6 gage, 4 conductor cable info/

This is a cable on a motor home with a 4 terminal plug. The box on the home says 240 volts, 50 amps service. Conductor colors are red, black, green, white. Which color is considered the 4th? I'm not real sure of how to use the 4th conductor in a box on the side of a building where this cable will be plugged into. Thanks to all of you electrical experts.

(quoted from post at 21:33:24 12/01/22) This is a cable on a motor home with a 4 terminal plug. The box on the home says 240 volts, 50 amps service. Conductor colors are red, black, green, white. Which color is considered the 4th? I'm not real sure of how to use the 4th conductor in a box on the side of a building where this cable will be plugged into. Thanks to all of you electrical experts.

Click to expand...

Red and black are the ''hot'' wires, 120 Volts each to the neutral, 240 Volts across them.

White is ''neutral''.

And GREEN (imagine that) is ground.

Not familiar with a motor home but I'd say Black and Red are both 120V and feed the two busses at the breaker panel. White is Neutral and Green is Ground.

This is a 50 amp RV service. As wore out said, red and black are hot, white is neutral and green is ground. So to properly hook this up, you'll need a 240 volt, 50 amp circuit with separate neutral and ground. But what do you currently have on the building? Is it 240V? If so, does it have separate ground and neutral wires?

Note that 30 amp RV service is 120V, NOT 240. So if your existing box at the building is 30 amp RV, you'll need to upgrade it to 240V.

You can adapt a 30 amp RV outlet to 50 amp, provided 1) you have no 240 volt appliances in the RV; and 2) you don't intend to run the air conditioner(s). But it's best to have 240V, 50 amp, four wire service.

I lived in a house trailer when in College in the 60s.
60 amp services were common.
Some old trailers were only wired with a 40 amp main.
If I recall, the power cord to my old trailer was 4 wires.
The trailer was built in the 50's.
So 4 wire 220v service has been around for at least 70 years.
The green wire was also attached to the metal siding on the trailer.

I re-read your post and you said the box on your house is labeled '240 volt 50 amp'. If so, it should have a four-wire outlet installed. If it's only three-wire, it's possible somebody wired it up for 30 amps. They would have just left the extra wire disconnected. Or maybe they only ran 120 volts to the box. You need to see if you actually have 240 volts at the box.

Good Morning Ron, as a 50 year RV owner and retired power engineer I can describe for you how a 50 Amp RV is configured and (maybe NOT yours) SOME 50 Amp 240 Volt Receptacles are configured. HOWEVER I can NOT know how the receptacle you mentioned is configured !!!!!!!


(A) SHORT ANSWER To your specific question Conductor colors are red, black, green, white. Which color is considered the 4th? I'm not real sure of how to use the 4th conductor in a box on the side of a building where this cable will be plugged into.

Red Hot L1, ,Black Hot L2,, Green Ground,, White Neutral
If it has Four terminals and 120 L1 OR L2 to Neutral OR Ground and 240 L1 to L2 Thats how many 50 Amp
RV's are often configured IE thats NEMA 14-50 !!!!!!!!!

That can be referred to as THREE POLE FOUR WIRE GROUNDING


(B) LONG ANSWER

Is your receptacle a straight 240 ONLY Volt 50 Amp THREE WIRE (used for some appliances tools or welders or compressors) consisting of two Hots L1 & L2 240 VAC plus a Green/Bare Equipment GroundiNG Conductor but NO Neutral orrrrrrrrrrrrrrr is it a 120/240 FOUR WIRE with two Hots, Neutral, Ground consisting of 120 plus 240 ??????????

1) A 50 Amp RV often uses a NEMA 14-50P Plug which plugs into an RV parks power pedestals NEMA 14-50R Receptacle.

2) If wired as most (no warranty some are different) RV park pedestals NEMA 14-50R receptacles

Black Hot L1
Red Hot L2
White Neutral
Green/Bare Equipment GroundING Conductor

3) If wired as most common (not all) there is 240 VAC L1 to L2,,,,,,,,,120 VAC L1 OR L2 to Neutral,,,,,,,,,,,120 VAC L1 OR L2 to Ground

4) MOST 50 Amp RV's do not use any of the available (if wired that way as typical) 240 VAC but the two legs of 120 L1 and L2 which are 120 to Neutral IE one AC is on L1 other AC on L2

5) HOWEVER there are some RV's that if plugged to 120/240 NEMA 14-50R receptacles actually use 240 VAC for perhaps appliances such as a clothes dryer or water heater or a heat pump NOT COMMON BUT ITS DONE

6) YOUR HOME 240 VOLT 50 AMP RECEPTACLE See above. Is it Three or Four terminal (does it have a White Neutral) ??? Is it a NEMA 14-50R Four terminal like RV parks use ??? Is it 240 L1 to L2 ??? Is there 120 VAC available Just because its a 240 Volt 50 Amp DOES NOT mean it has a Neutral, it may well be a straight 240 ONLY (Two hots and ground) for like a welder or a 240 compressor

Your 50 Amp RV IS MOST LIKELY as I described above HOWEVER you have to figure out that receptacle before I can advise further........

