Tuesday, October 1, 2013

Direct Burial Cable for Fire Alarms

Did you know you could direct bury fire alarm cables if codes and standards are followed?


Have you ever used direct burial cable in your fire alarm installations? Typically in fire alarm you will not see much of it as most of our outdoor work is typically in Rigid conduit or schedule 80 PVC.  Also a small portion of our fire alarm designs involve running out side for connections.  Without getting too deep in the design aspects, more than likely, if you are running circuits outside, are likely for a PIV (Post Indicator Valve), or Backflow Preventor with OS&Y switches (OS&Y standards for Outside Screw and Yoke)

Direct Burial Cable for Fire AlarmDirect burial cable is a cable that is designed and U.L. approved to be installed directly in trenches without the need for conduit or other raceways.  The wires themselves are encased with what is known as a thermoplastic sheath that seals out moisture to help protect the wires. Direct burial cable often referred to as UF Cable and commonly ships with a grey jacket. However, there are some wire manufacturers such as Beach Wire and CableArrow Wire and Cable, and Windy City Wire that make their own listed direct burial cable and it comes in black. Please note that this type of cable is only listed for this use if it is installed at the proper depths.

An easy way to notice the difference between standard non-metallic sheathed cable (NM) and underground feeder cable (UF) is the coating around each cable within the jacket. NM cable is simply a jacket to house multiple conductors whereas the UF cable separately coats each conductor.