Undersize earth conductor

[davesparks]

Not contracting anymore, but 16th iee regs section 547-02-01 table 54h, cant of changed.?

Under the 16 th and 17th the selection from the table is
Live of 1mm to 16mm is equal size cpc
Live of 25 or 35 is 16mm cpc
Live of over 35mm is cpc >\= 1/2 size of live

Or it can be calculated by the adiabatic.

The commonly accepted size for a 100A service is 25mm tails with 16mm earth

 

[Geoffsd]

That's 543.1.4 Table 54.7 when too lazy to do sums .

Otherwise 543.1.3 - then bonding conductors are half of that, except PME.

 

[Deleted member 9648]

I thought the 4mm was the earthing conductor and the OP was worried because it was smaller than the main bond.

If 4mm is satisfactory as the earthing conductor - which we don't know yet - then only a 2mm bond is required but 6mm being the minimum allowed.

But you are taking the cpc for the distribution circuit as the earthing conductor. It is the main earthing conductor at the intake which will determine the size of the main bonding conductors.

 

[Geoffsd]

Ok, but even that is determined by the adiabatic regardless of what is actually fitted.
So, we would need to know the DNO fuse rating and the Ze.

There is a 10mm bond fitted anyway.

However, it is the 40A distribution circuit CPC that the OP is worried about.

 

[Engineer54]

The main earthing conductor on a TN-S system is the conductor between the cable sheath on a PILC cable or the earth conductor within a split concentric cable to the MET. From the MET they will be earthing conductors or CPC's and main bonding conductors...