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How
to wire GFCI devices
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What
is GFCI?
Ground fault outlet detects grounded circuit that can potentially
electrocute you.
For
example outdoor outlets have GFCI protection. You plug-in
extension cord. Then use power tool while standing
in water. Or wet grass. Electricity wants to flow to
ground through easiest path. Since you are standing on
wet surface that is touching ground, electricity can jump from power
tool and race through your body to ground. This
faulted circuit will kill instantly. The GFCI instantly detects open circuit, and cuts power so electricity is stopped.
Same
can happen while holding electric shaver and touch metal
faucet. Faucets are grounded because metal pipe leads outdoors into the
ground. Homes with plastic or pex plumbing might not conduct to ground,
but risk is present so GFCI is code.
Outdoor plugs, kitchen plugs and bathroom plugs are GFCI
protected. |
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Larger image |
Ground wire is not discussed since ground wire is connected exactly same on ordinary outlet and GFCI outlet:
Ground wires connects to green screws, and all ground wires are twisted together and covered with wire nut
Ordinary
outlet has 1 Hot wire from circuit breaker and 1 Neutral
wire from Neutral busbar.
See inside main breaker box
Ground wire is not shown, and connects to green ground screw.
Ordinary outlets have screws on each side.
The Hot side screws feed power to the narrow blades.
The Hot side screws are brass, and Neutral side screws are silver.
The
Hot side screws are bonded (electrically connected) to each other by break-away fin. So
wire that is connected to one screw also feeds power to other screw.
To separate brass screws on Hot side, remove break-away fin
The Neutral side screws are also connected to each other by a metal
plate.
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Look on back of device for marks identifying Line and Load |
GFCI
outlet is different than ordinary outlet
Hot side has narrow blade/ Neutral side has wide blade = same as ordinary outlet
There is no break-away fin because all 4 screws on GFCI are independent of each other
There are two set of screws on GFCI outlet, same as ordinary outlet.
Except each screw is independent and not connected by metal. So all 4 GFCI screws are independent.
Back of GFCI device identifies Line screws and Load screws.
Load screws are usually covered with yellow tape when device is fresh out of box.
Hot and Neutral wires from breaker box attach to Line screws, as
illustrated.
At this point, anything plugged into the GFCI outlet is protected from
fault.
Both outlets are GFCI protected at this point, and Load screws are not used
1) Load screws are usually covered with yellow tape when device is
purchased. This indicates that GFCI is wired differently than ordinary
outlet.
2) If you want more outlets and switches protected by same GFCI, then
attach wires
to Load screws, as illustrate below.
3) If you do NOT want GFCI protection on subsequent outlets and
switches, then
attach wires to Line screws, as illustrated below.
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How to identify Hot and Neutral wiresFollowing description does not mention ground wires. All ground
wires are
either twisted together or attached to green ground screw exactly like
ordinary outlets, and are not
immediately important for understanding how to wire GFCI.
So
which wire is Hot and
which is Neutral?
1) Each
residential box (excluding 240Volt boxes, 3-way switches, and some single light
switches) will have 1 Hot wire and 1 Neutral wire that comes
from circuit breaker.
For example
each circuit breaker supplies power to one area of home. To
do this, the Hot wire and Neutral wire leave breaker box and travel to
a junction box. The junction is usually a ceiling box where light
fixture is attached. But any box can be a junction box. From the
junction box, the Hot and Neutral split off and jump from one box to
the next box, and to the next box. The very last box will have 1 Hot
and 1 Neutral, and no additional wires. So each box between the last
box and the junction box will have several wires.
Despite
having several wires, there will be only 1 Hot and 1 Neutral in
each box. Hot wires are usually black
Each switch
will connect to Hot wire, but not to Neutral.
Each outlet
will connect to both Hot and Neutral. So if you see a Black
wire that connects to both a switch and outlet, then that is the Hot
wire.
Neutral
wires are usually white and are twisted together and covered with wire
nut, then pushed to back of box
GFCI has an
outlet, so it will connect to both Hot and Neutral, just like ordinary outlet.
To identify
the Hot and Neutral: Take photo of wires so everything can
be put back. Separate all wires except bare ground wires. Tape tester
leads to wood sticks for safety. Stand
on dry boards, and
never on wet surface.
Turn power on. Test each wire to
bare ground wire. Only 1 wire will light up tester. This is the Hot
wire. Next test Hot wire to all other wires except bare ground.
Tester will light up on Neutral wire.
