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Home 'Switch and Outlet Wiring Made Easy'

Basic Switch Circuits

Power Source at Fixture

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For Preparation Instructions Click HERE

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...

Basic switch circuit with power at fixture

Basic switch circuit with power at fixture

Connections Instructions:
(as depicted in the diagrams above)

At the Fixture box...

Two cables entering this box, one is the circuit power supply cable, the other cable coming from switch.

* a)  using an insulated wire nut connect / join  the black wire from the 'power supply cable' + the white wire coming from switch.
* b) connect the white wire from power supply cable to the grounded conductor (neutral) of fixture - if the fixture has screw type connections then connect to the silver color screw.
* c) connect the black wire coming from switch to the switched ungrounded conductor (hot) of fixture - 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 box...

One cables entering this box coming from the fixture

* a) connect the white wire coming from fixture to one of the main screws of switch
* b) connect the black wire coming from fixture to the remaining main screw of switch.
* c) 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 configuration depicted on this page, the white wire going from the fixture to switch  has been used to carry a ungrounded conductor (hot) part of the circuit and therefore as stated should have a piece of black electrical tape wrapped around the wire in the box. The white wire from the power supply cable that goes to the fixture itself 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.

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.

If there is an equipment grounding screw on the 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.

For Extension Options to this circuit - CLICK HERE


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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