Have you ever made an embarrassing mistake that was obvious to all those around you, and you had to just stand there with your head hung low?
I know of a guy that once drilled into a cinder-block wall to mount a manual pull box and, after setting the drill on the ground behind him, turned to see a constant flow of bright white granules falling into a growing mound on the floor in front of him. In addition to this local event, a fair amount was also being carried down the long open hallway by air currents, causing other contractors to become really curious. It turns out this was special insulation that had been poured into the concrete block’s hollow cavities to provide extra thermal insulation, as well as an additional barrier against fire and sound. A thumb over the hole was a gut response, but this now pinned the poor guy to the scene of the crime.
How could this situation have been avoided? Awarding the fire alarm contract in time for the conduit and back boxes to be built in was a moot point. Fishing wires into these block walls was going to be a crummy alternative.
As it turns out, there was another option afforded by the National Electric Code (NEC). In section 300.4 (F) which is named, “Cables and Raceways Installed in Shallow Grooves,” you can locate this old rule that still allows for placing a cable in a cut groove as long as it is at least 1.25 inches from the surface, for the entire length of the groove. No conduit or protective plates are required. Concrete floors, ceilings and walls? Groovy.
New Fire Alarm Circuit Regulations
A new issue was addressed in the 2014 edition of the NEC that surprised many in the life safety business. To meet the “survivability” requirements for certain fire alarm circuits specified in NFPA 72, the NEC allows two methods for compliance. One is the use of Circuit Integrity (CI) cables; the other is an “electrical circuit protective system” — consisting of wiring wrapped in a special plastic tape and installed in rigid metal conduit to comprise a “system.”
As it turns out, the products meeting the UL test for fire resistive cables UL 2196 didn’t actually provide the two-hour resistance to fire as advertised! It appears that for the past 10 years, if the inside of the conduit in which the cables were inserted contained zinc, the chemical reaction that occurred between the zinc and the circuit wiring caused the circuit to fail sooner than two hours during a fire. While no known losses (other than credibility) have been attributed to this problem, the industry was left wondering what to do.
UL decided that the UL Listing standard would not be withdrawn, but that all products would be re-tested by UL under all the anticipated variables, using multiple tests. In the meantime, NFPA changed the 2014 NEC to specify that CI cables are not to be placed in conduit having zinc on the inside, which will be tough since rigid metal conduit is hot-dipped, not electro-plated.
As for the “electrical circuit protective system” products, they are to be reevaluated with a more complete testing process. Regarding the existing installations using the flawed systems, and any existing products not sold but already marked as meeting the cable fire/heat test requirements, they will probably just be grandfathered — not cool.
Greg Kessinger is SD&I’s fire alarm and codes expert and a regular contributor. Send him your fire & life safety questions at firstname.lastname@example.org.