Ground Bar

[SceneryDriver]

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.

You don't even need the jumper. Removing the paint and through-bolting is sufficient.


SceneryDriver

 

[jaggedben]

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.

So if you have two screws that each engage at least one thread, it seems to me you meet the letter of the code.

 

[infinity]

So if you have two screws that each engage at least one thread, it seems to me you meet the letter of the code.

That does not comply with 250.12.

 

[jaggedben]

That does not comply with 250.12.

Huh? I didn't say anything about about either removing paint or not.

 

[don_resqcapt19]

So if you have two screws that each engage at least one thread, it seems to me you meet the letter of the code.

• (5)
  Machine screw-type fasteners that engage not less than two threads or are secured with a nut

 

[electrofelon]

to add another wrinkle: This is interesting. This box does not have a factory provision for a ground screw or lug. Note the wording of the label. If one is very precise/nitpicky, sounds like manufacturer instructions dont allow bonding it with a wire EGC to a lug.

 

[Tulsa Electrician]

If it has 32 threads per Inch than the material thickness would need to be 2/32 or .0625.
If the material your drilling and tapping is .0625 and you use 32 threads per in machine screw or bolt than you good.

 

[jaggedben]

• (5)
  Machine screw-type fasteners that engage not less than two threads or are secured with a nut

Right. Fasteners (plural) that engage two threads. It's not explicit that each fastener must engage two threads individually.

 

[jaggedben]

If it has 32 threads per Inch than the material thickness would need to be 2/32 or .0625.
If the material your drilling and tapping is .0625 and you use 32 threads per in machine screw or bolt than you good.

Or simply, 2/32 = 1/16th of an inch. Which, coincidentally, is the same as 16 gauge. Which most metal enclosures seem to be made of.

 

[don_resqcapt19]

Right. Fasteners (plural) that engage two threads. It's not explicit that each fastener must engage two threads individually.

It is very clear to me that the two threads apply to each and every machine screw fastener used for a bonding or grounding connection.

 

[jaggedben]

It is very clear to me that the two threads apply to each and every machine screw fastener used for a bonding or grounding connection.

Charlies Rule. The code doesn't say 'each'.

 

[don_resqcapt19]

Charlies Rule. The code doesn't say 'each'.

It will get a red tag from me and you can take it up with a higher authority

 

[Tulsa Electrician]

Some follow up information.

When we have this discussion at work. I like to refer them to Article
250.8 then head over to
314
Part 3
314.40
For some boxes covered in part (C).
Is the catch to how to properly bond to the enclosure with a equipment grounding bar. Some times yes with the screws provided and sometimes no and paint shall be removed and a nut placed on back side. Then I'm fine with it. I also ask them to read 314.41.

Then I like to follow up with 408.40 when installing in a cabinet which contains a panel board.

I get ask a lot why based on 4 square 1-1/2 deep the table only allowed what it does based on the cubic inch of conductors.

Then I go on to explain how this impacts table 314.16(A).
Based on the UL listed box(.0625) and the number of allowed conductors.
The box area is reduce based on the .0625 minimum thickness to comply with 314.40.

I also explain why we use 6/32,8/32,10/32 screws for most of what we do. It's the two threads for the materials thickness for most common applications.
An example would be self grounding devices when installed using the supplied screws, which has two 6/32 screws. The plaster ring (.0625) it fastens to is attached to a four square box (.0625) with two 8/32 which most of the time has an EGC wire type conductor bonded to the box with a 10/32. Then most back that up with a wire type bonding jumper to the device.

 

[jaggedben]

It will get a red tag from me and you can take it up with a higher authority

I probably would. Particularly if you didn't take out your calipers and prove to me that the enclosure thickness is less than 1/16".

 

[SceneryDriver]

Or simply, 2/32 = 1/16th of an inch. Which, coincidentally, is the same as 16 gauge. Which most metal enclosures seem to be made of.

16ga steel is 0.06" to 0.063" thick, depending on tolerance and who you ask. At the low end, you might not exactly make two full threads. To avoid that argument with inspectors and others, we build our electrical enclosures from 14ga steel at 0.075"; we have a CNC laser and CNC press brake where I work, so we often fold up our own NEMA 1 enclosures. We've also found that the slightly increased thickness holds screws for DIN rail and other components better, with less chance of stripping out when the screws are tightened.

If you get a particularly pedantic inspector, they may make you break out the digital calipers. Or, you can just throw a nut on the back and call it a day.


SceneryDriver

 

[jaggedben]

I always attach groundbars with two screws for good measure and I've never been called on the box thickness and don't expect to ever be called on it.

 

[Tulsa Electrician]

pedantic
Interesting choice of word.

 

[don_resqcapt19]

I always attach groundbars with two screws for good measure and I've never been called on the box thickness and don't expect to ever be called on it.

That is because most people do not know that the typically panelboard cabinet walls are not thick enough to engage two threads of a screw that has 32 threads per inch. Many other enclosures are thick enough.

 

[jaggedben]

That is because most people do not know that the typically panelboard cabinet walls are not thick enough to engage two threads of a screw that has 32 threads per inch. Many other enclosures are thick enough.

As a sanity check I just took out my calipers and measured the subpanel in my house and it came out about .070". So, what typical panelboards are you talking about?

 

[electrofelon]

As a sanity check I just took out my calipers and measured the subpanel in my house and it came out about .070". So, what typical panelboards are you talking about?

FWIW siemens says their (true) panelboard cabinets are 16 gauge. I dont know about their loadcenters.