How to Install Hard-Wired Smoke Detectors

Turn off the power switches in the fuse box that route electricity to the circuits where alarms will be installed.

Hold an alarm's box to the installation area on the ceiling. Outline the box with a pencil. Put on the safety goggles and cut out the indicated area with a keyhole saw. Repeat this step for the next alarm.

Wire the No. 12/2G NM feeder cable into the circuit in the fuse box that you're using for the alarms. Hook the other end of that cable on the fish tape and guide the cable from the fuse box, up through the ceiling, and across to the nearest prepared hole.

Run the No. 12/3G NM traveler cable from the primary alarm's hole to the second location, moving it with the fish tape tool. Hold the alarm's box up to its opening in the ceiling, and pull the cables down through the box, leaving at least 6 inches of cable dangling from the box. Insert the box into the ceiling. Secure the cable in the box with cable clamps, if the unit is not self-clamping.

Strip off 6 inches of the outer coating, using a cable ripper to expose the now-dangling insulated wires. Cut off about 3/4 inch of sheathing from the ends with long-nosed pliers. Bundle together all of the like-colored wires from each box, and secure them together in wire connector caps.

Affix the brackets for the alarms to the ceiling, and plug the alarms onto the wires.

Return to the original ceiling hole and box, and pull all of the wires through the box. Connect together all of the like-colored wires and bundle them into wire connector caps.

Turn on the power from the main panel, and press one of the test buttons on an alarm. Turn it off. Screw together the two halves of the box and twist them together until they lock.