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-   -   Ground wire getting hot????? (http://www.airforums.com/forums/f449/ground-wire-getting-hot-49282.html)

86Scotty 03-14-2009 06:40 PM

Ground wire getting hot?????
 
OK guys, after reading up and studying, i purchased a 9260 (60) amp Intellipower for my 73 Sovereign. I also bought the very popular power dist. block that Vintage Trailer sells, but upon looking at it, i decided it would be easier to use the one off the Univolt, since it keeps the ampmeter, fuses i already have, etc. I wired everything and had no problems, ran new cables and terminals to the battery, grounded the converter from it's grounding lug to the trailer skin and also to the a/c ground that runs all the way to the inside of rear bumper. I have one positive and one negative out of converter to battery, and the other positive and negative from converter to positive and negative of fuse panel.
I had NO DC lights when i finished all of this except i had one white wire (about 8 guage) left sticking out of the wall above converter where they all go into the wall. I remembered this was tied in with ground from univolt, so i wired it also to the negative lug on the downstream side of univolt fuse panel (where it originally was, right beside that tiny 2amp "power on" fuse).
Then i had lights, and everything worked, and a few minutes later i started smelling a mild burning smell, and found that the 4 guage black/negative wire coming from the new converter to the neg. lug on distribution block and the block itself are REALLY hot.
What am i missing? Any help greatly appreciated. I unhooked it until i can solve this problem, this couldn't be right. I've never seen a HOT neg/ground wire.

Lumatic 03-14-2009 07:27 PM

Quote:

Originally Posted by 86Scotty (Post 676799)
What am i missing?

I would start with disconnecting all 4 circuits to the fuse panel and then plug in the Intellipower and check the ground wire. Then try one circuit at a time and check your ground. Hopefully this will help isolate the problem.

azflycaster 03-14-2009 07:43 PM

1 Attachment(s)
Maybe this will help.

Gene 03-14-2009 07:55 PM

This makes me wonder: "grounded the converter from it's grounding lug to the trailer skin and also to the a/c ground that runs all the way to the inside of rear bumper." A/C means air conditioner to me and and A/C is 120 v. and wouldn't be grounded to the trailer. What am I missing here? Any, disconnect that ground to the "a/c" ground and see what happens.

Gene

86Scotty 03-14-2009 08:09 PM

Sorry Gene, that's AC as in Alternating Current. The AC fuse box and each outlet have a ground wire (bare copper) which goes from each outlet all the way back to the breaker box, and then on to the frame inside the rear bumper. I believe it goes there (on Airstreams) so rigs that stay parked can have a grounding rod added like your home has. Not trying to insult your intelligence, just explaining.

thanks

86Scotty 03-14-2009 08:20 PM

Richard, thanks very much for the diagram. That is my distribution panel. I have this wired this way, i think, but can't check it all until tomorrow. I have the positive from the converter going to #2(trailer battery +) and the negative from converter going to #3(trailer -), so i'm still not sure why it's heating up. I didn't connect anything to the lugs on the backside, just used the screw down terminals on the top.

thanks

Lumatic, i'll try that in the morning but it just doesn't seem like it would work. I'll sure try it though.

ROBERTSUNRUS 03-15-2009 12:18 AM

:) Hi, I'm not sure about your system, but usually a hot ground wire means that: (1.) Poor or dirty connection. (2.) Overload in system, but possitive wire would be hot too unless larger and shorter in wire size. (3.) Undersized wire for the load used. With what you stated, I would check for a poor or dirty connection at one or both ends of the ground wire. Also if a large wire is trimmed down to fit into a smaller lug, the actual wire size is reduced. [therefore undersized]

Over59 03-15-2009 08:23 AM

Quote:

Originally Posted by 86Scotty (Post 676835)
Sorry Gene, that's AC as in Alternating Current. The AC fuse box and each outlet have a ground wire (bare copper) which goes from each outlet all the way back to the breaker box, and then on to the frame inside the rear bumper. I believe it goes there (on Airstreams) so rigs that stay parked can have a grounding rod added like your home has. Not trying to insult your intelligence, just explaining.

thanks

The AC should not be grounded to the trailer. The system is a "Floating Ground" so a short doesn't kill someone touching the trailer from the outside. So unless you have a grounding rod disconnect it.

