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| [GMCnet] Shocking Electrical Problem [message #146506] |
Fri, 14 October 2011 15:41  |
Gary Bovee
Messages: 177
Registered: August 2008
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GMCers,
I recently discovered that if I touched my bogie greasers when I had the coach plugged-in I would get an electrical shock. I was clueless how I was remedy this problem. Last night I started searching the and went to the Eastern State’s Clubs website and checked there tech documents for any info. I found a document Ken Burton wrote for the Fall Eastern States Rally back in 2009 titled "Grounding in a GMC Motorhome". After reading it the first thing I did was to check where the 110 breaker box was grounded. It was grounded to the steel frame. Ken’s document said this is a no, no. I reattached it to the aluminum frame and no more shocking problem. When I tested my plug-ins before I changed the wiring with a LED tester it told me I had an open ground. Now all the plug-in read correctly.
My coach is a 1978 Royale by Coachmen. The incorrect wiring ground I found looked like it was original. You may want to test your plug-ins with a LED tester and see if you get the proper reading.
Thank you so much for the very informative document Ken.
Gary Bovee
1978 Royale by Coachmen
Red Bluff, CA
Idiot's Internet Guide to Finding GMC Motorhome Information
http://www.gmceast.com/about/guide/index.html
Wireless Air System
http://www.gmcmhphotos.com/photos/showgallery.php?ppuser=1901&username=gcbgold
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| Re: [GMCnet] Shocking Electrical Problem [message #146509 is a reply to message #146506] |
Fri, 14 October 2011 17:02  |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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Wow!!! I'm shocked.
Someone actually read that document.
I'm happy it did you some good.
Let me also suggest that there should be a ground strap connecting the body to the frame. It probably is missing. The GM supplied on jumpering around the right front body mount. That is above and slightly in front of the passenger side front tire. Also if you have an Onan there should be another strap between the body and the frame in the rear Onan compartment.
Your immediate grounding problem is fixed. I'm just suggesting that these other two might also be missing or have a bad connections.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Shocking Electrical Problem [message #146525 is a reply to message #146514] |
Fri, 14 October 2011 19:09 |
zhagrieb
Messages: 676
Registered: August 2009
Location: Portland Oregon
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Ken,
If Gary was getting shocked with the coach AC grounded to the frame would that not suggest a problem with the grounding of his house AC?
Glenn
Glenn Giere, Portland OR, K7GAG
'73 "Moby the Motorhome" 26'
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| Re: [GMCnet] Shocking Electrical Problem [message #146529 is a reply to message #146525] |
Fri, 14 October 2011 19:41 |
James Hupy
Messages: 6806
Registered: May 2010
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Glenn, I had already been over all those possibilities with Gary off net. We
had narrowed it down to coach grounds when he first went on the net with his
praise of Ken's written material, which is spot on and should be required
reading for anyone who has a Coachman upfitted GMC. His is not the first one
to have ground faults, either opens or shorts. If your power cord enters the
rear of the coach behind the Generator door, you need to check these things
out. 120 V AC can really be hazardous to people under these conditions.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Fri, Oct 14, 2011 at 5:09 PM, Glenn Giere <glenngiere@gmail.com> wrote:
>
>
> Ken,
>
> If Gary was getting shocked with the coach AC grounded to the frame would
> that not suggest a problem with the grounding of his house AC?
>
> Glenn
> _______________________________________________
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| Re: [GMCnet] Shocking Electrical Problem [message #146551 is a reply to message #146525] |
Fri, 14 October 2011 21:31 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
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The ground wire in the shore power cable is a safety ground. It normally carries no current and is there only to prevent you from being shocked. This is why it should be attached directly to the body of the coach by the shortest path possible.
In order for the body to be energized to the point where he felt it, there has to be a short of some kind in the coach putting 120 volts VAC (or less) on the coach body. This is most commonly caused by a defective water heater electrical element, but it could be anything else running on 120 vac or a wiring error. Anything with a motor is always suspect. With the safety ground connected to the body, this stray voltage is bled off and you will not feel any AC voltage on the body.
