I have a 100amp service with 2 100amp breakers under my meter. Can I run a RV outlet box with a 30amp breaker and a 20amp breaker for a 20amp GFCI outlet in the box off the main panel, or should I run it off my house's 100amp subpanel, and what size breaker should I put in? I have one slot left in the subpanel.

image 1 image 2 image 3

This picture is of the box I am going to put in:

new box

  • 1
    Can you post photos of both your main meter box and your subpanel, including the labeling on the inside of the subpanel's door? Commented Apr 24, 2022 at 18:45
  • How can i send pics
    – Mike
    Commented Apr 24, 2022 at 19:52
  • 1
    Click the Edit button under the question and there should be a toolbar with a "mountain and sun" icon - click that and you can upload a picture from your computer or from a web site. Commented Apr 24, 2022 at 20:50
  • Should i use 10/3 wg or 8/3wg to wire box box says 10/3gw but thats total of 50 amps so 8/3 is for that right
    – Mike
    Commented Apr 24, 2022 at 23:43
  • Depends on how the box is wired. If the box uses /3 then it should be 2 hots + neutral + ground. And if that is the case, then you end up with 30A on one hot and 20A on the other hot and 30A service == 10/3 is all you need. Commented Apr 25, 2022 at 0:33

1 Answer 1


The 20A breaker opposite the main breaker cannot be moved or changed, however if it is powering a bog-standard 4500W water heater it needs to be changed to 25A. (siemens QP225). If it is a 3800W water heater 20A is the right size. Nothing else can ever be there because of stab limits.

If you want to put the RV breaker here, you would have to use a 20/30/20 quadplex, remove the solo 20A single breaker, move the other breaker down or up and get 2 adjacent spaces for the quadplex, and put the 20A solo on one of the 20's.

The house panel is pretty full, I would try to run it off the outside panel if you can.

You can do it with #10 copper. However if you can find #6 aluminum wire, I would run that instead for two reasons. First, it's cheaper. Second, that is 50A wire, so you can run a larger 50/30/20 RV panel without having to re-bury wires. That would let you use larger RVs or electric vehicle charging.

Aluminum feeder requires 2 things to be used safely. #1 the lugs must be rated for aluminum (all breakers and panels are). #2 you must use a torque wrench to set the lug torques to spec. But this is equally important on copper connections.

  • My watter heater has never fliped but it says 240v 4500w upper and lower bt then under that it says alternate 208v 3280w upper and lower ?
    – Mike
    Commented Apr 25, 2022 at 3:48
  • @Mike -- can you get us photos of your meter box/main disconnect panel please? Commented Apr 25, 2022 at 4:16

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