Power Source and Fixture Feed
at Different Switch
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 3 wire cable that is routed between
switch box 1 and switch box 2 - these wire cables comes with a black
/ red / white wire plus the bare equipment grounding wire.
2. A 2 wire cable that is routed between
switch box 2 and the fixture box - this wire cable comes with a
black / white wire plus the bare equipment grounding wire.
3. A circuit power supply source wire cable
that is feed to the switch 1 box.
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)
At the
Fixture box...
One cable entering this box .
* a) connect the white wire to the grounded conductor (neutral) of
fixture - if screw type connections then connect to the silver color
screw.
* c) connect the black wire to the switched ungrounded conductor
(hot) of fixture - if 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...
Two cables entering this box, one is the circuit power supply cable,
and one cable coming from switch 2.
* a) using an insulated wire nut connect /
join the white wire coming from the 'circuit power supply cable' +
the white wire from switch 2.
* b) connect the black wire coming from the 'circuit power supply
cable to the common screw of switch 1.
* c) connect the red wire coming from switch 2 to the one of the
remaining main screws of switch 1.
* d) connect the black wire coming from switch 2 to the last
remaining main screw of switch 1.
*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 the fixture.
* a) connect the black wire coming from
fixture to the common screw of switch 2.
* b) using an insulated wire nut connect / join the white wire
coming from switch 1 + the white wire coming from fixture.
* c) connect the red wire coming from switch 1 to one of the
remaining main screws of switch 2.
* d) connect the black wire coming from switch one to the last
remaining main screw of switch 2
* e) 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.
You are allowed to re-designate a white wire
to be used as a hot (ungrounded conductor) in switch circuits but in
those cases where a white wire is used in this manner, you must wrap
a piece of black electrical tape around that white wire inside the
box to signify that is being used as an ungrounded (hot) conductor.
You cannot re-designate a white wire that is actually connected to
the light fixture itself. At the fixture itself, the white wire must
be the grounded conductor (neutral) coming from the circuit power
supply cable.
In the 3 way configuration depicted on this
page, all white wires in this configuration are grounded conductors
(neutrals) and therefore no designation has been done and NO black
tape on the ends of them.
If the fixture has screw type connectors,
the switched 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 and
switch 2 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 equipment grounding screw in each electrical
box (if the box is metal), joined either through the equipment
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 equipment grounding screw (if there is one) on the
switch itself, as well as any equipment 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 equipment
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 switch itself 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 the
2 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.
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 explanation in regards to box
fill calculations...
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....
Only always on power is available from the
switch 1 location. Switch 2 only has onward switched power
available.
Switch 1 options...
Onward
Always On Circuit Power...
(showing bellow the switch 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 switch
electrical box.
Connection Instructions for onward
cable (always on)
* a) Using an insulated wire nut, attach /
join - the white wire of onward cable + the white wire from 'circuit
power supply cable' + the white wire coming from switch 2.
* b) Using an insulated wire nut, attach / join - the black wire of
onward cable + black wire connected to the common screw of switch 1
+ the black wire coming from 'circuit power supply cable'.
Identification
of wires in onward cable....
Black - Ungrounded conductor (hot - always
on)
White - Grounded conductor (neutral)
************
Switch 2 options...
Onward
switched power...
(example more than one light fixture controlled by the same 3 way
switches)
(showing bellow the switch 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 switch
electrical box.
Connection Instructions for onward
cable (switched)
* a) Using an insulated wire nut, attach /
join - the white wire of onward cable + the white wire coming from
fixture + the white wire coming from switch 1.
* b) Using an insulated wire nut, attach / join - the black wire of
onward cable + the black wire connected to common screw of switch 2
+ the black wire coming from fixture.
Identification of wires in onward
cable....
Black - Switched ungrounded conductor (hot -
switched)
White - Grounded conductor (neutral)
***************
From the fixture location...
At the fixture location only switched onward
power is available.
(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, attach /
join - the white wire of onward cable + the white wire connected to
the grounded conductor (neutral) of fixture + the white wire coming
from switch 2.
* b) Using an insulated wire nut, attach / join - the black wire of
onward cable + the black wire coming from switch 2 + the black wire
connected to the switched ungrounded conductor (hot) of fixture.
Identification of wires in onward
cable....
Black - Switched ungrounded conductor (hot -
switched)
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
