RV Grounding and Safety

sajohnson wrote:

Coach-man wrote:
A inexpensive electrical checker can be purchased, (at camping world & elsewhere), you simply plug it into your outlets, and the lights will indicate, ok, reversed polarity, no ground condition. I also purchased a "surge protector with meters, that basically did the same for the main power cord. In 12 years of camping, I only had one problem with the box being wired incorrectly, but then again it only takes one time to get electrocuted!!

These testers are great. I have one myself. They cost less than $10 and are quick and easy to use. No electrical knowledge necessary. Every RVer(and homeowner) should have one.

The RV surge suppressors (SS) are also a very good idea. I don't own one yet but plan to buy one soon (we just got our View last summer). I'm currently researching them.

Here's the problem:

Neither of these devices can detect the lack of a ground connection on a box, enclosure, door frame, or appliance.

What they _can_ detect is the lack of a ground connection at an outlet -- but only the round receptacle for the ground prong on the plug. The _box_ or _pedestal_ could have no ground and the tester or surge suppressor would have no way of knowing.

In fact, the pedestal or outlet box could be energized -- it could have 120 volts on it -- and the surge suppressor or tester would not detect that!

A surge suppressor's job is to confirm only that the incoming power is ok. The better ones check frequency, voltage, reverse polarity, no neutral, no ground, etc. However, the surge suppressor's job ends there. It has no way of knowing if the "downstream" wiring in the RV is ok, and it certainly can't detect that a hot wire has contacted ungrounded metal.

As a practical matter, when an outlet is grounded, the metal box or pedestal usually is too. Even if the enclosure does not have a proper ground wire, it will _usually_ (read: I wouldn't bet my life on it) be grounded through the screws that attach the outlet to the box.

In the case above (see OP) it was the junction box inside the electric cabinet that was hot (the generator outlet box was grounded). The owner never actually posted anything about the ground (or lack thereof). He just mentioned finding the wire nut worn through allowing a bare hot wire to contact the box.

Of course, that was only half of his problem. I suggested that he should confirm that the box is properly grounded but never heard back (as far as I recall). He may still have an ungrounded junction box. If so, the same problem could reoccur in the future.

There was obviously no ground path for the 120V to follow. Had the box been grounded, there would have been a short circuit to ground and the 30A breaker on the pedestal would have tripped immediately. In fact, that's exactly what happened when he accidentally touched the box with the coax cable. That provided an alternate path to ground, through the coax shield. There was an arc, and the breaker tripped. Of course, he could have just as easily touched that box with his hand -- while standing on damp ground, or, while touching the _grounded_ generator outlet box next to it with his other hand and been killed instantly.

One thing that I didn't realize that I discovered the other day is that some of the pricier surge suppressors have ground fault (GFI) protection. That is a _very_ good feature to have. It should protect anyone who accidentally becomes the path to ground for the 120Vac -- just like a GFCI outlet in a kitchen or bath.

Of course, having GFI protection is no substitute for verifying that all (or almost all) exposed metal is grounded.

It is quick and easy to do with a meter.