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Old 08-24-2017, 03:33 PM   #1
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50 amp charge receptacle for home

My previous trailer used 30 amp service and I had a 30 amp receptacle installed in my garage. My new AS has dual AC, hence 50 amp service. I have now installed a 50 amp receptacle, along with dual 50 amp breaker in my main panel. My understanding is that the 50 amp 4-wire receptacle will serve (and is labeled such) 125 or 250 volt service; dual 125 with neutral connected, or 250 with no neutral. I haven't plugged the trailer in yet because an "electrician" told me (via phone) that I would have to leave off one hot wire to get the proper voltage to the trailer. Everything else I've seen or heard indicates that all four wires are connected in their respective slots (the two hots, one neutral and one ground), and that the trailer will utilize that as essentially two separate 120ish volt feeds. Can anyone clarify or confirm that?

I couldn't find a direct answer anywhere else in the forum, so thought I'd try the direct approach.

Thanks, Larry.
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Old 08-24-2017, 03:58 PM   #2
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I am not qualified to answer your main question, but am wondering if you replaced the old wire to the 30 Amp outlet, with a heavier wire from the panel, and what is the AWG of the new feed?

In general yes the trailer needs two separate 120ish volt feeds in my lay opinion only. Some RV's use a 250 volt service with a plug which is very similar to the one you now have, I believe, so your electrician may be thinking of that situation.

Similar confusion has happened with 30 Amp services too, as that plug looks very much like a 250 volt "welder's plug."

Thanks,

Peter

PS -- You might want to check out the Electrical forum for relevant threads:

http://www.airforums.com/forums/f37/

Good luck!
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Old 08-24-2017, 04:12 PM   #3
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Hi

A "normal" feed for a 50A RV setup has a 240V "center tapped" circuit on it. That gives you a pair of 120V lines that are 180 degrees out of phase from each other. For various really odd reasons the RV world *loves* to call it a 120V system. Any electrician you ever talk to will call it a 240V outlet (which it is).

If you call up an electrician and ask for a 120V 50A outlet, he would wire something very different than your RV plug. It indeed would have only one "hot" wire. Rather than delivering 100A at 120V, it would only give you 50A at 120V. That's what you asked for, that's what you get.

My *guess* is that you are stuck in this nomenclature gap. If you ask the electrician for an "RV socket" he's going to look at you and ask for a better description. Show him a diagram of what the standard socket is and he'll happily wire one up for you.

The one thing you do *not* want to get is a 50A socket wired up with two 120V hot leads "in phase". That will overload the neutral line (it will have 100A on it and it's rated for 50). Worse still all the breakers and fuses will quite happily pass this current while the wire catches fire .... yikes ....

So, is your socket wired up right? That depends ....

Also keep in mind that some forms of fiddling with power, even in your own home require a pro (and maybe a permit). What is or is not required by your local government, I have no idea.

Bob
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Old 08-24-2017, 04:22 PM   #4
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Quote:
Originally Posted by graywhale View Post
My previous trailer used 30 amp service and I had a 30 amp receptacle installed in my garage. My new AS has dual AC, hence 50 amp service. I have now installed a 50 amp receptacle, along with dual 50 amp breaker in my main panel. My understanding is that the 50 amp 4-wire receptacle will serve (and is labeled such) 125 or 250 volt service; dual 125 with neutral connected, or 250 with no neutral. I haven't plugged the trailer in yet because an "electrician" told me (via phone) that I would have to leave off one hot wire to get the proper voltage to the trailer. Everything else I've seen or heard indicates that all four wires are connected in their respective slots (the two hots, one neutral and one ground), and that the trailer will utilize that as essentially two separate 120ish volt feeds. Can anyone clarify or confirm that?

I couldn't find a direct answer anywhere else in the forum, so thought I'd try the direct approach.

Thanks, Larry.
I'm not an electrician but I have studied this very issue. The plug at your house will be wired just like a 50 amp. stove plug, two hot, a neutral, and a ground. The trailer never sees 240 v. because there's no place that both hots are used together. What you have is (2) 50 amp, 120 v AC circuits. Leg 1 uses one hot and the neutral, while leg 2 uses the other hot and a neutral. Nowhere in the trailer is 240 v available.

You could plug a 240v appliance into the house and it would work because the appliance would be wired to use both hots together.

