Strange behavior in a GFI circuit

[schmidtd]

I have a circuit protected by a GFI outlet. The circuit starts in a downstairs bathroom, runs through a GFI outlet there, then heads upstairs to a couple other bathrooms. The GFI outlet downstairs has power, and the circuit breaker trips fine if you hit the test button. The outlets in the upstairs bathrooms are all dead.

Last week, some carpet cleaners came while I was out of town. I understand they had some kind of power trouble during their work (i.e. they thought they had tripped a breaker). Turns out, they did not trip a breaker in the box - nor were any of the GFI circuits that I know about in the house tripped.

The strange thing is this... I get my handy voltmeter out, and the "dead" outlets in the upstairs bathrooms all read 96 volts AC. I plug in a night light, turn it on, and the voltage drops to zero. I measured the voltage coming into the GFI outlet downstairs at 120 volts. I read the voltage leaving the GFI outlet downstairs at 120 volts. Upstairs, it's down to 96 volts. If I trip the GFI breaker and test the outlets upstairs, they all read zero volts. So I'm pretty darned sure this is all the same circuit.

What ever is wrong with this picture?

- David

[RBM]

Assuming you have removed the downstairs GFCI outlet from the wall to test the "load" terminals. If you get 120 volts and have nothing upstairs, there is probably a break in the cable or the upstairs outlets are not connected to that GFCI . Depending upon when your house was built, you could also find GFCI outlets in the basement, outside, and garage, which could be connected to and upstream of the bathroom outlets upstairs. My best guess though, is that you have a defective GFCI outlet in the downstairs bathroom

[Dave]

When you use a voltmeter on house circuits you have to be aware that leakage and capacitive coupling can produce misleading readings. Use a known good 100W lamp as a sanity check. Sounds like you have a bad GFI or a bad connection.

[Ralph Mowery]

If you are using a digital meter the 96 volts you are getting is either some leakage from the GFI or induced voltage. There is no solid connection. Sounds like you need to replace the GFI socket.

[BobK207]

First guess....loose connection somewhere in the circuit, trouble showed up due to the larger than normal household current draw required by their equipment.

Solution; start w/ screw terminals in the "problem" outlet and work back to the breaker. following the circuit path through the outlets tightening the connections

second guess............bad GFI (but much less likely)

cheers Bob

[schmidtd]

Thanks all for the suggestions. I've replaced the GFI outlet already, so I'm pretty sure that's not the culprit. I'll pull all the affected outlets and see what I can see in terms of loose connections.

The house was built in 1994 or so and there are several circuits protected by GFCI. There have been situations in the past where the upstairs bathroom has gone dead, and resetting the box in the downstairs bathroom was always the cure. There is definitely something wonky going on in this path.

- David

[BobK207]

Dave-

when you track down the problem, let us know what worked.

cheers Bob

[schmidtd]

So, I went around the whole house, all circuits live, with my trusty voltmeter. Figured some of the outside boxes must be tied in somewhere. Found my way to the back deck and... 96 volts. The night light test revealed a dimly glowing bulb. Ha! I've got you now!

Turned off the breaker, tested with the voltmeter, and out came the outlet. Turns out it had some corrosion going on (one of the sides of the box didn't seal particularly well, evidently) and one of the hot wires came out pretty easily. It was one of those "jam the stripped wire in the hole" sorts of recepticles. So, a quick trip to the friendly local neighborhood Despot of Homes and all is well again.

I lined the gasket surrounding the new outdoor cover with some RTV sealant this time around - we'll see how many years this one lasts.

- David

[BobK207]

Dave-

Great work! those backstab outlets suck!

screw terminals / screw clamps are the only way yo go.

cheers Bob

[J.C.]

Inside lights and outside lights, if GFIs are used, should be on separate ones.

[schmidtd]

I understand the original builder still lives in my neighborhood... perhaps I should take it up with him. :-) Might want to bring up the subject of the plastic water pipes (what's that banned building material from the early 90's again?) and the fact that they knock whenever you turn the hot water on...

Ah, the joys of home ownership. :-)

- David

[Bert Byfield]

No. Things have changed over the years. When you buy a home, it becomes

*your* problem. Take up the challenge. Your electricity must be connected to the earth. Your plumbing must have those little vertical extensions that prevent knocking. So on. Look at it as a challenge. ;-)