How to Replace the Firex 120-1072B Smoke Alarm

Updated February 21, 2017

The Firex 120-1072B smoke alarm uses electrical power from the home's electric lines to function. To replace the Firex 120-1072B with another smoke detector that uses the electric lines, assemble the tools that were used to mount the Firex 120-1072B to the wall at an earlier time. The circuit breaker that will interrupt the electric line power at the fuse box must be known, also.

Trip the circuit breaker at the fuse box to discontinue the electric power going to the room or area where the Firex 120-1072B smoke alarm is located. Plug a table lamp into a wall outlet in the room or area to verify that there is no power.

Place a ladder against the wall or beneath the ceiling where the Firex 120-1072B smoke alarm is mounted. Twist the Firex off the mounting plate with a counterclockwise motion.

Twist the screw-tab connectors attached to the wires that are now coming out of the wall or ceiling counterclockwise. Remove the connectors and place them in your pocket. Separate the twisted pairs of wires from each other. Dispose of the Firex in a proper manner.

Remove the screws from the Firex mounting plate using the Phillips screwdriver. Pull the plate off and dispose of it in the trash.

Run the wires from the hole in the ceiling or in the wall through the centre of the mounting plate of the replacement smoke detector. Mount the plate to the ceiling or wall, over the hole, using wood screws and the Phillips screwdriver.

Twist the top of the replacement smoke detector off its base with a counterclockwise motion. Place a battery for backup use in the battery compartment. Twist the top back on with a clockwise motion.

Wind the end of the black wire from the replacement smoke detector around the end of the black wire coming out of the hole. Wind the end of the white wire from the detector around the end of the white wire from the hole. Wind the end of the copper-coloured wire from the detector around the end of the copper-coloured wire from the hole.

Place a piece of electrical tape over the end of the yellow wire from the detector since an interconnection to other smoke alarms will not be taking place.

Screw the screw-tab connectors onto each pair of twisted wires. Push the wires back into the hole. Place the replacement smoke detector against the mounting plate. Twist the detector onto the plate with a clockwise motion. Place the ladder and table lamp away. Restore the electric power at the fuse box.

Things You'll Need

  • Ladder
  • Table lamp
  • Phillips screwdriver
  • Wood screws
  • Replacement smoke detector mounting plate
  • Replacement smoke detector
  • Battery
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About the Author

Marshal M. Rosenthal is a technology maven with more than 15 years of editorial experience. A graduate of Brooks Institute of Photography with a Bachelor of Arts in photographic arts, his editorial work has appeared both domestically as well as internationally in publications such as "Home Theater," "Electronic House," "eGear," "Computer and Video Games" and "Digitrends."