Recently I have noticed that they are installing a fire alarm system in
my building with pull stations and in some places detectors. As of now
they have installed a bunch of boxes throughout the building with rigid
pipe conduit and a single red wire fished through.
I noticed that in one spot there is a run of about 4~5 feet in the
ceiling where the red wire is exposed without conduit. It goes through
the wall and into a junction box mounted in the garbage room.
Is the purpose of this red wire only for a 9 volt signal between
alarms? Is that why you don't need to run it inside conduit? Or is this
a major code violation? It would seem silly to spend all of this money
to secure our building from fire and them have a dumb mistake which
compromises the entire system.
Long ago somebody told me the way the fire alarm systems work is there
is a single (red) wire that runs around. Any site can declare an alarm
by grounding this wire. Usually it is pulsed to indicate the box number
but I believe just holding it down will work.
So, there is no real reason to run the alarm wire in conduit. If you go
out to your street and look at the utility poles you'll probably be able
to spot the alarm wire. Usually the red insulation wears off after awhile.
That's some serious old school technology there. Current FA systems
work on a low voltage (24VDC) system, either zoned or addressable
(intelligent.) The one thing you got right is that on a conventional,
zoned system the zone is shorted to indicate an alarm condition, but I
haven't seen a coded pull station in years. Well, that's not true, a
coworker has one sitting on his desk, but it's a conversation piece
(and nearly a museum piece.)
Now that's something entirely different, like a 'municipal tie'
connection or McCulloch loop. Those are generally being phased out in
favor of autodialers.
That's perfectly legitimate. Fire alarm wire should be "plenum rated"
meaning that it is OK to free-run it above a ceiling or behind a
24 volts, actually. The conduit is only required in areas where the
wire would otherwise be exposed to a public area. This is normal and
standard practice for fire alarm retrofits, and no cause for concern.
Unless your codes are more restrictive than NEC, NFPA 72 etc. in your
area, there is no code violation.
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