GFCI and an Open Ground

There are lots of good reasons for carrying a non conducting ground throughout a facility or RV, but needing one for a GFCI to function is not one of them.

Well said.

Sam

BB_TX wrote:
A GFCI trips when stray current leaks off to ground thru some unintended path. If you do not have a ground, it can’t leak off. And therefore the GFCI would never trip, even if it should. Lack of a good ground is not a good thing. And is also not safe for you. You need to correct that problem.

The path that the GFCI protects is between either the hot or (with a modern GFCI, neutral) to the earth through an individual. That "tickle" you feel with an ungrounded RV metal shell is what the GFCI is designed to prevent.

The US NEC allows (in fact, encourages) replacing 2 pole receptacles with GFCIs. They do not need a ground to function, although code does require labeling the 3 pole GFCI receptacles with a note that there is no ground connection.

There are lots of good reasons for carrying a non conducting ground throughout a facility or RV, but needing one for a GFCI to function is not one of them.

The GFCI trips with 5 mA differential between hot and neutral. Just an open ground will not immediately trip a GFCI.

And with any luck you have a PI-EMS to prevent power from reaching the RV electric panel.

GFCIs will not trip due to open ground connection; if they did, you could not plug in any appliance with a two-prong plug to one.

They will detect and trip for leakage to ground even if the ground wire is disconnected. Obviously that leakage won't be going through the ground prong of the RV socket, but it could be going through your body to ground if you're standing next to the RV, for example.

A GFCI is the only way per code (so far as I know) to install a three prong outlet in an electrical circuit that has no safety ground. Such receptacles must by code be marked to indicate that there is no grounding, however.

RV plugged into house non-GFCI receptacle--two yellow lights per normal in RV receptacles. Same when RV plugged into house bathroom GFCI receptacle. No "open ground" (and RV does not have any GFCI issues at the moment).

As has been said Gfic's do not require a ground to operate. The RV is considered a subpanel by the electrical code so no ground neutral bonding is required and the gfi will trip if it is. Gfis have a circuit to detect a ground /neutral short and will trip if one is detected.

Sam

A GFCI trips when stray current leaks off to ground thru some unintended path. If you do not have a ground, it can’t leak off. And therefore the GFCI would never trip, even if it should. Lack of a good ground is not a good thing. And is also not safe for you. You need to correct that problem.

In the new/old (1955) house We're buying, none of the sockets are grounded. The inspector still recommends GFCI plugs be installed. So my guess is they work.

Harvard wrote:
Given: A 120 VAC GFCI supplying power to a 30 AMP RV. The RV has one problem, the 3rd Prong Ground wire at the 30 AMP plug is not making connection. (The RV chassis is floating because there are no other sources for a ground conduction path.)

Q: Will the GFCI trip because of this "one and only problem", an open ground?

I am guessing NOT.

I thought the RV shore cord plug's ground operated from the ground it gets from the bonded panel the RV is plugged into, where the RV is like an appliance. I get two lights (normal) with the three light tester when plugged in, not an open ground.

When I had a GFCI problem in the RV popping the RV's own GFCI receptacle, I checked if it was fixed after finding the problem in the RV, by plugging the RV, via 30/15 and extension cord, into the house bathroom GFCI receptacle. That house bathroom GFCI popped when the RV still had the problem, but did not pop afterwards,

. I did not check the three light tester in the RV when I was plugged into the house bathroom GFCI receptacle when the bathroom GFCI and the RV GFCI was not popped after that got fixed. ( I would expect to see the two yellows same as with a non-GFCI receptacle)

Not convenient right now to run a cord into the house bathroom and see what the three-light tester does in the RV

EDIT-- Did that. Got the two yellows per normal--no "open ground"

road-runner wrote:
I would think that detection of a downstream neutral-to-ground fault would be lost.

Good thought but it doesn't detect faults in the wires supplying it (other than reverse polarity - which shuts it down) and anything the GFCI feeds will still be protected.