Shore Power Wiring

[akadeadeye]

We are planning on getting an electrician to run some wiring for hookups from 200-amp service to either three or four hookup (pedestal) locations near the power source on a ranch we recently bought. We have many relatives with RVs (motorhomes, 5th wheelers, and a pop-up) and this would be a great way to get them all there (be careful what we wish for) and have a great "mini-RV-park" area instead of building a seven-bedroom ranch house.

My question is this: Can someone direct me to a resource on the proper wiring setup from a 200-amp drop to a meter and then extending out some 150 feet in one direction and the same in another direction to accommodate these hookups?

Copper or aluminum? RV boxes or something less than that; i.e., we don't really need a 30-amp and a 15-amp at each hookup, since those requiring less than 50-amp can adapt down to their requirements.

As I mentioned, we are in contact with an electrician, but many electricians don't completely understand the requirements of the RV systems and proper end-result amperage and voltage.

Thanks, in advance.

Don

[wolfe10]

Don,

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

30 amp RV wiring: http://www.myrv.us/Imgs/PDF/30-amp%20Service.pdf

Brett

[tbutler]

Here is a source, RV Power Outlet, that has a full array of outlet boxes for RV's at very competitive prices. With multiple boxes on a 200 amp feed, you could use the 50 amp breakers at the 200 amp box to individually turn on and off circuits but that would require running a separate set of 50 amp wires to each box. With the most distant box at 150 feet, you would need a heavier wire for the second box. Or you could run one 100 amp breaker and 100 amp wire feed two boxes each with its own 50 amp breaker. The most distant box would only need a 50 amp wire sufficient to carry the 50 amp load for the distance from the 100 amp feed wire to that box. I like to have a breaker at the plug in as it makes it simple and easy to turn on the power after plugging in and turn off the power before unplugging.

With the price of wire, the latter solution may be less costly than the first.

[akadeadeye]

Brett and Tom,

As usual, you are on the spot helpful and you can't imagine how valuable you are to a relative newbie like me. The shortcut to the information you provide is just very much appreciated.

Thank you and Safe Travels,

If you're ever coming through San Antonio, let me know. We'll spring for an enchilada on the Riverwalk.

Don

[ejmc77@hotmail.com]

I already have a 50a box and 3 wire 30a cable. I only plan on using 30a, and my question then is how to wire to the 4 recepticle posts with my 3 wire cable. I understand green is ground, white is neutral, and black would go to one of the 2 posts on the 50a recepticle. Would this work, or do I need to add another jumper wire to the other hot post?

[wolfe10]

I already have a 50a box and 3 wire 30a cable. I only plan on using 30a, and my question then is how to wire to the 4 receptacle posts with my 3 wire cable. I understand green is ground, white is neutral, and black would go to one of the 2 posts on the 50a receptacle. Would this work, or do I need to add another jumper wire to the other hot post?

To wire 3 wires (hot, neutral and ground) to a 50 amp outlet, you would connect the hot to either hot on the outlet (outer straights) and jumper to the other. Obviously, you will be limited in what you can draw.

Another option is to use a 30 amp male to 50 amp female adapter from any camping store and just plug into the properly wired 30 amp outlet.

Brett

[ejmc77@hotmail.com]

Thanks Brett

[tbutler]

You can jumper the hot wire from one hot feed on the 50A receptacle but you won't get more than 30A out of the circuit. As it approaches 30A, the circuit breaker should trip. Since you are using a 30A cable, drawing any more current on that wire would create heat and likely melt and short circuit the wire.

A second problem is late model coaches, many of which have electronic current monitoring which will not recognize a 50A circuit unless the two feeds are opposite phase. If you jumper from one hot terminal to the other, they will both be in the same phase and the computer in the coach will only recognize it as a 30A circuit.

[ejmc77@hotmail.com]

That's what I want my 08 Safari to see and use, only 30a. The reason for the question is I'm working with the stuff I already have..... a 50a box and 3 wire cable. I have no intention of trying to actually use 50a, just the box. Do you think a jumper wire is even necessary?

I apologize to Don for high jacking this thread, my typing got ahead of my brain.

[tbutler]

mccsix,

This is the way the forum works. You see a thread and from its discussion ask another related question. and the thread continues. No one owns a thread! Your question helps everyone elaborate on the factors related to the discussion. This is a good thing!

The jumper is required in order to activate all circuits in the motor home. Each of the 50A plugs hot prongs supply electricity to part of the coach. If you only connect one you will only have some of the circuits in the motor home active. The circuits from one prong do not interact with the circuits of the other prong. If this were not true, you would have 240 volts short circuiting in the motor home when hooked up to a normal 50A 240V outlet.

[ejmc77@hotmail.com]

Thanks TB.....slowly but surely getting a clearer picture of the basic mh circuitry.

Gene

[wolfe10]

Let me expand on Tom's excellent post.

50 RV Outlet:

Two hots to outer straight prongs.

One neutral to center straight.

One ground to center round.

EITHER hot to either ground or neutral reads 120 VAC.

Outer hot to outer hot reads 240 VAC.

Center straight (neutral) to center round (ground) reads 0 VAC.

Brett

[akadeadeye]

mccsix,

As Tom said, no apology needed. You guys keep this up. I'm learning.

Don

[tbutler]

Outer hot to outer hot reads 240 VAC.

Brett

All these are correct with one exception. If you jumper with 30A connection to both hot blades, the voltmeter will read 0 volts difference between these two blades (outer hot to outer hot). Since the two hots are not opposite phase, there will be no difference in their charge status and no voltage difference between the two. You will still register 120V between either hot and the neutral or the ground.

