I’m replacing the heat alarm in my apartment as the old one is faulty. They no longer make the deta 1111 so I bought a deta 1165. Unfortunately this means I have to replace the base.
I’m confused by the connections on the old alarm. Brown to brown is obviously live. Blue (neutral) on the alarm is connected to a grey colour wire from the ceiling. The white cable on the alarm (which I believe is the interlink) is connected to the black wire from the ceiling. I would have expected black to be neutral. I have photos I can send.
It sounds like whoever installed the previous heat alarm used grey as the neutral conductor, and black as the interlink. I an ideal world these cores should have been sleeved to indicate their purpose!
The easiest way to confirm what wire is doing what would be to use a multimeter to indicate the voltage coming through each cable. If you have access to one of these and measure between the brown and grey wires, you should have 230 volts.
Obviously great care should be taken when getting a reading, and if you're not 100% confident to do this I'd suggest calling someone in to give you some help.