For some reason I have a hard time shutting my mind down while trying to sleep. So at 4am this morning it came to me. Rather than sleeping I am awake thinking about electrical issues. I am indeed a mutant.
What came to mind is that I saw this once before in my early days of being a field tech. Yes electricity was in use back then. Anyway I responded to a service call where it was reported that people would receive a shock if they touched our equipment and other metal at the same time. I went in thinking there was no way this could happen as our unit was fed 24 volts DC from the power transformer plugged into the wall. But I was wrong.
I indeed found that you could get shocked as they had told me. Of course I used a voltmeter to verify that rather than using the touchy feely method. I also don't stick 9 volt batteries on my tongue to test them.
I was measuring 50 volts from our metal chassis to other metal in the area. Holy crap (technical term)! This problem was easily isolated by measuring the standard power outlet we were plugged into. The ground connection measured 50 volts above actual metal ground in the area. There were a few outlets in the area measuring the same while all others were fine. I assumed they were all on the same circuit.
Anyway, my job was done. I unplugged our unit and advised the customer of the safety issue and told them to have an electrician fix the problem. Never did wonder what caused the issue, that is until now. Ah, the memories that come back.
Now that I am in the twilight of my years (isn't there a song about that) I am scratching my gray haired head thinking about what may cause that type of problem.
I have a theory and it comes back to an open ground which was my first thought in this post.
If the ground were to open up say at the panel, you would have a nice long wire running in the same conduit as the other wiring. The current flowing in the other wires could inductively couple a voltage into the ground wire, much like a receiving antenna, since it is just sitting there. This voltage would carry down the line to the outlet.
If this could happen then my next logical (?) question would be, how long would the open wire have to be for a voltage to be induced on it. Would an open ground connection at the power outlet feeding the RV, leaving say a 20-30 foot wire open in the power cable, be enough to induce a voltage to the metal ground. Inquiring minds want to know.
Anyway, this is all theoretical. Where is Scotty when you need him? So for all that you who were wondering (OK, so none of you were wondering), I was finally able to go back to sleep.
PLEASE LET US KNOW WHAT THE PROBLEM TURNS OUT TO BE. I don't want any more sleepless nights.
The problem here may be two fold with an open ground and leakage between hot to ground.
Linear Mode
