Using electrical reducing washers

[smalltown]

Needed to add another section of 3/4" EMT and found a 1" plug installed.
Ran down and purchased 2 reducing washers 1" to 3/4".

Do I need to install a ground bushing. I am running a ground wire inside my conduit. I checked Home Depot and could not find ground bushings for 1/2" or 3/4" EMT, and online searching seems to imply only 250 volt, and above needing the ground bushing.

 

[alfredeneuman]

If you're using washers, I'm afraid so
250.96
Bonding Other Enclosures.
(A) General. Metal raceways, cable trays, cable armor, cable sheath, enclosures, frames, fittings, and other metal non–current-carrying parts that are to serve as equipment grounding conductors, with or without the use of supplementary equipment grounding conductors, shall be bonded where necessary to ensure electrical continuity and the capacity to conduct safely any fault current likely to be imposed on them.

If you need them, they're available at the HD

https://www.homedepot.com/p/3-4-in-Rigid-Insulated-Rigid-Grounding-Bushing-2-Pack-29522/100123427

 

[bjcouche]

Alfredeneuman might be right, but I've never seen that done in residential work before.. on 240V equipment. Plus, I 'm curious what exactly is meant by the NEC wording of "that are to serve as equipment grounding conductors", because since you added in the ground wire in the conduit, and terminated said ground wire inside EVERY box that the conduit goes to... You essentially are NOT relying on the electrical connection between the box / washers / conduit. Maybe if you had a suspect connection between your ground wire and conduit on BOTH ends of the conduit, then maybe I'd add the ground bushing on one end.
I have heard that inspectors require ground bushings for 240V SERVICE ENTRANCE conduits per 250.92B for concentric, eccentric or the use or reducing washers...
So I think you're NEC safe without the bushing because you're under 250V, and not a service entrance... but of course the inspector has the final say....
Brian

 

[dscheidt]

It means "add a grounding bushing where you have an oversized knockout".

 

[bigb56]

"Metal reducing washers are considered suitable for grounding for use in circuits over and under 250 V and where installed in accordance with ANSI/NFPA 70" which basically means the paint under the reducing washers must be removed prior to installation.

That said, if the raceway is being used as the sole grounding conductor, no way would I trust that connection with reducing washers alone, I would add a bonding bushing. However since you are running an appropriately sized equipment grounding conductor (EGC) and connecting it to every metal box along the way I would install the washers per NFPA 70, securely tighten and not worry about it one little bit.

 

[smalltown]

Curiously I have been searching for 3/4" EMT grounding bushing and none come up.
IMC and rigid yes. Do you think the threads on these would be the same as an EMT coupler ?

Now that I think about it the IMC or the rigid will not screw down enough to tighten the EMT coupler? Or maybe there are enough threads exposed to add the IMC/rigid ground bushing on top of the EMT lock nut ?

 

[bigb56]

yes same threads yes you use a lock nut first before installing any bushing, the thin steel lock nuts work better for this than the thicker die cast ones