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Long time reader, first time poster... so I thought I had my bathroom wiring layout pretty well nailed but the guy in the electrical department at the local big box store made me rethink my entire plan.

My original plan: 20A feed to bathroom from breaker box. That goes to the same wall box as GFCI outlet. The feed line from breaker is pigtailed to both the GFCI outlet above the sink (plus one normal outlet fed off this GFCIs LOAD) and the other feed goes to vanity light/fan/ceiling light 3-gang switch box. Inside 3 gang I would have a dead-front GFCI, a combo vanity light/fan switch, and a dimmer switch for the lights. The ceiling light/fan need GFCI because the manufacturer says so above the shower (broan 744).

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Now the issue: The guy at (big box store) said you cannot have two GFCI on the same circuit at all because it will make neither of them trip and to just run the light/fan/vanity light all off the one GFCI. I feel like this is a big no-no because if anyone trips the GFCI while they are in the shower (like a curling iron left on sliding into the sink) the lights will be off and they will have to get out of a slippery wet shower in the dark or even if they were just using a curling iron while in front of the sink they wouldn't be able to see to set it down. I think my original plan would eliminate this because if the GFCI on the outlet plug blows then the lights (on a different GFCI) would not blow. He also said I cannot use canned IC recessed lighting in a bathroom at all without a glass shower trim ring. I was under the impression that you could use normal baffled recessed lighting in a bathroom as long as it was not above the shower.

Is my proposed setup unsafe? I don't care if I am wasting money on an extra dead-front GFCI if it means the lights stay on when my girlfriends ancient favorite blow dryer starts. Also, I know I could just run another 15A lighting circuit to the breaker box but I am all out neutral lugs (generator transfer switch install, it's a mess I didn't do it). Thanks for your time :)

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  • Hello, and welcome to Stack Exchange. I can't address the rest of your question, but the concern about losing power AND lights is very valid. – Daniel Griscom Jan 30 '17 at 3:53
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    You should use more than one circuit anyway. Keep the lights/fan on a different breaker than the outlet(s). This is both a code requirement and practically smart. (Prevents people from killing the lights when they are using hair dryers, curling irons, etc.) – Brock Adams Jan 30 '17 at 6:16
  • The difference is that people are understanding “on the same circuit” differently. You can also hook up the gfci outlet different ways: protect all outlets downstream on the same leg, or protect that specific load only. The lights in the bathroom should be on a different leg than the outlets. – JDługosz Jan 30 '17 at 6:55
  • @BrockAdams Can you cite the code section for that? Take a look at the exception to NEC 210.11(C)(3). – Tester101 Jan 30 '17 at 11:58
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    @BrockAdams I agree 100%. I just don't like when folks say things are "code", but don't cite the article. Too many people propagating false information on the internet. – Tester101 Jan 30 '17 at 19:52
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The bloke at the big-box store is out of his mind. Having multiple GFCIs fed from the same feed is not a problem whatsoever -- it's something that's done all the time (just imagine a panel loaded with GFCI breakers). Furthermore, the requirements for fixtures in 410.10(D) only hold for a zone that extends 3' beyond the edge of the tub or shower stall and 8' high. Ordinary fixtures can be used outside this boundary.

In your case, given that your choice of fan/light combination apparently must be GFCI protected in order for it to be used in a damp environment, your solution is a reasonable compromise given that you are using a dimmer here. However, it is possible to make it so that the shower light is GFCI protected while the cans are not, while dimming them both synchronously, but that requires a fair bit of extra hardware.

In particular, you'd need to use a 3-wire fluorescent dimmer such as a Lutron Maestro MAF-6AM or Skylark SF-103, as well as two Lutron PHPM-WBX-120-WH units mounted in their own two gang or 4" square boxes to go with the 3 gang box you're already called for. (Other manufacturers make similar products, but both the Leviton and Eaton/Cooper versions are FCC Class A devices i.e. not intended for residential use.)

If you're curious as to how such a crazy setup is wired up, see the wiring diagram below. If you're not comfortable following the diagram below, ask your nearest electrician to follow it for you.

wiring diagram

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  • Thanks for the reply. I am using two recessed lights on the same lighting leg of a 12/3 NM-B as the light of the fan/light combo. I had not thought about this too much because I figure nobody will ever actually reach up into the fan while taking a shower nor (hopefully) would such a device short out from humidity, considering it is a bathroom shower fan.... but alas... now I am thinking maybe this is much ado about nothing and maybe I should just wire the fan/light to the gfci on its own switch... here is a diagram link I really wanted all lights on :( – itsttl Jan 30 '17 at 4:43
  • @itsttl -- I was able to find a way to get what you want (although it's not cheap). I'll have to find some time to knock a wiring diagram together though, as it's not exactly what one would call a trivial solution to wire. – ThreePhaseEel Jan 31 '17 at 0:48
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It isn't unsafe, it's just generally pointless. You aren't required to put your bathroom lights on a GFCI, just the outlets that you can plug equipment like the ancient hair dryer into.

EDIT: I guess I glossed over the fact that the UL listing on the fan requires it to be on a GFCI when it's installed over the shower. In which case, you're fine pigtailing the hot off into two different GFCI's. The GFCI's are independent of one another this way. What you're doing is creating two smaller branch circuits within the branch circuit feeding the bathroom. Every circuit in your house is effectively exactly this configuration. The breakers just protect the wires on the branch circuits from overcurrent (and provide a convenient way to cut the power to individual branch circuits).

A GFCI has little inductive coils around each conductor (hot and neutral, which is properly called the grounded conductor because it's bonded to ground at the main service panel and at the transformer).

If there is ever a current differential between those two conductors, it means that current is leaking somewhere outside the intended circuit, possibly through a person, and the GFCI will trip. The "hot" and "neutral" carry exactly the same current when the circuit is operating normally.

Even if one of the GFCI's was connected to the LOAD terminals of the other one, one or both of them would trip when there is a current differential on the two conductors. Of course, if you did that, you would be defeating the goal of leaving the lights on if the hair dryer causes a GFCI to trip.

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    The GFCI for the fan/light is required by the fan's UL listing. – ThreePhaseEel Jan 30 '17 at 3:58

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