Mike Dolt Enterprises
Mike Dolt Enterprises
User: Mull20014, Location: Maine
Asked on: Monday, May 31, 2021 at 8:52 am EDT
Answered on: Thursday, June 20, 2024 at 11:20 am EDT
Question: I've run into this a few times in residential and am hoping to find a definitive answer to settle an argument (if there is a definitive answer).I've run into a few houses wired just after 1965 with NM containing the safety ground that was properly bonded to the metal box, however, there were a few years where two-prong plugs were still the standard. When replacing said two-prong plug, is it necessary to connect a separate bonding pigtail from the new outlet (or switch) to the box, or is the metal-to-metal contact between the mounting tabs and the box a sufficient enough bond to satisfy code? It is electrically sufficient, but from everything I've found, there is a bit of a gray area in the code (if I'm not looking at it cross-eyed). And before anyone says it, yes, we know it's good practice to go ahead and bond it with a pigtail for redundancy.Thanks,Nick
NEC 2023
250.146(A)(2) states that where a metal outlet box is used, the grounding path can be provided by the metal raceway, armor, or cable sheath, or by a separate equipment grounding conductor. The metal outlet box shall be effectively grounded.250.148(A) states that where nonmetallic sheathed cable is used, the grounding path is the equipment grounding conductor within the cable. If no grounding conductor is provided in the cable, the grounding path shall be provided by a separate equipment grounding conductor.
Interpretation
The metal-to-metal contact between the mounting tabs and the box is a sufficient bonding path for a properly grounded metal outlet box. However, since the code allows for a separate equipment grounding conductor to be used as the grounding path, it is recommended to install a bonding pigtail from the new outlet (or switch) to the box for redundancy.Therefore, while not explicitly required by code,
it is considered good practice to install a bonding pigtail to ensure a reliable and redundant grounding path. Flag for review