Kitchen Hood Suppression Acceptance Deficiencies
A new 120-seat restaurant has a Type I hood over a gas range and two fryers. The wet-chemical hood suppression system has a 2.5-gal cylinder, two appliance nozzles, and one plenum nozzle. The manual pull station is mounted 44 in. above the floor, 12 ft from the hood, behind a stainless prep table. The gas line has a manual ball valve only; the contractor says the cook can shut it off. The hood exhaust fan is not interlocked to the suppression system and continues running after a test actuation. The fusible link above the range is stamped 450°F. The cylinder label shows a hydrostatic test date 6 years old. The contractor wants to use test cartridges and sign off the same day.
1. List the deficiencies and explain why each matters under NFPA 17A and NFPA 96.
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The manual pull is at 12 ft and behind a prep table, so it fails the accessible, path-of-egress location and distance expectation for manual actuation. The gas line has only a manual ball valve, but the suppression system must automatically shut off fuel and heat-producing power to protected appliances on actuation; a cook-operated valve is not an automatic fuel shutoff. The 450°F fusible link must be checked against the appliance listing and the system manufacturer’s required rating; the wrong link can delay or prevent actuation. The cylinder hydrostatic test date must be verified against NFPA 17A and the manufacturer’s interval. Test cartridges are acceptable for acceptance testing, but they do not excuse unresolved deficiencies. Signing off the same day without correcting these items would be premature.
2. Describe the correct sequence of operation and the acceptance test you would require.
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On detection, the system should actuate, discharge agent through the appliance and plenum nozzles, and automatically shut off fuel and electric heat to the protected appliances. Manual pull must also actuate the system and shutoff. During acceptance, verify cylinder weight and hydro date, nozzle caps and aiming, link rating and location, manual pull accessibility, fuel shutoff operation, and required signage. Use test cartridges or the manufacturer’s approved test method, then verify that the system is returned to service and the cylinder is not left discharged. Provide owner training and record the test results.
3. The contractor argues that the exhaust fan must shut down on system actuation. How do you evaluate that claim?
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Do not treat fan shutdown as automatic without checking the governing code and listing. NFPA 96 generally does not require the cooking exhaust fan to shut down on suppression system activation; continued operation can help clear smoke and heat. However, local amendments, the system manufacturer’s instructions, or the hood listing may require a shunt trip or fan shutdown. The mandatory item is automatic fuel and heat-source shutoff. I would verify the local AHJ requirement in writing and test whatever sequence is approved, rather than failing the job solely because the fan continues to run.