Wiring a GFCI Receptacle

Almost everyone has
heard of a GFCI (Ground Fault Circuit Interrupter). These devices precisely monitor
the balance of electrical current moving through a circuit and immediately cut
off the electricity when a short occurs. For more on the basics of a GFCI see
our article on Ground Fault Interrupter Circuits.

Wiring a GFCI may vary
slightly from manufacturer to manufacturer, but for the most part they follow
the same general principles. We’ll try to simply and succinctly outline those
below so that you understand how to correctly connect a GFCI into your
electrical circuit and provide protection for an outlet or series of outlets
and fixtures.

About Ground Faults
Any electric path between a source
of current and a grounded surface is referred to as a “ground-fault.”
A ground-fault occurs when current is “leaking” and escaping to the
ground. How this occurs is significant in t hat, if your body provides a path
to the ground for this leakage, you could be injured, burned, severely shocked,
or electrocuted. Since water is such a good conductor, ground-faults are especially
common in areas where water can provide a conduit for electricity to
“escape” and find an alternate path to the ground.

Method 1: Simple Replacement of a Traditional Receptacle

A standard receptacle
can always be replaced with a GFCI receptacle and wiring it up is very
straightforward. This should go without saying, but always cut power to the
circuit (and verify with a circuit tester) before replacing an outlet. As shown
below, you simply wire the ground connection and then connect both the hot and
neutral wires to the GFCI’s LINE terminals as indicated to complete the
replacement.

GFCI
receptacle – The LOAD terminals are only used if you are passing power through
the GFCI to protect additional receptacles downstream.

Breakdown of Installation Steps:

1. Turn off the breaker at the
   panel which controls the circuit you are working on. If the circuit
   breakers aren’t labeled (as is often the case), you can find the right one
   by plugging a light or clock radio into the receptacle you are updating. Then
   you simply turn off the breakers one by one until the light or radio goes
   off. It helps to have an assistant during this phase. Once you turn off
   the correct breaker it’s always a good idea to mark it with tape to make
   sure a “helpful” person doesn’t accidentally flip it back on
   while you’re still working.
2. Test the outlet with a circuit
   tester to be verify that the power is indeed off (there’s nothing worse
   than finding out the hard way).
3. Remove the receptacle’s cover
   plate and the screws holding the outlet in place and unscrew/disconnect
   the wires from the outlet.
4. Re-strip and connect the
   power-supply wires to the terminals marked “LINE”. Remember, the
   White wire connects to the Silver LINE screw and the Black wire connects to
   the Brass LINE screw. Connect the bare ground wire to the green (Ground)
   screw. (See Diagram A).
5. Replace the receptacle, screw
   it back into the box and attach the cover plate.
6. Turn the power back on at the
   circuit-breaker panel.
7. Plug a clock radio or light into
   the outlet.
8. Test the GFCI by pressing the Black
   “Test” button on the outlet. If the radio turns off, the outlet
   is working.
9. Reset the GFCI by pressing the Red
   “Reset” button on the outlet until it clicks into place. The clock
   radio or light should come back on.

 

Diagram A – Connections
for LOAD and LINE circuits

Note: While you can opt for the less
expensive models, many 20A outlets will enable you to simply strip the ends of
the 12/2 wire and insert it into the back of the receptacle in order to make
the electrical connection. You then screw down the retention screws which
internally clamp down on the wire. Less expensive models will require you to
make a bend in the wire so that it may wrap around the outside screw terminal
and get locked in place in that manner.

Method 2: Replacement of a Traditional Receptacle & Downstream
Circuit Protection

When you replace a
standard receptacle with a GFCI, you can also protect any outlets or fixtures
which exist downstream from the GFCI. To do this you’ll need to use the LOAD
terminals on the GFCI which are typically covered by a yellow (or other color)
sticker.

 

GFCI
receptacle – The LOAD terminals are only used if you are passing power through
the GFCI to protect additional receptacles downstream.

Breakdown of Installation Steps:

1. Turn off the breaker at the
   panel which controls the circuit you are working on. If the circuit
   breakers aren’t labeled (as is often the case), you can find the right one
   by plugging a light or clock radio into the receptacle you are updating. Then
   you simply turn off the breakers one by one until the light or radio goes
   off. It helps to have an assistant during this phase. Once you turn off
   the correct breaker it’s always a good idea to mark it with tape to make
   sure a “helpful” person doesn’t accidentally flip it back on
   while you’re still working.
2. Test the outlet with a circuit
   tester to be verify that the power is indeed off (there’s nothing worse
   than finding out the hard way).
3. Remove the receptacle’s cover
   plate and the screws holding the outlet in place and unscrew/disconnect
   the wires from the outlet.
4. At this point you’ll need to
   take note as to which wires are the power supply “LINE” wires
   and which are the downstream “LOAD” wires (which allow the GFCI
   to work as intended and protect all the outlets on the “LOAD”
   side.) To do this, make certain the wires are completely separate from one
   another then turn the circuit-breaker back on in the panel box.
5. Use a circuit tester to
   determine which set of wires carries the power (the “LINE”
   wires).
6. Turn the power back off and
   re-tape the breaker in the panel box to avoid accident re-activation.
7. Re-strip and connect the
   power-supply wires to the terminals marked “LINE” and the downstream
   wires to the terminals marked “LOAD”. Remember, White wires connect
   to Silver screws and Black wires connect to Brass Screws. Connect the bare
   ground wire(s) to the green (Ground) screw. (See Diagram B).
8. Replace the receptacle, screw
   it back into the box and attach the cover plate.
9. Turn the power back on at the
   circuit-breaker panel.
10. Plug a clock radio or light into
    the outlet.
11. Test the GFCI by pressing the Black
    “Test” button on the outlet. If the clock radio or light turns
    off, the outlet is working.
12. Reset the GFCI by pressing the Red
    “Reset” button on the outlet until it clicks into place. The clock
    radio or light should come back on.

 

Diagram B – Connections
for LOAD and LINE circuits

Conclusion

Ground Fault Circuit
Interrupters are critical in any home. If you are doing any rewiring or simply
updating your house to bring it up to code you should pay attention to where
GFCIs may be required. This is one of the least expensive things you can do to
provide an incredibly beneficial level of safety to your family. It is
important to understand exactly how the GFCI circuits can be wired
(specifically, the LOAD function). In this way you can protect entire areas
without having to replace each receptacle with the more expensive GFCI
versions.