Reuben's Home Inspection Blog

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Ground Fault Circuit Interrupters (GFCIs), Part 1

For this this week and next week's blogs, I'll be waxing on GFCI outlets.  I'll talk about what they do, why they're so important, what you need to know about them, and how to test the outlets in your own home.  GFCI Outlet

First, a quick refresher. In my blog about reversed polarity outlets, I explained that there are two wires that conduct current - one get connected to the earth (grounded) and the other doesn't.  The grounded conductor should always be white, and is referred to as the "neutral" wire.  The ungrounded conductor is usually referred to as the "hot" wire, and it can be any color besides white or green, but it's typically black.  Because the neutral wire is connected to the earth, any time you're in contact with the earth and you touch an ungrounded wire, you'll complete the circuit and you'll get a shock.  The general, technical name for this event is a ''ground fault", because current is getting back to the ground in a way that it shouldn't (it's using you!).

Not all shocks are the same. Here's where we'll get in to a little more detail about what happens when a human comes in contact with an ungrounded (hot) conductor.

  • No shock. If I could magically levitate and grab on to a ungroundedconductor, I wouldn't get a shock.  I'm not providing a path back to the earth, so the electricity doesn't have anywhere to go.  This is why birds can sit on power lines without getting a shock.  No ground fault.
  • Small shock. If I were working on the second story of my wood-framed house, wearing rubber soled shoes, standing on the carpet, and then came in contact with an ungrounded conductor, I would probably receive a relatively mild shock.  The current has a difficult time traveling through my skin, through my body, through my shoes, through the carpeting, through the wood framing in the house, and eventually back to the earth.  I say 'relatively' mild because this has happened to me several times, and I'm still here to tell about it.  It still hurt like hell every time, and it's always dangerous. This is a ground fault.
  • Severe / lethal shock. If I were holding on to the kitchen faucet with a wet hand and I touched an ungrounded conductor with my other hand, which was also wet, I'd probably get killed.  Having a wet hand will make it easier for electricity to pass through my skin.  After the electricity passes through my body, it has a very easy time getting back to the earth; it will pass through the kitchen faucet to the water pipes, which are directly connected to my electric panel.  This ground fault could easily be enough to kill me.

To prevent lethal shocks through ground faults, special electrical devices called Ground Fault Circuit Interrupters, or GFCIs, are required in homes.  If a GFCI device detects a ground fault, it will shut off (or 'interrupt) current within a fraction of a second.  It won't be fast enough to prevent a painful shock, but it's enough to keep you from getting killed.

GFCI devices were first required near swimming pools in 1971.  Today they're required in all the areas that lethal shocks are most likely to happen - typically at areas that are wet and have good contact with the earth.  These areas include the exterior, garages, kitchen counter tops, bathrooms, unfinished basements, crawl spaces, and outlets within 6' of laundry sinks, utility sinks, and wet bar sinks, among other places.  For an excellent one-page chart that lists all the locations and shows when the specific requirements went in to effect, click here.

That's enough information on GFCI's for this week.  Next week I'll talk about the different types of GFCI devices available, the difference between new and old GFCI outlets, how to test them, how they irritate me, and how to save money while installing them.

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

Reuben Saltzman, Structure Tech Home Inspections

        

Comment balloon 10 commentsReuben Saltzman • November 03 2009 06:13AM

Comments

Great post Reuben,

 

You might touch on this in your part II blog but I'm curious as to how you test GFCI type receptacles during an inspection? Personally I use a SureTest but I've also heard inspectors say the only way to properly test a GFCI is by pushing the test and reset buttons.

Posted by Vince Santos, Southeast Michigan Home Inspector (StepByStep Home Services LC) almost 9 years ago

Vince - what's a SureTest?  I just use a cheap GFCI outlet tester.  If the GFCI outlet trips with this tester, it's working properly.  If it doesn't trip with this tester, I use the test button at the outlet.  

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 9 years ago

http://cableorganizer.com/ideal-industries/suretest-circuit-analyzer.html

Posted by Vince Santos, Southeast Michigan Home Inspector (StepByStep Home Services LC) almost 9 years ago

Wow, that's an expensive outlet tester!  Do you think it's worth it?  Do you mind many bootlegged grounds?

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 9 years ago

I own two of them and I think they are worth it. However they do provide the inspector with testing that is beyond the scope of a home inspection and some feel that's a good reason not to own one.

Posted by Vince Santos, Southeast Michigan Home Inspector (StepByStep Home Services LC) almost 9 years ago

I think that will be my next toy tool.

As far as this being beyond the scope of an inspection... wouldn't a cheap three-prong tester be beyond the scope of an inspection too?  

Posted by Reuben Saltzman, Delivering the Unbiased Truth. (Structure Tech Home Inspections) almost 9 years ago

Thanks for the info.  I am an old Navy electronics person and find that more often then not the press to test is bad but that makes the whole switch bad.

Posted by Gene Allen, Realty Consultant for Cary Real Estate (Fathom Realty) almost 9 years ago

"I own two of them and I think they are worth it. However they do provide the inspector with testing that is beyond the scope of a home inspection and some feel that's a good reason not to own one."

Just push the test button on the device. Besides it is the only approved way to test GFCI's.

Posted by Mike Parks, Inspector (Residential Building Inspectors) almost 9 years ago

Hi Ruben,

Thanks for the information!  I always have heard the only approved way to test the GFCI's is what Mike says - push the test button on the device!

Posted by Dorie Dillard CRS GRI ABR, Serving Buyers & Sellers in NW Austin Real Estate (Coldwell Banker United Realtors® ~ 512.346.1799) almost 9 years ago

FYI:  If the GFCI outlet is installed in an older home without a ground circuit, then the 3 light tester won't work anyway.  You will have to use the button on the device, as recommended!

Great article, looking forward to the next!

Posted by Glen Kotulek, Austin Home Inspector, schedule online www.homecritiquepi.com (Home Critique Property Inspections LLC) over 8 years ago

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