[wolfe10]

All these are correct with one exception. If you jumper with 30A connection to both hot blades, the voltmeter will read 0 volts difference between these two blades (outer hot to outer hot). Since the two hots are not opposite phase, there will be no difference in their charge status and no voltage difference between the two. You will still register 120V between either hot and the neutral or the ground.

Correct.

My description was for a standard (correct) 50 amp RV outlet.

Brett

[akadeadeye]

OK, Another question for some clarification.

I had a private message from another FMCA electrician. And I am very grateful at the generosity from people to help those who are new to all this. But, he offered an alternative set-up which, he claimed, could save on some wiring costs since I have two relatively long runs.

His suggestion was to use 2-pole 30 amp breakers at the pedestal, from which could be run a 50 amp plug, and a 30 amp plug. I am sure I am leaving out some details. He also mentioned alternating feeds from pedestal to pedestal to keep the load even overall. He and I talked on the phone and his knowledge of all this is way above mine, but he is right that the cost of long runs of heavy gauge wiring is significant.

Any thoughts?

Don

[wolfe10]

OK, Another question for some clarification.

I had a private message from another FMCA electrician. And I am very grateful at the generosity from people to help those who are new to all this. But, he offered an alternative set-up which, he claimed, could save on some wiring costs since I have two relatively long runs.

His suggestion was to use 2-pole 30 amp breakers at the pedestal, from which could be run a 50 amp plug, and a 30 amp plug. I am sure I am leaving out some details. He also mentioned alternating feeds from pedestal to pedestal to keep the load even overall. He and I talked on the phone and his knowledge of all this is way above mine, but he is right that the cost of long runs of heavy gauge wiring is significant.

Any thoughts?

Don

Don,

I suspect something has been left out.

The use of a two pole breaker suggests two HOTS.

With only three wires: One HAS to be neutral and one HAS to be ground, that only leaves one wire as the hot.

Eliminate the neutral and you would not have 120 VAC (two hots and a ground= 240 VAC). Eliminating the ground (so that wire could be used as the second hot) would violate every electrical code in the country.

Perhaps more information on what he suggests each of the three wires will do would clear it up.

Brett

[Guest Wayne77590]

Try this web site for information

[genenick]

When I was explaining all of this to my son I was telling him that motorhomes only use the 2 circuits of the 120 Volt, never the 240 Volt. 120 covers part of the camper and one a/c, then the other leg of the 120 covers the other a/c. If you have a 50 Amp camper and pluged into a 30 circuit then there is a smart switch (usually) that will only let one a/c work at a time. Everything else works as normal. If you are using the front a/c and want to use the back a/c then you will have to shut down the front one and wait a few minutes; then turn on the back one. And Vice Versa if you need to change back to the front. I know some of the older Fleetwoods had a manual selector switch as to which a/c you wanted to run. One the newer ones and the one I have now (Damon Challenger) it is all automatic. Maybe this is add a litttle clarity for a couple of people.

Gene

[rossboyer]

Don,

I suspect something has been left out.

The use of a two pole breaker suggests two HOTS.

With only three wires: One HAS to be neutral and one HAS to be ground, that only leaves one wire as the hot.

Eliminate the neutral and you would not have 120 VAC (two hots and a ground= 240 VAC). Eliminating the ground (so that wire could be used as the second hot) would violate every electrical code in the country.

Perhaps more information on what he suggests each of the three wires will do would clear it up.

Brett

Hi Brett:

Use 4 wires. First let us assume a short run of say 10 feet. Using 4 conductor #10 wire, one green, one white, one red, & one black. In the main panel connect the red and black wires to the two poles of a 30 amp 2-pole breaker and the white to Neutral and green to Ground. At the other end connect per your diagram to a 50 amp outlet. Yes, I know that there is only 30 amps available on each leg for a total of 60 amps, not 100 if it were wired to a 50 amp 2-pole breaker in the main panel using larger wire. Now below that 50 amp outlet add a 30 amp outlet, wiring as your diagram shows, green to Ground, white to Neutral, and black to Hot. On the next pole running from another 30 amp 2-pole breaker in the main panel, wire the circuit the same, but use the red wire to Hot on the 30 amp outlet. All of this is perfectly safe as long as both plugs on one pole are not used. For longer runs larger wire would have to be used, but all is still safe because the 30 amp breaker protects the wire. The RV can plug into the 50 amp receptical allowing more load than would be allowed in the common 30 amp circuit. If the RV is 30 amp, plug into the 30 amp outlet. The max load is only 30 amp.

RWB

[wolfe10]

Hi Brett:

Use 4 wires. First let us assume a short run of say 10 feet. Using 4 conductor #10 wire, one green, one white, one red, & one black. In the main panel connect the red and black wires to the two poles of a 30 amp 2-pole breaker and the white to Neutral and green to Ground. At the other end connect per your diagram to a 50 amp outlet. Yes, I know that there is only 30 amps available on each leg for a total of 60 amps, not 100 if it were wired to a 50 amp 2-pole breaker in the main panel using larger wire. Now below that 50 amp outlet add a 30 amp outlet, wiring as your diagram shows, green to Ground, white to Neutral, and black to Hot. On the next pole running from another 30 amp 2-pole breaker in the main panel, wire the circuit the same, but use the red wire to Hot on the 30 amp outlet. All of this is perfectly safe as long as both plugs on one pole are not used. For longer runs larger wire would have to be used, but all is still safe because the 30 amp breaker protects the wire. The RV can plug into the 50 amp receptical allowing more load than would be allowed in the common 30 amp circuit. If the RV is 30 amp, plug into the 30 amp outlet. The max load is only 30 amp.

RWB

Of course. Your description is right on.

The issue concerns Mccsix's attempt to wire a 50 amp outlet with only three wires vs the (correct) four wire.

Brett