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Old 08-06-2015, 04:26 PM   #1
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What power supply should i hook up to?

I just purchased a 35 foot class A motor home. I am putting it into an RV park for the time being. They asked if i need a 30 amp or 50 amp... I have no idea which one. Any input would be appreciated.
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Old 08-06-2015, 05:08 PM   #2
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Welcome to the forum and the wonderful world of RVing.

This is the short answer to your question. If you can manage with one air conditioner, then 30 amp will do. If you want/need both a/c units then get 50 amp. 50 amp, which is actually 100 available amps, will power most everything electrical at the same time. 30 amp will cause you to be selective in what you run at the same time, example microwave, water heater, a/c, etc.
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Old 08-06-2015, 05:24 PM   #3
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What amprege is your motor home? 30 or 50 amp? You don't have your rig details in your signature, so that would be the starting place. If you don't know, post a pic of your Male plug in or describe it.
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Old 08-06-2015, 05:25 PM   #4
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Show me a picture of your male plug and I can answer your question. 1 AC or 2.
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Old 08-06-2015, 05:54 PM   #5
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I am at work right now so so I cant post a pic right now. It is a 1994 Coachman Sanatra. It does have dual AC units and A 7kw gen set. I was told that 3 prongs means 30amp and 4 prongs mean 50 amp.
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Old 08-06-2015, 05:56 PM   #6
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Quote:
Originally Posted by leftcoastdc View Post
I just purchased a 35 foot class A motor home. I am putting it into an RV park for the time being. They asked if i need a 30 amp or 50 amp... I have no idea which one. Any input would be appreciated.
Well, there's no use to pay extra for 50amp, if you can get by with 30. Sounds like you aren't planning on staying in it full time, so you may not need to run two ac's.
I can usually run both ac's on 30amp, depending on the pedestal, but that's another story.
If your cord is kinda fat and there's four prongs on the plug, then you have a 50amp service. A 30amp plug will have 3 prongs. Having said that, you should always have a conversion cord on board for going either way and both the 50/30 and the 30/50 are available at a super Walmart or Camping World. Might as well pick up a 30/20 while you're at it for those odd situations, as well.
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Old 08-06-2015, 05:57 PM   #7
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Quote:
Originally Posted by leftcoastdc View Post
I am at work right now so so I cant post a pic right now. It is a 1994 Coachman Sanatra. It does have dual AC units and A 7kw gen set. I was told that 3 prongs means 30amp and 4 prongs mean 50 amp.
This is correct for the norm, but do read my post above.
I have a 50amp plug on a 30amp service, but again, that's another story.
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Old 08-06-2015, 07:42 PM   #8
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If in doubt choose 50

Look at the shore power cord for your rv

Two flat blades, at an angle, and one roundish one (May be U or D shaped) that is 30 amp

3 flat blades, parallel one higher than the other with a roundish one (As above) at the bottom.. That is 50 amp

That simple

50 amps is two 50 amp legs 120 volt to neutral and 240 volt leg to leg, the exact same power that is most likely delivered to your house by the electric company.. Only less (most houses are 100-200 amp, some more) But the wiring is exactly the same.

Take a look at the link I'm about to add.. YOu need one of two devices. This is one.

http://www.ebay.com/itm/RV-Electrica...17e35c&vxp=mtr

The link (To Ebay) shows a 50 amp plug and a TT-30 (30 amp) outlet IF your RV is 30 amp you need one of these just in case the park's 30 amp plug is flakey.. If your rig is 50 amp, they make one that goes the other way.. but it limits what you can use in the RV (Can't do both A/Cs for example)

