NFPA 731 Section 4.6.3.12(2) requires raceways to be sized properly in accordance with the NEC^®. Raceways, conduits and tubing are not always used with security system wiring but if they are, the raceway conduit or tubing must be sized according to the NEC^®.

In the NEC^®, there are two main locations (near the back of the book) used when determining the maximum number of conductors in a conduit or tubing:

• NEC Annex C is used for determining the maximum number of conductors permitted in conduit or tubing, when all conductors in the conduit are of the same size and insulation type.
• NEC Chapter 9 is used for combinations of conductors of different sizes or insulation types installed in the same conduit or tubing.

There are many tables in NEC Chapter 9.

For example, Table 4 provides the dimensions and percent area for specific types of conduit and tubing. Table 5 provides dimensions of insulated conductors and fixture wires being installed in the raceway types mentioned in Table 4.

Table 5 provides dimensions of insulated conductors and fixture wires. Across the top of Table 5 from left to right are the type of wire used, the size of the wire in AWG (American Wire Gauge) or kcmil (thousands of circular mils), the approximate area and the approximate diameter.

For example, use NEC^® Chapter 9 Table 5 to determine the maximum dimension for the following mixed group of insulated conductors installed in a raceway:

• Three type THWN 10 AWG and, two type XHHW 10 AWG conductors installed in the same raceway.
• A single 10 AWG insulated type THWN conductor has an approximate area of .0211 in². If installing 3 of these conductors in a raceway, the total area occupied by the conductors would be .0633 in². (.0211 X 3 = .0633 in²).
• A single 10 AWG insulated type XHHW conductor has an approximate area of .0243 in². If installing 2 of these conductors in a raceway, the total area occupied by the conductors would be .0486 in². (.0243 X 2 = .0486 in²).
• .0633 + .0486 = .1119 in² total dimension of all five conductors in the raceway.

Refer to the image of NEC^® Chapter 9 Table 5 to answer the question below.

Below is a sample of NFPA 731. For the complete section, see the actual NFPA 731 text at NFPA.ORG. Once there, click on the free access link to the latest edition of  NFPA 731.

4.6.3 Wiring.

4.6.3.12 At raceway connections to junction boxes and open ends of raceways, the following shall apply:

(1) Conductors shall be protected from abrasion.

(2) Raceway shall be sized and installed in accordance with NFPA 70.