Manual stations, waterflow and supervisory devices

At Cartwright Distribution Center, the sprinkler system is the building's main fire detection. The warehouse roof is too high for smoke detectors to work well, so a fire is detected when a sprinkler opens and water flows past the waterflow switch on the riser. Luis, the sprinkler foreman, meets Sasha and Gerry at riser 2 with a bucket and a hose for the inspector's test connection. 'You test my switches, I test my valves,' he says. 'Between us, we prove the building will call the fire department.' This lesson covers manual stations, sprinkler waterflow switches and supervisory devices, and the coordination between fire alarm and sprinkler trades that their testing needs.

Manual stations

Manual stations, also called pull stations, let a person who sees a fire raise the alarm. Each one is inspected and tested every year.

• Inspection: the station is in its required location near the exit, visible, unobstructed, mounted at the right height, undamaged, and of the right type, such as a two-action station or one with a protective cover where the design calls for it.
• Testing: the station is operated as a person would operate it, using its key or reset tool where needed, and the correct alarm appears at the control unit with the right location. The station is then reset and checked to confirm it latched and restored properly.

Protective covers, the clear hinged covers that sound a local horn when lifted and are used to deter malicious alarms, are tested too: the cover must open freely and its local signal must sound, and the station beneath must still be operable. A cover whose hinge has seized or whose battery is dead keeps people from raising the alarm.

Stations in public areas suffer most. In a school or an apartment lobby, a station may be broken, missing its glass rod or reset tool, or have its cover glued shut. The inspection finds them, and the report lists them with their locations.

Waterflow switches

A waterflow switch, usually a vane type inserted into the sprinkler pipe or a pressure switch on a dry or deluge system, signals that water is flowing in the sprinkler system. It is the link between a sprinkler opening and the fire alarm. The test shows that flow equal to one sprinkler causes an alarm at the control unit within the required time.

Waterflow switches are tested by flowing water through the system's inspector's test connection, which is sized to flow about as much as one sprinkler. The time from opening the valve to the alarm at the control unit is measured; the switch's retard, a built-in delay that keeps pressure surges from causing false alarms, is part of that time. NFPA 72 requires the alarm signal within 90 seconds of waterflow equal to one sprinkler, and NFPA 72 and NFPA 25 both call for waterflow devices to be tested semiannually. The sprinkler side of the test is done to NFPA 25 by the sprinkler contractor or the owner's staff.

# Waterflow test times against the 90-second limit
limit_s = 90
tests = [("riser 1", 48), ("riser 2", 71), ("riser 3", 104), ("dock dry system", 58)]
for name, t in tests:
    print(f"{name:16s} alarm after {t:3d} s  {'OK' if t <= limit_s else 'TOO SLOW - check retard setting and switch'}")

riser 1          alarm after  48 s  OK
riser 2          alarm after  71 s  OK
riser 3          alarm after 104 s  TOO SLOW - check retard setting and switch
dock dry system  alarm after  58 s  OK

Riser 3 is too slow. Gerry checks the switch's retard dial and finds it set to its maximum. The setting is reduced to the value the design and the maker call for, and the test is repeated; the alarm now arrives in 52 seconds. Dry systems are different: the flow is detected by a pressure switch that operates when the dry pipe valve trips, and the test is part of the trip test the sprinkler contractor schedules.

The test also checks the outputs. On most systems a waterflow alarm sounds the building alarm, transmits to the monitoring station, and may start the fire pump, which the sprinkler contractor and the building operator watch for. At Cartwright the waterflow alarm also sounds an outside bell by the fire department connection; Sasha checks that it rings.

Valve supervisory switches

Sprinkler control valves must stay open. A valve supervisory switch, often called a tamper switch, signals when a valve is moved from its fully open position. The signal is a supervisory signal, not an alarm or a trouble, because a closed valve isn't a fire and isn't a fault in the fire alarm, but it means the sprinkler system may not work.

Each valve supervisory switch is tested by closing the valve and confirming that the supervisory signal appears at the control unit within two revolutions of the handwheel or when the valve has moved one-fifth of the way from fully open, as NFPA 72 requires, and that the signal restores only when the valve is fully open. NFPA 72 and NFPA 25 call for valve supervisory switches to be tested semiannually. The valve is operated by the sprinkler contractor or the owner's staff, and the valve is confirmed fully open, and sealed or locked where required, before the crew moves on.

The restoring check matters as much as the operating one. A switch that restores before the valve is fully open can let a valve sit half-closed with no signal at the panel. Luis turns each valve back slowly while Gerry watches the panel, and confirms the signal clears only at the last turn.

