How to Calculate Outlet Box Dimensions According to the 2023 NEC?

Overview 

The power consumption and requirements vary for each user, resulting in different needs for conductors and power devices to deliver energy. These components are housed in outlet and device boxes, whose size and dimensions vary based on what they must accommodate. NEC Section 314.24 outlines factors for calculating the necessary dimensions of these boxes to prevent damage to the conductors or devices from abrasion against box surfaces. The NEC 2023 edition also addresses protecting conductors and devices from damage at their entry points on the sides of the box.

Applying the 2023 Code 

Power distribution within buildings and appliances relies on electrical connections facilitated by outlet and device boxes. The dimensions of these boxes are pivotal for electricians as they dictate the capacity for accommodating conductors and power devices. Historically, until 2020, NEC Section 314.24 addressed factors determining box depth until 2020. However, a notable concern arose regarding conductors entering boxes from the sides, where insufficient depth posed a risk of damage if devices extended too far. Consequently, in the NEC 2023 edition, Section 314.24 was renamed ‘Dimensions of Boxes,’ and Sub-Section (C) ‘Clearances for Side Wiring Entrances’ was introduced. This sub-section mandates protection against abrasion by prohibiting conductors/devices from protruding beyond the knockout’s centerline and maintaining clearance between them and the box’s side wall. 

What’s New for the 2023 NEC? 

2020 NEC 

In the 2020 NEC, Section 314.24 focused on the depth of the outlet and device boxes.  

2023 NEC 

In the 2023 NEC, Section 314.24 was renamed and refocused on the dimensions of outlet and device boxes, and a new sub-section (C) was added to highlight the clearance requirements for side-wiring entrances. The new sub-section now reads as follows: