Reuben's Home Inspection Blog


Ground Fault Circuit Interrupters (GFCIs), Part 2

Last week I gave an overview of what GFCI outlets are for - the long and short is that GFCIs are life safety devices; they prevent lethal shocks.  This week I'll talk about the different types of GFCI devices, how to test them, what drives me crazy with them on home inspections, and what some of the newer features are.

The two most common types of GFCI devices are circuit breakers and outlets.  A GFCI circuit breaker gets installed at the electric panel, and protects the entire circuit.  This is a handy way to make sure everything on the circuit gets protected, and there is no need for individual GFCI outlets anywhere in the circuit.  The other type, which everyone has already seen, is an outlet.  The most common type of outlet is a duplex receptacle, which is shown below left.

GFCI Outlet GFCI Breaker

One GFCI outlet can protect several other non-GFCI outlets when wired properly.  Every GFCI outlet has screws behind the outlet labeled "line" and "load".  The current coming in to the outlet must always be connected to the "line" side of the outlet.  If more outlets are going to be protected by the GFCI, they can be wired to the "load" side of the outlet.   Many houses built in the eighties will have the exterior outlets, garage outlets, and basement bathroom outlets wired downstream from a GFCI outlet in the upper level bathroom.  Today it's common for a GFCI outlet at the kitchen countertop to protect several other outlets.  This saves money.

GFCI Outlet Protection
A redundant way to wire  GFCI outlets is to wire one GFCI downstream from a second GFCI outlet.  This is wasteful, pointless, annoying, and it makes things difficult for the home inspector and anyone else that might trip the outlet, especially if the first GFCI outlet is hidden! Please don't do this.

GFCI outlets should be tested every month because they can go bad, and a defective GFCI outlet doesn't provide any life safety protection.  To test a GFCI outlet or circuit breaker, simply press the test button.  Here are the possible outcomes you can have by testing a GFCI outlet with the test button:

  • Acceptable - The reset button pops and the power goes off.  The GFCI device is functioning properly.  Simply press the reset button to restore power.
  • Unacceptable - The reset button doesn't pop.  This means the outlet is defective and should be replaced.
  • Lock symbol on a SmartLock GFCI outlet Unacceptable - The reset button pops but the power doesn't go off.  This means the line and load are reversed at the outlet. This should be corrected.  Newer "SmartLock" GFCI outlets that have a little lock symbol on the front have a built-in safety feature that prevents the outlet from getting energized if it's incorrectly wired.
  • Unacceptable - The reset button is already popped, the power is off, and the reset button won't go in.  This can happen on the newer "Smartlock" GFCI outlets if they're improperly wired or the outlet has gone bad.
  • Acceptable, but annoying - The outlet loses power when tested, but the reset button doesn't move.  This means someone wired the GFCI outlet downstream from a second GFCI outlet.  Shame on them.

GFCI TesterAnother way to test GFCI outlets is to buy a tester.  This is a great way to test standard outlets that are wired downstream from a GFCI device.  Just plug it in to an outlet and press the test button.  If the power goes out, the GFCI device is working properly.  If the power stays on, it doesn't mean the GFCI device is defective - sometimes GFCI testers won't trip GFCI outlets.  If this is the case, try the test button at the outlet.

Why do GFCI outlets go bad? I honestly don't know, and if anyone reading this blog can tell me, I'd be interested in hearing about it.  From my own experience, I've found that after a GFCI outlet has had a lot of power running through it, it will often fail.  For example, any time I'm working on a remodeling project and I'm running a bunch of power tools through a GFCI, it goes bad within about a month.  I've heard of home builders wanting to put all of their GFCI outlets on the inside of the house because there's this idea that cold Minnesota weather makes GFCI outlets go bad, but I haven't experienced that myself, and a study on GFCI outlets has shown that temperature doesn't have any effect.

RELATED POST:  GFCI Outlets, Part One

Reuben Saltzman, Structure Tech Home Inspections – Email  Home Inspector in Minneapolis

Reuben Saltzman, Structure Tech Home Inspections


Comment balloon 2 commentsReuben Saltzman • November 10 2009 06:06AM


I would guess it would be the mechanical portion is the weak link.  If you are getting a bunch of failures maybe you are buying the wrong ones.

Posted by Gene Allen, Realty Consultant for Cary Real Estate (Fathom Realty) over 10 years ago

Could be... but I don't think that's it.

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) over 10 years ago