Our house was completely re-wired and new wired smoke alarms installed in 2010. The smoke alarms were not interconnected. There are four wires: brown, gray, black, sleeveless.

Now I am installing an interconnected system. Is it possible that there is an interconnect cable in the 2010 wiring? As far as I can tell, brown = live, gray = neutral, sleeveless = earth. What could black be other than an interconnect cable?

  • in north america our smoke alarms are interconnected using 14/3 wiring and the colors are white/black and red. where are you located? Commented Dec 27, 2023 at 20:37
  • i had some wired up in 2006 and they were interconnected so yes 10 years ago they could have been wired up as interconnected. Commented Dec 27, 2023 at 20:38
  • Mine were interconnected in 1996. I am in NZ. Commented Dec 27, 2023 at 20:44
  • Thanks for all the comments. I am in Scotland. So it looks like the additional cable is the interconnect cable, which would make it the one part of the house that was built to a higher spec than absolutely necessary.
    – Johannes
    Commented Dec 28, 2023 at 20:33


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