So the Hot
and Neutral are identified, and these wires will connect to
the GFCI Line Screws. |
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Look on back of GFCI device for marks identifying Line and Load |
Connect additional outlets or switches to GFCI
All
devices connected to Load screws are GFCI-protected
This is true for switches and outlets
Maximum 12 boxes per circuit breaker.
A circuit consists of all boxes on 1 circuit breaker |
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Look on back of GFCI device for marks identifying Line and Load |
All
devices connected to Line screws are NOT
GFCI-protected
This is true for switches and outlets.
This technique lets installer put GFCI in bathroom, but other outlets
in bedroom are not portected for example.
Maximum 12 boxes per circuit
A circuit consists of all boxes on 1 circuit breaker
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Cooper VGFS15V-M-L
Look on back of device for marks identifying Line and Load
Line and
Load screws on combo device are wired identical to ordinary GFCI outlet
illustrated top of page |
How
to wire GFCI
Combo switch and outlet
With the combo GFCI device, both the outlet and switch
are GFCI protected.
The light fixture will connect to switch output wires.
Light fixture is GFCI protected
Line and Load screws are identified on back of device
Example Combo devices:
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Ordinary combination switch and outlet
Ordinary switch-outlet combo
Larger image |
How
to replace
ordinary combo device with GFCI combo
 TAKE PHOTO OF WIRES BEFORE
STARTING
Wires from ordinary combo device will each be connected differently
when connected to GFCI combo.
NOTE:
illustration shows Ordinary combo device before GFCI.
Screws and wires are labeled: Brass screws #1 #2 #3, and wires 1 2 3 4.
The
box
may have more wires. Note which screw each wire connects to. Note which
wires are on same side as narrow blade, and which wires are on wide blade.
Remember the outlet has a wide blade and narrow. The narrow is Hot side.
Illustration shows ordinary combo device.
Illustration shows Hot  and
Neutral 
Illustration shows wire 
connects to brass screw #3 > and this wire will not connect to a
screw on GFCI combo.
Illustration shows 
connects to Neutral
> these two wires will not be connected togerther on GFCI combo,
so remove wire nut.
Step
1: Identify the Hot and Neutral wires using test shown
above.
Read steps above How to test for Hot and Neutral.
Hot will connect to narrow-blade side of device
Neutral will connect to wide-blade side of device
Step
2: Identify both wires that go to light:
Illustration shows that wire is
connected to Brass screw #3, and wire is
connected to Neutral wire
with wire nut.
Notice that brass screw #3 is on wide-blade side of device.
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| TAKE PHOTO OF WIRES BEFORE REMOVING OLD
DEVICE |
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Illustration shows
typical GFCI combo device.
Your device can vary slightly
GFCI combo will have switch output wires sticking out of back.
Step
4: Identify Line and Load screws
Look on back of GFCI device for markings that show Line and Load
Step
5: Connect Hot and Neutral to Line screws as illustrated
Hot
connects to brass Line screw on same side of device as narrow outlet
blade.
Remember the outlet has a wide blade and narrow blade.
Neutral
connects to other Line screw
Step
6 Connect light to Switch Output wires as illustrated
Black Wire
is connected to output wire on same side of device as narrow outlet
blade
White Wire is
connected to other output wire
Does it make a dfference when Black and White are reversed? Yes and no.
The
light will work but the wiring is not code and can pose danger, except
the GFCI is designed to protect from that danger.
Troubleshoot household electric
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Step
7: If there are more wires in the box:
If the light switch controls more than 1 light fixture, then look for
additional black wire connected to brass screw #3 on original combo
device.
These additional wires
will also connect to switch output wires on back of GFCI combo. |
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Step
8: If there are more wires in the box:
Read all steps shown from top of this page so this explanation makes
sense.
If the box also feeds power to another box, then look for additional
black wire connected to black screw #2 or screw #1 on original combo
device.
Remember the wire
from the circuit breaker travels from one box to the next and to the
next.
Connect
the additional wires to the Load screws as shown in illustration
if you want GFCI protection for other boxes -or- connect these wires to
the Line screws if you do NOT want GFCI protection on other boxes.
Ground wires are not shown, and connect to green ground screws, and are twisted together and covered with wire nut. |
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Typical GFCI manuals:
Pass and Seymour Combo-GFCI manual
Leviton Combo-GFCI manual
Lutron GFCI outlet manual
Leviton GFCI-related manuals
Installing and testing GFCI |
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EJ500
Utilitec
Tork
ST01C
ETW350
Aube
Intermatic
Water heater
GE
Leviton
Hagar
Woods
Sylvania
