Has anyone ever heard of a single a/c unit not being able to start and run on a 20amp shore power circuit? We bought a new coach and the dealer says don't run a/c unless connected to a 30 amp service or connected to the gen. They say it will cook the compressor. We have always run a/c units in trailers or coaches off a 20 amp circuit without a problem when at home so I am perplexed about what I am missing?? Thoughts?

Sounds like a fair warning, though not fully explained. Depending on the draw and if other things are on a 20amp gang, you might be warned to monitor your power. Get a Kill-A-Watt or volt meter to monitor your 120 voltage. Read your AC manual. Less than 105volts on most AC will cause cumulative heat damage to your AC. This does not show right away but will take years of your AC life. I do not like going below 108 volts.

This is going to depend on the size of the A/C unit. If your talking about the rig in your signature (which i also have)you should have no problem. I run one A/C unit when getting ready for a trip or doing maintenance at home. I actually plug into a 15 amp circuit. One of my units pulls about 12 amps. I make sure nothing else is running on that circuit when the A/C is on.

20A is definitely borderline because of the smaller wiring. But everything depends upon your A/C draw, other rig draws and the actual voltage. I'd be cautious about running a 15K BTU A/C on 20A.

Ours simply kicks the Breaker off.

CA Traveler wrote:20A is definitely borderline because of the smaller wiring. I'd be cautious about running a 15K BTU A/C on 20A.This post makes no sense. The A/C circuit inside the RV will be a 20 amp circuit wired with a 12 gauge wire and a 20 amp circuit breaker.What's the difference?

A/C off of 20 amp service? | Good Sam Community

44 Replies

westernrvparkow
Explorer
Sep 15, 2016
It is much more likely the salesperson said to not run the AC on a 20 amp connection because there is very little margin for additional loads on 20 amps and it is highly likely the breakers are going to trip at some point. That isn't a problem in and of itself, but many appliances and the like have cool down periods and de-powering them in mid operation (which is what happens when a breaker trips) isn't good. Also, if breakers trip while the rig is unattended, there may be other things that can be harmed. The chassis batteries may very well totally discharge, again not good. If the fridge wasn't dual fuel, or didn't properly switch over, food could spoil. Pets could get overheated. If you think your rig is getting shore power and it isn't, there can be problems.
In my opinion, if you are operating the AC in an RV on a 20amp circuit, you need to monitor it frequently at the least. Not everyone would do that and that is where trouble would begin.
Effy
Explorer II
Sep 15, 2016
dougrainer wrote:
Effy wrote:
dougrainer wrote:
Effy wrote:
dougrainer wrote:
Effy wrote:
Yes, I do it all the time. Worst case it will trip a breaker.

You are SO arrogant. Just because YOU know the limits and the whys and how's of your RV 120 system, does NOT make you the correct person to post on these type threads. From your posts on this thread, you refuse to accept that what is being asked and posted is not a safe practice. I gave that story to illustrate what happens when you do unsafe things. In 37 years, I have just about seen all the idiotic things that can happen when people have no clue as to what they can do with their RV. Add to that , so called experts that think because they have been RV'ing for years, that somehow makes them an expert on all things RV. Just read the postings from these people on the various forums. I use these forums to help educate, occasionally learn something, but always, for the humor from some of the responses that make me laugh. Doug

I'm not arrogant. I'm factual. I don't have the issues you cite so to me it's a moot point. It's great you want to educate people but you seem to do so with a lot of doom, gloom and drama.
dougrainer
Nomad
Sep 15, 2016
Effy wrote:
dougrainer wrote:
Effy wrote:
dougrainer wrote:
Effy wrote:
Yes, I do it all the time. Worst case it will trip a breaker.

Sorry, Worst case is NOT tripping a breaker, but overloading the systems which results in HEAT buildup, which can lead to a FIRE. Your Post is a good example of the misconception of what a 120 breaker REALLY does. A Lot of bad things have happened to people that assume that the 120 breakers stop ALL bad results. I always ask customers, WHY do you think your 30 amp shore cord end is all burnt and pitted? Why is your 30 to 15 amp adapter slightly melted and burnt and pitted? WHY do you think your 50 to 30 Dogbone is Burnt and pitted on the 30 amp end? BECAUSE THEY OVERLOAD THE SYSTEM WHEN NOT CONNECTED TO 50 OR 30 AMP SERVICE. Doug

Sorry, but I've never had that issue. Plugs are fine and clean and not pitted or melted in any way and I run AC off 20A quite frequently at the house with no issue. The cords never even get warm. Maybe my coach is set up to do this better than more sophisticated models with more demand. So, perhaps it's a case by case basis. I do have an extension cord rated for the load and the circuit I use has nothing else on it.

