ECN Forum Forums General Topics of the Trade General Discussion Area Gfi's and testers.

Could use some insight on this; gfi receptacle trips with 'test' button, but not with a gfi tester. New type that supposedly won't work if wired wrong. Tester is ok. Ideas ?

No ground?

I agree with Fretwell. I think that the gfi tester works by allowing a small amount of current to flow from the hot conductor through a resistor to the grounding conductor. So if you have no ground connection at the gfi the tester's ground prong wouldn't have a good return path for the simulated ground fault.
This doesn't mean that the gfi won't work as intended though since it normally compares line current to neutral current, with no need for a ground.
Perhaps you could verify it's correct operation by unscrewing the gfi and, using a separate wire, make a temporary connection to a good remote ground point and then try your tester again?

Shawn.

The neutral carries the same current as the hot conductor. A ground would be necessary for the GFCI to work properly.

The GFCI will still work properly without a ground (hence its acceptability in ungrounded retrofit appliations) but the GFCI tester wouldn't work, as it can't shunt a small amount of current to ground if there's no ground to shunt to. Standing in a puddle and sticking a wet finger into the receptacle aught to do the trick, though. But it's certainly not recommend as the consequences if the test fails are potentially rather dire...

Thanks all. That's the case, no ground.