Wiring Done Right - Residential Wiring - The Right Way

Residential Wiring -  The Right Way!

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GFI Outlets / Circuits


GFI Ground Fault Interrupter Outlet

GFI (ground fault Interrupter) or GFCI (Ground fault circuit interrupter) is one of those marvellous inventions that saves lives.

It is available as an outlet that provides protection for one outlet or a few select outlets or as a breaker that protects the entire circuit.

What they do is they are designed to sense when there is a leakage of  current to ground, it senses when the ungrounded (hot) current feed and the return current are not equal which means that the difference in current must be going somewhere, such as through a physical person.  It will trigger shut down an outlet or circuit when as little as .005 milliamps is leaked to ground. When any minute leakage is detected the outlet / circuit is shut down preventing a person receiving a lethal shock.

GFI protection is required near water areas such as bathrooms and outside the home outlets. Most codes now require them in the counter area in kitchens. They are usually not recommended for Freezers / computers because of the loses that might be sustained in false trigger instances. GFI's saves lives, but they should never be relied on to overcome stupidity, use common sense and do not have any electrical item near or within reach of the bathtub, and the natural instinct is to grab the item that falls inside the sink full of water to save it, where in my belief you should be staying clear until you know the circuit power is cut. If the unthinkable happens GFI technology will hopefully save you but never tempt fake thinking that technology will always be there to save you from your own stupidity.

I have had problems with these when plugging in a block heater on a vehicle in they can be a pain in always triggering which defeats the purpose of plugging in the vehicle, part of the problem is that you have an exposed plug in the front of the vehicle that can get exposed to freezing rain / snow, and the outdoor extension cord being used may be left outside which again is exposed to the elements, which again can cause a moisture leakage to ground which triggers the GFI outlet, I am not sure how to solve this issue, but bringing inside the extension cord when not in use will keep that part dry, but keeping the vehicle side of the plug dry is another matter.

GFI Outlet with test and reset buttons

They come with a test and reset button, these should be tested at least once a month, replace if the test button fails to cut the power to the outlet assuming that the outlet was wired properly but if the test button worked before and now it does not then it is not likely a wiring issue, replace.

GFI Load and Line Terminal labels

Make certain that you do wire it correctly or it will not function properly. incoming circuit power gets connected to the LINE terminals of the GFI outlet, now you do have the option of protecting regular non gfi onward outlets, by connecting the onward outlets to the LOAD terminals of the GFI outlet.

Onward power that is protected by the same GFI outlet...

Extending circuit with GFI protection on onward outlets

As depicted in the above picture this will protect onward items such as regular outlets but if the GFI outlet is tripped it will shut down all onward items.


Onward power that is NOT protected by the same GFI outlet...

Extending circuit with NO GFI protection on onward outlets

As depicted in the above picture, onward items are Not GFI protected, and will still be powered even if the GFI is tripped.

Not shown in the diagrams but all bare wires (equipment grounding conductors) gets connected together and to the grounding screw of outlet as well as the electrical box itself if metallic.


Make certain the circuit power supply cable gets connected to the LINE terminals as they could be differently laid out than depicted in the pictures here, they will be labelled on the outlet itself. The same with the LOAD terminals if onward protection is desired, onward protection must be connected to the LOAD terminals.

By: Donald Kerr

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