A/C blowing the breaker

[Chuck]

went camping this week...it was just a bit warm, so I thought I'd try out the A/C. Had a full hookup site, and the utilities were placed well...no extention cord needed. plugged right into the 30-amp plug.

turned the a/c on fan-only, just to circulate air around, and It wouldn't come on. I checked the breaker, and it was tripped. don't know how that happened...haven't used the trailer in 6 months. so, I turned it back on, and the fan came on...all is well. I was outside puttering around, and the wife shut it off (or so I thought...turns out, it blew the breaker...just running on "fan"). next night, I went to turn on the a/c, and noticed that the breaker had tripped again. I figured that the wife used the breaker to shut off the a/c, as she saw me do that the day before. silly me...
so I turned on the a/c, and it ran for a few minutes, then the breaker tripped again. "ok, something is definately wrong" I thought. I checked the breaker box, and it was HOT HOT HOT! smelled funny, too. That was the end of that. Luckily, it wasn't that hot.

so, electrical/hvac guru's: what might this be? am I now in the market for a new A/C unit?

[thenewkid64]

I would first unplug the rig, then pull the cover on the panel. Breakers and the contacts inside do age and the breaker itself could be the trouble. The breaker should be able to be tipped out from the top or center depending ont the panel. The panel cover is what really holds it in. one wire (black) should be connected to the breaker with a screw. While you are in here, take a close look at them all, the heat from one may have affected the others.

If the breaker plastic is cracked, melted or btittle, then I would say the breaker has failed. Take it out and take it with you to the Hardware store to match it. Worse case it costs you 8-10 bucks and does not fix the problem, but if the panel is hot I would surmise that the Air Conditioner breaker, or the main one is the real problem.

[Chuck]

thanks for the tip. I was thinking that it might be some "basic" wiring fault, considering that it tripped just running the fan. that shouldn't be drawing much power by itself, should it?

there are only 2 breakers in the box; I assume that one is dedicated for the a/c circuit, and the other is for the 110v outlets. there are only 5 oulets in the trailer....

[Chuck]

I took off the box yesterday and took a look...looks like I got some toasted wires. of course, they could have been toasted before, I guess...never looked in here before. Anyway, it looks like the white (neutral?) wires on both circuits got their insulation lightly toasted. what could this mean? and why didn't the breaker blow before that much heat built up? (more evidence of a failed breaker, not tripping quick enough?).

what now? should I re-do all these connections, stripping the romex down to a "clean" area? there is some slack in the cables...not a whole lot, but some. I'd really hate to have to replace a whole run of romex from this panel up to the a/c...yikes!

[thenewkid64]

Chuck,

Normally the white wires would not get hot unless there is something causing a major short.

I would say you have found the trouble. The white wires need to be replaced. A new run is not necessaty but I am concerned about what caused the burning/corrosion

JohnHD will say this is not kosher, but you could cut back to good wire and wire nut in a small peice that is of the same gauge to make the repair. Is the wire on the right shorted to the hot side of the box?

[thenewkid64]

Upon further review you should be able to pull some of the wire from the power cord in and get a good connection there.

Take both romex wires out of the top of the box and bring them back in thru the bottom. That should get you enough good wire to not need to splice.

I had this same type of thing in my MH, water got in the box and cause a ton of corrosion and the wires burnt up.

Don't forget to cover the holes that you leave in the top, just in case something like this happens again the sparks will stay in the box and not start a fire.

[Chuck]

yeah, I'm concerned, too.

funny...there was no problem last year...and no leaks since then, either. at least none that I've caught. I wonder if its just "old age". if that is "corrosion", could it be just from the humidity in the air? perhaps a failure in the a/c is responsible.

I used a few of the 120v outlets last week, and they were fine.

I'm not sure what you mean about the "wire on the right". do you mean the black wire from the romex cable on the right? I'll have to get a meter on it and find out.

here's another pic that may yield more info....its difficult to get the camera in there...tight space. I didn't catch anything on the left side of the box, but things looked ok on that side, from what I could see. then again, those wires are supposed to be black

[thenewkid64]

Chuck,

I was looking at the white wire that is over the buss bar on the right.

