How to Wire an AC Powered Smoke Alarm

Prepare the location where you want to place the smoke alarm, be it on the wall or ceiling of a room. Locate the electrical junction box that is in the room's wall or ceiling -- there might be an exposed wall plate covering the electrical junction box or there will be a light fixture on the wall or ceiling that is wired to the electrical junction box.

Remove the fuse or trip the circuit breaker that supplies electrical power to the room where you will be installing the AC-powered smoke alarm.

Place a ladder in the room beneath the cover plate or light fixture on the ceiling, or against the wall where the cover plate or light fixture is. Unscrew the cover plate from the wall or ceiling in the room, or remove the screws from around the light fixture on the wall or ceiling -- use a Phillips screwdriver to remove the screws.

Unscrew the screw tabs that are holding the twisted pairs of wires from the electrical junction box and the light fixture together. Untwist the wires from each other and separate them. Remove the light fixture. If there is no light fixture attached to the wall or ceiling, pass over this step.

Pull the wires from the electrical junction box through the center or the smoke alarm cover plate. Place the cover plate against the wall or ceiling. Screw wood screws through the plate into the ceiling or wall with the Phillips screwdriver.

Strip an additional 1/2 inch of insulation from the ends of the wires attached to the electrical junction box with wire strippers. Strip an additional 1/2 inch of insulation from the ends of the wires attached to the smoke alarm pigtail connector with wire strippers.

Wrap the exposed end of the white wire from the electrical junction box around the white wire from the smoke alarm pigtail connector. Wrap the exposed end of the black wire from the electrical junction box around the black wire from the smoke alarm pigtail connector. Repeat this again, only with the yellow wire from the smoke alarm pigtail connector and the red wire from the electrical junction box.

Screw a screw tab clockwise onto each of the twisted pairs of wires. Plug the clip at the end of the smoke alarm pigtail connector into the socket on the back of the smoke alarm. Push the wiring up inside the ceiling or into the wall.

Place the smoke alarm against the ceiling or wall, over the cover plate. Screw the alarm into the plate with metal screws using the Phillips screwdriver. Restore power to the electric line going into the room.