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- Project Guide: Installing a Wired Smoke & CO Alarm
Installing Hard-wired Smoke and CO Alarms
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• Cable clamp with locknut
Materials:
Available Only at Your Local Store:
• Marking tool
• Stiff wire or coat hanger
Follow These Steps
Step One
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Cut Holes for Remodel Boxes
Follow this step for each location where an alarm will be installed. |
| 1. | Identify where the smoke alarm will be installed. |
| 2. | Use a stud finder to determine the location of wall studs around each alarm location. Mark a spot for each alarm in the open space between studs on the wall 12 in. down from the ceiling. |
| 3. | Use a marking tool to trace the outline of the remodel box on the wall. Use a level to make sure the box outline is straight. |
| 4. | Drill a ½ in. starter hole at a corner of your outline. |
| 5. | Starting at the hole, cut along the outline with your drywall saw. |
| 6. | Test fit the remodel box. It should fit into the hole snugly, but not so tightly that you have to force it. Do not set the remodel box yet. |
| 7. | Repeat this process at each location where an alarm will be installed. |
Step Two
| Run Cable to the First Alarm |
| See our Running Electrical Wire Behind Walls project guide project guide for step-by-step instructions on how to run wires behind walls. |
| 1. | Run Romex 14-2 NM-B cable from the breaker panel to the location of the smoke alarm closest to the breaker panel. Do not connect the cable to the breaker panel at this time. This is a step that will take place at the end of your project. |
| 2. | When the cable reaches the smoke alarm location, pull about 10 in. of the cable through the knockout of the first remodel box. |
Step Three
| Install Next Runs of Wiring |
| 1. | Run Romex 14-3 NM-B cable from the first alarm to the second alarm, leaving 10 in. of cable length hanging out of the work box. |
| 2. | Run Romex 14-3 NMB-B wire from the second box to the third, from the third to the fourth and so on until you reach the last alarm. |
Step Four
| Secure the Cable and Set the Box |
| 1. | At the last alarm, pull roughly 10 in. of the cable through the knockout of the remodel box. |
| 2. | Secure the cable in the box by tightening the wire clamp in the box. |
| 3. | Set the box in place. See our Installing Remodeling Boxes project guide for detailed instructions. |
Step Five
| Strip the Wires |
| 1. | Still working at the last remodel box, use wire strippers to cut the NM-B cable’s outside sheath and any paper insulator to expose the black, white, red and bare copper wires within. |
| 2. | Attach the copper wire to the box with a ground screw. |
| 3. | Use wire strippers to strip ¾ in. of insulation from the ends of the wires. |
Step Six
| Wire the Alarm |
| The alarm has two parts—the alarm itself, and the harness with wires coming out of it that plug into the alarm after the wires have been connected. Use the harness with black, white and red wire for the following steps. Do not attach the plug to the smoke alarm yet. |
| 1. | Connect the black wire coming out of the box to the black wire on the harness and secure the wires together with a wire connector. |
| 2. | Connect the white wire to the white wire on the harness in the same manner. |
| 3. | Connect the two bare copper ground wires together and connect them to the remodeling box. |
| 4. | Connect the red wire from the harness to the red wire coming out of the box. |
| 5. | Secure all the wiring connections with wire connectors. |
| 6. | Wrap electrical tape around the base of each wire connector. |
Step Seven
| Attach the Mounting Plate |
| 1. | Place the smoke alarm’s mounting plate on the remodel box and align the screw holes. Make sure the wire connection runs through the bracket’s center hole. |
| 2. | Carefully pull the connected wires and plug through the mounting plate. |
| 3. | Connect the wired harness to the back of the smoke alarm. These are usually configured to ensure they can only fit one way. |
| 4. | Use appropriate sized screws to connect the mounting plate to the remodel box. |
Step Eight
| Attach the Smoke Alarm to the Base |
| 1. | Line up the notches on the back of the smoke alarm with those on the base. |
| 2. | Twist the alarm until it locks into place. |
| 3. | Check the connection to ensure it’s secure on all sides. |
Step Nine
| Connect and Mount the Remaining Alarms |
| 1. | Continuing to work back towards the alarm closest to the breaker panel, repeat the actions in Steps4-5. |
| 2. | At each location: |
| • connect the black wire on the harness to the two wires coming out of the box. | |
| • connect the white wire on the harness to the two white wires coming out of the box, and | |
| • connect the red wire on the harness to the red wire coming from the box. | |
| 3. | Secure all the wiring connections with wire connectors. |
| 4. | Wrap electrical tape around the base of each wire connector. |
| 5. | Connect the harness to the smoke alarm. |
| 6. | When you reach the alarm closest to the breaker panel, connect the black wires, the white wires and the red wires. |
| 7. | Mount each alarm as detailed in Steps 7-9 |
Step Ten
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Connect at the Breaker Panel
Connect the 14-2 NM-B cable to the beaker panel following the step-by-step instructions in our Adding a New Circuit project guide. |
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