What is the maximum allowed cross-sectional area of conductors in a sealing fitting, relative to the cross-sectional area of RMC of the same trade size?

The maximum allowed cross-sectional area of conductors within a sealing fitting, in relation to the cross-sectional area of the Rigid Metal Conduit (RMC) of the same trade size, is 25 percent. This requirement is outlined in the National Electrical Code (NEC) to ensure safe operation and avoid overheating due to excessive conductor fill.

Sealing fittings are used to protect electrical connections and components from the ingress of moisture and other potentially damaging elements. By permitting only 25 percent of the cross-sectional area of the conduit to be filled with conductors, the NEC ensures that there is adequate space for heat dissipation and reduces the risk of electrical hazards such as short circuits or insulation breakdown due to the buildup of heat.

This regulation helps electrical professionals design systems that maintain both safety and reliability, as it recognizes the importance of spacing between conductors in managing thermal conditions within the conduit.