The correct grounding of the body did NOT fix the cause of the actual leakage. It just prevents someone from getting shocked. If the voltage leak gets bad enough it will eventually trip a circuit breaker.
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Shocking Electrical Problem [message #146553 is a reply to message #146551] |
Fri, 14 October 2011 21:37 |
midlf
Messages: 2212
Registered: July 2007
Location: SE Wisc. (Palmyra)
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| Ken Burton wrote on Fri, 14 October 2011 21:31 |
The ground wire in the shore power cable is a safety ground. It normally carries no current and is there only to prevent you from being shocked. This is why it should be attached directly to the body of the coach by the shortest path possible.
In order for the body to be energized to the point where he felt it, there has to be a short of some kind in the coach putting 120 volts VAC (or less) on the coach body. This is most commonly caused by a defective water heater electrical element, but it could be anything else running on 120 vac or a wiring error. Anything with a motor is always suspect. With the safety ground connected to the body, this stray voltage is bled off and you will not feel any AC voltage on the body.
The correct grounding of the body did NOT fix the cause of the actual leakage. It just prevents someone from getting shocked. If the voltage leak gets bad enough it will eventually trip a circuit breaker.
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If you want to find out if the leakage is really gone, plug into a GFCI outlet. If it trips there is some more investigation and repair to be done.
Steve Southworth
1974 Glacier TZE064V100150 (for workin on)
1975 Transmode TZE365V100394 (parts & spares)
Palmyra WI
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| Re: [GMCnet] Shocking Electrical Problem [message #146570 is a reply to message #146553] |
Sat, 15 October 2011 01:20 |
Ken Burton
Messages: 10030
Registered: January 2004
Location: Hebron, Indiana
Karma: 10
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| midlf wrote on Fri, 14 October 2011 21:37 |
| Ken Burton wrote on Fri, 14 October 2011 21:31 |
The ground wire in the shore power cable is a safety ground. It normally carries no current and is there only to prevent you from being shocked. This is why it should be attached directly to the body of the coach by the shortest path possible.
In order for the body to be energized to the point where he felt it, there has to be a short of some kind in the coach putting 120 volts VAC (or less) on the coach body. This is most commonly caused by a defective water heater electrical element, but it could be anything else running on 120 vac or a wiring error. Anything with a motor is always suspect. With the safety ground connected to the body, this stray voltage is bled off and you will not feel any AC voltage on the body.
The correct grounding of the body did NOT fix the cause of the actual leakage. It just prevents someone from getting shocked. If the voltage leak gets bad enough it will eventually trip a circuit breaker.
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If you want to find out if the leakage is really gone, plug into a GFCI outlet. If it trips there is some more investigation and repair to be done.
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Earlier this evening I sent him an off net note to that effect.
Thanks
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana
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| Re: [GMCnet] Shocking Electrical Problem [message #146571 is a reply to message #146570] |
Sat, 15 October 2011 04:14 |
James Hupy
Messages: 6806
Registered: May 2010
Karma: -62
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Ken, perhaps we can interject a few words of caution here. I was emailing
Gary on another subject when the grounding issue came up. I was trying to
determine, after he told me that he was getting shocked, the status of his
connections from the source of his 120 V to his coach. When he corrected his
ground fault, that was the first step in the process. There is still the
problem of 120V entering the ground path. The 120 V circuits need to be
isolated, one at a time until the guilty party fesses up. If he has an
electric water heater, that would be one suspect, but truly, any of his 120
V circuits could be the problem. At least he has a ground path that parts of
his body are not included in. I agree, further investigation is needed.
