Conduit & Grounding Bushings

Choosing Conduit Bushings by What the Throat Must Do

Three jobs share this category, and mixing them up is how the wrong
bag ends up on site. A reducing bushing changes size, threading into a
larger opening to accept a smaller conduit or fitting. An insulated
bushing changes texture, capping a cut metal edge with a smooth throat
so pulled conductors keep their insulation. A grounding bushing changes
electrical status, adding a lug that ties the raceway into the fault
path.

The lug on a grounding bushing lands a bonding jumper whose terminations come from the lugs range, which is worth ordering in the same pass.

The size pairs on the reducing side read large to small, so a 3 by 2
steps a 3 inch opening down to 2 inch, and the page one range covers the
middle of commercial work, with the steel series running 2 by 1-1/4
through 4 by 3 and the malleable series reaching 4 by 3-1/2.

Steel or Malleable Iron on the Reducing Side

Both Morris families do the same geometric job, and the split is
about toughness under torque. Malleable iron shrugs off the wrench abuse
and vibration of heavy industrial terminations, while the steel
versions cover the broad middle of commercial work at friendlier cost.
Whichever metal wins, the reducer becomes part of the grounding path it
sits in, so threads go in clean and tight rather than caulked and hoped
for.

When a Locknut Stops Being Enough

Ordinary terminations bond through their locknuts, and code stops
trusting that shortcut in specific places, around punched-out concentric
and eccentric knockouts, and on higher voltage feeders, where a
grounding bushing with a real jumper is generally required instead. The
exact triggers vary with the code cycle and the inspector, so confirm
the rule in force before value-engineering the lug away.

Fault current that lands on a bushing's jumper ultimately heads for the electrode system, whose hardware lives over in ground clamps.

Armored cable brings its own version of the throat problem, since the
cut jacket edge is razor sharp, and the anti-short bushings the trade
calls redheads exist to sit between armor and conductors at every such
termination. Check each listing for the cable types a given anti-short
piece is sized for.

The Rest of the Raceway Order

Bushings close a run that other collections started, with set-screw and compression terminations for steel tubing coming from EMT fittings.

The corners a wire pull cannot survive get an openable back from conduit bodies instead of a blind bend.

The generic hardware between those points, in contractor pack counts, fills the electrical fittings
aisle. Bonding decisions carry real consequences in a fault, so the
jumpers, lugs, and terminations described here are specified and
installed by a licensed electrician, not improvised at the panel.

Conduit and Grounding Bushing Questions

How do I read a reducing bushing size like 3 by 2?

First number is the opening it threads into, second is the size it
accepts, so a 3 by 2 lets a 2 inch conduit or fitting land in a 3 inch
hub. Buy by the pair, not by either number alone, and the page one range
covers pairings from 2 by 1-1/4 up to 4 by 3-1/2.

Do I need a grounding bushing on every conduit?

No. Most terminations bond adequately through their fittings and
locknuts. The grounding bushing earns its place where the code stops
accepting that, typically at rings of punched knockouts and on higher
voltage feeders, and the authority having jurisdiction settles the
borderline cases.

What is the difference between a bushing and a locknut?

The locknut clamps the fitting to the enclosure wall and carries the
mechanical joint, while the bushing dresses the throat that conductors
pass through. They work as a pair on threaded terminations, one outside
the metal, one over the raceway end inside.

Why choose malleable iron over steel?

Durability under abuse. Malleable iron takes repeated wrenching,
vibration, and impact without cracking, which suits industrial gear that
gets serviced hard. For the ordinary run of commercial terminations,
the steel versions do the same job for less.