If you wire a GFCI outlet to multiple ordinary outlets, you must connect them properly.
By connecting other ordinary outlets to a GFCI one, you can extend its protection to the additional outlets.
Quick Summary to wire a GFCCI outlet with multiple outlets:
- Multiple outlets can be connected to a GFCI outlet in a parallel arrangement.
- The line terminals of the additional outlets are connected to the load terminals of the primary outlet.
- The line terminals of the main source GFCI outlet are connected to the main electricity supply.
- All black wires should be connected to live (known as hot) terminals.
- All white wires should be connected to neutral terminals.
- All green or bare wires should be connected to ground terminals.
I will go into more detail below.
Connecting Multiple Outlets
You Can Help with a GFCI
A GFCI (Ground Fault Circuit Interrupter) outlet incorporates a special circuit breaker to protect the outlet against electric shocks.
If there is any surge in current, leakage, or a ground fault, it will cut off the power supply. It also has a feature whereby you can connect multiple other ordinary outlets to offer them the same protection. Some homeowners save money connecting ordinary (non-GFCI) outlets to a single GFCI outlet.
This way, they can extend the GFCI protection across all the connected outlets. It is also a requirement, for example, in a garage, i.e., to connect additional outlets inside the garage to the GFCI one (as per NEC 211.10(C)(4).
Under this arrangement, a current leak or surge in any connected outlets will cause the GFCI outlet to power off, cutting off the supply to all the other outlets.
But Should You Do It?
Is it recommended to wire a GFCI outlet with multiple other outlets?
If you use a single GFCI to serve multiple outlets, don’t automatically assume the source of the problem, when there is one, is the GFCI outlet. [Family Handyman, 2017]
So although it may seem convenient, in the event of a problem, you must check all the connected outlets until you find the one to fix it.
GFCI protection is particularly important in your home’s wet or moist areas, including kitchens, bathrooms, laundry rooms, basements, wet bars, spas, swimming pools, and any outlets near plumbing.
Parts of a GFCI Outlet
Before you start wiring a GFCI with multiple outlets, make sure you’re able to recognize its parts and terminals.
Especially important here are the two pairs of LINE and LOAD terminals. These are marked in the illustration below.
As different terms are sometimes used, be clear that the live wire is also called the ‘hot’ or ‘line’ wire, and the ground wire is also called the ‘earth’ wire.
The types of screws used on the terminals may also differ. If they do, you will normally see bronze screws on the live terminals, silver ones on the neutral terminals, and green screws on the ground terminals.
As for the wires, black or red wire is used for the live or hot wires, and white or gray wire is used for the neutral wires. The ground wire is either green, green with yellow stripes, or bare copper and is used for the ground connection.
Wiring for Single and Multiple Locations
GFCI wires can be wired to protect themselves (a single location) or other outlets, switches, and fixtures (multiple locations).
The pictures below illustrate the difference between the two setups.
Wiring an Isolated GFCI Outlet
When a GFCI is wired for a single location (isolated from other outlets), the hot and neutral wires are only connected to the LINE terminals.
This is the most common configuration.
Wiring a Connected GFCI Outlet
If you prefer to wire one for multiple locations, one pair of wires (hot and neutral) will be connected this way, while the other pair will be connected to the LOAD terminals.
If you cannot see the load terminals, they might be covered by a yellow sticker if the GFCI outlet is new. As for the ground wires, they will be pigtailed together and connected to the single green/ground terminal.
This pattern is repeated for any additional outlets, as explained further below.
Which is Preferable?
Although both arrangements are possible (isolated and connected), GFCI outlets work more effectively when wired to protect a single location due to their high sensitivity.
Single-location GFCI outlets also avoid ‘phantom tripping,’ which happens when power is shut off because of a tiny (but normal) fluctuation in current. [Black & Decker, 2008]
Wiring Multiple Outlets to a Single GFCI Outlet
If you’re convinced that it is worth wiring multiple outlets to a single GFCI outlet, or you must do so, I will explain the setup in more detail.
As you can see in the above wiring diagram for connecting multiple outlets to a single GFCI outlet, the wiring is not complicated.
The GFCI outlet has two pairs of terminals on each side for these extra connections: one is the LINE bus, and the second is the LOAD bus, each with a pair of terminals at both ends. Each additional outlet is connected in parallel.
The LINE bus is for INPUT or supply connections. On the GFCI terminal, the live and neutral connections from the main supply are connected here. On all additional outlets, they connect to the LOAD terminals of the GFCI outlet. Conversely, the LOAD or OUTPUT terminals of the GFCI outlet connect to the LINE terminals of the additional terminals.
All the outlets’ ground terminals are connected to the main ground connection in your home.
Can you use more than one GFCI in the same connected outlets with GFCI protection?
Yes, you can. You can include more than one GFCI outlet, and the procedure will be the same. But it is unnecessary and will increase the chances of tripping. If you do, only one GFCI will be the source, and the other GFCI will function as an additional outlet, albeit with built-in GFCI protection.
Can you wire the additional outlets to a GFCI outlet in series?
Yes, you can, but I would not recommend you do that. If you were the additional outlets in series, it would reduce their voltage. Without proper voltage, the appliances connected to them may not operate. The only advantage is that the current will remain the same across all the outlets. It’s only an option if you have only a few additional outlets to connect, and the appliances on all of them can operate on less voltage.
I recommend you stick to the parallel arrangement described in this article for normal use.
Can you wire a GFCI outlet with four wires?
Yes, you can. But this article was about wiring with three wires, which is common in most US homes.
What do the lights on the GFCI outlet mean?
Everything normally works if you see a green light on the GFCI outlet.
Something is wrong if you see a red light on the GFCI outlet. You will have to investigate further.
If you see no light, the GFCI outlet is turned off, or the circuit tripped.
Black & Decker. The Complete Guide to Wiring: Upgrade Your Main Service Panel – Discover the Latest Wiring Products – Complies with 2008 NEC. Black & Decker Complete Guide. Editors of Creative Publishing International. Cool Springs Press. 2008.
Eaton (GFCI outlet – side view): https://www.eaton.com/us/en-us/skuPage.SGF15W.html.
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