GFCI Installation

In a previous newsletter we talked about Ground Fault Circuit Interrupters GFCI's or GFI's. The discussion covered the role they play in residential wiring, why we use them, and where you need to have them. This month's article tells you how to install GFCI's.

Electrical current flows in a circuit. When the current comes into a receptacle or a switch or a fixture in residential wiring, it comes in on a black wire, and when it has done its job lighting the light bulb, running the hair dryer or burning the toast, then it goes back out through the service panel (circuit breaker box) on a white wire. The current coming and going on this circuit is equal; only the pressure of the current drops.

The GFCI monitors the current on the black wire coming in, and on the white wire going out, and if there is any difference between the two, it shuts the power off to the outlet within one-fortieth of a second. That's what it does, but why? If the current is equal coming in on the black wire, and going out on the white wire, and all of a sudden the current drops, then the current has gone somewhere other than the path it is supposed to be on. This causes what is called a "short circuit."

The circuit is short in the sense that it has not completed its trip back to the service panel, and the current has gone somewhere it shouldn't, like the skin of a refrigerator, the cover of a microwave, or the outside of the toaster. Our obvious safety concern is that a human being is becoming part of the circuit by coining in contact with the charged device, and that current is flowing through the person instead of the wire. That's why all the hubbub.

So how do they put one in'? First of all, there are instructions that come with each one. The instructions used to be cumbersome and confusing. They appeared to be written by someone for whom English was a second language for a doctoral candidate in electrical engineering. Not so any more. The instructions are pretty clear in the ones that are on the shelves today. They will take a person through step by step and show you with some pretty clear pictures. just what has to happen and how to safely and correctly install a GFCI. Basically, here is how it is done.

Turn the Power Off

Plug a lamp or radio into the outlet you want to change to a GFCI outlet and turn the appliance on. Now go to the breaker box and turn off the circuit that controls that outlet. The power is off when the appliance goes off. Be sure to plug the appliance into the other outlet of the receptacle to make sure it there really is no power to the outlet. If the appliance comes on when you plug it into the other outlet on the receptacle, stop and call an electrician because this one is going to need special handling. If the appliance does not come on, remove the outlet from the electrical box in the wall.

Identify the Cables and Wires

Cables are usually covered in a white plastic sheath and have separate black, white and bare wires inside them. If there are more than four wires in the electrical box, call the electrician, because it is beyond what the handyman should be involved with.

If you see one cable only (with three wires inside,) then you can proceed to the next step of removing the outlet and installing the GFCI. If there are two cables coming in (six wires total,) then will have to separate them by cable, turn the power back on and use a pig tail tester to determine which cable is the line side of the circuit.

Line side means that the electricity comes into the outlet on this cable. Load side means that the electricity continues out through that outlet to the next on that cable. This identification is important when you start attaching wires to the GFCI. When you have identified the line side, turn the power back on and go to the next step.

Attach the Wires to the GFCI

On the back of the GFCI you will see that it is divided into two halves - top and bottom, the line side and the load side. Today, most GFCI's come with a piece of yellow tape on the load side to help you see right away where to put the wires. If you have only one cable (three wires) coming into the box, then you attach them to the exposed (line) side. If there are two cables, (total six wires) coming into the box, then the line side will connect to the exposed screws, and the (load) side will connect to the screws under the yellow tape.

Which wires to which screws? Black wires always go to the brass colored screws. White wires will always go to the silver colored screws. Bare copper wires will always go to the little green screw that is offset to one side on the bottom of the GFCI. This color code is the same when you replace a regular outlet: black is the hot leg and will always go to under the brass screw.

If you get the wires reversed (black to silver screw, white to brass screw,) then you will have a condition called Hot/Neutral reverse, which has to be corrected. If you reverse them on the GFCI, the GFCI will not work. If you reverse the line side and the load side on the GM, the GFCI will not work. You will get power to the device, but it just won't trip the way it is supposed to and you might as well not have it there at all.

Wires should go under a screw head and two-thirds of the way around the screw. The screw is then tightened very tightly so that the wire is thoroughly secured under it. If not, you run the risk of the connection arcing and that is a conducive to fire (Electrical arcing happens when that pretty little blue spark jumps from one conductor to another. It is 13,000 degrees Fahrenheit, and that is hot enough to melt steel.). Double check all your connections before you carefully bend the wires and push the GFCI back into the box.

Check Your Work

At this point I always turn the power on and check my work either by tripping the GFCI with the TEST button on the front of the device, or using a plug in circuit analyzer that simulates a ground fault (they have a little button on the top to do it.) If the device does not trip, turn off the power and recheck your connections. Chances are that you have reversed either the line and the load, or the hot and the neutral. If everything checks out O.K., then strike up the band and declare a success because you've just done something else right!

GFCI's are a little bigger than regular receptacles, so be gentle and firm in pushing them back into the box.

Always be careful that the bare wire (ground) does not come in contact with the brass screw, the silver screw or any bare wire except for the ground wire. Put it all the way in, drive in the screws that hold the device in the box, and attach the cover plate over the device.

As always, if this work makes you nervous, or you are afraid that you might make a hash of it, then perhaps it is better left to more experienced hands. If you have someone else do it, watch them and ask questions as they go along. Ask them what they are doing and why, so you will know for the next time.

Even if you don't ever do one yourself, it is important that you know why they are installed, how they work and how they are installed. Most important, learn to test them so that you will be sure they are installed properly. A lot depends on it.


Reprinted by Permission. The author, of Forward Assist, has conducted "Mr. Fixit" workshops, and served on the Realty Investment Club of Houston Board of Directors as “The Enricher” Newsletter Editor for three years. He shares his treasure chest of secrets with anyone who asks. You can reach him at (713) 858-1330

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