How to install a GFCI receptacle

Wiring a GFCI receptacle: The basics

Wiring a Ground Fault Circuit Interrupter receptacle isn’t all that different from hooking up a level-1 49-cent outlet. There are a couple of key differences, but the protection against deadly shocks is well worth the effort.

The National Electrical Code (NEC) requires ground-fault protection for all «wet locations» in your home. This includes your bathroom, counter areas near the kitchen sink, and ANY outdoor outlet location. Years ago, it was acceptable to use one GFCI breaker in the panel to control all of thse on one circuit. Today, you’re best bet is to use GFCI receptacles for each place.

While using an interrupter-type breaker is acceptable, it’s annoying to reset and more costly than individual outlets. Here’s how to wire your new GFCI receptacle.


Step 1

Choose an outlet location

Bathrooms, kitchens, and outside outlets should all be GFCI-protected. Ideally, you should replace an existing grounded outlet in a single-gang box. Typical locations are:

  • Beside a bathroom sink
  • Kitchens, within 4 feet of the sink
  • Covered, weather-proof outdoor outlets near decks, walks, and pools
Step 2

Check to be sure the existing outlet is properly hooked-up

outlet tester from Techni-ToolUse a 3-prong, plug-in outlet tester to make sure the existing outlet is correctly connected. This type of tester is simple to use, provides clear information, costs less than $50, and will last for years.

Step 3

Purchase TWO possible GFCI replacement outlets

Unless you already know the circuit rating of the outlet you’re replacing, buy one of each — 15-amp and 20-amp GFCI receptacles. You can return the extra one when you’re done.

Step 4

SAFETY: Turn off the power to that outlet!

Use your tester and a helper to find out which circuit controls the outlet that you’re going to replace. This will be either a 15-amp or 20-amp breaker, possibly even an existing GFCI breaker.

Occasionally, the correct circuit will be labeled. Be sure to turn off computers and other electronic devices if you’re going to search «blindly» for the right breaker.

If you have to locate the circuit alone, simply plug in a portable radio, turn it on and turn it up so you can hear it when you’re at the panel box. When the radio goes off, you’ve found the right circuit.

Step 5

Decide: 15-amp or 20-amp?

Once you’ve located the right circuit, you’ll know the amperage rating of it. The number is clearly printed on the circuit breaker. Choose the matching-amperage GFCI outlet from the two you purchased. Set the other aside for later return.

Step 6

Remove the old outlet

Once you’re sure the power is off, remove the old outlet using a level-1 screwdriver. Pull it forward until the wire connected to it are straight.

For screw-type connections, unscrew the wires. For push-in wiring, simply clip each wire as close to the outlet as possible. First, check to be sure that:

  • A ground wire exists, required for GFCI outlets, and that:
  • The bare wire (ground) is connected to a green or frame-mounted screw
  • The black (hot) wire(s) is connected to a gold-colored screw, or to that side
  • The white (neutral) wire(s) is connected to a silver-colored screw, or to that side

Generally, the white side of the outlet is labeled, though the text is often difficult to read. An easy rule to remember which wires go where is:

«Black Gold (Texas Tea)»

Step 7

SUPPLEMENTAL: Identify the

If you have more than one black wire, you MAY need to know which one is the «hot» one. Here’s how to safely find out, without buying yet another electrical testing tool:

  1. Use a wire cutter to snip (disconnect) ONE of the two black wires
  2. Plug your 3-prong outlet tester back into the old outlet
  3. Keeping kids and pets away, turn the circuit back on
  4. If your tester shows power, you clipped the «out» (not-hotyet) wire
  5. If your tester shows no power, you clipped the «hot» (lead) wire
  6. TURN THE POWER BACK OFF before you proceed

If there are more than 2 black wires, you should consult a professional, or install a GFCI breaker rather than a new GFCI outlet. Overloaded boxes can be fire hazards!

Step 8

Check the existing wiring

Ideally, you are working in a single-gang box, one that only has three wires in it.

Most often you’ll find two of each color — an «in» wire set and an «out» set. Sort all the wires by color: bare to the bottom of the box, white to the left, and black to the right.

There may be even more wires inside the box you’re working in. That can be trouble. The new GFCI outlet takes up more space than the old outlet did, and it’s tricky to decide how to properly connect more than one pair of wires.

Check for broken or abraded (worn casing) wires, too.

Step 9

Clip and strip your white and black leads

Use a level-1 electrical stripper (shown, left) to remove any hook-shaped bare wire. To install your new GFCI outlet, you’ll need each wire to have a straight, stripped end. Use the guage on the back of the new outlet to determine how much bare wire needs to be exposed. (Usually, about 5/8 inch, or less)

Step 10

Notice LINE versus LOAD on your new outlet

GFCI receptacles are clearly labeled for «line» and «load.» Be sure you understand which is which. The Load section now comes with a piece of yellow tape over the connections, to make this even clearer.

Generally, you can attach all existing wires using only the Line section. But not always.

Step 11

Should you use the LOAD connections, too?

(See Step 8, above)

One GFCI outlet can protect more outlets if they are powered from the LOAD connections. This is important for kitchen outlets, but rarely used for bathrooms or outdoor locations.

Always connect the infeed («hot») wire set to the LINE connectors. If you want to protect downstream outlets, too, connect the outfeed («not hot yet») wire set to the LOAD connectors.

Never mix-up the wire set in this case: make sure the hot-group white and the not-hot group white wires are connected in tandam with their repective black wires. Confused? Get professional help, rather than risk trouble or injury.

Step 12

Connect, replace, and cover your new outlet

GFCI outlets use push-in and screw-clamp connections — you do BOTH. If you are connecting two wires under one screw (the maximum allowed), both wires must be connected at the same time before tightening the screw.

Always pull-test your wires, to be sure they are securely clamped.

Attach a single ground lead to the green ground screw. If there are multiple ground wires in the box, create a single lead using a crimp or wire nut (most Codes require the crimp).

Keep the bare wire safely tucked in the bottom of the box, bend your white and black wires so they’ll fold behind the GFCI outlet, and carefully push the new outlet back into the box. There may be very little extra room in there, so work carefully.

Screw the new outlet in place and install its cover. Note that outside outlets require weather-proof covers. Turn the power back on.

Step 13

Test it!

First, use your 3-prong tester to find out if you’ve correctly wired the new outlet. If there is no power available, try hitting RESET on the face of your new receptacle.

Now check the outlet’s function by pressing TEST. You should hear a click, and most GFCI outlets have a small green light that will turn on.

TEST should activate the RESET button. Try pressing that, and you should have power again. Use the 3-prong tester to confirm your hook-ups again, then plug in a portable radio as a double-check.

Final test:

  • Bathrooms: plug in and turn on a hair dryer, on «high»
  • Kitchens: use a toaster to test the circuit
  • Outdoors: try any power tool or a shop vacuum

Each of these are typical uses for each outlet. If the new GFCI receptacle «trips» under ordinary use as tested above, you have another problem. It’s possible you’ve purchased a defective outlet (not unusual, since these are delicate), or your existing circuit may be inadequate for normal use.It’s also possible there’s an electrical flaw in the item you plugged in.

Consult a professional electrician for further assistance, if problems persist.

You will Need
• Outlet tester
• Two new GFCI receptacles
• New outlet cover
• level-1 screwdriver
• Basic wire cutter/stripping tool

Tips & Warnings
• ALWAYS turn the power off!
• Be SURE the power is off!
• Check all connections carefully
• Unsure? Get help, not hurt


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