This week we will be exploring some of the uses of circuit integrity solutions for use in accordance with NFPA 502: Standard for Road Tunnels, Bridges, and Other Limited Access Highways.
According to section 12.1.2 in the new 2017 edition, emergency circuits installed in a road tunnel shall remain functional for a period of one hour under a typical or computer modeled fire event. A fire protection engineer will typically do these calculations in the design phase using a software package such as the NIST models on top of the tables in the Annex of NFPA 72. Some of the specific circuits listed are ventilation, exit signage, fire alarm, other detection, area of refuge systems, emergency communications, and traffic control systems.
There are four main types of circuit protection allowed. The first is a UL2196 (ASTM E119) circuit integrity in conduit system, like our Radix DuraLife in conduit solution for circuits capable of being run in a 300V jacket. Our cables are low smoke / zero halogen and well suited for this application. Typically, most applications will ask for a combination of a fire resistive cable system and redundant paths. Other ways that can fulfill these circuit protection requirements are cables located outside the roadway tunnels, redundant paths buried in concrete on opposite sides of the tunnel, and other AHJ approved methods. A deluge system will be specified in addition to these cable pathways.
Contact Radix at (877) 722-5444 for more information and to discuss your circuit integrity needs today.