OlympusMons:

Hi Graham, it could be argued that "an alarm or something similar" would be classed as a "signalling and control circuit", and the minimum CSA of 0.5mm2, or even possibly 0.1mm2 since most alarms are electronic.

Andy has commented about table 52.3 in this old thread https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=54291&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear

 

A supply to an alarm system or control system is definitely a power circuit. The function of the circuit is definitely not not "signalling and control".


The switched live to a timed fan, or the link wire in mains smoke alarms, may well be a control or auxiliary circuit, as would the secondary (alarm circuits themselves) of the fire or intruder alarm.


If you install the connection unit on a lighting circuit, then I can see an interpretation that the circuit is mainly for lighting, so 1.0 sq mm is OK ... but if it's a dedicated circuit for something else, I think that argument peters off somewhere.


However, linking back to the original post, I remembered this recent thread: https://communities.theiet.org/discussions/viewtopic/1037/26230


Which got me thinking that FCUs to BS 1363-4 are not necessarily suitable for termination, without special preparation, 1.0 sq mm (or 1.5 sq mm for that matter) - the manufacturer may choose to state otherwise, of course.

OlympusMons:

Hi Graham, it could be argued that "an alarm or something similar" would be classed as a "signalling and control circuit", and the minimum CSA of 0.5mm2, or even possibly 0.1mm2 since most alarms are electronic.

Andy has commented about table 52.3 in this old thread https://www2.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=54291&STARTPAGE=1&FTVAR_FORUMVIEWTMP=Linear

 

A supply to an alarm system or control system is definitely a power circuit. The function of the circuit is definitely not not "signalling and control".


The switched live to a timed fan, or the link wire in mains smoke alarms, may well be a control or auxiliary circuit, as would the secondary (alarm circuits themselves) of the fire or intruder alarm.


If you install the connection unit on a lighting circuit, then I can see an interpretation that the circuit is mainly for lighting, so 1.0 sq mm is OK ... but if it's a dedicated circuit for something else, I think that argument peters off somewhere.


However, linking back to the original post, I remembered this recent thread: https://communities.theiet.org/discussions/viewtopic/1037/26230


Which got me thinking that FCUs to BS 1363-4 are not necessarily suitable for termination, without special preparation, 1.0 sq mm (or 1.5 sq mm for that matter) - the manufacturer may choose to state otherwise, of course.