Help, please Electrical Question

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Help, please Electrical Question

Postby CaptainCurious » Fri Aug 26, 2011 12:10 am

Here's my dilemma. Someone broke into my motor home trashed it, stole mostly worthless crap (at least to sell), and I've just noticed they clipped my power cable. I am heading off to burning man on Sunday and really want to get this fixed so I can use my generator.

I purchased some new 4 wire heavy duty cable and a tt-30 plug. I just don't know which color wires to attach to the new plug (also, 4 wires and 3 prongs, hmmm?). I posted a similar request on Craigslist with pictures: The clipped cable. The electrical box with the individual wires from that cable (Red, black, green and white) still attached. The remaing socket that the missing plug mates with. The pictures are here http://sfbay.craigslist.org/sfc/wan/2567467724.html
I'm trying to get it fixed before I leave for home. Any advice would be truly appreciated. I think if I know the configuration I could do this myself without much hassle, but I am also willing to pay someone to reconnect it for me (I'm in SF).
Thanks for taking your time to read this!

See you in the dust )'(
Last edited by CaptainCurious on Fri Aug 26, 2011 2:12 pm, edited 3 times in total.
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Re: Help, please

Postby alkalinenerd » Fri Aug 26, 2011 1:21 am

I'm not an electrician or anything, but typically red and black would be your hot in wires and white would be your negative out, green would be the grounding wire which would likely not connect to the plug. Just a screw somewhere. I looked at the pictures but feel like i'm still missing something. Best of luck.
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Re: Help, please

Postby alkalinenerd » Fri Aug 26, 2011 1:26 am

Also it might help to put "electrical question" in your title, these days forum folks are so tired of seeing "help need ticket" or "help miracle please" threads that blindly asking for help might not even warrant a second glance.
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Re: Help, please

Postby trilobyte » Fri Aug 26, 2011 1:27 am

Nudging this over to Q&A, I think that might be a better fit. Good luck!
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Re: Help, please

Postby BBadger » Fri Aug 26, 2011 2:58 am

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Re: Help, please

Postby junglesmacks » Fri Aug 26, 2011 3:53 am

This is correct.

alkalinenerd wrote:I'm not an electrician or anything, but typically red and black would be your hot in wires and white would be your negative out, green would be the grounding wire which would likely not connect to the plug. Just a screw somewhere. I looked at the pictures but feel like i'm still missing something. Best of luck.
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Re: Help, please

Postby headquarters » Fri Aug 26, 2011 11:22 am

I'm an amateur electrician. However your photo has been removed.
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Re: Help, please

Postby headquarters » Fri Aug 26, 2011 11:23 am

alkalinenerd wrote:I'm not an electrician or anything, but typically red and black would be your hot in wires and white would be your negative out, green would be the grounding wire which would likely not connect to the plug. Just a screw somewhere. I looked at the pictures but feel like i'm still missing something. Best of luck.


Red could also be a switch traveler wire, or signify 277v volt. Both of those uses are common.
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Re: Help, please Electrical Question

Postby CaptainCurious » Fri Aug 26, 2011 12:25 pm

Thanks for the advice.
Can I hook red or black to either hot side of the plug, or are there polarity issues?
Being clear, is the green is only connected where it currently is in the coach, and not at all on the plug?
pictures are back up.
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Re: Help, please Electrical Question

Postby FIGJAM » Fri Aug 26, 2011 12:38 pm

Red is+, black is-.
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Re: Help, please Electrical Question

Postby billvon » Fri Aug 26, 2011 12:58 pm

FIGJAM wrote:Red is+, black is-.


In AC wiring, white is neutral, green is ground, black and red are hot. Often black and red are opposite sides of a 240 volt circuit.
In newer solar and DC installations, white is generally negative, red or black is positive.
In older DC installations (car stereos etc) red is + and black is -.

What all that means is that you sometimes can't trust the colors, but there are some general assumptions you can make.

Most RV generators are 120VAC, which means there will be one hot, one neutral and one ground. The hot is generally black or red, neutral is almost always white and ground is green (often with other colors striped in.)

TT-30 plugs are 120VAC 30A plugs, so you will end up with 3 wires that are doing something. (The 4th wire is either disconnected or is connected in parallel with another wire.) To verify this borrow or buy a multimeter (they're only $10 or so at Radio Shack) and measure resistance from black to red. If it's zero they are connected together.