Finding problems like this one, and solving them, are challenging at best,
and it is hard to remain focused on what we are looking for, because
sometimes we make changes, the diagnostic clues change, but the problem did
not go away. We can all learn from this example, and we all do not need to
receive an electrical shock to learn it like Gary did. He has been there,
done that. Use caution Gary, you may only have fixed one part of the
problem.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Fri, Oct 14, 2011 at 11:20 PM, Ken Burton <n9cv@comcast.net> wrote:
>
>
> midlf wrote on Fri, 14 October 2011 21:37
> > Ken Burton wrote on Fri, 14 October 2011 21:31
> > > The ground wire in the shore power cable is a safety ground. It
> normally carries no current and is there only to prevent you from being
> shocked. This is why it should be attached directly to the body of the
> coach by the shortest path possible.
> > >
> > > In order for the body to be energized to the point where he felt it,
> there has to be a short of some kind in the coach putting 120 volts VAC (or
> less) on the coach body. This is most commonly caused by a defective water
> heater electrical element, but it could be anything else running on 120 vac
> or a wiring error. Anything with a motor is always suspect. With the
> safety ground connected to the body, this stray voltage is bled off and you
> will not feel any AC voltage on the body.
> > >
> > > The correct grounding of the body did NOT fix the cause of the actual
> leakage. It just prevents someone from getting shocked. If the voltage
> leak gets bad enough it will eventually trip a circuit breaker.
> >
> >
> > If you want to find out if the leakage is really gone, plug into a GFCI
> outlet. If it trips there is some more investigation and repair to be done.
>
>
> Earlier this evening I sent him an off net note to that effect.
>
> Thanks
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
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| Re: [GMCnet] Shocking Electrical Problem [message #146573 is a reply to message #146506] |
Sat, 15 October 2011 07:18 |
Dan Winchester
Messages: 61
Registered: August 2006
Karma: 0
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Gary must be getting a ton of scary emails as I also sent him this warring shortly after the first posts yesterday.
Now that the problem has been masked the trick is how to find the culprit. As mentioned by someone yesterday a GFI plug is probably the best way to do this. Plugging the coach into a GFI circuit in the house should cause it to trip. If so then you can start isolating circuits in the GMC breaker pannel by starting with all breakers off and turning each circuit on individually until one trips the GFI breaker at the house. Only the circuit beeping tested should be on.
One might ask, why not have the plug where the GMC is plugged in be a GFI. This is infact a great idea and under new building codes it probably would be as they require GFI breakers or plugs on all outside plugs. If you do this and do it with a plug rather then a breaker in the house breaker panel be sure to use a weather rated GFI plug and proper plug cover that keeps plug dry when being used.
There are down sides to the GFI plug, they are very sensitive and are not designed for the 30 amp and 50 amp plugs so you will be forced to use an adapter which will most likley be exposed to the weather and when it gets wet it can cause inadvertent trips. Even without that issue they can have inadvertent trips when something as complicated as a motor home is plugged in. Since you are depending on this circuit to keep your batteries up when coach is stored this can create a problem unless you continually monitor ac status in your stored GMC. You could find yourself with dead batteries when you are getting ready for your next trip.
Dan Winchester
www.dwinchester.com
----- Reply message -----
From: "James Hupy" <jamesh1296@gmail.com>
Date: Sat, Oct 15, 2011 2:14 am
Subject: [GMCnet] Shocking Electrical Problem
To: <gmclist@temp.gmcnet.org>
Ken, perhaps we can interject a few words of caution here. I was emailing
Gary on another subject when the grounding issue came up. I was trying to
determine, after he told me that he was getting shocked, the status of his
connections from the source of his 120 V to his coach. When he corrected his
ground fault, that was the first step in the process. There is still the
problem of 120V entering the ground path. The 120 V circuits need to be
isolated, one at a time until the guilty party fesses up. If he has an
electric water heater, that would be one suspect, but truly, any of his 120
V circuits could be the problem. At least he has a ground path that parts of
his body are not included in. I agree, further investigation is needed.
