Power Source at Fixture
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 1 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
fixture 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 to the edge of
stud then you 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:
At the Fixture box...
Two cables entering this box, one is the circuit power supply cable,
the other cable (wire cable # 1) coming from switch 1.
* a) using an insulated wire nut connect / join the black wire from
the 'circuit power supply cable' + white wire of the cable coming
from switch 1.
* b) connect the white wire from 'circuit power supply' cable to the
grounded conductor (neutral) of fixture - if screw connections at
fixture connect to the silver color screw.
* c) connect the black wire coming from switch 1 to the switched
ungrounded conductor (hot) of the fixture - if screw connections at
fixture 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 coming from the fixture (wire
cable # 1), the other cable coming from switch 2.
* a) using an insulated wire nut connect / join the white wire
coming from fixture + the black wire of cable coming from switch 2.
* b) connect the black wire coming from fixture to the common screw
of switch 1.
* c) connect the white wire coming from switch 2 to one of the
remaining main screws of switch 1.
* d) connect the red 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...
One cables entering this box coming from switch 1.
* a) connect the black wire coming from
switch 1 to the common screw of switch 2.
* b) connect the white wire coming from switch 1 to one of the
remaining main screws of switch 2.
* c) connect the red wire coming from switch 1 to the last remaining
main screws of switch 2.
* d) please see under important notes in regards to the equipment
grounding conductor (bare wire).
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, the white wire going from the fixture to switch 1 and the
white wire going from switch 1 to switch 2 have been used to carry a
switched ungrounded conductor (hot) part of the circuit and
therefore as stated should have a piece of black electrical tape
wrapped around that wire in the box. The white wire from the power
supply cable that goes to the fixture itself at the fixture box
location is a grounded conductor (neutral) and therefore is left as
white with NO black tape on it.
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 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 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 then 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 has the
switched 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 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....
No onward connections are possible from
either of the switch locations because a grounded conductor
(neutral) does not exist with this configuration at these locations.
From the fixture location...
Onward 'always on circuit power' and
'switched power' is possible from the fixture location.
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, attach /
join - the white wire of onward cable + the white wire from the
'circuit power supply cable' + white wire connected to the grounded
conductor (neutral) connection at fixture.
* b) Using an insulated wire nut, attach / join - the black wire of
onward cable + black wire of 'circuit power supply cable' + white
wire coming from switch 1 (wire cable # 1).
Identification of wires in onward
cable....
Black - Ungrounded conductor (hot)
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, attach /
join - the white wire of onward cable + the white wire from the
'circuit power supply cable' + white wire connected to the grounded
conductor (neutral) connection at fixture.
* b) Using an insulated wire nut, attach / join the black wire of
onward cable + the black wire coming from switch 1 (wire cable # 1)
+ 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)
*****************************
Option 3:
Onward 'Always On' & 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 & switched)
* a) Using an insulated wire nut, attach /
join the white wire of onward cable + the white wire from the
'circuit power supply cable' + the white wire connected to the
grounded conductor (neutral) of fixture.
* b) Using an insulated wire nut, attach / join the red wire of
onward cable + the black wire coming from switch 1 (wire cable # 1)
+ the black wire connected to the switched ungrounded conductor
(hot) of fixture.
* c) Using an insulated wire nut, attach / join - the black wire of
onward cable + the black wire of the 'circuit power supply cable' +
white wire coming from switch 1 (wire cable # 1).
Identification of wires in onward
cable....
Black - Ungrounded conductor (hot - always
on)
Red - 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
