Q: I changed the batteries in my smoke detector, but when I tested it afterward nothing happened. The batteries are new, but the smoke detector is very old. I know that it’s hard-wired into my home’s electricity and that all the breakers are on. What should I do?
A: It sounds like your smoke detector is dead. Many people complain about the annoying “chirp” indicating a weak battery, but knowing the detector is completely broken is enough to keep anyone awake at night.
It’s recommended that smoke detector batteries be changed when you set your clock for Daylight Saving Time and again when you set it back to standard time. It’s also recommended that the entire unit be replaced if it’s more than 10 years old because the circuits wear out and eventually stop working. Also, years of dust and clumsy painting can interfere with the sensor.
Smoke detectors are inexpensive. You can buy a direct-wired unit with a battery backup for about $18 or a six-pack for $75. If you have an area where you want to add one, install a battery-operated unit, which is about $15.
To replace your direct-wired smoke detector, first turn off the power at the main panel. The top of the old smoke detector will either pop off or will twist off with a slight turning motion.
On the old units, you have to remove the body of the detector to access the wires that connect it to the electricity. The body is held in place by two screws. Remove these screws and the detector will dangle from the ceiling.
Test the wires to make sure the power is off, then untwist the wire connections (most modern smoke detectors will twist off from the mounting plate attached to the ceiling, so if you buy the same brand that is currently installed, you may not need to replace the mounting plate).
Screw the new smoke detector mounting plate to the electrical box with the two screws that you removed from the old unit. Your new smoke detector will come with a connector plug that attaches to the electricity. After you make the electrical connections, simply plug this connector into the detector.
The electrical connections are the same as replacing a light fixture, except for what is called an interconnect wire. If you have multiple smoke detectors that are interconnected, when one goes off, they all go off.
You can tell if your detector is interconnected if it has a third colored wire. Connect the white neutral wire from the ceiling to the white wire on the connector plug. Connect the black hot wire from the ceiling to the black wire on the connector plug. If your old smoke detector had a third colored wire connected to it, then connect this wire to the yellow interconnect wire on the connector plug.
New smoke detectors are wired for either single or interconnected use, so just connect the new detector with the same number of wires as the one you are replacing. Use wire nuts for tight connections.
Once the wiring is done, plug the connector into the new smoke detector and twist it onto the mounting plate. This is really a simple job.
However, it’s a job that is vitally important. If this one smoke detector is old, the other ones in your home probably are old, too. Do yourself a favor and spend the money to change them all. You might also consider a detector that senses both smoke and carbon monoxide.
Mike Klimek is a licensed contractor and owner of Las Vegas Handyman. Send questions to email@example.com or 4710 W. Dewey Drive, No. 100, Las Vegas, NV 89118. Visit handymanoflasvegas.com.
Do it yourself
Project: Replace old smoke detectors
Cost: Less than $20 each
Time: Less than 15 minutes each