Finding problems like this one, and solving them, are challenging at best,
and it is hard to remain focused on what we are looking for, because
sometimes we make changes, the diagnostic clues change, but the problem did
not go away. We can all learn from this example, and we all do not need to
receive an electrical shock to learn it like Gary did. He has been there,
done that. Use caution Gary, you may only have fixed one part of the
problem.
Jim Hupy
Salem, OR
78 GMC Royale 403
On Fri, Oct 14, 2011 at 11:20 PM, Ken Burton <n9cv@comcast.net> wrote:
>
>
> midlf wrote on Fri, 14 October 2011 21:37
> > Ken Burton wrote on Fri, 14 October 2011 21:31
> > > The ground wire in the shore power cable is a safety ground. It
> normally carries no current and is there only to prevent you from being
> shocked. This is why it should be attached directly to the body of the
> coach by the shortest path possible.
> > >
> > > In order for the body to be energized to the point where he felt it,
> there has to be a short of some kind in the coach putting 120 volts VAC (or
> less) on the coach body. This is most commonly caused by a defective water
> heater electrical element, but it could be anything else running on 120 vac
> or a wiring error. Anything with a motor is always suspect. With the
> safety ground connected to the body, this stray voltage is bled off and you
> will not feel any AC voltage on the body.
> > >
> > > The correct grounding of the body did NOT fix the cause of the actual
> leakage. It just prevents someone from getting shocked. If the voltage
> leak gets bad enough it will eventually trip a circuit breaker.
> >
> >
> > If you want to find out if the leakage is really gone, plug into a GFCI
> outlet. If it trips there is some more investigation and repair to be done.
>
>
> Earlier this evening I sent him an off net note to that effect.
>
> Thanks
> --
> Ken Burton - N9KB
> 76 Palm Beach
> Hebron, Indiana
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
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| Re: [GMCnet] Shocking Electrical Problem [message #146629 is a reply to message #146613] |
Sat, 15 October 2011 19:08 |
 |
Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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| Ken Henderson wrote on Sat, 15 October 2011 14:17 |
Many of them do on the 30A sockets, but I've never seen one on a 50A socket.
Once had to try about 8 sites at a COE campground in Washington before
finding one that wouldn't trip on the 3 mA leakage I had.
Ken H.
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Ken,
I was just reading this and thinking (dangerous) to myself (I'll forget it by evening) that I don't think I have ever seen a 3-wire GFCI as would be required for a 50amp outlet. So, I went right to Square D's site and looked it up. They are available. So, I went the price/availability check, yes, they have them MSRP 413$us. ...
I think I know why I haven't ever seen one.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Shocking Electrical Problem [message #146634 is a reply to message #146631] |
Sat, 15 October 2011 19:55 |
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Matt Colie
Messages: 8547
Registered: March 2007
Location: S.E. Michigan
Karma: 7
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Senior Member |
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| ahamilto wrote on Sat, 15 October 2011 20:19 |
| Ken Henderson wrote on Sat, 15 October 2011 14:17 |
Ken,
I was just reading this and thinking (dangerous) to myself (I'll forget it by evening) that I don't think I have ever seen a 3-wire GFCI as would be required for a 50amp outlet. So, I went right to Square D's site and looked it up. They are available. So, I went the price/availability check, yes, they have them MSRP 413$us. ...
I think I know why I haven't ever seen one.
Matt
|
A Square D 50A GFCI breaker is $95 locally. Not sure I have ever seen a 50A outlet that wasn't on its own dedicated breaker, so I guess most people that want that protection put the GFCI functionality in the breaker box.
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Aham,
I just came back from Graingers on-line catalogue.. They are not the cheapest house, but their price on a 2-pole 50Amp GFCI is 277$.
