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I wanna install a ground bar on a 8x box that's flush mounted to a concrete ceiling. Can I drill 2 holes out to the inside of the box on the side and mount it with a nut and bolt? If so what size or can I use self tappers? Im in nyc
 

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250.8 Connection of Grounding and Bonding Equipment.
(A) Permitted Methods. Equipment grounding conductors, grounding electrode conductors, and bonding jumpers shall be connected by one of the following means:
(1) Listed pressure connectors
(2) Terminal bars
(3) Pressure connectors listed as grounding and bonding
equipment
(4) Exothermic welding process
(5) Machine screw-type fasteners that engage not less than
two threads or are secured with a nut
(6) Thread-forming machine screws that engage not less
than two threads in the enclosure
(7) Connections that are part of a listed assembly
(8) Other listed means

Pete
 

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A nut and bolt would most likely be acceptable but remember to remove any paint or other non-conductive coating from behind your ground bar.

The self-tapper may be ok as long as you end up with 2 threads fully engaged in the metal of the box.

Pete
 

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You can probably find machine thread self tappers but, who is going to pull them out and measure them? :rolleyes:




This (using standard thread self tappers for grounds) is one of the more extreme examples of a purely technical violation of the NEC.

The self-tapper may be ok as long as you end up with 2 threads fully engaged in the metal of the box.
But....there is only one thread on a screw, right? :laughing:
 

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But....there is only one thread on a screw, right? :laughing:
Is it a thread or an inclined plane?:laughing:

Interestingly, as far as the NEC is written you may have pointed out a brand new violation.

Pete
 

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You can purchase 10-32 tap ends that fit into a cordless drill from the hardware stores, usually they come in packs of ten . While you are there you can get 10-32 screws also , or you can purchase the nicely painted green ones (not required..) from your supply house or the home improvement stores , which are easier to spot in your mess of a tool pouch in dark rooms..


I keep the tap handy at all times. I won't say what else I keep handy in my toolbags for grounding fluorescent lights cause that would be hack...


But that is a nice picture two posts uphill by the way......
 

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You can purchase 10-32 tap ends that fit into a cordless drill from the hardware stores, usually they come in packs of ten . While you are there you can get 10-32 screws also , or you can purchase the nicely painted green ones (not required..) from your supply house or the home improvement stores , which are easier to spot in your mess of a tool pouch in dark rooms..

I keep the tap handy at all times. I won't say what else I keep handy in my toolbags for grounding fluorescent lights cause that would be hack...

But that is a nice picture two posts uphill by the way......
That's what I would do. Drill holes, send in tap, install ground bar. I like 8-32s or 10-32s. As long as the metal is 1/16" thick or more, you have 2 threads.
 

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tell me about it..
I have broken more than I have successfully drilled holes with those things. On the plus side it they give you hope of getting them out because you have the drill part sticking out the back of whatever you are drilling till it snaps off.


And for the op. Mount the ground bar with 10-32 screws with it off the wall then grind off whatever is sticking out the back
 
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