Bonding screw threads at panel stripped

Barbqranch said:
How about a rivet nut? That would give you lots of threads and good contact to the panel.
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don_resqcapt19 said:
Listed as a grounding and bonding connection?
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Does it need to be? Regular bolt and nut isn't either.

I guess I'm not certain what is meant by "rivet nut". If something you still thread a bolt/screw into how is that different than regular bolt/nut.? If depending on this rivet for electrical continuity I can see listing being necessary but if only providing mechanical securement I don't see it needs to be. Either way you still need a listed lug or other terminal under the bolt head, nut, etc. and remove any paint or other insulating material so you have a good bond with the metal enclosure. If you can achieve the "two threads" into the metal then that is presumably sufficient bonding contact area and shouldn't need to remove paint.
 
kwired said:
Does it need to be? Regular bolt and nut isn't either.

I guess I'm not certain what is meant by "rivet nut". If something you still thread a bolt/screw into how is that different than regular bolt/nut.? If depending on this rivet for electrical continuity I can see listing being necessary but if only providing mechanical securement I don't see it needs to be. Either way you still need a listed lug or other terminal under the bolt head, nut, etc. and remove any paint or other insulating material so you have a good bond with the metal enclosure. If you can achieve the "two threads" into the metal then that is presumably sufficient bonding contact area and shouldn't need to remove paint.
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A regular bolt and nut is on the list of permitted grounding and bonding connections in 250.8. The rivet nut is not. The body of the rivet nut provides the electrical connection to the enclosure.
 
don_resqcapt19 said:
A regular bolt and nut is on the list of permitted grounding and bonding connections in 250.8. The rivet nut is not. The body of the rivet nut provides the electrical connection to the enclosure.
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Yes but I would take and make it into a bolt stud by feeding from back and adding a star lock washer under the nut and the you can add MBJ with a eyelet and another nut. But be sure to create a clean surface (no paint) for the bolt stud to bond with the enclosure. I would torque the locking bolt stud beyond the recommended torque of the Jumper so it doesn't spin out or loosen when removing.
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Drill a hole in the top, bottom or side and use a nut and bolt with a lug. Run a wire over from the lug to the neutral bar. may not be "listed" but if the hole is stripped what are you going to do? Or have a nut tack welded to the back of the panel and touch up the paint. Hollow out the plywood or the wall so the nut will fit or space the panel out with washers.
 
petersonra said:
fasteners are not required to be listed at all.
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Correct, but the rivet nut is not on the list of permitted connection methods in 250.8(A). Machine screw fasteners are if they engage at least two threads or are secured by a nut. The only way to use a rivet nut is if it complied with 250.8(A)(8) which requires a listed product.
 
Siemens OEM 1/4-28 MBJ screw does do more than mechanically fasten a lug to the panel cabinet, since the neutral bar is elevated away from the back of the cabinet the screw acts as conductor (bonding jumper) from the neutral bar to the cabinet.
don_resqcapt19 said:
A regular bolt and nut is on the list of permitted grounding and bonding connections in 250.8.
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My book has item (5)
(5) Machine screw-type fasteners that engage not less than
two threads or are secured with a nut
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I use a 1/4-28 bolt the same thread as Siemens did (grade 8 bolt), I would consider 28 TPI a 'fine thread' thus a 'machine screw', a regular 1/4-20 nut and bolt your right that would be a no. 250.8 (5) is not very specific on the nut, so a even 1/4-28 rivet nut would not be prohibited.
 
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thomasg88 said:
I have a Siemens SN series 200 amp load center which is the first point of disconnect. The bonding screw was over torqued and I cannot achieve the 45 in-lb torque spec’d. the screw itself is fine. It is the panel bonding tap hole that is not providing the necessary resistance. Any tips?

Thank you
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id just install a wire type MBJ sized properly in accordance with 250.102(c) to connect the service disconnect enclosure and egc to the grounded conductor terminal/buss
 
don_resqcapt19 said:
Take a look at the back side of the enclosure. If there is additional metal raised above the surface at the factory holes for grounding connections, the panel is not thick enough for two threads, so they use a special punch to "add" thickness.
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I don't know what the thickness is of the typical 4x4 box or other common metal outlet/device boxes is or if it has gotten thinner over the years but majority now have a raised portion (and usually one less KO than they used to) where they have a hole for grounding screw. I think many thought it was so your screw doesn't bottom out on the mounting surface - but very well may been more so because of not enough thickness to the wall of the box? This raised portion does have more thickness then the rest of the box does.
 
kwired said:
I don't know what the thickness is of the typical 4x4 box or other common metal outlet/device boxes is or if it has gotten thinner over the years but majority now have a raised portion (and usually one less KO than they used to) where they have a hole for grounding screw. I think many thought it was so your screw doesn't bottom out on the mounting surface - but very well may been more so because of not enough thickness to the wall of the box? This raised portion does have more thickness then the rest of the box does.
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Most device and outlet boxes are still 1/16" so you can drill and tap those, but most panelboard enclosures, especially residential ones, are less than 1/16".
You are correct about the reason they raised the ground screw point up into the box for device and outlet boxes.

I have only see the holes with the punched out material on the back side of panelboard enclosures.
 
tortuga said:
Siemens OEM 1/4-28 MBJ screw does do more than mechanically fasten a lug to the panel cabinet, since the neutral bar is elevated away from the back of the cabinet the screw acts as conductor (bonding jumper) from the neutral bar to the cabinet.

My book has item (5)

I use a 1/4-28 bolt the same thread as Siemens did (grade 8 bolt), I would consider 28 TPI a 'fine thread' thus a 'machine screw', a regular 1/4-20 nut and bolt your right that would be a no. 250.8 (5) is not very specific on the nut, so a even 1/4-28 rivet nut would not be prohibited.
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I will hang a red tag as the on that installation as I do not know that the contact between the outside of the rivet nut to the enclosure wall is suitable for this purpose. That is the only conduct between the enclosure in that installation. I would require the rivet nut to be listed per item 8.
 
kwired said:
That would open a big can of worms if they were. Now you can only use them for what they are listed for, according to some people. Even if the application doesn't require them to be listed.
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There is NOTHING in the NEC that requires listing unless it specifically states that in the code.
 
petersonra said:
There is NOTHING in the NEC that requires listing unless it specifically states that in the code.
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The rivet nut is not one of the permitted bonding and grounding methods in 250.8(A). The only way it could be used is if it complied with list item (8) which permits other listed methods.
 
I usually just pick up scrap 12gauge off the floor and ask one of the hvac guys for a sheet metal screw.

Has worked fine for many 1200amp services

Have never had a breaker trip since doing this.

Jk :p
 
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