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We just moved into our home and the previous owner upgraded the master bathroom. There is a fancy toilet that has features that require electricity, a heated floor, a heated towel rack that never worked, and a whirlpool tub. There are two 15 amp breakers that supply electricity to the master bathroom.

The inspector said that the GFCI outlet wasn't grounded, and we also discovered that when we ran the electric clothes dryer (it's in the utility room next to the bathroom) it sometimes caused the GFCI in the master bathroom to trip. The only thing plugged into the GFCI outlet is the toilet and so we would unplug the toilet and plug it back in. I was thinking that maybe the clothes dryer circuit shared a neutral with the circuit the GFCI is on. The GFCI has no load wires coming out, only line wires coming in.

We decided to replace the GFCI outlet and when I took it out I discovered that the ground wire was next to the neutral wire. There are two "stab in" inlets for the neutral wires and the neutral wire was in one and the ground wire was in the other. When I put on the new GFCI outlet I connected the ground to the ground screw at the bottom of the GFCI and the hot and neutral wires in the proper "stab in" inlets on the line side. I used a 20 amp Leviton and the previous GFCI was a Pass and Seymour legrand 15 amp. I discovered later that's against the code. In and of itself it doesn't pose a threat to have a 20 amp receptacle on a 15 amp circuit but the danger is that someone might think it's a 20 amp circuit and plug in a 20 amp device.

When I finished putting the new GFCI outlet in place I turned the two breakers back on and plugged in the toilet and there was no power to the toilet. What's more, the floor heater control panel was blank and there was no heat going to the floor. There was nothing else plugged into the bathroom circuits; no high amp devices turned on anywhere.

My question is, "Why would putting in a new GFCI outlet cause this no power condition in the GFCI circuit and in the floor heating?" The floor heating system is a NuHeat product and it has its own GFCI built in. But why would it go out as well? The breakers didn't trip at all. Could it be an open circuit? If so how could that happen just by installing a new GFCI?

2 Answers 2

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This sounds like some improper use of ground wires. Ground connected together with neutral on a GFCI (actually, on any receptacle) is not allowed. You properly separated that ground wire and connected it to the ground screw, which solved that problem. (Note that you should also be using screws for the hot and neutral wires rather than back-stabs, but that is a "should" because "more reliable", not "required by code".)

Since you are not getting any power, my hunch is that the neutral wire connected to the GFCI is broken or disconnected somewhere between the panel and the GFCI. Somebody tried to fix this by using ground instead of neutral (though they actually connected both) with the result that everything worked but you now had current running for the toilet over ground instead of neutral. That's a bad thing for a bunch of reasons.

It is possible that there may also be a ground fault of some sort with the dryer. That might cause some current to flow on the dryer's ground. Normally that would not affect the GFCI on a different circuit, but with ground connected as neutral, there could be some strange effects.

To fix this:

  • Get a new GFCI 15A duplex receptacle. That's the right thing to use on a 15A circuit.
  • Turn off the breaker, disconnect the existing GFCI, and separate the hot, neutral and ground wires.
  • Turn on the breaker and check voltage between the wires. In a normal setup you will have 120V between hot and neutral, 120V between hot and ground and 0V between neutral and ground. If you get that, great. If not, STOP and report what you find.
  • Turn off the breaker. Install the new GFCI with hot and neutral on the LINE side screws and ground to the ground screw.
  • Turn on the breaker and check voltage in the holes in the GFCI receptacles. You should find hot/neutral 120V, hot/ground 120V and neutral/ground 0V. If not, STOP and report what you find.
  • Connect the toilet and see whether it works or not.

Note that in current code a bathroom is supposed to have a 20A circuit for receptacles. In older houses it can be a 15A circuit, but given all the stuff (toilet, heated floor, heated towel rack, whirlpool), 2 x 15A sounds way underpowered.

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  • In step 3 of "to fix this" these are my readings: hot to neutral 4.92 V, hot to ground 125.9 V, and neutral to ground 123.8 V. Commented Dec 29, 2021 at 20:55
  • Could it be that the ground wire and the neutral wire are reversed at the panel? Commented Dec 29, 2021 at 21:25
  • Could this be an open neutral issue? Commented Dec 29, 2021 at 22:20
  • Ground and neutral reversed at main panel would be against code but not cause any sudden problems. Open neutral on a circuit (not the whole house) that was "fixed" by using ground instead could cause something like this. Commented Dec 29, 2021 at 22:36
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    How can I trace the circuit back to the location of the open neutral, assuming that's what the issue is? My multimeter has an audible continuity check and I wonder if people use that feature to trace a circuit without having to tear out sheetrock. Maybe we have a loose connection at an outlet along the circuit and I could test other outlets to see if I get the same reading I got in the master bath outlet. I've also read about people using a test lamp; turning off the other breakers and seeing if any of the outlets light up when inserting a test lamp, What do you suggest? Commented Dec 29, 2021 at 23:08
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Thank you, manassehkatz. Thank you everyone.

I found the open neutral in one of the outlets in the bathroom and now I'm getting good voltage readings!! I put everything back together and it all works as it should.

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