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I recently purchased a prewired 30a rv subpanel to plug in a travel trailer while sitting at home. The subpanel is complete with a 30a breaker and receptacle. Is it acceptable to run the romex (10-2) to a new 50a breaker in the main panel having the 50a feed the 30a breaker?

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  • If you're going to go to the trouble of installing an RV power post, I highly recommend just using 6/4 and putting in a panel with both 50A service (14-50 receptacle) and 30A (TT-30) service. The parts/wire cost is really not that big of a deal compared to the cost (in either dollars or time) of the installation labor. You'll need a 50A two-pole breaker in the main panel to feed the 6/4 and then the RV subpanel will likely have a 50A two-pole for the 14-50, a 30A single pole for the TT-30, and a 20A single pole for a 5-20 duplex.
    – Josh
    Apr 22 at 12:20
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No, you can't do that. The 10-2 romex has a 30 to 35 amp maximum depending on the insulation. The breaker in the main panel's job is to protect the 10-2 so it has to be a 30 AMP breaker, not the 50 AMP.

If this is going to be a permanent type installation you need to think about running your cable in such a way that it's not a safety hazard or a code violation. You can't have it lying on the ground running from you panel to the trailer.... maybe conduit from the panel to the outside wall and have a receptacle.... then a plug from you subpanel.

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  • If I'm understanding this correctly, I can use a 30a breaker in the main panel to feed another 30a breaker in the rv subpanel? I can also go to an 8-2 romex if needed.
    – Gordon
    Aug 12 '19 at 18:39
  • Yes, two 30's are ok. The 8-2 is good for 40 to 50 AMPS depending on the insulation. You don't need the extra capacity and the larger wire size would cost more than getting a 30 AMP breaker.
    – JACK
    Aug 12 '19 at 19:06
  • Thanks so much!
    – Gordon
    Aug 12 '19 at 19:22
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If you want to wire in 50A for a future, larger RV, then you need to run the cabling with 6/3 UF cable (not NM/Romex, you cannot use Romex because you will be going outdoors).

If you were to do that with e 6/3 cable, with the panel you have bought, that would be fine.

However, it's a common case for someone to buy the wrong thing and then go into backflips doing even more wrong things trying to make the wrong thing work. Don't bother; get the right thing. If you are mail ordering this stuff, thats a mistake - local electricians must shop somewhere; shop there.

They make RV panels which have all the breakers and sockets necessary to support all of

  • a 240V, 50A large RV (with NEMA 14-50 receptacle)
  • a 120V, 30A small RV (with TT30 receptacle)
  • typically a 120V/20A plain old outlet for hand tools etc.

This works off a 50A breaker because it is presumed you will only be powering one RV at a time. But you still need 6/3 outdoor cable; 10/3 won't do.

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  • There are exactly two types of RV plugs in North America, and neither of them are a NEMA 10-anything. The 30A service (120V) RV plug is a TT-30 (line, neutral, ground), and the 50A service (120/240 split phase) RV plug is a 14-50 (line 1, line 2, neutral, ground). 30A on 120/240V is non-standard and will not be found in any modern RV park, and perhaps not in any RV park period. As a side note, the NEMA 10- receptacles are line 1, line 2, neutral and do not have a ground conductor. They are deprecated and cannot and should not be used in any new installations.
    – Josh
    Apr 22 at 0:45
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    Thanks @Josh. The 10-50 was a typo. I thought I had seen a 14-30 on an RV stand but I was mistaken. Apr 22 at 5:35
  • Some temporary power outlets provide other types of receptacles, but that's mostly for jobsite use and such Apr 22 at 11:44

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