Six Sensitivity Failures, Two Dead Duct Detectors, One Weak Battery
You are performing the annual test on a twelve-year-old addressable system serving a nine-floor office tower: 84 spot smoke detectors, 9 duct detectors on packaged rooftop units, 12 waterflow switches, and one 24 V FACP whose four batteries are now five years old. Results: 6 detectors out of sensitivity (4 too insensitive, 2 too sensitive); 2 duct detectors alarm on magnet test but not when aerosol is introduced at the sampling tube with the AHU running; a waterflow switch alarms 3 min 40 s after the inspector's test valve is opened; the batteries fall below 20.4 V within 20 minutes of a load test; the last notification appliance on one floor measures 19.4 V with all appliances sounding. The building manager wants the report to say "system operational."
1. Which findings are impairments, and what immediate action does each require?
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Rank by what the system can still do.
Battery failure and 19.4 V at the last appliance are impairments of secondary power and of notification. On loss of AC the panel dies within minutes, and under fire conditions the end-of-line appliances may not sound at all - NFPA 72 expects notification appliances to function at 85% of rated voltage, roughly 20.4 V on a 24 V system, and 19.4 V is below that. Both require immediate written notice to the owner, a documented mitigation recommendation (fire watch, occupancy limits, or accelerated repair), and notification to the AHJ per the owner's impairment procedure.
Duct detectors that fail the smoke test are a partial impairment of HVAC shutdown and supervisory signaling: the unit will not shut down on smoke. Correct promptly.
Six detectors out of sensitivity degrade detection but do not disable the system; they need correction but do not by themselves justify a fire watch.
Nothing gets marked "operational" because a magnet test or a reset made it look functional.
2. What is the likely cause of the duct detector and waterflow results, and how do you correct and record them?
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Duct detectors that respond to the magnet but not to aerosol at the sampling tube, in order of likelihood: no airflow during the test (fan off - the unit must be running), sampling tubes cut wrong or reversed, tubes not extending into the airstream, tubes packed with dust, or smoke introduced outside the sampling inlet. Correct the installation, retest with the fan running, and verify shutdown at the unit.
The 3 min 40 s waterflow alarm is a retard or paddle problem. NFPA 72 expects a waterflow alarm within 90 seconds of sustained flow, so check the retard setting, the paddle-to-pipe-wall clearance, and the vane length against the pipe size. Correct, then retest with a stopwatch and record the actual time.
Record device, location, deficiency, correction, retest result, date, and initials on the inspection and testing record. Carry anything unresolved to the owner in writing with a correction deadline - an unrecorded verbal warning is worth nothing when the file is pulled after a loss.
3. The owner asks: "Can't we just swap the batteries and deal with the rest next year?"
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No, and put the refusal in writing.
Battery replacement is easy but is not a swap: a correct replacement includes a calculated load check (24-hour standby followed by 5 minutes of alarm for a protected-premises system, with end-of-life derating applied) and a measured load test on the new set. NAC voltage is a separate defect - 19.4 V at the last appliance with the whole floor sounding points to undersized conductors, too many appliances on the circuit, or a poor connection, and none of those are fixed by new batteries.
Sensitivity failures are a required test item, and six out of 84 is a pattern that suggests widespread contamination - construction dust in a building of this age - meaning many more detectors are near the edge than failed. Sequence realistically: batteries and the NAC circuit investigation first (days), duct detectors when the AHU schedule allows, then sensitivity testing of the full population once the contamination source is corrected. Put acceptance of the residual risk in the owner's hands, in writing, with your recommendation attached.