Options for bonding to this box

[mark32]

A customer had a wall knocked down in his high rise condo and who ever did the work broke off a piece of emt flush with the ceiling that was feeding a switch on the now non existing wall. The home owner attempted to relocate the switch to an adjacent wall and called me in to finish it. What to do now? I need to mount a box to the ceiling (He has a synthetic piece of wood that will act as a cover for the box and bx that will run from ceiling box to adjacent wall) where the emt is/was and pull a ground from the light, where the feed is. Problem, the light box is in poured concrete with emt and no separate ground, but I need to bond the ground I need for the new switch. What do you think about chiseling a small channel next to the box for one of those grounding clips or how about hitting the lug on a bonding bushing or maybe the ground screw on the fixture bar? Also, how about the flush piece of emt, all I can think of is placing a box over it, thus the need to pull a ground. Any ideas?

 

[LarryFine]

How about routing the concrete from around the EMT with, say, a 1" or so (presuming 1/2" EMT) core bit, or maybe drilling several 1/4" or 3/8" holes around it, chiseling away the concrete against the EMT, and installing a compression-type connector on it?

 

[augie47]

I'm having a bit of a time picturing, but if the existing box is grounding by the EMT and you add BX (actually AC or MC-Cap) then the jacket is considerd an approved ground. If you do need to use a conductor at some point, your idea of chiseling for a ground clip should work.

 

[LarryFine]

Gus, unless I'm wrong (hey, it could happen), he's saying that the switch EMT, which broke flush with the concrete, is a 2-wire switch loop, and the feed is in the still-existing box where the fixture is.

He was talking about installing an EGC in the EMT from the still-in-the-ceiling fixture box, through the still-in-the-ceiling-but-broken EMT, and bonding it to the new box for the switch-loop extension.

That would allow the new EGC to "jump the gap" between the broken EMT and the new box. My suggestion is to restore the EMT to bonding duty, effectively restoring original conditions without a wire.

 

[mark32]

Larry, you described the scenario perfectly, sorry Gus, I could have been more descriptive but dinner was being served. Larry, I couldn't get a close look (I didn't have a ladder with me) at the broken emt but it appeared as though it broke at the tail end of a 90 as it had an angle to it. If it did run a bit up next to the emt (thanks for the tip) I'm unsure whether a set screw connector or a compression type would be easier to properly tighten in such a situation. Blah, is my original idea about pulling in a new egc lame?

 

[wireguru]

I'm unsure whether a set screw connector or a compression type would be easier to properly tighten in such a situation. Blah, is my original idea about pulling in a new egc lame?

set screw connector, you can chisel out a channel for access to the screw.

 

[LarryFine]

. . . it appeared as though it broke at the tail end of a 90 as it had an angle to it. If it did run a bit up next to the emt (thanks for the tip) I'm unsure whether a set screw connector or a compression type would be easier to properly tighten in such a situation.

If you're correct, a set-screw connector will be easier to install and the screw should be tilted enough to tighten.

If it's straight, a compression connector can be tightened by rotating just the connector's body, and not the nut.

Blah, is my original idea about pulling in a new egc lame?

No, but the EMT "should" connect to the box; otherwise, it's really a sleeve and not a continuous conduit system.

Your idea would work, and wouldn't be a hazard, but the 'retentive' side of me would want the EMT system intact.