Waterflow Alarm Delay and Misprogrammed Tamper
A 180,000 ft² distribution warehouse has a wet-pipe sprinkler system and a new fire alarm panel monitoring the dock expansion riser. The riser has a 6-in. check valve, a vane-type waterflow switch, and a tamper switch on the main control valve. At the acceptance test, the inspector opens the inspector’s test valve. The panel immediately displays a supervisory signal for the control valve tamper, then displays the waterflow condition 2 minutes 40 seconds later as a supervisory event. The contractor says the waterflow switch has a built-in 90-second retard and that the delay is normal. The inspector also finds the waterflow switch paddle installed against the direction of flow and the tamper switch landed on an alarm-initiating module rather than a supervisory module. The building is occupied and the sprinkler system is in service.
1. Identify the code and programming deficiencies in the waterflow and tamper monitoring.
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Waterflow is an alarm condition, not a supervisory condition. NFPA 72 requires a waterflow switch to initiate an alarm within 90 seconds of flow; 2 minutes 40 seconds is late. The vane installed backward can stick or under-travel, so even a correct retard setting is unreliable. The tamper switch is correctly a supervisory function, but it is landed on an alarm-initiating module, so the panel annunciates the wrong priority and may confuse responders. A built-in retard may be adjustable; it must not exceed 90 seconds and must be verified by test. I would also verify that the flow switch is on the system side of the check valve so it sees flow from the inspector’s test valve.
2. What corrective work and retest sequence should be required?
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Reorient the paddle to the direction of flow, verify that the switch is on the system side of the check valve, and correct the wiring and panel programming so waterflow is an alarm and tamper is supervisory. Set the retard to no more than 90 seconds and test at the inspector’s test valve and main drain, recording the time from flow to alarm. Notify the monitoring company of the signal changes. Retest with the AHJ present and update the as-builts and sequence of operations. Do not accept a verbal explanation that the delay is normal when the measured time exceeds the code limit.
3. How should the building be protected while the system is impaired?
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Follow the impairment procedure before taking the sprinkler or fire alarm system out of service: notify the AHJ and monitoring company, tag the control valve, and post a fire watch if the AHJ requires it for the affected area. The building is occupied, so an unprotected power-down or a riser out of service is not a routine maintenance item. Restore the system, verify signals at the panel and central station, and close the impairment record before leaving the site.