Rewire a Switch that Controls an Outlet to Control an Overhead Light or Fan

February 9, 2009 | by Fred (email) |

Last week I described how an outlet should be wired for switch control when the voltage enters the circuit at the outlet.  This setup is how our master bedroom was wired before I installed an overhead ceiling fan.  As promised, I detail below how to modify this wiring setup with minimal effort so that the switch can instead control an overhead fixture.  Later this week, I’ll post some before and after pics from our ceiling fan installation.  Before we get started, let’s briefly review last week’s diagram:

Review of Switched Outlet Wiring (Power Enters at the Outlet)

In this diagram, voltage enters the circuit at location (A) in a standard 2-wire (+ground) Romex.  The white neutral wire from this Romex is connected directly to the silver terminals on the receptacle (E), and the black hot wire is connected to the white wire running to the switch (B).  The white and black wires from this Romex are connected to the switch (C).  The black wire at the switch is now switched hot which is run back to the receptacle and connected to the gold terminal (D).  The result:  the outlet is only hot when the switch is turned on.

Notice that in this diagram, the neutral wire never leaves the receptacle box.  Voltage exits the receptacle box on the white wire to the switch, and then returns as switched power on the black wire, both in the same Romex cable.

To rewire this circuit to control an overhead fixture, we need to get both hot and neutral to the switch box, and ultimately out a second Romex to an overhead fixture.  We do this by repurposing the Romex between the receptacle and the switch, and adding an additional Romex to the overhead fixture.  Here’s how the wiring diagram changes:

Rewire a Switch to Control an Overhead Fixture

Diagram Explanation

• Step 1: We need to alter the wiring in the receptacle box to move hot, neutral, and ground up to the switch.  To do this, we use the receptacle as a bridge for the hot and common wires.  For both Romex’s in the receptacle box, the black wires are wired to the brass terminals, the white wires to the silver terminals, and the ground (copper) wires are nutted together and attached with a pigtail to the receptacle itself.
• Step 2: Add an additional piece of Romex from the switch box to the overhead fixture.  This Romex should be sufficient gauge for the current (12 gauge for 20 amp circuits, 14 gauge for 15 amp circuits).  In our diagram we add 2-wire Romex with the intention that all of the voltage traveling to the overhead fixture will be switched.  We could also add 3-wire Romex and have one switched hot wire, and one constant hot wire running to the overhead fixture.  (This would be useful, for instance, if we were installing a fan with a separate fan and light control).
• Step 3: Wire nut the neutral wires from both Romex’s in the switch box together.  (This sends neutral up the wire to the fixture).  Connect the black wires from each Romex in the switch box to the switch.  (The black wire running up to the overhead fixture is now switched hot.  Wire nut the ground wires together and add a pigtail to connect the switch.

Additional Notes

• Note that once hot and neutral are both at the switch, we have a lot of options for expanding this circuit.  We could split the hot wire onto two switches that run to an overhead fixture.  This could be used to give us independent control of a fan and light fixture.  (Alternatively, modern technology gives us the ability to retrofit the switch with a “smart switch” that will independtly control the fan and light on a traditional two-wire circuit).
• It goes without saying:  Only perform this work if you are qualified (and licensed if necessary) and always turn off the power at the breaker panel before you start work.

ProTool Reviews has a similar guide for wiring a ceiling fan that accounts for several different scenarios- pull chains, multiple switches and more. If this article hasn’t answered all your questions, check out their guide and helpful diagrams.