Home Forums DSC Technical Questions Wire gauge and number of smoke alarms

This topic contains 9 replies, has 3 voices, and was last updated by  Tim 6 years, 8 months ago.

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  • #5152

    Tim
    Member

    I set up an DSC Power 832 last W/E.  It would have been impossible without frequently checking this site.  I used 22 gauge wire.  I'm going to install 2-wire smoke alarms this W/E.  Am I reading correctly that they should have 18 gauge wire?  Should I be using thicker wire from the transformer to the board or from the board to the siren?  How many of the 
    2-wire detectors can I connect together?  The info with the FSA-210 detectors mention a Polarity Reversing Module.  Is this on the board or some extra hardware which I should purchase?  Much thanks in advance.
    - Tim   

    #28270

    Hi Tim, welcome to the forum.

          22 gauge wire is the accepted standard for burglary zones and data transmission (keybus). Fire warning systems, being life safety devices, have higher standards. You should use 18 gauge wire for the fire circuit, and if you really want to do it properly, you'll use 18 gauge FPLR (fire-rated) wire. Keep in mind that local codes can vary, and you should check with your AHJ (Authority Having Jurisdiction) to make sure you're in compliance.

    Wire from the transformer to the board and from the board to the siren should be 18 gauge as well, though it need not be fire-rated.

    Couldn't find an answer for that DSC smoke, but System Sensor 2-wire smokes will allow 25 on the 832 fire loop, so that should give you some idea.

    The Polarity Reversing Module is an extra piece of hardware that causes all the smokes on the loop to sound if one trips. This only applies, obviously, to smokes with built-in sounders.

                                                                –Ken

    #28289

    Tim
    Member

    Much thanks for the help.
    - Tim

    #28312

    gsti
    Member

    Hi Tim
    To use the DSC smokes with the sounders, and to have all the sounders working together in an alarm event, you will need another module that hooks up to the keybus. The DSC smokes will then be connected to this module. In alarm the module will reverse the polarity on the smoke loop and make all the smoke sounders sound together.

    I prefer the System Sensor i3 2WTAB smokes used with the System Sensor RRS reversing relay module. Don't forget that the end of line resistor for the 2wire smokes is different than the 4wire.

    #28318

    Tim
    Member

    Thanks.  I have one of those polarity reverser coming and I will post if things aren't straight forward.  I was wondering how long the smokes last.  I just bought 3 smokes at $57 each from a retailer in Ottawa and another 3 identical ones from an EBAY  store in Florida for $35 each which haven't arrived yet.  The ones from Ottawa have a date on them from a few months ago and I don't know the date on the ones from EBAY.  Do smokes have a certain operating life after which they need to be replaced?  Anyone?  Thanks again.
    - Tim   

    #28321

    Tim,

        Conventional wisdom is that smoke detectors have a useful life span of ten years, at which time they should be replaced, even if they test OK.

                                                            –Ken

    #28340

    Tim
    Member

    Thanks again, Ken.
    I can see where all of that Karma comes from.
    - Tim

    #28457

    Tim
    Member

    I have my PRM-2W and would like to check the wiring.  There are 10 terminals.  I am most unsure about GND and EOLR.  Here is the list:
    +12  to  Aux + on main panel
    GND  to ? Aux – on main panel or EGND on main panel
    T1 to nothing as I'm only going to trigger as a Bell Circuit Follower
    T2  to  Bell – on main panel
    P+  to  + on smokes
    P-  to  – on smokes
    C  to  C on main panel
    NO  to  Z1 on main panel – zone attributes
    EOLR
    EOLR  -  wiring diagram shows a resister across these terminals but doesn't say how many ohms.
    Thanks again.
    - Tim

    #28476

    Tim,

          You want the +12 and GND to go to AUX+ and AUX-, not EGND. The EGND terminal is for connecting the panel to an earth ground.
         

    #28505

    Tim
    Member

    Hi Ken:
    I wired it the way you suggested and it works perfectly.
    Much thanks.
    - Tim

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