Swapping a Light Fixture for a Ceiling Fan on Old BX Wiring

This Old House electrical contractor John Barros replaces a ceiling light fixture with a ceiling fan, and the key change is the box: the thin pancake box that held the light has to go, because a fan needs a fan box.

Safety and removal

The first step is safety. The circuit breaker is shut off downstairs before the light fixture comes down. Two small brass nuts hold the fixture, and three wires are disconnected: the black feed from the switch, the white neutral that completes the circuit, and the ground wire, which is attached to the ground screw on the fixture strap and removed with a straight screwdriver.

The fixture strap comes off next. The box is attached to the joist with two wood screws. Once it is down, a clamp is visible that joins two wires, one going to the circuit breaker panel and the other to the switch.

Pancake box versus fan box

The old box is a pancake box, thin metal that sits flush with the plaster on the ceiling. For the fan, a fan box is used instead. It is thicker steel with larger screws that can hold not only the weight of the fan but also its movement.

Older BX wiring

The house has older armored cable, called BX, a two-wire system surrounded by a metal sheath. The sheath serves as the ground. Anti-short bushings go around the cable to protect it from the sharp edges of the sheath. Both cables enter the box through one connector; tightening its screw compresses the metal sheath and creates the ground for the fan. A 1/2 in. lock nut connects the fan box to the cables, and the box is fastened to the joist with a screw gun.

Wiring the fan

The fan motor hangs from a down rod with a ball at the top, which sits on a fan bracket mounted to the fan box. Meanwhile the blades are assembled. The fan has a black wire for the fan, a blue wire for the light, a white neutral common to both, and a green ground.

The fan is controlled by its pull chain and the light by the wall switch. The hot feed from the breaker panel connects to the fan and also sends power down to the switch. When the switch is on, power returns through a wire and connects to the blue light wire. Neutrals connect together, as do the grounds. Wires are twisted together and capped with plastic wire nuts, then the canopy is secured.

Finishing

The light fixture attaches with two plug-in connections and screws onto the fan. Power is restored from the basement and the light is tested, then the fan.