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My rental house was built in 1985 and there is some kind of master GFI (for lack of a better term) in the garage that controls all the GFI outlets in the house. I'm told all the houses are built like this now. My property manager sent out an "electrician" to check on a light switch that wasn't working. While there, he said he noticed the outlets in the kitchen and bathrooms were not GFI and took it upon his self to install GFI outlets. He didn't even know enough to know they were controlled by a central GFI. Anyway, now I have GFI outlets but also still have the GFI that controls them all.

A friend of mine said they basically cancel each other out now and that now it's unsafe! Does anyone know how this works? I am totally ignorant of electricity and how it works and I'm trying to explain this as best I can.

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    Your friend is wrong.
    – Tester101
    Commented Apr 27, 2015 at 19:59
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    Can you elaborate on the "master GFCI"? To my knowledge there is no such thing as a GFCI that controls more than one circuit (they are either a GFCI outlet or a GFCI circuit breaker in the breaker box). Maybe the device in the garage is actually a whole-house surge arrester?
    – Hank
    Commented Apr 27, 2015 at 22:48
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    In what country is this located? Electrical standards and devices vary a lot around the world.
    – Ecnerwal
    Commented Apr 28, 2015 at 2:10
  • Thank you for the quick responses. The house is located in the US, California to be exact. Regarding the "master GFCI" I'll try to explain it. The outlets in the rooms with water do not have the red tab on them. All the houses in this tract are like this and I guess that's how new homes are made. The GFI is not at the outlet but elsewhere. There may be more than one for each room but they are not controlled at the outlet. I'm sure I'm making no sense at all...but it sounds like my fear that they essentially cancel each other out is unfounded. I will ask about the new codes. Thanks!
    – Ann
    Commented Apr 29, 2015 at 15:39

2 Answers 2

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Your problem isn't at all what you think it is

A GFI receptacle has "line" and "load" terminals -- power comes in on the "line" hot and neutral and is fed through the GFI's internal 'switch' (it's really closer to a circuit breaker, just set up to trip on current differential between hot and neutral instead of overcurrent) both to the outlets on the front and to the "load" terminals, which allows you to daisychain lights, outlets, etal off of the "load" terminals of a single GFI and have them all protected that way.

Furthermore, your friend is wrong when he says that two GFI's in series "cancel each other out" -- the configuration of two GFI's in series is legitimate and will not cause a hazard or damage them; it's simply indeterminate which one trips on a ground fault downstream of the second GFI. Think of it as a game of quick-draw, just with tripping GFIs -- whichever one "wins" trips first and "shoots the circuit dead" so to speak. (A similar problem arises with regular breakers and short circuits, as well.)

But there is a problem here

However, the configuration you describe is simply impossible without violating other parts of the electrical code -- the kitchen/dining room outlets must be on dedicated small-appliance branch circuits, and the bathroom and laundry room are required to be on their own circuits as well, yet the kitchen counter outlets, bathroom outlets, and laundry room outlets (new for 2014 it appears) all must be GFCI protected. Point your property manager and electrician at sections 210.8 and 210.11(C) of the 2014 NEC...

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    Code only applies to new work. If/when code changes, there's no requirement to bring previous installations up to the new code (unless of course you're doing permitted work). The wiring in the building would only have to meet whatever code was adopted in 1985 when the building was built (unless there were renovations done between then and now).
    – Tester101
    Commented Apr 28, 2015 at 0:55
  • @Tester101 -- agreed re: the laundry room GFCI. The small-appliance and bathroom/laundry room separate branch circuit provisions and the application of GFCIs to kitchen countertop and bathroom receptacles are not at all new, though...
    – ThreePhaseEel
    Commented Apr 28, 2015 at 2:03
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    Kitchen GFCI was 1987. Bathroom and laundry room GFCI was 1975.
    – Tester101
    Commented Apr 28, 2015 at 3:02
  • @Tester101 -- thanks for the hard data -- I don't think the OP's setup ever complied with Code, even without GFCI in the kitchen being needed, though.
    – ThreePhaseEel
    Commented Apr 28, 2015 at 4:13
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I actually worked on a job pretty much identical to your situation. In each bathroom I put a GFCI to independently protect and rewired the "master gfci" as to independently protect too. I did this because the concept of having one "master GFCI" usually is a bad idea as they get covered up by refrigerators, shelves, or other things and the home owner has no idea. I only use them were I can explicitly know they are easy to see and not get covered up.

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