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Thread: help with adding device to FA system.

  1. #11
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    Quote Originally Posted by electrofelon View Post
    Next question. What is the procedure for disconnecting or interrupting a NAC or SLC loop? Will this set off the system or just give some sort of fault message at the control panel? What about taking the SD off its base?
    Check in with your point-of-contact (POC) and let him/her know you will be working on the fire alarm system so they can make the appropriate announcements to the occupants. If required, contact the fire department or AHJ and tell them you will be taking the panel off line. Contact, or have your POC contact, the central station (if there is one) and have the panel put on test.

    If you short the NAC loop or open it you'll get a trouble message on the panel. If you remove a smoke detector you'll get a trouble message at the panel. If you short the SLC loop, you'll get a trouble message on the panel AND you'll bring down every device on the loop. If you don't have an addressable panel and short the indicating device circuit (IDC), which is the equivalent of the SLC, you'll get an alarm. Back in the day, if I was lifting a loop I'd do it one wire at a time and tape the end or put a wire nut on it to prevent shorts.

    Once your are done, make sure the panel is clean and reverse the steps in paragraph one.

  2. #12
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    You probably aren't going to like this answer. Right off the top, the picture you included shows Simplex. Simplex is a proprietary system for which you will have to get parts from them if they need to be new and have a factory warranty. Second you give no indication of the year the system comes from. Way back all systems were what we refer to as conventional. Then around the 90's systems became "addressable' this referred only to the signalling devices like smoke detectors, just recently Simplex has been pushing addressable notification devices, (horns and strobes).

    The short answer for you is that you just need to bite the bullet, call Simplex. You can do parts and smarts install where they just provide the device and programming, but they will also walk you through the installation.

    Regarding other questions:
    The reason smoke detectors don't generally require tandem wiring is because they each have a unique digital address so the panel "knows" when one gets disconnected. NAC circuits require wiring such that they are hooked up lie a ladder with a resistor at the end. If a wire comes loose or shorts the resistance changes and the panel detects it. If a "branch" was sent off, then those wires could come loose and have no effect on the resistor, hence not legal.

    In the old days, smoke detectors were hooked up similarly. This is still an acceptable system, just not often economical so usually not done any more.


    I know what I don't know, and I know where to go to find it!

  3. #13
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    Quote Originally Posted by gadfly56 View Post
    Check in with your point-of-contact (POC) and let him/her know you will be working on the fire alarm system so they can make the appropriate announcements to the occupants. If required, contact the fire department or AHJ and tell them you will be taking the panel off line. Contact, or have your POC contact, the central station (if there is one) and have the panel put on test.

    If you short the NAC loop or open it you'll get a trouble message on the panel. If you remove a smoke detector you'll get a trouble message at the panel. If you short the SLC loop, you'll get a trouble message on the panel AND you'll bring down every device on the loop. If you don't have an addressable panel and short the indicating device circuit (IDC), which is the equivalent of the SLC, you'll get an alarm. Back in the day, if I was lifting a loop I'd do it one wire at a time and tape the end or put a wire nut on it to prevent shorts.

    Once your are done, make sure the panel is clean and reverse the steps in paragraph one.
    Sort of good advice, but not if one isn't comfortable with fire alarm. For example, in a high rise in Oakland which had a Simplex system in the 1990's there was a ground fault that couldn't be found. Because of that, a short of the positive wire on a NAC circuit would send the entire 12 floors in to alarm. That is the moment that electrofan will wish he had just called Simplex first.


    I know what I don't know, and I know where to go to find it!

  4. #14
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    Quote Originally Posted by Strathead View Post
    Sort of good advice, but not if one isn't comfortable with fire alarm. For example, in a high rise in Oakland which had a Simplex system in the 1990's there was a ground fault that couldn't be found. Because of that, a short of the positive wire on a NAC circuit would send the entire 12 floors in to alarm. That is the moment that electrofan will wish he had just called Simplex first.
    First, I am under the impression that this is a small system and only the NAC is under discussion for modification.

    Second, I do not see how shorting the NAC can cause them to actually ring. For one thing, you have to reverse polarity to get the horns to rock and roll, for another you shouldn't have more than one floor on a NAC.

  5. #15
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    Quote Originally Posted by gadfly56 View Post
    First, I am under the impression that this is a small system and only the NAC is under discussion for modification.

    Second, I do not see how shorting the NAC can cause them to actually ring. For one thing, you have to reverse polarity to get the horns to rock and roll, for another you shouldn't have more than one floor on a NAC.
    it isn't surprising that you don't "see" how ground faulting (not shorting) the NAC can cause an alarm. The best we could figure, the positive ground fault caused a voltage in the conventional initiating circuit (this was pre SLC) that led the panel to believe an initiating circuit had gone in to alarm. For further reference, the ground fault actually ended up being in the fireman's communication jacks int he elevator, but was intermittent. I personally remover resoldered and replaced all 12 floor's jacks. I very good solderer. I am nuclear submarine trained in soldering. The problem finally went away.

    Also, I believe the OP was asking about a NAC and a smoke detector.


    I know what I don't know, and I know where to go to find it!

  6. #16
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    Thanks guys for the crash course in FA. To clarify I am adding one strobe and one SD. Nothing is real high stakes here, its in a boiler room that is off line now, not like an apartment building or anything.

    Ill be going to tomorrow and Ill call simplex too.
    Ethan Brush - East West Electric. NY, WA. MA

    "You can't generalize"

  7. #17
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    Quote Originally Posted by electrofelon View Post
    Thanks guys for the crash course in FA. To clarify I am adding one strobe and one SD. Nothing is real high stakes here, its in a boiler room that is off line now, not like an apartment building or anything.

    Ill be going to tomorrow and Ill call simplex too.
    Not to add to your woes, but if the device is going in a boiler room you may want to confirm that the ambient temperature doesn't exceed 100°F. This is the operating temperature limit for smoke detectors, whether conventional or addressable based on the UL listing, although Simplex says that the operating limit can be up to 122°F. If the heat detector is addressable it has the same limits. See the cut sheets I linked to up-thread. In addition, it is typical to place heat detectors in a boiler room in case you have any smoke as a result of startup or maintenance procedures.

  8. #18
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    Quote Originally Posted by electrofelon View Post
    Thanks guys for the crash course in FA. To clarify I am adding one strobe and one SD. Nothing is real high stakes here, its in a boiler room that is off line now, not like an apartment building or anything.

    Ill be going to tomorrow and Ill call simplex too.
    I always design the boiler room with a Heat Detector instead of a Smoke Detector. It really help if we know the model of the FACP

    John.
    My Journey Towards NICET certification
    Fire Alarm Design Services

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