How to Hard-Wire a Smoke Detector in New Construction

Turn off the power at the main panel.

Screw the smoke detector's ceiling box to the joist in the ceiling before the drywall has been installed. If you've already installed drywall, cut a hole in the drywall using the keyhole saw for the ceiling box and screw the box to the joist. Run a NM-B 14/3 cable from the home's power source through one of the box's openings. Run a NM-B 14/2 cable through the second opening in the box.

Rip 6 inches of the cable sheathing from the cables, then strip 0.75 inches of insulation from each wire end. There should be seven wires total, four from the NM-B 14/3 cable and three from the NM-B 14/2 cable.

Connect the two black wires to the smoke detector wiring module's black wire by attaching a wire connector and clamping it in place using a crimper. Connect the white wires the same way. Connect the red wire from the NM-B 14/2 cable to the red or orange wire from the smoke detector. The ground wires are not used by the smoke detector, so you can connect the two ground wires to each other.

Wire any remaining smoke detectors following Steps 2 through 4, if you are using multiple smoke detectors.

Attach the smoke detector's wiring module to the smoke detector and attach the unit to the ceiling box's mounting bracket, pushing the wires inside of the ceiling box. Repeat with additional smoke detectors. Turn the power on and test to ensure they are working properly.