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Master alarm indicators signal wires: Solid wire vs. stranded wire pairs.

  • Monday, January 27, 2020 9:26 PM
    Message # 8696715

    The question has risen of using solid wires for the 18 - 22 gauge twisted shielded pairs for the master alarm panel signal wires.

    The only thing I find in the NFPA 99, 2018 is the verbiage referencing how the wires are to be run (protected, cable trays, conduit, etc.).

    The only area where wiring specifically come in to NFPA 99, 2018 is the section stating all medical gas components shall be installed per manufacturer's installation instructions.

    Good, I buy that. Then, I see a manufacturer's instructions and the issue of stranded vs. solid is not there!


    What am I missing here??????


    I had this thought stranded wires would be best due to the nature of the alarms are all components monitored are Normally Closed indicators. 


    Wouldn't solid wire, if broken, be an issue? Or, if the solid breaks then a stranded wire would break also give the same circumstances?


    I have seen solid wire cause errant alarms.


    Please enlighten me to what I am missing or am I much ado about nothing!!???

  • Tuesday, January 28, 2020 6:18 AM
    Reply # 8697059 on 8696715

    Carsten,

    The type of wire is a manufacturer - specific issue and of no interest to NFPA at all.  You are correct in that stranded twisted pair is probably more resistant to the vicissitudes of life (on a construction site particularly), but whether the alarm can use one or the other, or requires one or the other, is pure electronics design - which is of course down to the manufacturer. 

  • Tuesday, January 28, 2020 9:53 AM
    Reply # 8697434 on 8696715

    It really doesn’t matter. A solid wire can carry a better current.

  • Thursday, January 30, 2020 6:51 AM
    Reply # 8702239 on 8696715
    Al Moon (Administrator)

    I did a fast look at all the major manufactures of medical gas alarms.

    Allied, Amico, Beacon, Ohio & Tri Tech.

    In their O&M's and all have come type of verbiage concerning the type and gauge of wire. The general statement was shielded twisted pair from 18 to 24 gauge.



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