What's confusing is how it looks to be 240 v, but is never used that way. It's really two separate circuits in one plug.
(and, yes, you use all four prongs. The two on the sides are the hots, the flat on the top is the neutral, and the round lug is the ground.)

Look at the sine wave below. One circuit in the RV is wired to go from 0 (Neutral) to +V (120v.) The other circuit is wired to go from 0 to -V.
(120v.) Nothing is wired to go from +V to -V (240v.)
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Old 08-24-2017, 05:02 PM   #5
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With the current demand for home appliances like stoves, dryers, etc. in the larger Class As, they use the full 240 volts. Airstreams, from the factory, use the two separate 120 volt circuits.

If your receptacle is wired with two hots, one neutral and ground per the specifications for the 4-pin 50A RV service, you will be fine.

Al
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Old 08-24-2017, 05:37 PM   #6
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Al & Missy and Mollysdad are correct, the 4 wire RV receptacle is no different than the one for your stove. The RV is set up to utilize 120 volts only so it uses 1 pole breakers but just divides the loads up on each half of the 240. At your house panel, each hot is on a different leg which means 240 volts is available at the RV receptacle since each is on a different leg of the service. It is no different than a multi-wire branch circuit which most homes contain, where there are two hots, each serving a separate circuit but sharing the neutral. Each hot must be on a different leg of the service to prevent the neutral from being overloaded and in fact recent codes require a 2 pole breaker be used on all multi-wire branch circuits to ensure this ( and to prevent injury to non qualified workers). In your trailer all the loads are fed with single pole breakers so they only have 120 volts available to them, just like the 120 volt loads in your home are fed from a 240 volt panel with 1 pole breakers.

Household voltage here in the US is 240 volts single phase consisting of two legs, commonly called "A" & "B". Your house is fed with 3 wires, 2 hots and a neutral. Leg A is fed from one end of the transformer and leg B from the other. There are 240 volts between those two legs. The neutral is tapped into the center of the windings effectively cutting the voltage in half, so voltage from either leg to neutral will be 120. This arrangement simply continues on to all your multi-wire circuits including your trailer.

A common mis-understanding is that the 30 amp RV service is 240 volts. This is wrong and has been the cause of damages to trailers by DIY owners and un-informed "electricians".

Hope this helps (I am an "informed" electrician).
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Old 08-24-2017, 05:42 PM   #7
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Thanks for all the inf!! It appears to be just what I thought, and is in fact wired correctly.
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Old 08-24-2017, 06:34 PM   #8
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Is there any way to SAVE a thread? I am remodelling a home and what to be able show this to the electrician so I can have my Airstream plugged into the house.
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Old 08-24-2017, 06:41 PM   #9
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In your browser you should save this thread in your bookmarks, favorites, or whatever that is called in your browser. [Safari, Firefox, Internet Explorer, etc. etc.]

On this Apple Mac laptop, we use Firefox, which permits Bookmarks to be saved, and we can create folders to contain all threads saved.

In your User Control panel here ["User CP" at the top left in the blue menu bar] I think you can toggle on to be notified if anyone replies in a thread -- called Subscribe To Thread I think].

Sorry the above explanation is a bit general and vague.

Good luck,

Peter

PS -- Or you can go up into the box with the Internet address for this page at the very top, in your browser, highlight the entire URL, and send this "link" to your electrician in an email. If you don't know how to do this, further education on using the Internet might be found to be rewarding.
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Old 08-24-2017, 06:45 PM   #10
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Thanks for all the inf!! It appears to be just what I thought, and is in fact wired correctly.
In an abundance of caution regarding a DIY electrical installation, may I recommend that you have a licensed electrician come to the house to verify the installation?

If there is anything amiss, you could fry a lot of valuable stuff . . . with unintended 240 volts . . .

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Old 08-25-2017, 05:11 AM   #11
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Saved, thanks.
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Old 08-25-2017, 11:02 AM   #12
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Hello
Here is a good description of what you need for the RV.

http://www.myrv.us/Imgs/PDF/50-amp%20Service.pdf

Good Luck
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Old 08-25-2017, 02:39 PM   #13
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I guess I'm pretty lucky. I had a 50 amp female outlet installed in my garage to connect my generator when there is a power failure. When I brought my Classic home the first time I never thought about the conversation above and just plugged it in the 50 amp outlet. It must be the right config, as all is well with the classic. Both AC units function fine in the driveway and all appliances have also functioned fine. I guess I'm just lucky.
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Old 08-25-2017, 02:45 PM   #14
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This is an interesting post. When I had my home built, I had a 50 amp female outlet installed in the garage to accommodate my generator.

