electricalforum.nz

It states main earth shoukd be sized to the largest active conductor

But what if active conductors are in parallel. I feel like the actives csa should be combined and main earth relevant to that but the wording does not read like that.

But in practise not combining the actives doesn't not seem correct.

Help on this one much appreciated

5.3.3.1.2 may be under protective earth conductors but I believe the information at the bottom of this clause is more relivant to using table 5.1 rather than strictly to PECs, I'd definitely apply this same logic to MECs despite not being mentioned in 5.3.3.2

Yes, for mains in parallel it's the combined CSA that counts;
the CSA of each phase is 2 x CSA of the individual conuctors that make up the phase
Eg 2 x 25 mm Cu = 50 mm total, so MEC 16 mm2

Thanks. I was hoping for that response

Thanks.

I think 3000 wording is a bit of a let down here.

Isn't this clear enough?

"Where the active conductor comprises a number of conductors, connected
in parallel, the earthing conductor shall be determined in relation to the
summation of the cross-sectional areas of the individual conductors forming
the largest active conductor to be protected."

Doug I think it's the fact that's in clause 5.3.3.1.2 under PECs where as 5.3.3.2 for MECs doesn't have that as mentioned above

Although as I said i believe that logic was more intended for using Table 5.1 rather than strictly related to PECs