The other thing to watch is the type of connection made (how well the Cu is clamped to the rod and the metal prep) and how well the joint is protected - there are specific paint sprays electricians use to protect the joint after construction. If you want to know the R to earth of the rod alone you clearly need 2 independent rods and a source of say 20A to run through the circuit to check the volt drop. B and C MCB types allow longer route lengths.ĪS 3000 our federal wiring code does not say how you are to achieve the resistance required to cause fault clearance - that is your problem.Ĭlause 5.6.2.2 suggests 12mm dia non ferrous rods driven to a depth of 1.2m. This would be based on 140mm2 active conductors for the 400A feed. Minimum recommended earth conductor size in table B 5.1 is 25mm2 for 200A so make it 50mm2 for 400A Maximum circuit length (out and back) is 84m for and HRC fuse and 60m for a type C MCB.

Resistance values should be halved for your current of 400A. Yessir that was for 200A - 400A is not even covered. 09R - trips at 12.5 x rated currentīS88 type fuse (HRC) 0.13R for a computed 400ms disconnect time.(you have to have the mafr fuse curve and know the source impedance to calculate the disconnect time.)

Table B4.1 of AS 3000 - 2000 version standard only slightly changed in last 4.5 years.Ģ00 A - maximum value of fault loop impedance at 230 VAC (this is the impedance from the DB, through the fault and back to the earth point at the MEN link ) MCB = moulded case breaker As3000 = AUS and NZ Wiring rules - Federal law here.

Ground wire size chart