Ground Bar

[Jimmy7]

I would like to add a ground bar to a 12“ x 12“x 4” Nema 1 indoor metal junction box for a bunch of 14-2 and 12-2 cables I need to extend. Is it okay to drill and tap any ground bar ( Like a 15 or 20 slot) into this junction box? Is there any rating or listing problems doing this? If it’s okay to do, I was also wondering if it would be a good idea to scrape the paint off the box where the ground bar would go before installing it?

 

[infinity]

IMO the paint behind the bar needs to be removed. Or you could just install a bonding jumper from the bar to the box. Just remove the paint behind the terminal on the box.

 

[Little Bill]

IMO the paint behind the bar needs to be removed. Or you could just install a bonding jumper from the bar to the box. Just remove the paint behind the terminal on the box.

Never understood why just the drilling/tapping of the box wasn't good enough. I know that sometimes paint might be in pre-drilled holes, but if you drill and tap, there is a conductive path. No different than running the bonding screw in on a panel.

 

[Rick 0920]

Never understood why just the drilling/tapping of the box wasn't good enough. I know that sometimes paint might be in pre-drilled holes, but if you drill and tap, there is a conductive path. No different than running the bonding screw in on a panel.

Once you drill and tap, you have bare metal to metal contact. I've done it that way for years and never been called out on it. But having a bare metal space behind the ground bar itself assures good continuity even more.

 

[Little Bill]

Once you drill and tap, you have bare metal to metal contact. I've done it that way for years and never been called out on it. But having a bare metal space behind the ground bar itself assures good continuity even more.

I've also added ground bars without scrapping any paint on my newly drilled holes and never been questioned. I often take a meter and check continuity between the new bar and the cabinet/can.

 

[don_resqcapt19]

Never understood why just the drilling/tapping of the box wasn't good enough. I know that sometimes paint might be in pre-drilled holes, but if you drill and tap, there is a conductive path. No different than running the bonding screw in on a panel.

With most panels the metal is not thick enough to provide the required two threads in the metal. If you look at the factory holes for grounding and bonding connections, you will find that they have some of the metal "extruded" out the back side in order to provide enough metal for the two threads.

 

[infinity]

Never understood why just the drilling/tapping of the box wasn't good enough. I know that sometimes paint might be in pre-drilled holes, but if you drill and tap, there is a conductive path. No different than running the bonding screw in on a panel.

It would make sense that it's good enough but the NEC is specific as to how it needs to be done unless it's a connection using listed ground bar in the hole in a panel tested with that ground bar. A painted Square D panel only requires that you use the mounting screws that came with the bar and install it in the proper location in the panel. Otherwise the paint needs to be removed.

250.12 Clean Surfaces.
Nonconductive coatings (such as paint, lacquer, and enamel) on equipment to be grounded or bonded shall be removed from threads and other contact surfaces to ensure good electrical continuity or shall be connected by means of fittings designed so as to make such removal unnecessary.

 

[Jimmy7]

Can I use any ground bar (If I remove the paint and use the proper mounting screws) in a junction box?

 

[Buddyboy]

With most panels the metal is not thick enough to provide the required two threads in the metal. If you look at the factory holes for grounding and bonding connections, you will find that they have some of the metal "extruded" out the back side in order to provide enough metal for the two threads.

 

[LarryFine]

With most panels the metal is not thick enough to provide the required two threads in the metal. If you look at the factory holes for grounding and bonding connections, you will find that they have some of the metal "extruded" out the back side in order to provide enough metal for the two threads.

Suppose you put nuts on the backside?

 

[infinity]

Suppose you put nuts on the backside?

Pretty much the same as bolting a lug to the panel.

 

[don_resqcapt19]

Suppose you put nuts on the backside?

That meets the requirements in 250.8, but in a typical panelboard a field drilled and tapped hole does not.
With the nuts on the back side and less then two threads engaged in the panel, I would require the paint behind the bar to be removed.

 

[tom baker]

I tapped into wireway and used machine screws to hold ground bar. Then ran a 6 AWG EGC to panel

 

[infinity]

I tapped into wireway and used machine screws to hold ground bar. Then ran a 6 AWG EGC to panel

This meets the requirement by not having to remove all of the paint behind the ground bar. I've done the same thing with ground bars in screw cover boxes.

 

[OldBroadcastTech]

With most panels the metal is not thick enough to provide the required two threads in the metal. If you look at the factory holes for grounding and bonding connections, you will find that they have some of the metal "extruded" out the back side in order to provide enough metal for the two threads.

A quick and easy way to provide enough metal for two threads is to drill a very small hole, then enlarge it with a hammer and awl; this pushes the metal toward the rear of the enclosure. Then tap it for the screw or use a self-tapper.

You would obviously want to do this before installing the box, you need a solid platform to hammer the awl into the hole.

 

[don_resqcapt19]

This meets the requirement by not having to remove all of the paint behind the ground bar. I've done the same thing with ground bars in screw cover boxes.

Only if the material is thick enough to engage two threads of the attachment screws.

 

[infinity]

Only if the material is thick enough to engage two threads of the attachment screws.

I was referring to the part where he ran a bonding jumper and was not relying on the screws into the metal.

 

[Jimmy7]

Could I use something like an Eaton ground bar in this junction box (Picture attached) if I scrape the paint behind the ground bar, scrape the paint on the opposite side, through nut and bolt it, and run a jumper to the green screw pictured in the box. The largest circuit is 20 amps, so I think I could use a #12 jumper.

 

[infinity]

Could I use something like an Eaton ground bar in this junction box (Picture attached) if I scrape the paint behind the ground bar, scrape the paint on the opposite side, through nut and bolt it, and run a jumper to the green screw pictured in the box. The largest circuit is 20 amps, so I think I could use a #12 jumper.

If you remove the paint behind the bar and nut and bolt the bar you do not need the jumper. You could leave the paint and use the jumper instead.

 

[Jimmy7]

Thank you!