How to Replace Wired Smoke Detectors

120-Volt Smoke Detector

• 1

  Turn off power to the smoke detector. This will generally require turning off breakers one at a time until you find the right one. If the smoke detector has a power light, that can be fairly easy. If not, then you may have to remove the smoke detector before you can use the multi-tester to tell if it's de-energized.

• 2

  Open the smoke detector cover per the manufacturer's procedure. If you don't have the instructions, look for text, a catch or a hinge that will give clues to opening the smoke detector.

• 3

  Remove the screws that attach the smoke detector to the wall or ceiling.

• 4

  Disconnect the smoke detector.

• 5

  Wire the black, white and ground wires from the new smoke detector to their matching household power supply wires.

• 6

  Mount the new smoke detector to the ceiling or wall where the old one was previously attached.

• 7

  Turn power back on to the smoke detector.

Two-Wire and Four-Wire Smoke Detectors

• 8

  Disable your fire alarm system. You most likely will need to contact your monitoring agency or the fire department.

• 9

  Open the smoke detector cover per the manufacturer's procedure. If you don't have the instructions, look for text, a catch or a hinge that will give clues to opening the smoke detector.

• 10

  Remove the screws that attach the smoke detector to the wall or ceiling.

• 11

  Note how the existing detector is connected into the system. If necessary, make a wiring diagram so you can reconnect the new detector in exactly the same way. For a four-wire unit, the red and black wires are power for the smoke detector; the yellow and green wires are for the alarm contacts.

• 12

  Disconnect the smoke detector from the system wiring.

• 13

  Install batteries into the new smoke detector, if needed.

• 14

  Connect the new smoke detector exactly as the old one was connected.

• 15

  Mount the new smoke detector to the ceiling or wall, and close the cover.

• 16

  Restore the fire alarm system to normal operation and notify your monitoring agency or the fire department that work is complete.