When doing home inspections we find GFCI receptacles with a jumper wire from the ground screw to the neutral screw on two wire ungrounded circuits. This is being done to trick the hand held circuit tester into thinking the circuit is grounded. Two questions: first am I correct in assuming this is unsafe and secound where can I find supporting lititure to back up my point?
It is unsafe in the sense that it defeats the entire purpose of having a separate safety ground. As far as the operation of the GFCI is concerned, though, it won’t make a difference. A GFCI works by measuring the current through the hot and the neutral, and trips if they don’t match. A safety ground isn’t required for the GFCI to operate properly, and having multiple return paths back to the breaker box for the neutral doesn’t matter for the GFCI as it is only measuring what is going through the neutral of the GFCI, which in this case will be all of the return current.
The real danger comes from having the neutral fail. In that case, since your neutral and safety ground are both tied together, they both float. Any device that has a metal case typically connects this case to the safety ground, so that device’s case would float and would therefore be a shock hazard.
If you have two wire ungrounded outlets (two-prong outlets) that were originally installed in the house, it is perfectly legal to replace a failed outlet with the same type of two prong outlet. If you don’t replace like with like though, then you need to upgrade the entire circuit to code, and the current NEC doesn’t allow two wire ungrounded circuits for new installations. You can’t put in three prong outlets or three prong GFCI outlets without converting it to a grounded three wire circuit.
Technically, what they’ve done is safer than having the original two-prong outlets and no GFCI, but they did it in a way that’s not to code.
The NEC contains all of your documentation.
My understanding - which may be wrong or outdated - is that installing a GFCI on a two-wire circuit provides an increase in safety, albeit without the added safety of a hard ground. But in such cases the ground terminal MUST be left unconnected.
It has to be labeled that the ground is unconnected, also.
You can in fact install a GFCI on a two-wire ungrounded circuit, but it most be labeled “NO EQUIPMENT GROUND.” This is so you know not to plug in things like surge suppressors that may want to dump fault current to ground. But it is safe to plug in most things to a GFCI-protected receptacle with no grounding.
OK, the NEC clearly allows GFCI receptacles on existing two wire circuits when they are labled something to the effect of “GFCI protected no equipment ground” these labels come in the box with ever GFCI receptacle. The question was how to explain to handy men and Do-it Yourselfers that it is dangerous to use the jumper and is not allowed.
Draw a little diagram showing what happens during a neutral fault. With their extra jumper, the ground becomes hot and is a shock hazard. Without the extra jumper, it doesn’t.