Fire Alarm Underground Conduits

Is it OK to Install Fire Alarm Cable underground?

Post Indicator Valve  with Fire Department Connection

A common task when installing a new fire alarm system is undergrounds. Typically when a C-16 or fire protection (fire sprinkler) contractor installs their incoming lines they will at the same time install the necessary fire alarm underground conduits for the connections to the backflow prevention switches (OS&Y Outside Screw and Yoke) or PIV (Post Indicator Valve) switches. However, sometimes this task could be a part of the fire alarm contractor's scope of work. If you find yourself installing underground conduit or direct burial cable make sure to follow all of the national codes and regulations.

Direct Burial Cable as an Alternate to Conduit

Backfloe Preventor with OS$Y Switches for Fire Alarm

Some contractor's may choose to use direct burial cable also referred to as UF Cable commonly identified by its grey coating. Direct burial fire alarm cable not protected in conduit must be installed at a depth of 24" below grade with either schedule 80 PVC or Rigid conduit stubs up to your box. When fire alarm cable is installed within plastic conduit it must be 18" deep and installed with schedule 80 PVC. This is a more durable plastic conduit (grey color) than the common household irrigation lines. The best way to install these conduits or cable is with a Ditch Witch. Simply set the depth and go.

Junction boxes that are run out into the middle of a remote area without an anchor point must have the schedule 80 PVC embedded in the concrete to support the box. Another method is to attach the box to a post that is either driven or buried in the ground 18" and connects directly to the schedule 80 PVC conduit. Junction boxes should be installed at least 12" above grade but not more than 18" for the unattached method.

See also conduit bending videos.

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