You never had that issue? Well, do you have 37 years and still working on RV's? I DO. I have repaired fire damaged units from what I have posted over the years. I even had a customer that video'd his Allegro 30 amp unit that he had a 100 foot extension cord coiled up and feeding his coach with the single AC running and it showed it smoking and then the cord caught on fire and was snaking up the side of the RV until he unplugged and got the water hose to it. Burnt the side metal skin and he had me replace the 30 amp cord since it was burned and melted. THE BREAKER OBVIOUSLY NEVER TRIPPED. Something he thought would happen. Loose connections causing melted pitted pins? WHO CARES. They are degraded and not safe to use regardless of how it happened. The reason they are "LOOSE" is because people overload the circuit and the heat build up causes the rubber to heat up and melt and then degrades the metal pins. NOT loose, but loose NOW because of overloading. WE no longer provide 30 to 15 amp adapters due to liability issues. We sell them, but do not provide for free on new sale delivery. Doug

Good for you and that's a riveting story. Kept me on the edge of my seat til the very end. I still don't have a problem though.

You are SO arrogant. Just because YOU know the limits and the whys and how's of your RV 120 system, does NOT make you the correct person to post on these type threads. From your posts on this thread, you refuse to accept that what is being asked and posted is not a safe practice. I gave that story to illustrate what happens when you do unsafe things. In 37 years, I have just about seen all the idiotic things that can happen when people have no clue as to what they can do with their RV. Add to that , so called experts that think because they have been RV'ing for years, that somehow makes them an expert on all things RV. Just read the postings from these people on the various forums. I use these forums to help educate, occasionally learn something, but always, for the humor from some of the responses that make me laugh. Doug
Effy
Explorer II
Sep 15, 2016
usersmanual wrote:
EFY obviously you have never overloaded your circuits by watching what your running and using good equipment and that's what one should.
What dougs saying and its very true A lot of people use those crappy reducers, wrong size cords, poor voltage supplys and try and run AC and other stuff off 15-20 amp cicuits causing low voltage when u get low voltage you get over heated power cords and melted ends and wires and thats a fact
Like I said obviously you don't do this then no you will never see such problems

Correct. I tried to say that in my response. I use properly sized cords and connectors and limit my draw to only the AC. (If I use the vacuum at the same time it will trip the house breaker as an example) And I use a circuit that has nothing else on it. I am aware of the dangers - 2 of my best friends and my BIL are electricians (I always run this stuff by them) , but I also know that it's not all doom and gloom and can be done.
usersmanual
Explorer
Sep 15, 2016
EFY obviously you have never overloaded your circuits by watching what your running and using good equipment and that's what one should.
What dougs saying and its very true A lot of people use those crappy reducers, wrong size cords, poor voltage supplys and try and run AC and other stuff off 15-20 amp cicuits causing low voltage when u get low voltage you get over heated power cords and melted ends and wires and thats a fact
Like I said obviously you don't do this then no you will never see such problems
Effy
Explorer II
Sep 14, 2016
dougrainer wrote:
Effy wrote:
dougrainer wrote:
Effy wrote:
Yes, I do it all the time. Worst case it will trip a breaker.

Sorry, Worst case is NOT tripping a breaker, but overloading the systems which results in HEAT buildup, which can lead to a FIRE. Your Post is a good example of the misconception of what a 120 breaker REALLY does. A Lot of bad things have happened to people that assume that the 120 breakers stop ALL bad results. I always ask customers, WHY do you think your 30 amp shore cord end is all burnt and pitted? Why is your 30 to 15 amp adapter slightly melted and burnt and pitted? WHY do you think your 50 to 30 Dogbone is Burnt and pitted on the 30 amp end? BECAUSE THEY OVERLOAD THE SYSTEM WHEN NOT CONNECTED TO 50 OR 30 AMP SERVICE. Doug

Sorry, but I've never had that issue. Plugs are fine and clean and not pitted or melted in any way and I run AC off 20A quite frequently at the house with no issue. The cords never even get warm. Maybe my coach is set up to do this better than more sophisticated models with more demand. So, perhaps it's a case by case basis. I do have an extension cord rated for the load and the circuit I use has nothing else on it.

You never had that issue? Well, do you have 37 years and still working on RV's? I DO. I have repaired fire damaged units from what I have posted over the years. I even had a customer that video'd his Allegro 30 amp unit that he had a 100 foot extension cord coiled up and feeding his coach with the single AC running and it showed it smoking and then the cord caught on fire and was snaking up the side of the RV until he unplugged and got the water hose to it. Burnt the side metal skin and he had me replace the 30 amp cord since it was burned and melted. THE BREAKER OBVIOUSLY NEVER TRIPPED. Something he thought would happen. Loose connections causing melted pitted pins? WHO CARES. They are degraded and not safe to use regardless of how it happened. The reason they are "LOOSE" is because people overload the circuit and the heat build up causes the rubber to heat up and melt and then degrades the metal pins. NOT loose, but loose NOW because of overloading. WE no longer provide 30 to 15 amp adapters due to liability issues. We sell them, but do not provide for free on new sale delivery. Doug

Good for you and that's a riveting story. Kept me on the edge of my seat til the very end. I still don't have a problem though.
dougrainer
Nomad
Sep 14, 2016
Effy wrote:
dougrainer wrote:
Effy wrote:
Yes, I do it all the time. Worst case it will trip a breaker.

