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How to Install a Light Fixture

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How to Install a Light Fixture

Install a light fixture and switch (es) to control it.


Select the location of the fixture for the area that requires (additional) illumination. Typically, this would be a wall, ceiling or pole mount.

Determine type of light source. Incandescent, fluorescent and HID are the most common choices, but there are others.
Select the appropriate fixture that meets the requirements of light source and mounting orientation.

Determine voltage and current requirements for the fixture.

 The fixture must operate on a voltage available at (or can be brought to) the location to be installed. Nearly all fixtures available at home centers will be the 120 volt variety or have the ability to choose from two or more voltages by connecting specific wires while leaving others disconnected. This is usually only an issue on commercial fixtures, where 277 / 480 volt systems are prevalent. Current (amps or amperage) requirements for 120 volt incandescent fixtures (this includes tungsten, quartz, halogen) is .83 amps per 100 watts. A 100 watt fixture can usually be added to existing circuits without incident. Adding the fixture to a heavily loaded existing circuit however, may prove to be an issue. If the new fixture has equal voltage and equal or lower current requirements than that of a fixture it is replacing in a working circuit, there should be no cause for concern of overloading. An amperage measurement of the circuit while fully loaded should be conducted to remove any doubt.

Locate a suitable power source. This can be a nearby outlet, existing junction box in the ceiling or even a new "run" to the electrical panel.

Determine a location for a switch (or switches) to operate the light.

Determine your ability to get from the power source to the fixture location and the switch. Modify any or all of these variables by balancing desires with ability, appearance and cost. A desire to use the basement electrical source to feed a switch on the 3rd floor to operate a fixture that illuminates the front sidewalk will probably prove to be too difficult, unless installing pipe on the walls in the front hallway, which would be unsightly. Perhaps the basement panel with timer or a photocell on the fixture would provide a reasonable alternative.

Plan the wiring route. There are (3) possible ways to wire this circuit. Power to switch, power to fixture and power and load point at same switch. The three points, source, switch and fixture need to be connected together all with simple 2 wire cable such as Romex when there is one switch controlling the fixture. When wiring multiple switches to multiple fixtures it is important to think of both of these groups as separate systems as far as wiring. The fixtures need to be wired to each other with a 2 wire cable, the switches need to be wired to each other with a 3 wire cable. The power source can be brought to either of the 3 way switch boxes, or any fixture box, with 2 wire cable. The cable between the switches and fixtures is also 2 wire type, but must be run from either three way switch box to the fixture box that has the power source. Do not deviate from the requirement.

Cut openings into the ceiling / wall surfaces for the boxes for the switch(es) and fixture support by tracing the box on the surface. Match the switch box height to those in the rest of your home. If a fixture is to be installed in the ceiling, box should be a 4" round or octagon box. It is important to note that even if a small light fixture is planned to be installed here, consider installing a fan rated box, as in the future a paddle fan might be installed here.

Install the wiring. After determining there is enough capacity in the circuit to support the additional load, extend wiring of the same size from the power source to the switch and fixture locations. If running direct from the electrical panel, the new wire should be sized according to the fuse or circuit breaker size. A 15 amp circuit breaker or fuse should have #14 gauge wires and a 20 amp circuit breaker or fuse should have a #12 gauge wire connected. Install the cable between the power source and boxes in the voids of the walls, ceilings and floors with a snake or fish tape.

Connect the devices as shown in the diagram that matches your application.

Three Way switch with power source at the light fixture box.

Three Way switch with power source at the Three Way switch box.

Power source and load at the same 3 Way switch box.

Simple Single Pole switch with power source at the light fixture.

Simple Single Pole switch with power source at the Single Pole switch box.


Always remove power before opening electrical boxes or doing electrical work.

Have a helper assist snaking walls, etc.


Shut off power before connecting the new wiring to existing wiring.

Things You'll Need

Sheet rock saw
Lineman pliers
Assorted screwdrivers
Wire nut assortment
NM type cable (a.k.a. "Romex")
Snake or Fish tape
Switch box(es)
Spackle or other patching compound
Putty knife / scraper
Drill and bits.