How many duct detectors are allowed on a single zone?
The maximum number of flow switches allowed is five, but are there any requirements or restrictions for duct detectors beyond the equipment capability?
Thanks in advance.
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11/1/2022 08:52:36 am
As an AHJ, it’s per unit, you cannot have us guessing which RTU it is. We only require them to be an alarm in critical facilities and healthcare occupancies (I realize that can be controversial). But I can’t imagine having to get on the roof and guessing from one of five or even four units being in alarm.
11/1/2022 11:01:10 am
i totally agree with. not only are you dealing with possible false alarms, but you also have to monitor the trouble contacts as well. trying to figure out a ground fault or open circuit can be a HUGE HEADACHE!
11/1/2022 09:40:04 am
NFPA 72 states maximum size of zone is 22,500 sq ft. Only limitiations for amount of devices on zones is for waterflow and supervisory signals for sprinkler systems in protected premise. Assuming this is a conventional system, if you are using two wire duct detectors then you are going to be limited on how many you can use because of the voltage draw. If you are using four wire duct detectors then you are only monitoring a set of conacts which will drastically change the amount of detectors you can monitor. When it comes to identification of which duct detector is in alarm, that is covered by NFPA 72 requirement for remote indicators for smoke / duct detecors in concealed locations. If this is an addressable system the same rules apply. Theoretically you could use one monitor module to supervise multiple duct detectors but doesn't make practical sense.
What one person means by the word “Zone” is one definition; what another person means by the word “Zone” is often a different definition.
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