adding 30amp rv breaker panel

[BrianMc]

I'm putting in a 30 amp breaker box for my 5th wheel at my lease.  The box I bought has a 30 amp rv plug and a regular 20amp plug.  The box is going to be around 85 ft from the electric pole where the main breaker box is.  I'm planning to bury the wire in grey conduit.  I know code says I need to bury it 18 or 24 in. but this is way out in the country so do I really have to go that deep?  Also, can I use 8 wire or do I have to use 6. And do I need two hot wires or just one.  And for the breaker in the main box do I put a 30 amp or 50 amp breaker.  And last, do I have to put a grounding rod in for the new box.  Sorry for so many questions but Thanks for any help you can give me.

[seilerbird]

I'm putting in a 30 amp breaker box for my 5th wheel at my lease.  The box I bought has a 30 amp rv plug and a regular 20amp plug.  The box is going to be around 85 ft from the electric pole where the main breaker box is.  I'm planning to bury the wire in grey conduit.  I know code says I need to bury it 18 or 24 in. but this is way out in the country so do I really have to go that deep?

Yes you do. This is to protect it against freezing, animals and people digging.

  Also, can I use 8 wire or do I have to use 6.

I would use number 8 copper.

And do I need two hot wires or just one.

One black hot wire, one white neutral wire, and one green ground wire.

  And for the breaker in the main box do I put a 30 amp or 50 amp breaker.

30 amp in the main box will do.

And last, do I have to put a grounding rod in for the new box.

No, that would cause a ground loop. The ground rod at the main panel is all you need.

  Sorry for so many questions but Thanks for any help you can give me.

You are welcome. BTW, I am a retired union electrician.

[Ned]

If you intend to use both the 30A and 20A outlets at the same time, you need to use wire large enough for the combined 50A.  The main box would have a 50A breaker and you should have 30A and 20A breakers in the new box.

If you'll only use one out let at a time, you can wire it for 30A and use a 30A breaker in the main box, but I would still use a 20A breaker in the new box for the 20A outlet.

[seilerbird]

You do not determine the value of the breaker in the main panel by adding the values of the breakers in the sub panel. A 30 amp in the main panel is all you need. My sub panel in my motorhome home has 5 - 20 amp breakers in it. By that logic I should be hooking up to a 100 amp breaker in the main panel, but it is a 30 amp service. There is virtually no chance he will be drawing the full 20 amps and the full 30 amps at the same time or anything close to it.

[blueblood]

You do not determine the value of the breaker in the main panel by adding the values of the breakers in the sub panel.

True - breakers are to protect the cable or wiring in the circuit and have nothing to do with the overall usage i.e 20 amp breakers are for circuits wired for 20 amps and main breaker is to protect shore power cable. So, what breaker to use at home main box should be sized to the home wiring ampacity - could be 15- 20- 30 or 50 

[Tony_Alberta]

What happens if your next RV likes 50 amps?    Is it worth the extra expense to put that in now with the same amount of labour?  Maybe still using the current 20/30 amp pedestal?  Or at least running wiring for 50 amps as well as the 50 amp breaker in the house?

[BrianMc]

True - breakers are to protect the cable or wiring in the circuit and have nothing to do with the overall usage i.e 20 amp breakers are for circuits wired for 20 amps and main breaker is to protect shore power cable. So, what breaker to use at home main box should be sized to the home wiring ampacity - could be 15- 20- 30 or 50

If I'm understanding you correctly, you mean the size of the breaker is determined by the size of wire I'm running to the new box, or by the size of the wire coming to the main box?  Thanks to everyone for all the replys!

[Ned]

You size the main panel breaker based on the total possible loads in the subpanel.  If he wants to use both the 30A and 20A outlets at the same time, this would require wiring for a possible 50A maximum load and thus a 50A breaker in the main panel.

[BrianMc]

Here's another question.  The new rv breaker box I bought has 120/240 on it.  And it has a place for two HOT wires on it.  I know that my 30amp rv plug is 120 only.  So when would someone have to run two hot wires.  If you ran two hot wires to it does that make it 240 and would that damage my fifth wheel?

[Lou Schneider]

Does your box have a 50 amp RV socket on it?  That is 120/240 volts, and takes two hot leads, a neutral and ground.

If you have a 30 amp socket, you would take ONE hot lead, a neutral and ground to it.

Taking two hot leads to a 30 amp socket does indeed make it 240 volts, and will damage your 5th wheel.

Each hot lead needs it's own circuit breaker, so a 50 amp socket uses a dual breaker and a 30 amp socket uses a single breaker.

[pondguy]

On the 18 OR 24 inch depth, it should be 18" if GFI from the source, or 24" if not. I just put an outlet outside and that was the way the depth was explained to me.

[Gary RV_Wizard]

I agree with Ned - wire it for a 50A load instead of 30A. Residential wiring allows for more outlets than the breaker can handle because it is assumed that not all outlets are in use at once and that sustained loads are only 80% of max. Statistically that is fine, but statistics go out the window when you have only one circuit and two outlets, both of which are expected to be in use at the same time.  That means you need both wire and a breaker for 50A total (30A outlet + 20A outlet). That means 6 Ga wire if using standard Romex, or 8 ga is using THHN or similar higher capacity wire.  Err on the side of too large rather than small to avoid voltage drop and overheating.

You can also use type UF wire which does not require conduit when buried.  6 ga would be suitable for a 50A load and 8 ga for 30A.

[BrianMc]

Thanks everyone for all the great advice.  I'm going out there this weekend and hopefully everything will go smoothly.  I'm going to go with 6/2 and a fifty amp breaker at the main.  I was planning on mounting the rv box on a 4x4 post I will cement in.  Will that be sufficient?  There is a pipe metal fence next to the trailer, would it be a no no to mount the box on it? 

[Molaker]

Even if you do not hook it up now running an extra hot wire through the conduit when you bury the witring would leave you the capacity to upgrade to a 50 amp plug later of you decide on newer RV. All you would have to do is add aopther 50 amp breaker at the main box and a 50 amp plug at the new box.

Good idea.  I recommend running 6/3 w/g and just leave one line open (capped on ea. end) until you want/need to upgrade.  If you already have the the 6/2, then get some single line 6 ga. and run it, too.  To save some money, 6 ga. is plenty heavy enough for a 30 amp 85' run, so you could use aluminum as long as your connections at either end are rated for aluminum as well as copper.

[denmarc]

Has anyone else determined that this particular OP should seek a qualified electrician? 

Although some of the answers are adequate, It sounds to me that too many variables are involved for a safe answer.

While I agree that wiring for a 50 amp service would be the best route with the future in mind.  Cost savings should be on the back burner if planning for something long term and a safe means of preparing.