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John Grabowski John Grabowski is offline
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Default RMC conduit going into box w/concentric KO's


"RBM" wrote in message
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wrote in message
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I'm using rigid steel conduit with steel boxes where I have elected to
use the conduit as the grounding conductor. I have a 1/2" conduit
going into a masonry box with concentric 1/2 & 3/4 knockouts. I'm not
crazy about concentric KO's so I thought I'd knock out to 3/4 and use
a 3/4 to 1/2 reducing bushing where the conduit enters the box. (In
this case it would actually be an "expanding" bushing.) ... and a
locking nut on both sides of the
connection.

Isn't what I propose better than using the 1/2 knockout then praying
that the 3/4 knockout doesn't come loose? -- better for insuring a
good ground? The code does not say much about reducing bushings. I
really rather not run a separate grounding conductor.

--zeb


Sure it is, and just spin on a 1/2" threaded grounding bushing and you'll
be well grounded



I agree. The reducing bushing will look kind of hokey. Put a 1/2" bonding
bushing on after the locknut and attach a grounding pigtail to it. Once the
box and conduit are fastened securely the concentric KO should not work
itself loose.

I think running a separate grounding conductor is the best way to go.