For a #4 to get hot you have wired something wrong. May have cooked your battery also.

Charger to battery to block is the usual method. Do you have 100amp fuses on both legs or is the #4 wire your fuse?

azflycaster 03-15-2009 08:30 AM

Quote:

Originally Posted by 86Scotty (Post 676845)
Richard, thanks very much for the diagram. That is my distribution panel. I have this wired this way, i think, but can't check it all until tomorrow. I have the positive from the converter going to #2(trailer battery +) and the negative from converter going to #3(trailer -), so i'm still not sure why it's heating up. I didn't connect anything to the lugs on the backside, just used the screw down terminals on the top.

thanks

Lumatic, i'll try that in the morning but it just doesn't seem like it would work. I'll sure try it though.

The wires from the converter should connect to the back side of the distribution panel. The lugs you used are for the trailer battery connection. Your new converter does not have an isolated wire for the power light as the univolt did, so that will no longer function.

86Scotty 03-15-2009 09:22 AM

OK guys, good info. I'm feeling like a dope here, thought this would be much simpler as i've worked on DC electric all my life. I'm rewiring from converter to back of univolt fuse panel and out of the top to battery. Also, i will drill a better ground for battery/fuse through floor to trailer frame and reground converter on a seperate ground not using the one i currently have through AC breaker box.
Does that sound more correct? Also, is 10g wire OK from dist. panel to battery or should it be bigger? I'm thinking bigger but not sure what these bigger wires will carry.
thanks

Gene 03-15-2009 09:30 AM

Quote:

Originally Posted by Over59 (Post 676947)
The AC should not be grounded to the trailer. The system is a "Floating Ground" so a short doesn't kill someone touching the trailer from the outside. So unless you have a grounding rod disconnect it.

Terms: A/C = air conditioning. AC = alternating current. But either way, grounding A/C to trailer is the same as grounding AC to trailer. The trailer is the 12 v. ground; grounding AC to the trailer to it asks for trouble. I've never looked to see if there's a 12 or 14 gauge ground wire at the bumper, but unless the bumper is isolated from the trailer, I would be surprised to find one. My understanding is the 120 v ground comes from the shore power and there would be no need for a grounding rod (unless shore power had none or it was nonfunctional).

Gene

86Scotty 03-15-2009 09:39 AM

Gene, i've heard debate on this one here and on the VAP but either way, i am not using it for grounding anything DC again!!! My apologies for confusion using A/C term. My air condition is fine and is not a part of my problem here, and for some reason, there is a factory bare copper grounding wire run from my AC breaker panel to a lug in the rear bumper on the frame. It looks to be original, and i think i've seen it on other Airstreams.
thanks

Gene 03-15-2009 09:48 AM

Ah, the mysteries of electrical systems in trailers and cars! I'm certainly no expert on older trailers, something I'm sure I've demonstrated plenty of times, but I can't understand a 120v ground to the bumper. Maybe they did it long ago and later learned it was a bad idea, or maybe it is insulated from the rest of the trailer. Still if there was a 120v. short, wouldn't the bumper be hot? There has to be a rationale explanation for that.

Gene

Aerowood 03-15-2009 10:13 AM

My 71 GT had a 120VAC ground lug on the rear frame, and that mystified me also. I do not plan on reinstalling that ground when I rewire the 120VAC. I am currently wiring some of the 12VDC and I am not using a floating ground but a common ground. More wiring at first but well worth not having ground problems in the future. This will also reduce or eliminate feedback issues with new electronics.

Kip


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