Matt
Matt & Mary Colie - Chaumière -'73 Glacier 23 - Members GMCMI, GMCGL, GMCES
Electronically Controlled Quiet Engine Cooling Fan with OE Rear Drum Brakes with Applied Control Arms
SE Michigan - Near DTW - Twixt A2 and Detroit
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| Re: [GMCnet] Shocking Electrical Problem [message #146636 is a reply to message #146634] |
Sat, 15 October 2011 20:08 |
A Hamilto
Messages: 4508
Registered: April 2011
Karma: 39
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Senior Member |
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| mcolie wrote on Sat, 15 October 2011 19:55 |
| ahamilto wrote on Sat, 15 October 2011 20:19 |
| Ken Henderson wrote on Sat, 15 October 2011 14:17 |
Ken,
I was just reading this and thinking (dangerous) to myself (I'll forget it by evening) that I don't think I have ever seen a 3-wire GFCI as would be required for a 50amp outlet. So, I went right to Square D's site and looked it up. They are available. So, I went the price/availability check, yes, they have them MSRP 413$us. ...
I think I know why I haven't ever seen one.
Matt
|
A Square D 50A GFCI breaker is $95 locally. Not sure I have ever seen a 50A outlet that wasn't on its own dedicated breaker, so I guess most people that want that protection put the GFCI functionality in the breaker box.
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Aham,
I just came back from Graingers on-line catalogue.. They are not the cheapest house, but their price on a 2-pole 50Amp GFCI is 277$.
Matt
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So installing a Square D 50A GFCI breaker is about a third the cost of the Grainger solution and less than a quarter the cost of the Square D outlet.
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| Re: [GMCnet] Shocking Electrical Problem [message #146642 is a reply to message #146631] |
Sat, 15 October 2011 20:46 |
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mike miller
Messages: 3576
Registered: February 2004
Location: Hillsboro, Oregon
Karma: 0
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| ahamilto wrote on Sat, 15 October 2011 17:19 |
... A Square D 50A GFCI breaker is $95 locally. Not sure I have ever seen a 50A outlet that wasn't on its own dedicated breaker...
|
I this $95 GFI breaker a single or double pole?
A 50 amp RV plug would need a double pole.
Mike Miller -- Hillsboro, OR -- on the Black list
(#2)`78 23' Birchaven Rear Bath -- (#3)`77 23' Birchaven Side Bath
More Sidekicks than GMC's and a late model Malibu called 'Boo'
http://m000035.blogspot.com
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| Re: [GMCnet] Shocking Electrical Problem [message #146696 is a reply to message #146692] |
Sun, 16 October 2011 11:50 |
Ken Henderson
Messages: 8726
Registered: March 2004
Location: Americus, GA
Karma: 9
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Senior Member |
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Gary,
Just because your GFCI didn't trip doesn't mean that the one plug into at a
campground won't. While most should trip at 5 mA, some will trip at 1/2 of
that. It's not uncommon for the interior of campground power posts to be
populated with spiders, etc., and quite dirty, allowing some current leakage
across the terminals of the sockets. The GFCI circuit doesn't care whether
the leakage is from your coach and wiring; it will trip when the total
reaches 5 mA+-1mA. Just looking at that spec. should warn you: Your
in-spec. GFCI may trip at 6 mA while the in-spec. GFCI in a campground may
trip at 4 mA.
So, you may not want to stop checking until you've truly eliminated the
leakage in the coach. Bob Hendrickson's paper on GMCEast should help:
http://www.gmceast.com/technical/Hendrickson_House_Electrical_Maint.pdf
Better fix it now than while camping.
Ken H.
On Sun, Oct 16, 2011 at 12:34 PM, Gary Bovee <gcbgold@digitalpath.net>wrote:
> I went out to the shop this morning to see if I could find my voltage leak.
> I plugged the coach into a GFI outlet to see if it would trip. It did not.
> All the breakers were on an everything works, smart charger, frig, a/c etc.
> I guess it just another one of those mysteries of the universe.
>
> I guess for now the only thing I can do is what Ken B. suggested. If the
> GFI never trips then forget about the problem. Oh well.
>
> Time to go work on something else on the GMC to do list.
>
>
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Ken Henderson
Americus, GA
www.gmcwipersetc.com
Large Wiring Diagrams
76 X-Birchaven
76 X-Palm Beach
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