jar546
Forum Coordinator
This is not allowed per NEC?
Hint: It’s not in 250
Hint: It’s not in 250
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Self tapping screws as ground screws
- Thread starter jar546
- Start date
ICE
Oh Well
Could you provide the first number of the Section? It seems to me that there's plenty in Article 250 that could be used to deny this. But I know that you like to find a needle in stacks of needles.
wwhitney
Registered User
jar546
Forum Coordinator
OK, you did not fall for it. Yes, it is 250.8(A)
ICE
Oh Well
And you have accused me of trolling.
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 or more 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
jar546
Forum Coordinator
steveray
SAWHORSE
And just to clarify...that screw doesn't meet #6 or it would/ could be allowed
jar546
Forum Coordinator
Correct and could.
ICE
Oh Well
No matter what screw is used, the sheet metal is too thin to get two threads. There is a solar racking company that has a bonding jumper strap with two screws on each end so that there will be two threads in contact. It is listed that way. So two ineffective connections were better than one.
This came about after I was invited to a mockup at Santa Fe Springs Ca. It was early in the solar wars. Major company lost their UL Listing that day. It was prior to integrated grounding and there were many straps from module to module. There were wrong straps all over the USA that had to be retrofitted. I wasn’t on friendly terms with them after that.
This came about after I was invited to a mockup at Santa Fe Springs Ca. It was early in the solar wars. Major company lost their UL Listing that day. It was prior to integrated grounding and there were many straps from module to module. There were wrong straps all over the USA that had to be retrofitted. I wasn’t on friendly terms with them after that.
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wwhitney
Registered User
I don't follow this comment. The picture in the OP looks like a 4 square junction box or the like. NEC 314.40(B) requires such boxes to have a wall thickness of 1/16", unless listed. Are there listed boxes out there that are actually thinner, per the exception? If not, then a 32 tpi machine screw will provide the two threads required.
And even a thinner listed box could have a formed boss where the effective thickness is greater, allowing the use of a 32 tpi machine screw. But such a box would not permit the use of a 32 tpi machine screw elsewhere.
Cheers, Wayne
ICE
Oh Well
The extruded aluminum was thin. The screws were self tapping sheet metal screws. 10-32 machine screws come in self threading. Not self tapping. The power above me accepted two self tapping sheet metal screws to get two threads. It didn’t perform as touted. Stripped easily and there was no torque value provided. It wasn’t my problem to deal with as I was just a guest at another jurisdiction. It was County but not my part of the county.