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4 Way Switch Circuits
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WHILE EXTREME CARE HAS BEEN IMPLEMENTED IN THE
PREPARATION OF THIS SELF-HELP DOCUMENT, THE AUTHOR AND/OR PROVIDERS
OF THIS DOCUMENT ASSUMES NO RESPONSIBILITY FOR ERRORS OR OMISSIONS,
NOR IS ANY LIABILITY ASSUMED FROM THE USE OF THE INFORMATION,
CONTAINED IN THIS DOCUMENT, BY THE AUTHOR and / OR PROVIDER.
You will need...
1. A 4 wire cable that is routed between switch box 1 and switch box
2 - these wire cables comes with a black / red / blue (or white
striped) / white wire plus the bare equipment grounding wire.
2. A 4 wire cable that is routed between switch box 2 and switch box
3 - these wire cables comes with a black / red / blue (or white
striped) / white wire plus the bare equipment grounding wire.
3. A 3 wire cable that is routed between switch box 3 and the
fixture box - this wire cable comes with a black / red / white wire
plus the bare equipment grounding wire.
3. A circuit power supply source wire cable that is routed to
fixture.
4. Insulated wire nuts to connect / join wire together, variety of
sizes out there so make sure you obtain the correct size.
5. Wire staples, to affix the wire cables to wall studs as needed.
Wire cable must be secured within 6 inches of entering the
electrical box.
6. Wire cable / wire strippers.
7. Screwdrivers as required.
Holes drilled to feed wires through studs must be 1 1/4" from edge
of stud, in instances where the wire cable is closer then the edge
of stud must have a 1/16-in. thick protective metal plate over the
area where the cable is being feed through (may want to notch the
stud so that that the protective plate does not create a bump on the
drywall). Also read the article called ' Wire
Routing Basics'
Wire cables entering the electrical box - secure the cable clamp at
the box snug enough that the cable cannot come out but not too tight
as to pinch the cable and break through the insulated cover of the
cable.
You must have at least 6 inch length of wire inside the electrical
box, it can be a bit more but not less, it can fail an inspection if
the length of each wire is less than 6 inches. Also read the article
called
'Box Fill Calculations' as there is a
limit on how many wires are allowed for a certain size electrical
box.
STEP 1 - Make
certain that the power supply cable is dead - turn off the
electrical breaker at the service panel. Make certain that everyone
in the house is aware of what you are doing so that they do not get
the notion to reset the breaker when another light in the home is
not working.
STEP 2 - Make the
box openings (if a existing home)
STEP 3 - Feed /
Route the wire cables.
STEP 4 -Mount /
Install the Electrical Boxes (make sure the electrical boxes are
secured as some fixtures are heavy and may require additional
support) [The electrical box should not extend beyond the edge of
the finished wall or ceiling so that the fixture can mount flush to
the ceiling and the wall switch cover will mount flush - but it also
should not be recessed too far into the wall or ceiling]; then feed
the wire cables into the electrical boxes. Sometimes because of
tight openings in existing homes, the wire cable may to be feed into
the electrical box then the box put in position and secured.
STEP 5 - Connect
the wires...
Connections Instructions:
(as depicted in the diagrams above)
A t the Fixture box...
Two cables entering this box, one is the circuit power
supply cable, the other cable coming from switch 3.
* a) using an insulated wire nut connect / join the black
wire from the 'circuit power supply cable' + the red wire of
the cable coming from switch 3.
* b) using an insulated wire nut connect / join the white
wire from the 'circuit power supply cable' + the white wire
coming from switch 3 + the grounded conductor (neutral) of
the fixture itself - if the fixture has screw type
connections then connect to the silver color screw.
* c) connect the black wire coming from switch 3 to the
switched ungrounded conductor of the fixture itself - if the
fixture has screw type connections then connect to the brass
color screw.
* d) please see under important notes in regards to the
equipment grounding conductor (bare wire).
At switch 1 box...
One cable entering this box, coming from switch 2.
* a) connect the black wire coming from switch 2 to common
screw of switch 1.
* b) connect the blue wire coming from switch 2 to to one of
the remaining main screws of switch 1.
* c) connect the red wire coming from switch 2 to the last
remaining main screw of switch 1.
* d) using an insulated wire nut cap off the white wire
coming from switch 2.
