Should a 13,500 BTU A/C be wired to a 15 or 20 amp breaker?

[jayspi]

Hi everyone, we bought a 2004 Colorado 5th wheel last year. We've had problems with the A/C not blowing as hard as we think it should, and the circuit breakers (mostly the main, but also the one for the A/C) tripped more and more. The A/C was replaced last year. It is 13,500 BTU and the rig is 30 amp.

The circuit breaker it's on is a 15/20 duplex 2 pole Eaton Cutler-Hammer. The other circuit on that breaker is labeled "General Purpose", and seems to control all of the outlets in the RV that are not GFCI. The microwave and hot water heater are on their own circuits.

I got around to replacing the breakers today and noticed that the listing on the panel said that the A/C is on the 20 amp circuit, but when testing it I found that it was actually connected to the 15 amp.

This is an old RV so I'm thinking that the previous owner might have replaced the circuit breaker at some point and reconnected it improperly. However, the panel could also be labelled incorrectly.

When I reconnected it I put the A/C on the 20 amp and so far so good. Nothing has tripped and the A/C is blowing noticeably harder. I'm wondering though if that was a mistake. What do you guys think? Does it make sense for the A/C to be on 15 amp or 20 amp?

Thanks!

[Bobbo]

kmb1966 wrote:

dougrainer wrote:
ALL RV Roof top AC units the install instructions require a minimum of a 20 amp breaker and Minimum 12 /2 Romex wire. Doug

Except the Dometic BriskAir2 H.E. unit.
I have one and the specs on it call for a 15amp breaker. It's the only one I know of that specs a 15 amp instead of 20.

Here is the installation manual for the Dometic BriskAir2 H.E. unit.

http://manuals.adventurerv.net/Brisk-Brisk-II-Penguin-II-HP-mech-ABD-Operating-Manual.pdf

Page 4 of this manual calls for a 20 amp circuit.

[kmb1966]

dougrainer wrote:
ALL RV Roof top AC units the install instructions require a minimum of a 20 amp breaker and Minimum 12 /2 Romex wire. Doug

Except the Dometic BriskAir2 H.E. unit.
I have one and the specs on it call for a 15amp breaker. It's the only one I know of that specs a 15 amp instead of 20.

[dougrainer]

ALL RV Roof top AC units the install instructions require a minimum of a 20 amp breaker and Minimum 12 /2 Romex wire. Doug

[Roadpilot]

Good advice above. I'd ask though how the size of the breaker could make "the AC not blow as hard". I can understand the breaker tripping, since it's either working or tripped, but not affecting how hard it blows.

[j-d]

Let me say at the git-go, I really don't like the two-breakers-in-one design. Just can't convince me that they don't have more heat buildup than single breakers would have, making it easier to trip falsely.

Anyhow, we have a 30/20 as Main and A/C. I called around for a replacement, and the "Yep we got it" place only had a 20/30. I swapped the wires so the 20 for A/C occupies the Main position and Main is now one down on the stack where A/C should be. Possibly, a previous replacement was done that way.

[pianotuna]

What is the voltage when running the roof air?

My 13500 Dometic is connected to a 15 amp breaker, which has never tripped.

[jayspi]

OK, I just pulled the panel and looked and the wire going to the 20 amp circuit (which the A/C is on) is noticeably thicker. I think we're OK, but tonight when it's cool I'll turn off the main and take a better look.

[jayspi]

ktmrfs wrote:


Now if you go to a 20A breaker MAKE SURE THE WIRING IS 12GA, not 14GA!!!!! 14GA wire is only rated for use on a 15A or lower breaker.

Thank you, I'll sure sure to check that!

[ktmrfs]

NEC code says that dedicated appliances can't draw more than a certain % of rated load for wire or breaker. I think it's like 80%. So for a 15A breaker, max load shouldn't exceed about 12A. Most of the non high efficiency 13.5K units have a max draw near 12-14A, so 15A is IMHO marginal. And once a breaker starts tripping, it will eventually trip at below the rated current.

A quick check on the coleman site says the MachIII has a rated running current of 13.1A. standard draw is listed at 1400W and desert conditions listed at 1700W. 1700W is over the limit for a 15A breaker. That would be 14A or so draw, well in excess of NEC code for a dedicated appliance on a 15A circuit.

And AC draw is dependent on temperature as well, going up as temps go up. It may draw only 10A or so on a cool day but 14+ on a hot day.

Now if you go to a 20A breaker MAKE SURE THE WIRING IS 12GA, not 14GA!!!!! 14GA wire is only rated for use on a 15A or lower breaker.

[jayspi]

Thanks guys! Appreciate the information. Hopefully putting it on the 20 amp will solve all the problems.

[Ductape]

20 amp. Check and make sure the circuit is 12 gauge wire, too.
12 gauge = 20 amps
14 gauge = 15 amps (a.c. circuits) < "alternating current"

[Old-Biscuit]

13.5K RV A/C Unit roughly 2750W to start (22A) and 1250W running (10.4A)

20A Circuit Breaker for A/C Unit