Another Electrical concern Help Please!

D+C4106 · August 03, 2007, 07:56:33 PM

We went for a short trip today. Plugged in 50 amp shore cord to 30 amp dog bone to 30 amp extension cord to wall outlet. Microwave went crazy made funny noise and smelled like something was burning. Unplugged as quick as we could.

Disconnected, revised the layout, went 50 amp shore cord to 30 amp dog bone with 15 amp adapter to wall outlet. (I tested the wall outlet with the small plug in type tester, it showed ok and grounded as did the outlet inside the bus.)

Now, I have a hot bus?

I just happened to be in the generator bay and touched the unit and got a poke. Pulled out my tester and I have 120 volt from various places to the dirt. Sorry for the confusion I am not an electrician but, I can't figure out why I am not grounded correctly. I have used this connection layout before without a problem and I am confused. I need to stay in the coach for another two nights and need to correct this problem. Any help would be appreciated!!!! Thanks Denis

jjrbus · August 04, 2007, 05:28:07 AM

I would unplug the coach and go without electricity! Then find an electrician to troubleshoot for you. This is difficult to do on the internet. What area are you in? Maybe somebody is near that can help.

JackConrad · August 04, 2007, 05:32:54 AM

Just a guess, but maybe a hot wire has come loose and is touching the bus chassis? You really need to have this checked by an electrician. Where are located? Jack

Dallas · August 04, 2007, 06:40:49 AM

Denis,
Try this, if you feel comfortable with it:

I am doing this over.... my method works for me, but if you aren't comfortable working with electric, the following is a simpler method

Unplug the the shore power cable from the bus and the pole.
Test each prong for continuity with the other prongs on the 30A end.
If there is continuity, there is a short in the power cord, narrow it down by removing one piece of the setup at a time and retesting. When there is no longer continuity between prongs, the last piece you removed is probably the culprit.

If there is no continuity on the shore cord, go on to the next step:

Without restoring power, place your continuity tester between the bus body and each plug in the bus receptacle.
If any of them have continuity, remember which ones they are and move on to the breaker panel, leaving the meter hooked up between the two that have continuity.

Trip one breaker at a time and check the meter.
If you find one that stops the continuity, you have found your offending circuit.
Follow it to it's terminations and check the connections to make sure no bare wires are touching anything they shouldn't be.

If you don't find any problems by tripping the breakers one at a time, check for continuity between ground and neutral by removing the neutral wires from the bus bar one at a time and checking your meter.
If you find one that stops the continuity reading on your meter, you have found a ground/neutral bond that shouldn't be there.
Follow it to the terminations and check for a ground and a neutral touching.

If none of this works, get back to us and maybe we can help you go farther in your search.

Dallas

Len Silva · August 04, 2007, 06:55:01 AM

Somewhere you have lost the ground connection to the bus and have power leaking to ground. This could be because of a bad neutral somewhere.

If there is a good physical ground nearby (conduit, metal water pipe, ground rod), try using a battery jumper cable from the bus chassis to ground. That will at least provide you some protection.

If this connection causes breakers or fuses to open, then you have a hard short somewhere. More likely (but harder to find) is a loose neutral connection.

This, of course, is after you have verified the pole outlet and all your cables/adapters are OK.

I'm sure many of us are saying "wish I was there, it would be easy" but trying to trouble shoot this way is difficult.

Len

Len

Jerry Liebler · August 04, 2007, 04:27:40 PM

Dennis,
YOU HAVE MORE THAN 1 PROBLEM!!!! You have a short of a hot wire to ground AND an open ground connection
First unplug the microwave, it'sprobably scrap. Hopefully it was where the short was but you've still got a problem! Somehow there is no 'continuity' in the ground wiring from your bus to the shore cord. If you have a volt-ohmeter, unplug the cords and carry the plug to where your electrical panel is. On the 15 amp plug one of the three pins is not flat, that is the ground put one probe of the ohmeter on that pin and one on any metal part of the bus and the ohmeter should show '0' ohms. If it doesn't you need to fix it. look in your distribution panel by taking the cover off you should see a strip with several green and bare copper wires clamped under set screws, that's the ground bus. With one probe of the ohmeter on the ground pin of the cord and the other on the ground bus you should read '0' ohms, if not the problem of an open ground is in the cords or shore wiring. The non flat pin of the 50 amp plug is also ground remove the dogbone and see if the ohmeter reads 0 between the 50 amp plug and the panel. Or if the cord has ground to the panel you've lost a connection to the bus frame from the panel's ground bus. Send me an off board email with your phone # & I'll give you a call to sort this out.
Regards
Jerry 4107 1120

Cary and Don · August 04, 2007, 05:12:58 PM

Hi,

Don is a contractor and there is a little gadget he has to plug into plugs that tells if they are wired right. It has a series of lights on it and when pluged in it will tell if there is a problem and what it is. Not grounded, reversed polarity, open common, etc. Any good hardware store has them. Might help.

Cary
GMC4107

D+C4106 · August 04, 2007, 08:08:04 PM

First, I would like to thank everyone for all your replies and information! I truly appreciate it!! We are in Akron/Canton, Ohio area on a remodeling project, that is why I haven't responded sooner. We have been doing alot on 12 volt only. I have tried many of your suggestions and so far I believe that I have isolated the problem at the auto transfer switch. (ESCO model) With power off I found continuity between all 3 leads and the ground bar from the generator side only. None on the shore side of the auto transfer switch. I disconnected all 4 lines from the generator, I think that took the generator out of the circuit. I Plugged shore power in and had the problem still. I have run the generator and don't seem to have the problem while running.

I shut off the breaker to the microwave/convection oven at the inititial sign of the problem. All of your help has led me to believe the problem is in the generator or the auto transfer switch itself, but, I don't understand why the generator running has no trouble. Do you think I am in the right direction?? Thank you everyone very much!!! Denis!

Jerry Liebler · August 04, 2007, 08:43:04 PM

Dennis,
You should have continuity between ALL grounds ALL the time regardless of the transfer switch. The ground of the shore cord plug should show continuity to the bus chassis and the ground bus in the panel. It sounds like you may have an improperly wired transfer switch that's switching ground instead of neutral.
Regards
Jerry 4107 1120

Jerry Liebler · August 04, 2007, 08:53:22 PM

Denis,
The continuity from ground to all the generator wires is to be expected. What's wrong is the lack of continuity between your panel's ground bus and your shore cord's ground pin of the plug. You need to trace the shore cord to the panel and find, then replace, the missing ground connection.
Regards
Jerry 4107 1120