Please move if this is the incorrect place.

I have a portable generator that is mounted to a car trailer. No earth grounds are made from the generator to the ground. There is a service panel inside the trailer with 2, 110v connections and 1, 220v connection. The wires coming out of the trailer are black, white, green and solid bare copper.

I want to make sure to wire this up correctly and is based on US standards. On the L14-30 plug I had the white and black going to the hot poles on the plug and green going to ground. What I did not know is where the solid, bare copper wire went. I had to convert from a NEMA 6-30 plug. When I was disassembling the plug the bare copper appeared that it was just pushed into the end of the plug but not attached to any connections within it.

Breaker Box 1

Breaker Box 2

  • The bare copper and ground wire must be bonded to the grounding system, which in this case are metal boxes and conduit. A NEMA6-30 has no neutral, but a L14-30 does. How are you achieving a neutral conductor? The generator frame must be bonded to the trailer frame.
    – bcworkz
    Mar 12, 2014 at 19:46
  • The generator frame is mounted to the trailer frame. The generator has the neutral bonded to its frame. I do not know how the neutral is achieved. From a few places on the net a few folks wired it up in this fashion and did not have a neutral from the panel to the plug. I have ran the generator and everything is working in the trailer and frame is not energized.
    – Travis
    Mar 13, 2014 at 2:57

1 Answer 1


Use the right colors

First off, if you're wiring to US standards, you've got the wire colors wrong.

Green and bare copper are both used to identify an equipment grounding conductor. White is typically used as a grounded (neutral) conductor (grey is also acceptable), though can be used as ungrounded (hot) if there are appropriate markings at each termination. From there, basically anything that's not green, bare, white, or gray, can be used as an ungrounded (hot) conductor.

Wiring L14-30 Plug

To properly wire a NEMA L14-30 device, you'll need 4 conductors.

NEMA L14-30 Wiring

Proper Wiring

In your situation, I'd pull an extra red or black conductor from the panel to the receptacle location and remove either the green or bare conductor. Then you'll connect the original black conductor from the breaker, to X on the receptacle. Connect the new red/black conductor from the other terminal of a double pole 30 ampere breaker, to Y on the receptacle. Next connect the white wire from the neutral bus bar in the panel, to the N terminal of the receptacle. Finally, connect the green/bare conductor from the grounding bus bar, to the G terminal on the receptacle.

  • I'm not wiring anything. This is the wiring the trailer had from the factory in 1995. I am not plugging in a single device, I am running "shore power" from a generator to operate the trailer. The two (middle), 20a breakers are double poled and runs the 220v A/C. They are "stuck" together. The one single pole, 20a breaker runs the left side 120v wall outlets and the other runs the right side 120v wall outlet and overhead 120v, 4' fluorescent lights. I simply cut off the existing 6-30 to replace it with the L14-30. My old generator had the 6-30, the new one has the L14-30.
    – Travis
    Mar 13, 2014 at 16:21
  • Replacing with 30a breakers is not an issue if that is what it should have. What I want to know is by looking at the panel connections do I have the wires going to the right place on the plug, ignoring wire colors.
    – Travis
    Mar 13, 2014 at 16:23
  • Sorry I thought you were adding a receptacle to draw power, not one for supplying power.
    – Tester101
    Mar 13, 2014 at 18:40
  • So should my bare copper hook into the ground and the green be the neutral?
    – Travis
    Mar 13, 2014 at 19:50
  • No. Bare should be ground, and you should run a new grey or white wire for neutral. Or you should run a red wire for another hot, and switch the white you have to neutral. All my advice stands, except the section about the breakers.
    – Tester101
    Mar 14, 2014 at 0:36

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