Advise and we can give you the "rules" for 30 amp.
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Old 08-06-2015, 07:48 PM   #9
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Well, there's no use to pay extra for 50amp, if you can get by with 30. Sounds like you aren't planning on staying in it full time, so you may not need to run two ac's.
I can usually run both ac's on 30amp, depending on the pedestal, but that's another story.
If your cord is kinda fat and there's four prongs on the plug, then you have a 50amp service. A 30amp plug will have 3 prongs. Having said that, you should always have a conversion cord on board for going either way and both the 50/30 and the 30/50 are available at a super Walmart or Camping World. Might as well pick up a 30/20 while you're at it for those odd situations, as well.
Although they make conversion plug ins for running a 30 amp cord in a 50 amp pedestal. I am very much against doing that and think it is an unsafe condition. For a newbie that does not know the type of service he has I would not have even told him that he could run a 30 amp cord with a 50 amp adapter. In the event of a short your 30 amp cord becomes a fuse. since it can melt before the 50 amp breaker trips. While melting it will put out a lot of heat as in enough to catch the rig on fire.
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Old 08-08-2015, 07:52 AM   #10
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Originally Posted by gemini5362 View Post
Although they make conversion plug ins for running a 30 amp cord in a 50 amp pedestal. I am very much against doing that and think it is an unsafe condition. For a newbie that does not know the type of service he has I would not have even told him that he could run a 30 amp cord with a 50 amp adapter. In the event of a short your 30 amp cord becomes a fuse. since it can melt before the 50 amp breaker trips. While melting it will put out a lot of heat as in enough to catch the rig on fire.
I agree it's not an ideal solution, but I don't think it's as dire as you make it out to be.

First off, I'm talking about a coach that only has 30 amp service. If you use an adapter to plug it into a 50 amp outlet, there is some risk to the shore cord, but I don't think as much as you state. It seems the premise of your argument is that the coach could be drawing up to 50 amps which would overload the shore cord. In reality the 30 amp main breaker in the coach is going to trip before it gets to that point.

The real risk is if there is an excessive load in the shore cord before it gets to the coach -- in other words a short in the cord itself. It would need to be a high resistance internal connection in the cord that draws more than 30 amps, but less than 50, and it would need to draw that current for some time before the cord got hot enough to cause a fire. That would be exceedingly rare - if there is any kind of short in the cord, it will generally be a a hard short that will draw more then enough current to immediately trip the 50 amp breaker, before the cord has enough time to get significantly hot.

No, it's not an ideal solution, and there is some risk, but I don't think it's as bad as you make it. It's not an incendiary firestorm waiting to happen. But it is indeed worthwhile pointing out the risk, and I don't fault you for that. Personally, I think that using an adapter to get down to 20 amps, then using a long thin extension cord to reach the outlet and running the air conditioner is a far larger risk. Yet people do it every day.

Fortunately, using an adapter to go from 50 amp to 30 amp is not a very common solution. 99% of the places that have a 50 amp outlet will also have a 30 amp outlet, so the need for the adapter is rare. I do have such an adapter, and so far I've only had to use it at one site: a dog show that is held on a county fairground, where they only have 50 amp sockets. I have a 50 amp coach, but the socket is far enough away that the cord doesn't reach. I use an adapter to go down to 30 amp, use a 30 amp extension cord, then the adapter to go up to 50 amp. Now that is the scenario you mention, and there is good reason for concern: there is a section of cord that is only rated for 30 amps, but it is being protected by a 50 amp breaker at the pedestal, and a 50 amp breaker in the coach, so there is a very real chance of overload. Anybody doing this MUST be aware of the situation and the risk. I've analyzed it and am comfortable with it in this particular case, because I have a power monitor that watches the current draw and automatically sheds loads to keep it under 30 amps. In addition, this particular show is in late November so we never have to run the air conditioning.

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Back on the original subject:
  • If you have a 30 amp coach, get a 30 amp site: there's no need to pay extra for power you can't use.
  • If you have a 50 amp coach, then you have a decision to make: (This is the decision tree I use)
    • If you want to run both air conditioners at the same time, and/or want to run other heavy loads, get the 50 amp.
    • If you will only want to run one air conditioner and not a lot of other heavy loads, get 30 amp, but consider 50 amp if it's not significantly more expensive.
    • If you're not going to run any air conditioners, get 30 amp.
    • If in doubt, get 50 amp.
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