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.

Across the top of Table 4 are the following percentages: 40%, 60%, 53%, 31%, and the total area of the raceway at 100%. The percentage values that are less than 100% represent the maximum amount of room the wiring installed in the raceway can take up without exceeding the applicable percentage. For example, if installing 3 conductors in the raceway, use the 40% column since there will be over 2 wires in the raceway. The 60% column aligns with note 4 at the beginning of Chapter 9 which is only for conduit or tubing nipples 24 inches or less.

Example: If a group of 5 conductors had a total combined area of .1119 in², then a ½-inch EMT raceway would be appropriate. Using the 40% column (since there are more than 2 wires in the raceway), the ½ inch EMT raceway can hold up to .122 in² of wire without the wire exceeding 40% of the raceway.

Refer to the image of NEC^® Chapter 9 Table 4 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.