Other supervisory devices

Other conditions are supervised in the same way, each giving a supervisory signal when it is abnormal:

• low air pressure on a dry pipe sprinkler system, and high air pressure where the switch is fitted;
• low temperature in a dry pipe valve room or a building that could freeze;
• low water level in a gravity tank, or low pressure in a pressure tank;
• fire pump conditions, such as pump running, loss of a phase, phase reversal or the pump controller not in automatic;
• duct smoke detectors, where the design uses them to give a supervisory signal rather than an alarm.

Each is tested by producing the condition or, where that isn't practical, by operating the switch in the way the maker allows, and confirming the correct signal at the control unit and the monitoring station. Fire pump signals are tested during the fire pump's own test, with the building operator and the pump contractor.

# Classify each sprinkler-related signal as it should appear at the panel
signals = {"waterflow riser 2": "alarm", "valve VS-4 moved": "supervisory", "dry system low air": "supervisory",
           "fire pump running": "supervisory", "valve room low temperature": "supervisory",
           "switch wiring open": "trouble"}
received = {"waterflow riser 2": "alarm", "valve VS-4 moved": "supervisory", "dry system low air": "trouble",
            "fire pump running": "supervisory", "valve room low temperature": "supervisory", "switch wiring open": "trouble"}
for name, want in signals.items():
    got = received[name]
    print(f"{name:28s} expected {want:11s} got {got:11s} {'OK' if got == want else 'WRONG TYPE - reprogram and retest'}")

waterflow riser 2            expected alarm       got alarm       OK
valve VS-4 moved             expected supervisory got supervisory OK
dry system low air           expected supervisory got trouble     WRONG TYPE - reprogram and retest
fire pump running            expected supervisory got supervisory OK
valve room low temperature   expected supervisory got supervisory OK
switch wiring open           expected trouble     got trouble     OK

Coordinating with the sprinkler trade

Waterflow and supervisory testing involves two trades, two standards and the owner's staff, and it goes smoothly only if everyone agrees in advance who does what. The sprinkler contractor operates valves and test connections and inspects the sprinkler side; the fire alarm technician watches the control unit and confirms signals, times and outputs; the owner's staff or the building operator handles the fire pump and anything that affects the building's operation. The results go on both companies' reports.

Water damage is a real risk. The inspector's test connection must discharge to a drain that can take the flow; in winter, outdoor discharges can freeze. Gerry's crew never opens a sprinkler valve or test connection itself unless it is trained and authorized by the owner to do so; that is the sprinkler trade's work.

At the end of the test, every valve must be confirmed fully open, and the control unit must show no supervisory signals. A valve left closed after an inspection is one of the most dangerous mistakes in fire protection, because the building looks protected and isn't. Bramwell's checklist ends with a walk past every valve with the sprinkler foreman, and a photo of each one open.

Manual stations in special settings

In some buildings manual stations are deliberately not where the public can reach them. In psychiatric units and some correctional settings, stations are placed where staff can operate them, sometimes key-operated, so that patients or detainees can't misuse them. In buildings where malicious alarms have been a problem, the authority may accept stations with protective covers. The inspection checks that the stations are where the design and the approval put them, and that staff know how to use them; a key-operated station whose key nobody on shift can find is effectively not there.

Sprinkler supervision and the monitoring station

Sprinkler signals are among the most important the monitoring station receives, because a waterflow alarm is often the first sign of a fire in a sprinklered building, and a valve supervisory signal is often the only sign that the sprinkler system has been shut off. During the tests, the technician confirms with the station that each waterflow alarm arrives as an alarm and each valve signal as a supervisory signal, and that the station's response for each is correct: dispatching the fire department for a waterflow, and calling the building contact for a supervisory signal. At Cartwright, Luis also asks the station to confirm the time it received each signal, so that the flow-to-station time can be recorded alongside the flow-to-panel time.

# Flow-to-panel and flow-to-station times for each riser
tests = [("riser 1", 48, 63), ("riser 2", 71, 84), ("riser 3 (after adjustment)", 52, 70), ("dock dry system", 58, 75)]
for name, panel_s, station_s in tests:
    print(f"{name:28s} panel {panel_s:3d} s  station {station_s:3d} s  transmission {station_s - panel_s:3d} s")

riser 1                      panel  48 s  station  63 s  transmission  15 s
riser 2                      panel  71 s  station  84 s  transmission  13 s
riser 3 (after adjustment)   panel  52 s  station  70 s  transmission  18 s
dock dry system              panel  58 s  station  75 s  transmission  17 s

The station's response is tested as well as its receipt. Gerry asks the operator, after the waterflow test, what the station would have done if this had not been a test, and checks that the building contact list the station holds is current: an old number for a building manager who left two years ago means a supervisory signal at night reaches nobody.