Hood-fire interlock: NFPA 96 critical scope.
Hood-fire interlock systems integrate fire suppression activation with cooking equipment electrical shutdown per NFPA 96. Inspection-critical scope.
By Steven Lockhart · Reviewed by Alex Towery, C-10 #989290
Updated 2026-06-16
Hood-fire interlock implementation: fire suppression panel (Ansul, Range Guard, Pyro-Chem) provides shutdown signal on activation. Shunt-trip breakers on all cooking equipment circuits receive signal and trip within required timing. Hood ventilation continues operating (clearing smoke). Manual reset required after activation. Fire marshal witness required at acceptance testing. Critical scope for restaurant occupancy approval.
01How the interlock actually works.
Fire suppression panel (typically pre-engineered wet chemical or dry chemical system installed by suppression contractor) monitors hood for fire conditions. On detection (manual pull station or automatic fusible link activation), suppression discharges chemical and simultaneously activates electrical shutdown signal. Signal routes to shunt-trip control units on cooking equipment circuits.
Shunt-trip breakers receive the shutdown signal and physically trip the breaker within milliseconds — cutting power to all cooking equipment. Standard non-shunt breakers can't be remotely tripped; shunt-trip is required for this application. Ventilation circuits (hood exhaust and makeup air) are intentionally NOT included in the shutdown — they continue running to clear smoke after suppression activation.
02Three implementation details that matter.
Shunt-trip vs standard breakers
Cooking equipment circuits must use shunt-trip breakers (Square D QO-SHU, Eaton BR-SHU, equivalent). Cost premium $80-$200 per breaker vs standard. Standard breakers can't accept remote trip signal — shunt-trip is required for code compliance.
Ventilation isolation from shutdown
Hood exhaust fan and makeup air fan circuits NOT included in shunt-trip shutdown. Ventilation must continue running after suppression activation to clear smoke. Common implementation error: including ventilation in shutdown panel. Acceptance testing verifies.
Manual reset after activation
After fire suppression activation, all cooking equipment circuits remain de-energized until manually reset at panel. Code requires this — prevents reigniting fire after suppression discharge. Reset procedure documented in panel labeling.
03Acceptance testing process.
Fire marshal witnesses acceptance testing as part of restaurant final inspection. Test procedure: manual pull station activation simulates fire condition, suppression panel sends shutdown signal (without actual chemical discharge for testing purposes), shunt-trip breakers trip within required timing (typically 10 seconds maximum), all cooking equipment circuits verified de-energized, ventilation circuits verified still operating, manual reset confirmed.
Failed acceptance tests delay restaurant opening. Common failures: ventilation incorrectly included in shutdown (won't pass — must continue running), shunt-trip timing exceeds maximum (electrical connection issue or wrong breaker model), interlock connections to suppression panel incorrect (signal not received). Quality installation prevents these issues; pre-test verification minimizes risk of failed acceptance.
Common questions.
Who installs the suppression system?
Fire suppression contractor (typically Ansul-certified, Range Guard-certified, or Pyro-Chem-certified). Coordinates with electrical contractor on shunt-trip interface. Suppression contractor and electrical contractor must coordinate — interlock failure usually traces to coordination gaps.
What's the cost impact of shunt-trip?
Hood-fire interlock adds $1,500-$4,000 to restaurant electrical scope — shunt-trip breakers, control wiring, interlock module, acceptance testing coordination. Modest relative to total restaurant TI; non-negotiable for code compliance.
What happens after suppression activation?
Restaurant immediately closed for fire investigation and cleanup. Suppression chemical residue cleaning (significant scope), suppression system recharge ($800-$2,500 per system), hood and equipment cleaning, fire department clearance, manual reset of electrical shutdown. Typical reopen 1-5 days depending on suppression discharge extent.
How do you handle pricing — flat fee or hourly?
Both, depending on scope. Routine service calls and predictable scope (panel replacement, EV charger install, transfer switch install, fixture replacement) are flat-fee quoted up front. Diagnostic visits and emergency scope are hourly because we don't know what we'll find. Either way, you get a written quote before work starts on anything significant, and we don't proceed beyond the quote without your sign-off.
How quickly can you schedule?
Depends on scope and season. Emergency dispatch: same-day across Marin County (1-3 hours business hours, 1-4 hours after-hours). Same-day standard service: 3-6 hours from call when capacity allows; otherwise next business day. Scheduled service work: 1-3 weeks typical. Larger projects requiring permits and PG&E coordination: 4-12 weeks depending on scope. We're upfront about timeline at the quote stage.
What warranty do you offer on work?
Our standard residential warranty: 2 years on labor, manufacturer warranty on parts (varies by product — typically 1-10 years). Major installs (panels, generators, EV chargers) often have longer manufacturer warranties (5-10 years). If there's an issue with our work in the warranty period, we come back and fix it at no cost. We also stand behind work past warranty — repeat customers and referrals matter more than a transactional fix.
Are you licensed and insured?
Yes. California State License Board C-10 Electrical Contractor #989290, in good standing. Carry general liability insurance and workers' compensation insurance as required by California law. Bondable on projects requiring it. Happy to provide proof of insurance to clients or property managers on request. License lookup: cslb.ca.gov.
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Family-run, C-10 #989290, 20+ years in the trade. Honest scoping, fair pricing, work that lasts.