* e) please see under important notes in regards to the
equipment grounding conductor (bare wire).
At switch 2 box...
Two cables entering this box, one cable coming from switch 1
and one cable coming from switch 3.
* a) using an insulated wire nut connect / join the black
wire coming from switch 1 + the black wire coming from
switch 3.
* b) connect the red wire coming from switch 1 to one screw
that is a matching pair of screws on switch 2 (both the red
and blue wires coming from switch 1 must go to a matching
pair of screws at switch 2)
* c) connect the blue wire coming from switch 1 to the 2nd
screw that is a matching pair of screws on switch 2 (both
the red and blue wires coming from switch 1 must go to a
matching pair of screws at switch 2)
* d) connect the red wire coming from switch 3 to one screw
from a different matching pair of screws. (both the red and
blue wires coming from switch 3 must go to a matching pair
of screws at switch 2)
* e) connect the blue wire coming from switch 3 to the 2nd
screw that is a matching pair. (both the red and blue wires
coming from switch 3 must go to a matching pair of screws at
switch 2)
***Just to clarify
further - The red and blue wires coming from switch 1 go to
one set of matching screws at switch 2 -- The red and blue
wires coming from switch 3 go to a different set of matching
screws at switch 2 - A matching set is 2 screws of the same
color.***
* f) using an insulated wire nut connect / join the white
wire from switch 1 + the white wire from switch 3.
* g) please see under important notes in regards to the
equipment grounding conductor (bare wire).
At switch 3 box...
Two cables entering this box, one coming from fixture, and
one cable coming from switch 2.
* a) connect the black wire coming from fixture to the
common screw of switch 3.
* b) using an insulated wire nut connect / join the red wire
coming from fixture + the black wire coming from switch 2.
* c) connect the red wire coming from switch 2 to one of the
remaining main screws of switch 3.
* d) connect the blue wire coming from switch 2 to the last
remaining main screw of switch 3.
* e) using an insulated wire nut connect / join the white
wire coming from fixture + the white wire coming from switch
2.
* f) please see under important notes in regards to the
equipment grounding conductor (bare wire).
Important Notes:
By electrical codes you MUST have at least 6 inches of wire
in the electrical box itself, and also the wire must be able
to reach at least 3 inches outside the box, it can fail an
electrical inspection if the required min. wire length is
not met. You may have the wires a bit longer (within reason)
but they cannot be shorter. Also see the note on box fill
further down in this article.
If the fixture has screw type connectors, the ungrounded
conductor (hot) is connected to the brass color screw, and
the grounded conductor (neutral) is connected to the silver
color screw. If it has black and white wires coming from
fixture, then just connect black to black and white to
white. Use wire nuts of the correct size to join wires
together.
The wire cable running between switch 1 & switch 2 and
between switch 2 & switch 3 has 4 wires in it - black / red
/ blue / white (plus the bare equipment grounding wire). The
wire cable between switch 3 and fixture has 3 wires in it -
black / red / white (plus the bare equipment grounding
wire).
What is not shown in the drawings to avoid confusion, is
that each wire cable also has a bare equipment grounding
wire included. This wire is connected to a grounding screw
in each electrical box (if the box is metal), joined either
through the grounding screws in the box itself or via a wire
nut to the bare wire of the next cable entering / exiting
the box, it is also connected to any grounding screw (if
there is one) on the switch itself, as well as any grounding
screw at the fixture (green wires that attach to the fixture
are grounds). Now if using a plastic box, it is made of a
material that is non conductive, however some plastic boxes
have a metal strip inside that can still be used to connect
equipment grounding wires, in the event that it does not use
wire nuts to join the bare grounding wires together. The
equipment grounding wire (bare in most cables) must be
electrical conductively joined throughout the circuit. Green
wires are also equipment grounding conductors.
At the 3 way switches (switch 1 & 3) there are 3 main
electrical screws, one of these 3 screws is distinctly
different in color (perhaps darker) than the other 2. This
screw connection is called the common screw. It is very
important that in order for all the switches to work as they
are intended to that the correct wire is attached to the
common screw. Basically as depicted in the drawings one
switch has the ungrounded conductor (hot) from the circuit
power supply cable attached to the common screw, where the
other switch had the ungrounded conductor (hot) feed to the
light fixture itself.
