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Posted By Topic: Double Screw earth and MEN

Kelectrical
Aug 29 2019 06:11

I've used a small switchboard for a small shed install and I've only noticed afterwards that it has only one double Screw on the earth bar.

Does the MEN have to be under a double Screw?

Or

Can I use the same double Screw terminal for the MEN and earth?

Thanks guys.
   

DougP
Aug 29 2019 07:39

Double screw is not required if the single screw is 80% or more of the diameter of the "tunnel".

2.9.4.3, 2.9.4.2
And 3.7.2.11 which also references 2.9.4.2 for the bars and links.
   

AlecK
Aug 29 2019 10:33

"Can I use the same double Screw terminal for the MEN and earth?"

NOT a good idea; the MEN should be readily removable for testing; without affecting anything else.
   

zl2aj
Aug 29 2019 13:07

Another option is if you have a tunnel assembly with single screws you can either

- Split the strands into 2 groups and put each under a separate screw (parallel tunneling if you will)
- Form a 180 degree loop with the conductor so that it travels in and out of one tunnel and back into another (adjacent) tunnel (series tunneling).

But as mentioned above - double screws are not always a requirement.
   

AlecK
Aug 29 2019 13:59

Neither of those methods complies with 2.9.4.2 for conditions (a) to (d), because thrroding is "the" (ie singular) terminal shall ....

So regardless of efficacy; using two terminals simply does not comply.