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Threads and Self tapping screws?

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I

Isaiah

Senior Member
Location
Baton Rouge
Occupation
Electrical Inspector
City inspector cited the green grounding with 10-24 self tapping screws as unacceptable. He stated it had to be 10-32 thread due to the sheet metal thickness on the disconnect switch. Is this an NEC requirement?


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C

CoolWill

Senior Member
Location
Alabama
Occupation
Electrical Contractor
Yes. The code requires at least two threads engage the metal. 250.8(A) doesn't specifically require 10-32, but it does specify a machine screw thread. If the metal was thick enough for 10-24 to engage two full threads, that would also work.
 
kwired

kwired

Electron manager
Location
NE Nebraska
Occupation
EC
infinity said:
Is this a factory installed or a field installed screw?
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Isaiah said:
Field installed


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Question maybe should have been is it installed with manufacturer provided screw into a hole manufacturer provided for the purpose, or is it totally fabricated in the field?

Depending on the circumstances I don't know I would want to replace with a 10-32 screw into same hole after having the 10-24 in there, if this is totally field fabrication kind of situation. I don't know it would be any better connection after "re-tapping" threads and likely losing more contact material in the process

If it is a screw that is manufacturer option such as neutral bonding screw in a panel or disconnect - it should be listed and inspector has no ground to stand on asking you to do it differently.
 
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