RV Grounding and Safety

Puttin wrote:
We use these at work:



And...it seems like a good time to mention this:

http://www.arrisistore.com/product.php?pid=718844

http://www.myrv.us/electric/

The non-contact voltage detectors are very useful. There are many available by companies like Greenlee and Fluke. I have a Fluke that only cost about $20.

Unfortunately, they can't be used to check for proper grounding.

In order to check any particular piece of metal to see if it is grounded, you can:

a) With power disconnected, use an ohmmeter and measure the resistance between that metal (an electrical box/panel, appliance, door frame) and a known good ground -- like the ground receptacle in a nearby outlet that's been tested. The resistance should be zero, or very close to it. The resistance between any two pieces of metal that are grounded should be close to zero.

b) With power connected, use a voltmeter to measure the voltage present at an outlet. Measure between hot (the smaller slot) and neutral. It should be equal to the supply voltage (typically ~115-120Vac). Next measure from hot to ground -- you should get the identical reading (because the neutral and ground should be tied together at the source). Next measure from hot to the metal in question. If that metal is grounded, you should again get the same reading. If it is not grounded, you will measure something less, often about 50-70Vac.

I used procedure b.

~~~~~

Edit to add:

In order to check the boxes in the electrical cabinet, I used an ordinary grounded extension cord and plugged it into the same outlet the RV's electrical cord was plugged in to. I used it in the same way as described above. Checked the voltage between hot>neutral; hot>ground; and then measured from hot to both boxes. In all cases the voltage measured was identical.