I recently bought a house that has wired smoke alarms, but they look pretty old. Before I replace them, I took off the housing and used my non-contact voltage detector while the alarms were still wired. Surprisingly, I couldn't detect any voltage at all. Does that mean there's no power, or could the voltage be too low to pick up? Also, I noticed that the previous owners replaced some of the wired detectors with battery-operated ones—could that affect the connection for the others in the circuit?
3 Answers
Don't worry; if a smoke detector isn't connected, it shouldn't break the power chain. Try checking if smoke detectors have their own breaker, as I've seen setups where they’re linked to other circuits. If you have a multimeter, it might give you clearer readings than the non-contact tester.
It's possible that the wired smoke detectors are using DC power, which non-contact voltage detectors might not pick up. You might want to look for a test button on the smoke detectors themselves—it could indicate whether they have power. Just a heads up, smoke detectors should be replaced every 10 years because the radioactive source inside can decay over time.
These smoke detectors typically run on standard 120V AC, so it could be that the circuit breaker is off or the previous owner didn’t secure the power wires properly. They should still show power whether or not a smoke detector is connected.