Within what time limit shall a sprinkler waterflow alarm-initiating device activate?

NFPA 72 defines a time requirement for how quickly a waterflow switch must respond when a sprinkler system activates. The waterflow initiating device (typically a paddle-type switch) must send an alarmwithin 90 seconds, but the system may have aretard delayof up to90 seconds, making the total allowable time120 seconds.

NFPA 72 (2022), Section 17.13.2:

“Waterflow alarm-initiating devices shall be set to operate within 90 seconds after the flow begins. Retard devices shall not delay the signal more than an additional 90 seconds.”

Thus, the maximumtotal activation timeis:

90 seconds operation + 90 seconds retard =120 seconds max

Correct answer: C. 120 seconds

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