What is the maximum number of 12 AWG THHN copper conductors permitted through a standard 3/4" LB conduit body?

To determine the maximum number of 12 AWG THHN copper conductors allowed through a standard 3/4" LB conduit body, it is essential to refer to the National Electrical Code (NEC) and the fill capacity tables that outline the allowable number of conductors for various conduit sizes.

For a 3/4" conduit, the conduit fill calculation is based on the interior diameter and the cross-sectional area of the conductors. According to NEC guidelines, THHN wire has a specific outside diameter that contributes to the overall fill calculation.

When using the data from NEC Table 1 (for the conduit fill), the maximum amount of conductors depends on their gauge. In this case, for 12 AWG (American Wire Gauge) conductors, the allowable fill for a 3/4" conduit typically results in a capacity that permits up to 18 conductors.

This is derived from the NEC's consideration of both the physical space required for conductors to avoid overheating and allow for easy installation. The specifications ensure safety and efficiency, providing a clear capacity limit for the number of conductors practical in a conduit of this size.

Thus, the choice of 18 reflects the maximum number of 12 AWG