Replacing mains wired smoke alarms

[Matt_C]

Hi, first time poster.

I've had to replace one of the three mains wired smoke detectors in our house which have been in since it was built, about 12 years ago.

Obviously the replacement is a different model to what was there.

When I put the power back on the other 2 detectors go off and the only way to stop them is to turn the power off or detach the replacement alarm.

Is there some way of resetting the old 2 or should I replace all 3 at the same time or is there something else obvious I'm missing?

Cheers for any pointers
Matt

 

[Silentrunning]

Welcome To The Forum Matt. Replace all 3 with the new model. It’s your family’s safety you’re dealing with here. The advances in electronics in the last decade make it a sound investment as well as the active element in the detector degrades over time.

 

[Cableman]

you have to replace all three, signaling method and communication is different

 

[piglet11]

Agree with all the others.
Replace all, not just one.
However, it's not as simple as just using the old wiring.
You, or someone else needs to check that the signal or interconnecting wiring is either voltage free, AC or DC. It should be, when working, a low DC voltage, but never rule out AC mains.
Interconnected alarms were mandatory in UK major refurbishments and it makes sense. These had to be hardwired. I don't know if regs allow wireless units, but with a hardwired system you know where you are. I always wire where possible.
The advice then, was to use a lighting circuit to power as it was obvious if the circuit had failed. A better solution is a dedicated circuit, but definitely not on RCD (GFI ? Ground Fault device?)
As Doug says, fire detectors have a limited lifetime. Ionisation detectors are fickle things and rely on a radioactive isotope called Americium 241, which has a long half-life, but needs to be clean to work. Do not try to clean!!! Photo detector types do get dirty and will degrade. I have cleaned them in the past, but again, the infrared LED and detector degrade over time.
The only one that doesn't degrade is the heat detector, best used in kitchens and garages.
Ditch detectors every ten years or as advised and write the installation or manufacture date on them (pencil only).
Make sure you get the right type for the situation and test regularly.