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QuiGonJohn

Rooftop A/C on 20-Amp Circuit

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I was wondering about this. I fully realize that, in an ideal world, you are not supposed to plug your RV into a regular household 120-volt 20-amp circuit, with an extension and an adapter. But, let's assume for a minute that you have to do this. I know for most of the loads in the RV, this is probably OK, as long as you don't use the microwave/convection oven and the A/C. Now let's assume that you need to use the A/C and also that your A/C does not trip the breaker and that your extension cord is beefy enough to handle the heavy current.

Now here is my question. In such a setup, can it hurt the A/C to be running off power like that? To my mind, as long as it has power, and doesn't trip the breaker or overheat the extension cord, it ought to be OK, (not an optimal way to run), but not anything that will be detrimental to the A/C system. But, the guy at the RV Service Shop I had my RV into recently, said this does hurt the A/C, that it causes it to work harder and can be detrimental to the system.

So, if anyone here feels they are an expert on A/C Systems and would like to chime in, your feedback would be appreciated. Personally, I have done this, I do keep it to a minimum. Maybe a little while getting ready for a trip and working in or loading the RV, I might have the air on a bit.

I am in the process of installing a 30-amp circuit with a plug outside my home. But also, when on the road, I have visited family and stayed at their house 1 or 2 nights and hooked up in this fashion. As I said, I do try to keep this to a minimum.

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The operative issue here is "what is voltage at the A/C" on that 20 amp circuit with extension cord?

THAT will determine if you are damaging the A/C. 120 +/- 10% is spec. So as long as voltage at the A/C is 108 or above, go for it.

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As Brett stated. I use to do it all the time with dog bone adapters. With the 5er I could only use one AC at a time. Even plugging a vacuum in and running it would throw the house breaker. In the 40ft MH, before I had 50 amp installed, I could run the AC. Only one AC would comeon in the basement AC model but that was enough. The energy management system built into the RV took care of distirbuting the load. Typically only the AC could be run and any other appliance would trip the 20 amp breaker. Make sure you use a 12 gauge or better yet a 10 gauge cord. Do not use one of the lawn and garden extension cords that are only 14 gauge, as they will get very hot with any load on them.

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Thanks. I will shop for a really good 10 gauge extension cord for when I am traveling. I just bought the last of all the parts I need to put in the 30A circuit at my home, beside where I park the RV, when at home. Now I just have to install it all.

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Best is to get another 30 amp RV cord and only adapt down to the 15/20 at the very end (house outlet) end of the cord.

We carry our 50 and two 30 amp RV cords-- the two 30's are our "extension cords".

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If you are sure that your receptacle is in fact 30 amp with both the correct wire gauge and breaker, why not just install a 30 amp RV receptacle?

If you must use an extension be sure to monitor for over heating. If it is too hot to touch then you have a potential problem.

Be safe.

Herman

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Brett, that is what I was thinking. If I'm going to get a 10 gauge extension, I'd really only ever need that for the RV, so it might as well be one that has the 30 Amp connectors on both ends.

Herman, I am in the process of putting in a 30 Amp circuit, with a TT30R receptacle at home. The extension rig would be mostly for if I stay at someone's house that does not have a 30 Amp circuit. Or the rare time the campground outlet is too far from where I need to park the RV.

I also plan to pick up a 30A to 20A dogbone adapter vs. the one-piece adapter I currently have.

The cord attached to my RV is 25', (I just measured it). I am leaning toward a 30ft extension, but also saw a 25ft. Price difference is only $8. Any reason not to go with the 30ft? That would be 55ft total, if in use.

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Brett, that is what I was thinking. If I'm going to get a 10 gauge extension, I'd really only ever need that for the RV, so it might as well be one that has the 30 Amp connectors on both ends.

Herman, I am in the process of putting in a 30 Amp circuit, with a TT30R receptacle at home. The extension rig would be mostly for if I stay at someone's house that does not have a 30 Amp circuit. Or the rare time the campground outlet is too far from where I need to park the RV.

The additional 30 feet of 30 amp power cable should get you to most every power post in a CG.

I would still be concerned about putting a friends home in jeopardy of a fire by using a undersized outlet.

Herman

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Most roof airs will run on a 20 amp circuit. They draw about 18 amps to start and 14 amps to run. A 20 amp outlet and plug have one blade vertical and one horizontal. 15 amp has both blades vertical or parallel . 15 amp circuit might not start the compressor. This of course is assuming 108 minimum voltage.

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Make sure the outlet on your friends house is truly on a 20 amp circuit. I stayed at my daughter's house last summer and was surprised to find that most of her outlets are on 15 amp circuits. I thought that 15 amp went out years ago but her house is only three or four years old. It is called cutting corners to cut costs. The trouble is 15 amp circuits are not really adequate to run any kind of space heater to even one of the new hair dryers that are rated at 1800 watts. I found out her neighbor's house next door is wired the same way. Of course I found all this out after popping the breakers in both houses.

Skip

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We were at our daughters home in California and plugged into a 20A circuit there and ran one air conditioner, battery charger, lights, etc. with no problem. Our Windsor has the Intellitec power management system which can be set for 20A and will shut off loads if the total load comes within 5% of the amperage we are using. I think the Intellitec shut off the air conditioner one or two times but when the other loads drop away, it turns the air conditioner circuit back on. If you don't have Intellitec, you will have to do the current management yourself or you'll be running to reset the breaker occasionally.

The lowest amperage we can set the Intellitec at is 20A. It wouldn't help with a 15A circuit. I can only think of one occasion when we tripped a breaker on a campground and that was a faulty 50A breaker. I knew the breaker was faulty as we weren't using anywhere near 50A when the breaker tripped. They replaced the breaker and that solved the problem.

I've done a good bit of electrical wiring and I've never seen circuits with outlets wired with anything less than 12 gauge wire which supports 20A. It is not uncommon to use 14 gauge wire for lighting circuits and these will then require a 15A breaker. If houses are being wired with 14 gauge wire for outlet circuits, they would be below national electrical standards. Of course not all areas impose national standards for buildings. Let the buyer beware!

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