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[Fire Alarm] Class "A" no return

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    [Fire Alarm] Class "A" no return

    I'm running a fire alarm job. The company I work for is subbed to the Fire System designers. I'm being told to install the system as if it were a class "A" system that just simply isn't a loop or like one giant Class "B" with no t-taps. The specs clearly state we are to install as a class B. It is an intelligent system.

    I'll install it however the designer wants but, a straight run with no t-taps and no return loop seems ridiculously unsafe. Every single point in that system directly affects every single item down the line. Has anyone ever heard of a Class "A" no return system?

    This is in a federal facility so there is no fire department or fire marshal to inspect the system or approve the drawings. The facility is used for patient care.

    #2
    Originally posted by i4c8e9 View Post
    I'm running a fire alarm job. The company I work for is subbed to the Fire System designers. I'm being told to install the system as if it were a class "A" system that just simply isn't a loop or like one giant Class "B" with no t-taps. The specs clearly state we are to install as a class B. It is an intelligent system.

    I'll install it however the designer wants but, a straight run with no t-taps and no return loop seems ridiculously unsafe. Every single point in that system directly affects every single item down the line. Has anyone ever heard of a Class "A" no return system?

    This is in a federal facility so there is no fire department or fire marshal to inspect the system or approve the drawings. The facility is used for patient care.
    Class B (actually Style 4) with no T-taps is generally how I like to design the signal line circuit (SLC) if Class A (actually Style 6 or 7) isn't called for. If the wire routing is completely up to you, you could always run the Class B in a giant loop and end it back near the panel. Later if someone says "Hey, this should really be Class A" you can convert with little problem. Of course, every install is different and maybe you can't do as I suggest.

    I'm a little unsure why you think this is unsafe. An addressable system reports the status of every device so as soon as there is an issue it will report to the panel. Absent repeated risk of mechanical damage, I don't see an issue.

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      #3
      Thanks for your response. I think it is unsafe because every single point in that system is a point of failure for every point down the line from it. A properly t-tapped system should have t-taps all along the main trunk. If any device or room has issues, if a random contractor damages the wires, if an actual fire occurs in a room, the rest of the system is active and working properly.

      Hypothetical situation time, lets say you have a hallway that is 300' long and off of this hallway there are rooms that are 20' x 20'. We place the smoke heads in the center of each room. We have a total of 30 rooms and a 300' hallway. Your system would require 900' of cable with 900' of potential failure for everything downline. Properly t-tapped, that system would only require 600' of cable and only 300' of that would have the potential to cause everything down stream to fail.

      That's how it's always been explained to me. The last NICET course I took just after the 2013 code came out was taught by one of the guys from NFPA, I can't remember his name. He also said this is the proper way to install a system, the safest system would be a cable going to every device but, that isn't really feasible.

      I typically design my routing to follow corridors then t-tap off into rooms. I had never utilized or come across a class B no t-tap system.

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        #4
        But, although the operation of the system might be compromised during any repairs, the whole addressable system is supervised and a disabling fault would no go unnoticed.

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          #5
          T tapping.

          [QUOTE=i4c8e9;1589378]Thanks for your respo nse. I think it is unsafe because every single point in that system is a point of failure for every point down the line from it. A properly t-tapped system should have t-taps all along the main trunk. If any device or room has issues, if a random contractor damages the wires, if an actual fire occurs in a room, the rest of the system is active and working properly.

          Hypothetical situation time, lets say you have a hallway that is 300' long and off of this hallway there are rooms that are 20' x 20'. We place the smoke heads in the center of each room. We have a total of 30 rooms and a 300' hallway. Your system would require 900' of cable with 900' of potential failure for everything downline. Properly t-tapped, that system would only require 600' of cable and only 300' of that would have the potential to cause everything down stream to fail.

          That's how it's always been explained to me. The last NICET course I took just after the 2013 code came out was taught by one of the guys from NFPA, I can't remember his name. He also said this is the proper way to install a system, the safest system would be a cable going to every device but, that isn't really feasible.

          I typically design my routing to follow corridors then t-tap off into rooms. I had never utilized or come across a class B no t-tap system.
          If you ever did any troubleshooting on a system you did not install you won't like t-tapping. If your worried about your slc getting damaged use ISO modules or bases. They will isolate the fault and you won't lose the rest of the devices. A lot of federal agencies use the UFC code and that requires Class A.

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            #6
            Screw t-tapping. That is just bogus.

            Glad our job specs forbid it.

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              #7
              Originally posted by iwire View Post
              Screw t-tapping. That is just bogus.

              Glad our job specs forbid it.


              So if it's addessable almost all of those panels have a class A SLC return built into the panel, just hook it up that way. You would never get crap for doing that, just don't tell anyone you're doing it so you don't have to explain.

              Comment


                #8
                Originally posted by nhfire77 View Post


                So if it's addessable almost all of those panels have a class A SLC return built into the panel, just hook it up that way. You would never get crap for doing that, just don't tell anyone you're doing it so you don't have to explain.
                Back in the 80s I was doing a lot of non-addressable systems in condos. They would be class B and the panels did not have class A capability.

                I still brought the EOL back to the panel and installed the resistor there. It just helps me troubleshoot when the time comes.

                Comment


                  #9
                  Originally posted by iwire View Post
                  Back in the 80s I was doing a lot of non-addressable systems in condos. They would be class B and the panels did not have class A capability.

                  I still brought the EOL back to the panel and installed the resistor there. It just helps me troubleshoot when the time comes.
                  And we all thank you for it. I helped a buddy on the 10th floor a resi high rise, opening the walls was going to be.... a huge ordeal. It was just like that and some how a ground fault developed on a circuit between two devices. Now, there are 2 10th floor west zones, but the ground fault is gone

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