NOTES A 50 Amp RV (most done use 240) can work from a receptacle that ONLY has 120 IE L1 and L2 are on the same phase NO 240 L1 to L2 HOWEVER you have to be careful NOT to overload the max amps available and NOT overload the Neutral.......

If your Receptacle DOES NOT HAVE A NEUTRAL DO NOTTTTTTTTTT use its Ground for a Neutral !!!!
If your Receptacle DOES HAVE A NEUTRAL AND A GROUND let me know

They make adapters so 50 Amp RV's can be powered from 120 ONLY receptacles even a NEMA TT-30R like 30 Amp RV;s use....All the adapter does is splice BOTH L1 and L2 to the 50 Amp so both legs in a 50 Amp RV work BUT REMEMBER THERES ONLY X AMPS AVAIALBE

It all boils down to WHAT YOUR RECEPTACLE HAS to see if it can power your RV and how if any adapters may be required.

SEE HOW YOUR RECEPTACLE IS CONFIGURED AND THEN I CAN ADVISE YOU FURTHER Is it a NEMA 14-50 R with FOUR terminals ??? and if so are there Red Black White and Green conductors feeding it ??? and if so is there 120 L1 or L2 to Neutral or Ground and 240 L1 to L2 ???

Let me know Ron, best wishes

John T Live in the RV at Davis Bayou Ocean Springs MS

Nice picture, good job

John T

Ground bar to be isolated not bonded to back box.

I see I didn't explain this well enough. The box on the home means the storage box on the motor home where the pigtail 6 gage, 4 conductor cable is stored when on the road. The label on this storage box says 240 volts, 50 amps service. The motor home is parked for the winter near an industrial building which has 200 amp, 240 volt, main panel service. The receptacle is what I need to supply on the outside of this building and connect it to the 200 amp panel with a 50 amp breaker. This receptacle is where the 4 terminal plug on the motor home pigtail cable will plug in. From your description, it needs to be the NEMA 14-50R as is used in an RV park's power pedestal. I think it would be useful for me to photo the inside of the 200 amp panel and post the photo here. I do understand basic wiring, but I tend to get puzzled with neutral and ground differences. Thanks to all who are contributing to this.

> I see I didn't explain this well enough. The box on the home means the storage box on the motor home where the pigtail 6 gage, 4 conductor cable is stored when on the road.

Ah. I got tripped up by the word 'home'.

OK, so you want to add an RV receptacle to the building. Assuming the breaker panel is separate from the service disconnect, you might have a couple of options. If you add it to the breaker panel, you'll run four wires (two hot: red & black; neutral white and ground) from the panel to your RV outlet. The ground and neutral wires will be separate in the panel and it will be obvious which is which.

The other option would be to add the receptacle to the main disconnect, assuming the main disconnect box has provisions to add breakers. That's where my RV outlet is. In this case, the ground and neutral are probably tied together in the box, so both the ground and neutral will go to the ground/neutral buss bar.

I would buy a box like this, just hang it next to the 200 amp panel.
Punch holes in sides if no knockouts.
That way when you leave that site you can take it with you.
Don't have to mess with a different breaker style for whatever panel it is wired to in the future. And it is all pre wired in this sub panel.
You won't be able to buy the individual parts to assembly your own for the price of this panel either.
$53 Panel

> You won't be able to buy the individual parts to assembly your own for the price of this panel either.

I don't think you can buy that box for 53 bucks, either. <a href=https://www.homedepot.com/p/GE-RV-Panel-with-50-Amp-and-30-AMP-RV-Receptacles-and-a-20-Amp-GFCI-Receptacle-GE1LU532SS/203393689>But you can buy it from HD for $229</a>. Since he only needs the 50 amp outlet, HD sells a similar box with only 50 and 20 amp outlets for $129. Still a bargain.

Did you notice the other merchandise on that site is all jewelry? Hmm.
50 & 20 amp RV box

Thanks Mark. I now understand what to do. It's just actually getting it done mechanically that I dislike. It's tough with those big wires when it's cold and part of the job will be outside. BBBRRRHHH!!!