How close must EMT be to each junction box, outlet box, or device box for support?

The requirement for the proximity of Electrical Metallic Tubing (EMT) to junction boxes, outlet boxes, or device boxes for adequate support is governed by the National Electrical Code (NEC). EMT must be supported at a maximum distance of 3 feet from any junction or outlet box. This support ensures the integrity and stability of the conduit installation, preventing sagging or misalignment which can lead to issues such as damage to wiring or difficulty in making connections.

The choice indicating 3 feet aligns with the NEC standards, which specify that EMT must be securely fastened or supported within this distance to ensure that the electrical system remains safe and reliable. Proper support is critical in maintaining electrical systems, as it helps prevent mechanical stress on conductors and maintains clear pathways for electrical installations.

Other distances, such as 1 foot, 2 feet, or 4 feet, do not meet the NEC requirements for support distances, and using them could result in a non-compliant installation, potentially posing safety risks or leading to difficulties during inspections.