Friday, October 12, 2012

Supervision of Fire Alarm wiring theres a reason for it

At left is a 24 V DC fire bell with 4  flying leads for connection to a fire alarm system. a red and black power in and red and black power out.
But as you can see in this picture it was wrongly done. You should never see wires hooked like this on a conventional fire alarm The correct way this job should have been done incoming power leads should have been hooked to one set of black and red  bell leads and then the resistor hooked to the second set. This insures that if one of the wires disconnects that a trouble signal is produced at the fire panel . with both wires hoked up to the resistor a wire could fall off or break and you would never know bell is not working. This is one of the reasons almost all fire alarm devices now use a terminal strip  instead of flying leads to encourage correct hook up. The instructions written and diagram  on how to hook up a Bell horn smoke or other device are always included with a   all you have to do is look at them  and do it correctly but again because a installer was lazy he puts lives in jeopardy.  If a fire alarm is properly hooked up  any single wire break should sound at the panel with in 30-90 seconds depending on age of panel . But how many times I can walk in pull wires off and no trouble. Very disturbing knowing how critical these systems are to saving lives. not just property.

                                                Top photo incorrect  bottom photo correct way to wire to have ready to attach to input leads

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