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Washtubman 09-05-2014 03:07 PM

Shocking!
 
Checking my tire pressure just now and when I touched the valve stem I got a shock! Not much of a one, but enough to know it was there. So I touched other metal components on the chassis, and same result. Guess something is shorting to ground, but where does one begin to look for the answer? Appreciate any input from the electrical gurus!

DieselTech39 09-05-2014 03:24 PM

Quote:

Originally Posted by Washtubman (Post 2215632)
Checking my tire pressure just now and when I touched the valve stem I got a shock! Not much of a one, but enough to know it was there. So I touched other metal components on the chassis, and same result. Guess something is shorting to ground, but where does one begin to look for the answer? Appreciate any input from the electrical gurus!

:Thanx: for your service.

Are you plugged into shore power? If so disconnect and check to see if you still are getting a shock. Could be a faulty shore power supply. Be careful.

TQ60 09-05-2014 03:24 PM

Unplug shore cord

Now check the safety ground or green wire.

You have a hot skin condition that is top priority to fix.

wa8yxm 09-05-2014 03:33 PM

You might not have a short at all.. But rather an open...

Questions time:

Were you plugged into shore power?
(Yes read on, NO sorry I can not help you stop here)

Did you check the ground on the shore outlet
YES: was it good: NO do so now, use a 3-light tester and/or a volt meter

Also using a multi-meter check for continuity between the round or roundish pin on your shore cord (The one you plugged into the park box if you use an adapter) and the chassis of the motor home.. You should see ZERO ohms. NOTE you will have to unplug to do this test.

Finally: What I think happened.

As I said, I think you have an open ground You have many yards of ROMEX and other cables in that motor home

Romex is (usually) 3 wires, a neutral, a ground and a hot layed side by side with the neutral in the middle, They are separated by insulation.

In electronics we study a device called a capacitor and how it works

The symbol for a capacitor looks like this -||-

Now if you want to make an AC voltage divider you can make one like this

-||-*-||-

Put 120 volts on one end, Ground the other and the * will be 60 volts

And that is exactly what Romex cable is electronically.

So the ground wire (Safety ground) is brought to 60 volts by capacitive voltage division from the other two wires. 100% normal. This is why it is tied to ground,, To protect you. from this, and a few other things which unlike this are faults.

BFlinn181 09-05-2014 03:36 PM

I would definitely unplug from shore power then check the ground of the outlet where you you were plugged in. If that checks out O.K., then check the ground pin in you shore cord to where it plugs in to your transfer switch. If that's O.K., you'll have to trace the ground through the transfer switch to your power panel. Sometimes the wires in and out of the transfer switch get loose from vibration, make sure all of them are tight.

ImagineIF 09-05-2014 03:42 PM

First, there shouldn't be and current on the ground if everything is working correctly. Hot skin cand be caused by a few things.
-- if you have current trying to get ground and the pedestal ground is gone or if you are a better conductor when touching the skin you will feel the current.
-- if you have a generator or inverter, they will have neutral and ground bonded together. These should be isolated when you are on inverter or generator. If they are not, they will provide a current path on the ground system, including the skin.
-- if you are not on shore power and have the generator running, your tingle may be unavoidable. There is a reason portable generators have ground rods.

Washtubman 09-05-2014 04:07 PM

I am plugged in at home. Will check the cord and outlet first.

Timay 09-05-2014 04:16 PM

Had the same problem - surprised me as I am an electrician and I installed the pedestal myself - correctly. I was getting a little leakage shock when I installed my Strongarms. I went around and looked at the pedestal and lo! It was pulled about halfway out starting with the ground! Plugged it back in, no more shocks - :dance:

I had brought the slide in and it had hooked the cord and pulled it partially out before I caught it and stopped. It is not supposed to allow the ground to pull out first - that's why the ground on the plug is longer - so it will be the first when plugging in and the last when unplugging.

Tim

Washtubman 09-05-2014 04:38 PM

Checked my outlet with the three light tester, Circuit is good. Checked continuity on the ground through the 30 amp cord; it has continuity.
When I plug the tester in the outlets of the motorhome, the left yellow and the red light up. According to the tester, that is "reverse polarity". Huh????????

-LB- 09-05-2014 07:09 PM

I just so happen to see this during the week....maybe it may shed some light on things....I found it very interesting.....

http://youtu.be/870zuHwEH30

Washtubman 09-05-2014 07:31 PM

LB, good info.
Fixed!!! Here's what I found. The big plug on the 50 amp cord had been replaced at some time and whoever did it, attached the red wire lug with the lug screw pointing inward which allowed it to rub against the ground wire and after so many plugging and unpluggings it wore thru the ground wire insulation and therein lied the problem! Glad I found this one when I did. Thanks for the replies.

BFlinn181 09-05-2014 07:48 PM

You're going to need a multimeter to test what's happening. The hot side should be the shorter slot on the outlet. If you put the probe in that one and the other in the ground, you should read 120 v. If you put the probe in the longer slot (neutral) and touch ground, there should be no volts. Check in your ATS (auto transfer switch) box and make sure wiring isn't crossed as it passes through. If it's O.K., then check in the power panel and see if hot and neutral are properly hooked up.

Oops, you posted while I was writing. Glad you found the problem!

BFlinn181 09-05-2014 07:53 PM

I have to add, if you had a Progressive EMS, it would have caught that issue with the plug and not allowed power to flow.

EMS-HW50C

ImagineIF 09-06-2014 08:42 AM

Washtubman...great news it was an easy fix and one you found now. It could have been far worse.

Bob, as much as I like PI's product I don't think it does any upstream sensing if you are using their portable unit. In your case it looks like you are using their hardwired unit. Yet another benefit to hardwired over portable.


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