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Interpretation of NFPA-12 (2015)

Question asked by keithc.frederick on Feb 9, 2017

This question pertains to Discharge Pressure Switch installation and operation on a multiple hazard High Pressure CO2 System.


I have a customer that has a common bank of High Pressure CO2 Cylinders that protects 12 individual test cells with Selector Valves at each hazard.  Each test cell hazard has it's own Horn/Strobe assemblies and all hazards are connected to the same addressable Releasing Control Panel.  Electrically, during a normal discharge, each individual test cell hazard's Horn/Strobe assemblies will activate FOR THAT HAZARD ONLY.  Currently, there are no Discharge Pressure Switches installed in the system.


I have recommended that each test cell hazard have it's own Discharge Pressure Switch installed which will activate that particular hazard's Horn/Strobe assemblies during a pneumatic manual discharge.  Each of the 12 hazards would have it's own Discharge Pressure Switch that will activate each individual Test Cell hazard's Horn/Strobe assemblies (Located inside the CO2 protected area and outside access doors).


The customer wants a common Discharge Pressure Switch installed between the CO2 Cylinder bank piping and the Selector Valves.  When this common Pressure Switch activates, they want it to activate the Building Fire Alarm Control Panel's Horn/Strobe assemblies (these are separate from the CO2 System Horn/Strobe Assemblies).  These electronic devices are located in a common corridor area.  Not inside the CO2 protected area and outside access doors.


Does the customer's preference to operated the Building Fire Alarm Control Panel's Horn/Strobes comply with this code? Should individual pressure switches be installed to activate each hazard's CO2 Horn Strobe Assemblies thru the addressable Releasing Control Panel, as I have recommended, to comply with this code?