to pcskier.
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Old 05-28-2018, 11:14 AM   #8
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The highest "rated amp" requirement for any Penguin II in the Dometic install manual is 13.4A, and every one requires a 20A breaker (per the specs.) The size of the breaker has nothing to do with how it starts, or how much power is available at start. That's a function of several factors, but the breaker at start is either closed or open. It's a bit like people putting Super in a vehicle that's designed for Regular and expecting it to make a difference, except that running Super doesn't increase the chance of an electrical fire.
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Old 05-28-2018, 11:32 AM   #9
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AC unit on 20 AMP breaker !!!

The breaker is there ONLY to protect the wiring. The AC unit is wired with 12 gauge wire, which is rated only for a 20 amp service and breaker. Going to a 30 amp breaker without going to 10 gauge wire is both dangerous and illegal. Don’t do it, as it buys you nothing. The AC unit only needs 20 amp service wiring and breaker.

DKB_SATX is absolutely correct in his explanation.
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Old 05-28-2018, 11:35 AM   #10
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You've run into the conundrum of 30 amp power. The sum of all the individual breakers SHOULD be what the main breaker will handle. So if you have 30 amp power, and a 30 amp main, then you can't have 30 amp A/C and 15 amp outlets and 20 amp water heater.
I said "should" because we all know everything is not running at once, so there's a safety factor.
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Old 05-28-2018, 12:17 PM   #11
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Yup. You have to manage loads. The breakers are there to protect the wiring, but they do not have the “brains” to do total load management. Humans have to do that. There are electronic systems to do this, but IMHO it’s easier to pay attention than pay for more complexity and failure points...
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Old 05-28-2018, 03:51 PM   #12
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Actually you may have another issue. If the 30 amp breaker was off in the trailer I do not think there should have been power to the AC.
A capacitor got him. They can hold a charge for quite a while after power is turned off.
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Old 05-28-2018, 06:31 PM   #13
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Originally Posted by Mollysdad View Post
You've run into the conundrum of 30 amp power. The sum of all the individual breakers SHOULD be what the main breaker will handle. So if you have 30 amp power, and a 30 amp main, then you can't have 30 amp A/C and 15 amp outlets and 20 amp water heater.
I said "should" because we all know everything is not running at once, so there's a safety factor.

The code specifically allows for the main breaker to be smaller than the sum of the branch circuit breakers. The breakers are there to protect the wire. All wiring fed by a breaker unless subsequently protected by a smaller breaker should be sized to carry the current that would be passed by the breaker. Wiring between a 30A breaker and a 20A breaker should be sized to carry 30A. Wiring after the 20A breaker should be sized to carry 20A, and so on.


Thus any circuit can use whatever its breaker will allow and the main breaker enforces the 30A (or 50A) total limit.



Al
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Old 05-28-2018, 07:06 PM   #14
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The code specifically allows for the main breaker to be smaller than the sum of the branch circuit breakers. ...

Reference NFPA-70 551.42(C)


Just thought I'd back up my claim....


Al
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Old 05-28-2018, 09:54 PM   #15
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Quote:
Originally Posted by jmpgino View Post
The old one is a Dometic 13,500 btu. My new unit is the same replacement that Airstream is installing a Dometic Penguin 2 rated at 15,000 btu.

Well I just checked the installation instructions and all of the units run on a 20 amp breaker.

I believe I will call both Dometic and Airstream tomorrow morning and talk about the advantages of plugging the new unit into a 30 AMP breaker. I will have to find out what is pulling off each breaker to be sure it is doable. I must admit the old unit was sluggish on getting the compressor going, sounded like it needed more snap.....


While you still have access to your new AC, would you mind taking a picture of the manufacture’s plate with the specs? It’s under the shroud riveted on.

You are going from 13.5 to a Penguin 2 HE (note the size on the plate). Is your current AC a Penguin?
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Old 05-29-2018, 06:03 AM   #16
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Quote:
Originally Posted by jmpgino View Post
The old one is a Dometic 13,500 btu. My new unit is the same replacement that Airstream is installing a Dometic Penguin 2 rated at 15,000 btu.

Well I just checked the installation instructions and all of the units run on a 20 amp breaker.

I believe I will call both Dometic and Airstream tomorrow morning and talk about the advantages of plugging the new unit into a 30 AMP breaker. I will have to find out what is pulling off each breaker to be sure it is doable. I must admit the old unit was sluggish on getting the compressor going, sounded like it needed more snap.....


While you still have access to your new AC, would you mind taking a picture of the manufacture’s plate with the specs? It’s under the shroud riveted on.

You are going from 13.5 to a Penguin 2 HE (note the size on the plate). Is your current AC a Penguin?
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Old 05-29-2018, 08:43 AM   #17
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Every Airstream I've ever checked has had a 20 amp breaker for the air conditioner. Every air conditioner should have its own 20 amp dedicated breaker, and no more than 20 amp.
Again, if it ain't broke, don't fix it.
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Old 05-29-2018, 09:19 AM   #18
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#14 wire can have a max of # 15A breaker
# 12 wire can have a max of #20A breaker
#10 wire can have max of # 30A breaker
Airstreams are wired with # 14 & # 12 wire...therefore 20A is the max size breaker unless you change out the AC wire to # 10
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Old 05-29-2018, 09:37 AM   #19
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Quote:
Originally Posted by jmpgino View Post
I removed my AC unit last week after doing some checks, I had turned of the breaker but still got bitten while up on the roof. So turned all off and disconnected the shore power, to make sure when removing the unit I did not get bitten again.
Well I have discovered that the AC is running off a 20 AMP breaker. Surely this is wrong, I would have thought it was on a 30 AMP breaker !!!!!!
Am I loosing it, or have I discovered an installation error ?
Cheers,
James.
Surely this isn’t wrong. AC is on its own 20 amp circuit. Total service to the trailer is 30 amps.

If you have 100 amp service to your home you certainly wouldn’t put your window AC on a 100 amp circuit!

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Old 05-29-2018, 10:33 AM   #20
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The new A/C units are almost 200% more efficient than the old units from the 60's and 70's. The new 15K BTU units only take about 15Amps. The 13.5K BTU units take about 13 amps. If the outdoor temp is less than 90 F my Honda 2000 runs the unit just fine. Noting else at the same time. So for over night sleeping it is great. For temp over 90 F the soft start kit is a must.


Happy Streaming..
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