Thomas & Betts Insulated Ground Bushing

Three trade sizes are offered: 1/2 inch (part 3870-TB), 2 inch (part 3889), and 5 inch (part 3998). Pick the bushing that matches the trade size of the rigid or IMC conduit threading into the enclosure, since the bushing threads onto the conduit end.

The 1/2 inch insulated grounding bushing carries a lug rated for 14 through 4 AWG. That covers the usual equipment grounding conductor sizes for small branch circuit runs, so a #12 or #10 ground lands in it without an adapter.

It threads onto the end of rigid or IMC conduit inside a box or enclosure and gives you a screw lug to land a bonding jumper, so the raceway is bonded back to the ground bus. The insulated throat protects the conductors where they leave the conduit, which is why electricians use this type at concentric or eccentric knockouts and at service equipment where a standard locknut alone will not do the bonding.

The body is malleable iron, so it is a metallic bushing with an insulating throat liner rather than an all-plastic bushing. Malleable iron gives you the mechanical strength for large trade sizes and a solid current path from the conduit through the lug.

Yes, and it is the right call whenever the raceway also has to be bonded. A plain insulated bushing only protects the wire insulation at the conduit end; this one is malleable iron with a lug so it does both jobs in one fitting. If there is no bonding requirement at that opening, a plain plastic bushing is the simpler part.

No. These bushings are size specific and each trade size is its own part: 3870-TB for 1/2 inch, 3889 for 2 inch, and 3998 for 5 inch. Order by the conduit trade size at each opening.