Sorry, Worst case is NOT tripping a breaker, but overloading the systems which results in HEAT buildup, which can lead to a FIRE. Your Post is a good example of the misconception of what a 120 breaker REALLY does. A Lot of bad things have happened to people that assume that the 120 breakers stop ALL bad results. I always ask customers, WHY do you think your 30 amp shore cord end is all burnt and pitted? Why is your 30 to 15 amp adapter slightly melted and burnt and pitted? WHY do you think your 50 to 30 Dogbone is Burnt and pitted on the 30 amp end? BECAUSE THEY OVERLOAD THE SYSTEM WHEN NOT CONNECTED TO 50 OR 30 AMP SERVICE. Doug

Sorry, but I've never had that issue. Plugs are fine and clean and not pitted or melted in any way and I run AC off 20A quite frequently at the house with no issue. The cords never even get warm. Maybe my coach is set up to do this better than more sophisticated models with more demand. So, perhaps it's a case by case basis. I do have an extension cord rated for the load and the circuit I use has nothing else on it.

You never had that issue? Well, do you have 37 years and still working on RV's? I DO. I have repaired fire damaged units from what I have posted over the years. I even had a customer that video'd his Allegro 30 amp unit that he had a 100 foot extension cord coiled up and feeding his coach with the single AC running and it showed it smoking and then the cord caught on fire and was snaking up the side of the RV until he unplugged and got the water hose to it. Burnt the side metal skin and he had me replace the 30 amp cord since it was burned and melted. THE BREAKER OBVIOUSLY NEVER TRIPPED. Something he thought would happen. Loose connections causing melted pitted pins? WHO CARES. They are degraded and not safe to use regardless of how it happened. The reason they are "LOOSE" is because people overload the circuit and the heat build up causes the rubber to heat up and melt and then degrades the metal pins. NOT loose, but loose NOW because of overloading. WE no longer provide 30 to 15 amp adapters due to liability issues. We sell them, but do not provide for free on new sale delivery. Doug
tropical36
Explorer
Sep 14, 2016
dougrainer wrote:
Effy wrote:
Yes, I do it all the time. Worst case it will trip a breaker.

Sorry, Worst case is NOT tripping a breaker, but overloading the systems which results in HEAT buildup, which can lead to a FIRE. Your Post is a good example of the misconception of what a 120 breaker REALLY does. A Lot of bad things have happened to people that assume that the 120 breakers stop ALL bad results. I always ask customers, WHY do you think your 30 amp shore cord end is all burnt and pitted? Why is your 30 to 15 amp adapter slightly melted and burnt and pitted? WHY do you think your 50 to 30 Dogbone is Burnt and pitted on the 30 amp end? BECAUSE THEY OVERLOAD THE SYSTEM WHEN NOT CONNECTED TO 50 OR 30 AMP SERVICE. Doug

Ummmmmm and I always thought it was because the hardware wasn't up to snuff these days. I mean when I'm not pulling no more than a constant 15amps and a 20amp plug and outlet is cooking a good bit, like when running the rear air off of a separate circuit, then I'm gonna believe it's not built as heavy as it should be. Granted, it doesn't help having low voltage and maybe the circuit is pulling more than it should be.
Whatever the case, these 15amp plug and outlets need to be upgraded to better than 20amps as well, since they're used interchangeably so much and with 12 wire and 20amp breakers feeding 15amp outlets in most homes throughout America.
As for 30amp hardware, I changed out for a 50amp plug on my old 30amp coach and rid myself of this problem forever. Thing is, if you plug into a loose and burned outlet, it will ruin what you have and then when you plug into a good one, it will ruin it, creating a chain reaction, that never quits. Again, many of this 30amp equipment, isn't worth a darn, either and should be good for at least 40amps IMO. I guess we could blame it on the Chinese, like everything else, but then where is UL coming from, with all this?
Ivylog
Explorer III
Sep 14, 2016
Yes it can be done BUT without much else drawing amps in the rig which has already been stated. Another item you need to turn off is the ice maker... took me awhile to figure that one out when it was a voltage drop that was shutting my power down.
time2roll
Nomad
Sep 14, 2016
Also many adapters are poorly made with inadequate wire crimps.
Wire is often cool and the connectors are hot for this reason.

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A/C off of 20 amp service?

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