Fire & Life Safety: Pop Quiz on NEC Wiring Methods

Test yourself on National Electrical Code issues


#3: Your electrician is installing a listed product according to the manufacturer’s documented instructions. You are not installing a product designed and tested as a system — you are providing wiring. Wiring is installed according to section 300.11 of the NEC, which states “cables and raceways shall not be supported by ceiling grids.” It does provide an exception that states “the ceiling support system shall be permitted to support wiring and equipment that have been tested as part of the fire-rated assembly.” The use of these clips doesn’t fit the exception.

#4: Show him NEC Section 300.11 Securing and Supporting — “cable wiring methods shall not be used as a means of support for other cables, raceways or non-electrical equipment.” Once the existing support rings are full, additional supports are needed.

#5: They meet NEC requirements because the rule for fire alarm system terminations and boxes are not found elsewhere in the NEC for other systems. According to 760.130 Wiring Methods and Materials on Load Side of the PLFA Power Source – (B) PLFA Wiring Methods and Materials, “cable splices or terminations shall be made in listed fittings, boxes, enclosures, fire alarm devices, or utilization equipment.”

#6. It isn’t a violation for the mechanical contractor’s electrician to do this, but it would be a violation for your fire alarm technician (and he’ll make your company look bad.) This is because NEC section 760.143 specifically states that “power-limited fire alarm circuit conductors shall not be strapped, taped or attached by any means to the exterior of any conduit or other raceway as a means of support.” No exceptions are shown here for fire alarm wiring, but section 300.11 under “Securing and Supporting” has an exception to our fire alarm rule. The HVAC contractor will be exonerated by “300.11...(2) Where the raceway contains power supply conductors for electrically controlled equipment and is used to support Class 2 circuit conductors or cables that are solely for the purpose of connection to the equipment control circuits.” Employer 101: Teach all your technicians to bring their questions and issues to their supervisor.

#7: A box is not required if a bushing is used at the end of the conduit where the wires exit. According to NEC 760.3 (K) Bushing, “a bushing shall be installed where cables emerge from raceway used for mechanical support or protection in accordance with 300.15(C).” Then section 300.15 – Boxes, Conduit Bodies or Fittings – Where Required – (C) Protection states “a box or conduit body shall not be required where cables enter or exit from conduit or tubing that is used to provide cable support or protection against physical damage. A fitting shall be provided on the end(s) of the conduit or tubing to protect the cable from abrasion.”

#8: Wiring must be protected if the edge of the bored hole is within 1 ¼ inch from the edge of a wood member. A 2x4 is actually only 3½ inches wide. To not be closer than 1¼ from each edge, the bit should be no larger than 7/8 inch. Even though your tech used a 7/8 bit, he was in the dead center of the stud only about half the time, meaning that about half the studs have the hole within less than 1¼ inch from the edge. The inspector is right, either drill smaller holes somewhere near the center of the stud, or 7/8 inch holes precisely in the center next time. The inspector seems familiar with NEC section 300.4 “Protection Against Physical Damage – (A) Cables and Raceways Through Wood Members – (1) Bored Holes: “In both exposed and concealed locations, where a cable- or raceway-type wiring method is installed through bored holes in joists, rafters, or wood members, holes shall be bored so that the edge of the hole is not less than 32 mm (1 ¼ in.) from the nearest edge of the wood member. Where this distance cannot be maintained, the cable or raceway shall be protected from penetration by screws or nails by a steel plate(s) or bushing(s), at least 1.6 mm (1⁄16 in.) thick, and of appropriate length and width installed to cover the area of the wiring.”

 

Greg Kessinger is SD&I’s fire alarm and codes expert and a regular contributor. Email him your fire & life safety questions at greg@firealarm.org.