When I brought the Classic home a few months ago, I just assumed that the circuit was fine....you know 50 amp plug....50 circuit....probably a real bad move, but it turned out OK, as everything works fine in the driveway. I should know better than to assume anything, so I'm glad this work out OK and my luck is holding up.
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Old 08-25-2017, 04:10 PM   #15
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Hi

One "other reason" to have a 50A outlet in the garage is for an electric vehicle charger. At some point there may be one in your future. At least it makes it a "plus" when you go to sell the house (as opposed to something you dance around).

If you feed a 50A outlet with a generator, be sure that it's a 240V generator. Putting 100A at 120V in phase into a socket like that is at least as bad as pulling power out of an in phase wired socket. The alternative is to feed only one of the "hot" leads and keep the current under 50A.


Bob
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Old 08-25-2017, 04:14 PM   #16
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A typical house has two phases and a neutral, hence three wires from the pole to your house.

The 50AMP receptacle requires both phases, neutral and a ground, there are your four wires. You will need a #6 wire .

The two breakers you are referring two are for Phase A and Phase B.

On the left side of the panel, it alternates, A, B, A B, it would be 1, 3, 5, and 7 (assuming left side) respectively.

Because you are dealing with electrical, I would get an electrician out there just to verify and correct as necessary.
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Old 08-25-2017, 09:32 PM   #17
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CAUTION, and I mean CAUTION! I had a licensed electrician install a 50 amp service for my trailer. All went well until several years later, I had him install a ground fault 110 outlet in the box next to the original socket for a pressure washer. When I tested the trailer electrical power, anything that was on or had standby power, including 12 volt DC items were fried. What happened was a loosened connection , for rewiring, that was not retightened on the neutral or ground side. Fortunately, my insurance paid for all the fried items. 240 volts is double the rated voltage on AC, as well as is 24 volts on DC. The converter went up in smoke, as did the GFI breaker plus the additional items already mentioned. It was an over site rather than ignorance, but the result was the same. I went out and bought the most expensive surge protector I could find.
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Old 08-25-2017, 09:50 PM   #18
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Yup! An open neutral on 240 system connected to you coach will get a lot of stuff.
Connecting a generator to a home using a female receptacle on the house side is a very dangerous practice.
Not only for you and family. The proper use of a transfer switch is required for a safe setup. A person working for the utility company could be killed by a back feeding generator in a home that is miss wired.
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Old 08-25-2017, 10:28 PM   #19
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Quote:
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This is an interesting post. When I had my home built, I had a 50 amp female outlet installed in the garage to accommodate my generator.
I'm glad this work out OK and my luck is holding up.
You were fine because the HOUSE end is exactly the same no matter if you are powering 240 or a 50 amp RV with two 120's. It's the trailer wiring that matters.

Not sure how the 50amp female accommodates your generator, though. Did you make a male to male cable? Naughty boy! Also in the event of a power failure, and you're on generator at home, don't forget to kill your main breaker so the poor guy repairing the power lines doesn't get knocked off his ladder.
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Old 08-26-2017, 07:59 AM   #20
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You were fine because the HOUSE end is exactly the same no matter if you are powering 240 or a 50 amp RV with two 120's. It's the trailer wiring that matters.

Not sure how the 50amp female accommodates your generator, though. Did you make a male to male cable? Naughty boy! Also in the event of a power failure, and you're on generator at home, don't forget to kill your main breaker so the poor guy repairing the power lines doesn't get knocked off his ladder.
Hi

In some areas, the "correct" thing to do is to pull the meter (yikes !!!) to disconnect from the grid before hooking up the generator. If you do that, make sure to cover the now open hole where the meter used to go. Also put up a note about when and why you pulled it. I'd flip the main breaker as well ....

Yes, this is one that's not for the faint hearted ....doubly so if you have ever had a "boom" incident when connecting to the grid .... (there's a reason you hold the meter just so when you re-attach it ... replacing the fuse up on the pole pig, not something for the homeowner to do ...)

Bob
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