Please also note that there are a variety of manufactures
out there that make 3 way switches so it is possible that
the switch you buy may have the common screw located in a
different spot or side of the switch then depicted in the
drawings in this article, just make sure that the wire
depicted to go to the common screw of each of the switches
is actually connected to the common screw of the 3 way
switch you bought. The other 2 wires going between the
remaining screws of one switch to the other switch does not
matter as long as one wire of the 2 remaining wires go on
each of the remaining 2 screws of the screw.
At the 4 way switch (switch # 2) there are 2 sets of
matching screws, one set will match in color and the other
set will be distinctly different perhaps darker in color, it
is important that the traveler wires (red and blue in the
design in this article) from the previous switch are
connected to one matching set, and the traveler wires going
to the next switch (red and blue in the design in this
article) are connected to a different matching set.
If there is an equipment grounding screw on the 3 way switch
it may be green in color and be separated away from the main
connections of the switch and likely part of the metal frame
that is also part of the mounting structure of the switch.
Extensions to this Switch
circuit...
Be Aware that there
is a limit by code on how many wires can be in a given size
electrical box, when adding more wires to the same box you
may have to install a larger and / or deeper box to allow
space for more wires coming and out of the box.
Here is an article / explanation in regards to box fill
calculations ' Box
Fill Calculation'
The instructions here are based on the fact that the circuit
has already been wired to the configuration shown in this
article and we are now making the wiring changes for onward
power.
From the switch
locations....
From switch 1 Location
(only onward 'always on' power available)
Onward 'always on'
Power...
Not shown in the diagram but
the onward cable also has a bare wire (equipment
grounding conductor) that also must be connected to
all the other bare wires at the switch electrical
box.
Connection
Instructions for onward cable (always on)
* a) Using an insulated wire nut, connect / join -
the black wire coming from switch 2 + the black wire
of onward cable + the black wire connected to the
common screw of switch 1.
* b) Using an insulated wire nut, connect / join -
the white wire from from switch 2 + the white wire
of onward cable.
Identification of
wires in onward cable....
Black - Ungrounded conductor (hot - always on)
White - Grounded conductor (neutral)
****************
From switch 2
Location
(only onward 'always on' power available)
Onward 'Always
on' Power...
Not shown in the
diagram but the onward cable also has a bare
wire (equipment grounding conductor) that
also must be connected to all the other bare
wires at the switch electrical box.
Connection Instructions for onward cable
(always on)
* a) Using an insulated wire nut, connect /
join - the black wire coming from switch 1 +
the black wire of onward cable + the black
wire coming from switch 3.
* b) Using an insulated wire nut, connect /
join - the white wire from from switch 1 +
the white wire of onward cable + the white
wire coming from switch 3.
Identification of wires in onward cable....
Black - Ungrounded conductor (hot - always
on)
White - Grounded conductor (neutral)
*************
From
switch 3 Location
(both onward switched & 'always on' power
available)
Option 1:
Onward 'always on' power...
Not shown in
the diagram but the onward cable
also has a bare wire (equipment
grounding conductor) that also must
be connected to all the other bare
wires at the switch electrical box.
Connection Instructions for onward
cable (always on)
* a) Using an insulated wire nut,
connect / join - the black wire
coming from switch 2 + the black
wire of onward cable + the red wire
coming coming from fixture
* b) Using an insulated wire nut,
connect / join - the white wire from
from switch 2 + the white wire of
onward cable + the white wire coming
from fixture.
Identification of wires in onward
cable....
Black - Ungrounded conductor (hot -
always on)
White - Grounded conductor (neutral)
*****************
Option 2: Onward
switched power...
Not
shown in the diagram but the
onward cable also has a bare
wire (equipment grounding
conductor) that also must be
connected to all the other
bare wires at the switch
electrical box.
Connection
Instructions for onward
cable (switched)
* a) Using an insulated wire
nut, connect / join - the
black wire coming from
fixture + the black wire of
onward cable + the black
wire connected to the common
screw of switch 3.
* b) Using an insulated wire
nut, connect / join - the
white wire from from switch
2 + the white wire of onward
cable + the white wire
coming from fixture.
Identification of
wires in onward cable....
Black - Switched ungrounded
conductor (hot - switched)
White - Grounded conductor
(neutral)
*************
Option 3:
Onward switched & 'always
on' power...
