Installing a GFCI (Ground Fault Circuit Interrupter) outlet

Ground fault circuit interrupters (GFCIs) are designed to prevent accidents leading to electrocution or severe electric shock, and are used most often for electrical appliances that may inadvertently come into contact with water.

These breakers are generally recommended for installation in kitchens, bathrooms and laundry rooms, as well as outdoors, for example near a pool or hot tub. The most common kind of GFCI receptacle looks like a standard wall outlet, but has “Test” and “Reset” buttons.

Some GFCI outlets also have an indicator, which can be green, red or amber. It indicates either that current is flowing or that the breaker has tripped and shut off the flow of current.

It is also possible to install a GFCI directly on your home’s main circuit panel; however, the instructions for this type of installation are not covered in this guide.
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How does the GFCI work and what does it protect you against?
Before installing the outlet
1. Switch off the power supply to the outlet
2. Identify the type of cables (if more than one cable)
3. Connect the new receptacle
4. Check that the outlet works properly

How does the GFCI work and what does it protect you against?

It is important to explain how a GFCI works, in order to understand its limitations.

A GFCI outlet is designed to protect people from electric shock only if the current ground-faults, i.e. if the electrical current strays or “leaks” outside the path where it should flow, to a grounded surface. To detect this, the GFCI monitors the level of current flowing out through the black wire against the level of current coming back in through the white wire. If it sees a difference between the two, it deduces that some of the current is escaping via another route (i.e. “leaking” to ground), and this trips the breaker.

For instance, say you have both feet on an insulated floor and you touch the black and white wires at the same time, the current will flow through you and the breaker will not trip, leading to electrocution or severe electric shock!

However, if you are in a wet area such as a bathroom or if you are standing directly on the grass outside, water or the earth can act as a ground towards which the current can escape. Since some of the outgoing current is not flowing back into the GFCI circuit, an imbalance is created between the outgoing and incoming current, thus causing the breaker to trip.

Always keep in mind that a GFCI protects against ground faults, but not against power surges and short circuits (this is the job of the main circuit breaker panel).

Before installing the outlet

You do not need a permit to replace an electrical outlet, but you must obtain one for changing or adding a new electrical circuit. Some municipalities require all electrical work to be carried out by qualified electricians.

NOTE: Whenever possible, always purchase electrical components approved by the CSA (Canadian Standards Association).

Grounding the outlet: The Canadian Electrical Code requires that electrical outlets and receptacle boxes in new homes be connected through an uninterrupted grounding network to neutral and ground bus bars. Outlets must have three holes, so that electrical appliances with three-prong plugs are grounded when operated.

You can replace a two-prong outlet with a three-prong one if:
  • The three-prong outlet has a Class A (GFCI) differential breaker.
  • The three-prong outlet is connected to another power outlet which itself has a Class A (GFCI) differential breaker.
  • The outlet is powered by a circuit protected by a Class A (GFCI) differential breaker.


NOTE: According to the Canadian Electrical Code, there must not be a bonding (grounding) conductor between an outlet protected by a differential circuit breaker and another outlet (on an old two-prong circuit with no ground).

1. Switch off the power supply to the outlet

Use method A or B:

Method A
Plug in an electrical appliance (e.g. a radio) and turn it on. Go to the main circuit panel to find the breaker or fuse protecting this outlet and switch the breaker to the OPEN/STOP/OFF position (depending on the panel) or remove the fuse. The appliance should shut off.

Plug the appliance into the other receptacle on the same outlet to check that it also has no power. Should one of the two receptacles on the same outlet still have power, stop immediately and call an electrician to carry out the work.

Method B
Insert a voltage tester into the outlet to check that the tester is working properly. Go to the main circuit panel to find the breaker or fuse protecting this outlet and switch the breaker to the OPEN/STOP/OFF position (depending on the panel) or remove the fuse. Use the voltage tester again to check that the power to the outlet is shut off.

Do the same thing for the other receptacle on the same outlet to check that it also has no power. Should one of the two receptacles on the same outlet still have power, stop immediately and call an electrician to carry out the work.

Remove the receptacle wall plate and once again, with the voltage tester, touch the ends of each exposed black and white wire to ensure that there is no power.

2. Identify the type of cables (if more than one cable)

If the receptacle to be replaced contains more than one cable, you need to determine which cable is incoming (line) and which is outgoing (load). If there is only one cable, go to step 3.

To identify which cable is which, proceed as follows:

2.1 

Disconnect the white and black wires of one cable from the receptacle and attach a wire connector onto the end of each (caution: do not attach both wires in the same connector!). Double-check that the two wires are indeed part of the same cable.

2.2 

For greater safety while carrying out the following steps, mount the receptacle back in the box and screw the wall plate back on.

2.3 

Restore the power at the main circuit panel.

2.4 

Check that there is power to the outlet by plugging in an appliance or using a voltage tester. If you now have power, this means that the wires you disconnected (the ones you screwed connectors onto) are the wires of the load cable. If you do not have power, then you know they are the wires of the line cable.

2.5 

Switch off the power again using either method A or B in point 1 above.

2.6 

Label the wires accordingly (line or load).

2.7 

Remove the receptacle.

3. Connect the new receptacle

If the receptacle has only one cable (i.e. the line cable), connect the wires to the screws or posts marked "LINE” on the receptacle, taking care to connect the white wire to the neutral terminal (SILVER) and the black wire to the hot terminal (BRASS).

If the receptacle has more than one cable and you want it to protect other receptacles on the same circuit, connect the wires of the line cable in the same way as described in the preceding paragraph, then connect the wires of the load cable to the screws or posts marked "LOAD”, taking care once again to connect the white wire to the neutral terminal (SILVER) and the black wire to the hot terminal (BRASS).

If the receptacle has more than one cable and you do not want it to protect other receptacles on the same circuit (in which case only this receptacle will be protected by the GFCI), attach, in the same connector: the two black wires (line and load) to a 3" length of black wire (stripped at both ends). In another connector, connect up the two white wires (line and load) to a 3" length of white wire (stripped at both ends). Connect the 3" wire to the screws or terminals marked "LINE” on the receptacle, taking care to connect the white wire to the neutral terminal (SILVER) and the black wire to the hot terminal (BRASS).

If the circuit (line cable) includes a ground wire, attach, in the same connector: the line cable ground wire (as well as that of the load cable, as applicable), a 3" wire whose other end is connected to the grounding terminal on the GFCI and a 3" wire whose other end is connected to the grounding terminal in the box. All the groundings will therefore be connected safely.

Replace the receptacle in the box, fasten the wall plate and switch the power back on.

4. Check that the outlet works properly

NOTE: GFCI outlets must be checked once a month to make sure they are working properly.

To test a GFCI, plug in a night light or a lamp, switch it on, and press the “TEST” button on the outlet. The “RESET” button should pop out and the light should switch off. Press the “RESET” button to reactivate the outlet.

CAUTION: If the “RESET” button does not pop out, the GFCI is probably faulty and should be replaced.
A GFCI outlet will protect you from serious or even fatal electrical shocks. It is not costly and can be installed in a matter of minutes. Visit your local renovation centre to talk to an expert who will be able to help you choose the most suitable type of outlet for your needs.
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