Fire alarm interface relay signal cable type

There was a fashion a few years ago for the detector side of fire alarm systems to be wired in ordinary cables, on the basis that all the signals failed-safe - i.e. if a cable shorted, or went open circuit, an alarm would be triggered. I think that approach has gone out of fashion again now, but the logic would suggest that if the fans were allowed to run by a 'no fire' signal from the alarm panel, safety wouldn't necessarily be compromised by using a non fire rated cable. Standards might take a more conservative view though.

   - Andy.

Those systems have a well defined termination resistance at the far end of the cable which allows the integrity of the wiring to be confirmed, the nicer systems have a loop through at each detector so that if a detector becomes disconnected for some reason., then that loop is broken and a system fault (not a fire alarm) is raised. This allows cables like FP200 which do not last for ever in a fire, (unlike pyrotenax/ MICC) but do last much longer than needed to raise an alarm.

M

Those systems have a well defined termination resistance at the far end of the cable which allows the integrity of the wiring to be confirmed, the nicer systems have a loop through at each detector so that if a detector becomes disconnected for some reason., then that loop is broken and a system fault (not a fire alarm) is raised. This allows cables like FP200 which do not last for ever in a fire, (unlike pyrotenax/ MICC) but do last much longer than needed to raise an alarm.

M