Not shown in the diagram but the onward cable also
has a bare wire (equipment grounding conductor) that also must be
connected to all the other bare wires at the switch electrical box.
Connection Instructions for onward
cable (switched & always on)...
* a) Using an insulated wire nut, connect / join - the black wire coming
from switch 2 + the red wire from fixture + the red wire of onward
cable.
* b) Using an insulated wire nut, connect / join - the white wire coming
from fixture + the white wire coming from switch 2 + the white wire of
onward cable.
* c) Using an insulated wire nut, connect / join - the black wire from
fixture + the black wire of onward cable + black wire connected to
common screw of switch 3.
Identification of wires in onward
cable....
Black - Switched ungrounded conductor (hot - switched)
Red - Ungrounded conductor (hot - always on)
White - Grounded conductor (neutral)
*************
From the fixture location...
Onward 'always on circuit power' and 'switched power' is possible from
the fixture location.
Option 1: Onward
Always On Circuit Power...
(showing bellow the fixture portion of the circuit)
Not shown in the diagram but the onward
cable also has a bare wire (equipment grounding conductor) that
also must be connected to all the other bare wires at the
fixture electrical box.
Connection Instructions for
onward cable (always on state)
* a) Using an insulated wire nut, connect / join - the black
wire from 'circuit power supply cable' + red wire coming from
switch 3 + black wire of onward cable.
* b) Using an insulated wire nut, connect / join - the white
wire from 'circuit power supply cable' + white wire connecting
to the grounded conductor (neutral) of fixture (shown as white
in diagram) + white wire of onward cable + the white wire coming
from switch 3.
Identification of wires in
onward cable....
Black - Ungrounded conductor (hot - always on)
White - Grounded conductor (neutral)
***************
Option 2:
Onward switched power...
(example more than one light fixture controlled by the same 3
way switches)
(showing bellow the fixture portion of the circuit)
Not shown in the diagram but the
onward cable also has a bare wire (equipment grounding
conductor) that also must be connected to all the other
bare wires at the fixture electrical box.
Connection
Instructions for onward cable (switched)...
* a) Using an insulated wire nut, connect / join - the
black wire coming from switch 3 + the black wire
connected to the switched ungrounded conductor (hot) of
fixture (shown as black in diagram) + the black wire of
onward cable.
* b) Using an insulated wire nut, connect / join - the
white wire from 'circuit power supply cable' + the white
wire connected to the grounded conductor (neutral) of
fixture (shown as white in diagram) + the white wire of
onward cable + the white wire coming from switch 3.
Identification of
wires in onward cable....
Black -Switched ungrounded conductor (hot - switched)
White - Grounded conductor (neutral)
**************
Option 3:
Onward 'always on' and 'switched' power...
(showing bellow the fixture portion of the circuit)
Not shown in the diagram
but the onward cable also has a bare wire
(equipment grounding conductor) that also must
be connected to all the other bare wires at the
fixture electrical box.
Connection
Instructions for onward cable (always on and
switched)
* a) Using an insulated wire nut, connect / join
- the black wire coming from switch 3 + black
wire connected to the switched ungrounded
conductor (hot) of fixture (shown as black in
diagram) + the black wire of onward cable.
* b) Using an insulated wire nut, connect / join
- the white wire from 'circuit power supply
cable' + the white wire connected to the
grounded conductor (neutral) of fixture (shown
as white in diagram) + the white wire of onward
cable + the white wire coming from switch 3.
* c) Using an insulated wire nut, connect / join
- the black wire from 'circuit power supply
cable' + the red wire coming from switch 3 + the
red wire of onward cable.
Identification of wires in onward cable....
Black -Switched ungrounded conductor (hot -
switched)
Red - Ungrounded conductor (hot - always on)
White - Grounded conductor (neutral)
Foreign
Users:
The colors of the
wires depicted are based on the standards and
code requirements / configuration in the United
States and Canada. If you are viewing this site
from a foreign country, your wiring standards
and color of wires may be different but the
principal and sequence of wiring will still
remain the same. Therefore the information in
this article may still be of use to you
regardless of what country you may be in. Just
translate the colors used here to the color of
wires used in your country in regards to
ungrounded (hot) conductors / grounded
conductors (neutral) and equipment grounding
conductors as well know applicable code
requirements in your country.
By: Donald Kerr
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