From your description the most likely connection scheme is:

Your old cable The new cable
============ ============
White White
Green Green
Black Black
(nothing) Red - just tape this one up and don't connect it.

If there's no green wire in your old cable, connect green to the RV chassis. If the red/black options aren't making sense it is sometimes OK to connect everything together (all reds and all blacks.) This is always OK on 120 volt only systems since both have to be at the same potential, and the TT-30 can't carry 240VAC anyway. If your RV load is expecting 240VAC, and you connect everything together, then all your 120 volt loads will work but your 240 volt loads (A/C?) won't - but they won't be damaged, they just won't turn on. The only time it is NOT ok to connect red to black is if you are using a 240V source. If you do that the circuit breaker will blow pretty much instantly.

If you are planning on connecting your RV to a generator it may be easier to just buy a 12 gauge extension cord, cut off the female end and wire that one in. That's guaranteed to have three wires so connection might be simpler, and most generators have a standard NEMA 5-15 or 5-20 plug (i.e. one that looks like it's a regular wall socket.)
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Re: Help, please Electrical Question

Postby headquarters » Fri Aug 26, 2011 1:55 pm

i don't see the pictures.
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Re: Help, please Electrical Question

Postby CaptainCurious » Fri Aug 26, 2011 2:23 pm

The pictures are back up at the craigslist link. Can I post pictures here?
Still a little unclear as to the exact wiring to the plug assuming I hook the cable to the electrical board the identical way it is now (in the pics).
Even though I have the cable and plug already, I would consider the cutting the end off adn extension chord idea. Any one know an rv place or anywhere else where I could buy one in SF or Marin? I needan adapter and some other rv related supplies too.
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Re: Help, please Electrical Question

Postby gyre » Fri Aug 26, 2011 2:54 pm

They sell these cords in the rv section at some walmarts.
They are usually twist locks though.

I'm not sure what the wiring protocol is for that one.

It looks like white is the neutral, and red and black are power.

You need to determine if it is used as a 240 source (as is typical to house boxes), or two conductors from one source- parallel.

You could simply ignore the red wire now and not connect it, as long as that won't disable something else.

If that is a three prong plug, it is 120 if the ground is connected to a prong.


Trailer Life is a great source for manuals on rvs.
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Re: Help, please Electrical Question

Postby billvon » Fri Aug 26, 2011 3:06 pm

CaptainCurious wrote:The pictures are back up at the craigslist link.


OK, you have a 240 volt panel, but nothing in your panel requires 240 volts; all the circuits in the picture are 120 volt circuits. That means you can connect the red and black wires in the old cord to the black wire in the new cord. White goes to white and green goes to green.

If you want to cut the end off an extension cord go to Home Depot or Walmart and get a 12 gauge extension cord in whatever length you like. Cut off the female end. You will see three wires inside - white, black and green. White goes to white, green goes to green and the black wire in the cord goes to the black and red wire in your box. You can use wire nuts if you like (they are in the electrical section at Home Depot) but if you do make sure you secure the cord to the RV. Wire nuts make good electrical connections but they cannot withstand any pulling at all, so cable-tie the new cord to some part of the RV. (You could even just attach it to the stub of the old cord with a few cable ties.)
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Re: Help, please Electrical Question

Postby gyre » Fri Aug 26, 2011 3:16 pm

You are better off with a 10 gauge or larger.

The rv wire is uv stable.


http://www.walmart.com/ip/Road-Power-30 ... 0/16817354

They used to sell Coleman, generally a high quality cord.

There should be several rv choices out there.

Truck stops?
Camping World, etc?
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Re: Help, please Electrical Question

Postby CaptainCurious » Fri Aug 26, 2011 10:59 pm

It's all rewired now. Thanks for all your help. You guys rock!
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Re: Help, please Electrical Question

Postby EastcoastEd » Sat Aug 27, 2011 1:21 pm

Are you , and can you trace it back to the curcuit panel and match the colors to their connections. Or if you're in a pinch cut the new cord strip the ends and wire nut the appropriate colors together and rock on with it. You can always fix it right when you get back home.
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