ECN Forum Forums General Topics of the Trade General Discussion Area Fire Alarm Pull Station

Is it somewhat accurate to say that "in general" fire alarm pull stations are wired in series and smoke detectors are wired in parallel for non-programmable systems?

[This message has been edited by Frank Cinker (edited 05-30-2005).]

[This message has been edited by Frank Cinker (edited 05-30-2005).]

No

Normally open non-addressable fire alarm devices such as smokes, pulls, heats etc. must be wired parallel.

Normally closed trouble indicators like tamper switches, pressure switches other panel trouble contacts etc. can be wired in series.

A series circuit can be considered "self-monitoring" because a break (accidental or malicious) will have the same effect as an alarm condition.

A parallel circuit can be made "monitor-able" by using a termination resistor, as long as the monitoring panel is set up for the purpose.

Larry


I have never seen a fire alarm system circuit treat an open as an alarm event.

A open condition in the circuit causes a trouble.

A closed condition in the circuit causes an alarm.

A circuit with the proper resistance results in a idle panel.

I was generalizing, as was Frank in the first post.

Some series-circuit systems do not see a difference between an alarm condition and a line break. Opening a circuit is opening a circuit.

"A open condition in the circuit causes a trouble."
In a parallel (N.O.) circuit with an end-of-line resistor, yes. In a N.C. circuit, that looks like a trip.

"A closed condition in the circuit causes an alarm."
In the aforementioned N.O. circuit, ditto. In a series circuit, a short is a bypass.

"A circuit with the proper resistance results in a idle panel."
Ditto again.

Back at ya!

[This message has been edited by Larry Fine (edited 05-30-2005).]