Sprinkler Flow Switch and Detector Spacing in a Warehouse
A 40 ft (12.2 m) high warehouse has a wet sprinkler system and an addressable fire alarm. The contractor installs a sprinkler flow switch on each riser and connects it to a monitor module. During acceptance testing, the AHJ observes that the flow switch operates only after 90 seconds of steady flow, and that the alarm signal is annunciated as a supervisory signal at the panel. The contractor argues that because the building is sprinklered, no heat detectors are needed and the flow switch is a sufficient waterflow alarm. The AHJ also notes that the panel's waterflow zone is shared with a tamper switch on the same module.
1. Identify the code problems with the waterflow arrangement.
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Several issues. (1) Signal type: waterflow from a sprinkler system is an alarm signal, not supervisory. Tamper switches are supervisory. Sharing one monitor module and annunciating waterflow as supervisory misclassifies the signal and can delay response. The module/zone must be arranged so waterflow annunciates as alarm and tamper as supervisory, on separate addresses where the panel supports it.
(2) Timing: waterflow switches typically must operate within a specified time (commonly 90 seconds or less) after steady flow; the observed 90 seconds is at the edge and should be verified against the listed device and the adopted code. The AHJ should require documentation of the device's listed response time and a retest.
(3) The contractor's premise is wrong: a sprinkler system does not automatically eliminate detection requirements. Detection may still be required by the building code, occupancy, or the system's design basis; the flow switch is a waterflow alarm, not a substitute for area detection where detection is required.
2. What acceptance test evidence should the AHJ require before signing off?
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A written record showing: each flow switch tested by opening the inspector's test connection (or equivalent) with time-to-alarm recorded; confirmation that waterflow annunciates as alarm and tamper as supervisory on distinct, correctly labeled points; the device listing and installation instructions; the sequence of operations; and a retest after any rewiring. The record should identify the tester, date, device address, and observed result. Any deviation should be documented as a deficiency with a correction date before final acceptance.