It looks like corrosion. It causes resistance and heat since the corrosion and the electrons travel on the outside of the wire. The corrosion has a cumlitave effect. It may not have been bad last year, just a little corrosion. Age and humidity may have just made it worse. Who knows, the leak may have happened before you got the trailer

I would pull it out, trim it down, and clean up as much of it as possible. Before reconnecting I would use ox-guard on the wires. It is in a small tube and designed for aluminum wire to prevent corrosion, but works on copper too. Reconnect and test everything.

I surmise the corrision just got so bad that the breakers started popping.

[john hd]

"JohnHD will say this is not kosher, but you could cut back to good wire and wire nut in a small peice that is of the same gauge to make the repair. Is the wire on the right shorted to the hot side of the box?"

nothing wrong with wire nutting a piece of good wire on, just as long as it is inside the box. tape the wire nut up just to be extra safe.

that green gunk on the neutral wire is from corrosion. humidity, salt air etc.

looks like your neutral block got hot too, you will want to clean that up as best as possible.

try and get the holes where the wire goes nice and shiney. a .30 caliber gun brush might do the trick.

if you cant get it to clean up good just replace it, most electrical supply houses should have one. be sure to get a neutral block that is insulated. otherwise you will blow breakers when hooked to a gfi circuit at the campground. also, make sure the insulating paper behind it is ok.

the reason you were blowing breakers is because the corrosion increased the current in the circuit beyond its rating.

everything worked like it should have, breaker snapped no fire!


john

[john hd]

btw,

pull slack in your wires if you can, no splices or wire nuts would be best. but if you can't you can't.

after looking at that photo again, it looks like the power cord neutral is toast too.

if your power cord is questionable in any other areas like the plug, just replace it too.

they wear out like any other extention cord.

john

[3Ms75Argosy]

Chuck,
outside the box, where the Romex is clamped to the left and down from the box, is that just a shadow on the two romex cables, or is the outside of the insulation blackened? From the photo, it looks blackened above the clamp. If so, some arcing could have happened outside the box (or just a shadow from the flash?)
Marc

[FrankR]

In viewing the subpanel breaker box, some basic requirements may have been ignored. In the beginning, the power cord is/was not properly connected to the "hot" lug, the ground buss or the neutral buss. Working with stranded wire requires a "pigtail" of solid wire be attached or the wire ends be soldered. Placing stranded wire under a mechanical attachment as a screw is not a good termination. A poor connection will not fail immediately but contribute heat and other poor connections. Any connection that becomes heated causes the connection to loosen and make more heat. After a while the length ofthe buss will become heated and all connections will fail. Many learned electricians recomment electrical paste to make better connections and continuity. While wire nuts are an accepted method of wire splicing, the copper coated crimp sleeves, work better, make smaller splice. and are nearly failure proof. Breakers wire set screws must be properly torqued. Too much or too loose screw torque is prolog for failure.
There is no substitution for informed quality workmanship. Frank

[Chuck]

Marc, I'll have to check that. it does look burnt in the picture...I thought it was just "dirt", but maybe not.

I thought the green gunk on some of those neutral wires was just cooked insulation. it flakes right off. you can see a couple of chunks of it on the bottom floor of the box. It certainly seems to be the same color as copper "patina".

Frank: I think that the breaker-panel in my house is wired the same way, with stranded wire screwed to the terminals. yikes! so you're saying that they should in fact be spliced to a piece of solid copper wire, and then attached to the screw terminal?

John: yes, the power-cord neutral is definately toasted. It seems to me that the breaker should trip before this much heat builds up...but what do I know? (a: just enough to get myself in trouble, that's how much I know). LOL!

Looks like the easiest thing to do here is to just replace the whole box. probably wouldn't cost too much, right? I really appreciate all your insights, guys.

-chuck

[thenewkid64]

Marc,

I think the black spot you are seeing is the PVC jacket of the romex absorbing the oils from the rubber of the clamp that is used to hold it to the wall. The clamp is normally a plumbing part, but Airstream also used them to hold wires and not chafe.

Chuck,

Frank is correect in asserting that stranded wire should either be tinned with solder or mated to a solid wire before being installed in the box unless the box is designed for a stranded application.

New box form Grainger is less than 30 bucks, but you will need to get proper breakers at 6-9 bucks each. So 50 dollars max, or 4-7 bucks for a new neutral buss bar and half the time to rewire. Not to mention the time to find the parts.

I would trim the main cord and strip back to clean wire then tin the ends with solder and screw it back down. Save the 40.00 for somehting that you want to spend it on and clean this up. It will work just fine once it is clean and you are making good contact.