Methods of Equipment Grounding, Part 1

What if you have short sections of metal raceway or armor that don’t connect to something metallic? If they are required to be grounded, connect them to an equipment grounding conductor (EGC) that complies with Sec. 250.134 [250.132]. If they aren’t required to be grounded, is there any reason not to connect them an EGC anyhow?

As a general rule, “Bond everything” (to that EGC) saves money in the long run. While the tail end of the EGC ultimately connects to earth, the EGC itself does the job you really need done: bring metallic objects to zero potential with each other.

What does Sec. 250.134 tell us about selecting that EGC?

• You can use an “exterior” EGC: any of the 14 types of EGCs listed in Sec. 250.118. These include metallic conduit, metallic tubing, armored cable, and metallic cable tray.
• You can use an “interior” EGC. That’s an EGC contained within the same raceway or cable (or otherwise run with) as the circuit conductors. Read the two Exceptions and the two Informational Notes to Sec. 250.134(B) before implementing anything.