Fireboy Automatic Shutdown Device — 2026 Installation, Wiring & Troubleshooting Guide

What does a Fireboy automatic shutdown device do?

When a fixed fire suppression cylinder discharges in an engine room, the running engines, generators, and ventilation blowers act like a vacuum cleaner — they pull the Novec 1230 or FM-200 agent out of the compartment in seconds. A Fireboy automatic shutdown device (model ASD or MA2 series) prevents that by opening the engine keyswitch and blower circuits the moment the cylinder's internal pressure switch trips. The result: the agent stays in the compartment long enough to reach the 7% concentration the system was designed for, and the fire is actually extinguished instead of momentarily smothered.

Under USCG 46 CFR 34.25 and ABYC A-4, any inspected vessel with a fixed clean-agent system in a machinery space must shut down the air supply on discharge. For recreational vessels the rule is not always enforced dockside, but every major insurer in Florida — including Travelers Yacht, Markel, and Chubb — now requires a documented shutdown loop as a condition of binding.

Where does the shutdown device install on the vessel?

The shutdown module mounts in a dry, vibration-isolated location within 4 feet of the helm or main DC panel — never inside the engine room itself, since that's the compartment being protected. The most common locations on a 35–65 ft yacht are behind the helm dash, inside the navigation electronics bay, or on the bulkhead beside the main 12V distribution panel. Mount it with the terminals facing down so any condensation drips off the wiring rather than into the contacts.

• Mount within 4 ft of helm or DC panel, outside the protected compartment
• Terminals face down, screws torqued to 12 in-lb
• Minimum 2 in clearance from heat sources and inverter chargers
• Label with discharge date and last functional test date

How do you wire a Fireboy shutdown device step-by-step?

1. Disconnect house and engine batteries at the master switches before any work begins.
2. Run 14 AWG marine-tinned duplex from the Fireboy cylinder's pressure switch (PS terminals) to the shutdown module's INPUT terminals. Keep this run under 25 ft to avoid voltage drop on trip.
3. Connect the module's POWER terminal to a dedicated 5 A breaker on the always-hot bus — not the keyswitch bus, or the device will lose memory at every key-off.
4. Tie each engine's keyswitch ground (the wire that grounds the ECU when keyed off) into a NORMALLY-CLOSED relay output. On discharge, the relay opens and the engine sees a key-off command.
5. Connect the blower kill in parallel through a second NC relay channel.
6. Add a manual override toggle on the helm, fused at 1 A, so the captain can re-energize systems after a confirmed false trip.
7. Bench-test by jumping the PS terminals at the helm — every engine must die within 2 seconds and blowers must stop.
8. Document the test with date, technician, and outcome on the system log, then affix a new tag to the cylinder.

What wire gauge and fuse rating should you use?

How do you test the shutdown function safely?

Never test by actually discharging a cylinder — that's a $500+ refill and a 24-hour out-of-service window. Instead, use the bench-test jumper method: with engines idling at the dock, place a small jumper across the pressure switch terminals at the cylinder head. Every protected engine and blower must shut down within 2 seconds. Remove the jumper, reset the manual override, and verify normal restart. Repeat with the second helm station if equipped. Log the test result in the vessel's fire-system binder and on the Fireboy tag.

Why isn't my Fireboy shutdown killing the engine?

1. Check the 5 A supply breaker — a nuisance trip kills the whole module.
2. Measure 12V across the module power terminals; if zero, the always-hot bus is broken upstream.
3. Verify polarity at the relay coil — reversed leads stop the NC contact from opening.
4. Inspect the pressure-switch terminals at the cylinder for green corrosion (very common in Miami-Dade salt-air slips).
5. Confirm the engine ECU keyswitch ground actually grounds the ECU — some Volvo Penta D-series require an additional interface relay.
6. Re-run the bench-test jumper to isolate whether the failure is in the input side (pressure switch wiring) or output side (engine kill loop).

When should you replace the shutdown module?

Fireboy ASD modules carry a 7-year service life from date of manufacture, stamped on the back label. Replace earlier if: the module has experienced an actual discharge event, the relay contacts show pitting on inspection, the unit has been submerged or exposed to standing water, or the vessel has switched suppression brands (a Sea-Fire NMD-style pressure switch is not always compatible with a Fireboy ASD coil voltage and vice versa).

How much does installation cost in South Florida?

Standard dockside installation runs $385–$650 for a single-engine vessel and $525–$895 for twin-engine, including the shutdown module, wiring, fuses, manual override toggle, bench test, and updated tag. Travel is included within the Miami-Dade and Broward corridor; Palm Beach and Monroe routes add a flat $75. Bundle with annual certification of the existing Novec or FM-200 cylinder and the second-engine surcharge is waived.

Documentation an inspector will ask for

• Wiring diagram showing relay outputs to each engine and blower
• Bench-test log with date, technician, and pass/fail per circuit
• Module manufacture date and installation date
• Compatibility statement matching the suppression cylinder model
• Manual override toggle location noted on the vessel's fire plan