Why 0.05 Ohms for main bonding conductors?

[Smugley]

Hi all,

This has been bugging me for a while, so can anyone explain how we arrive at the value of 0.05 Ohms as the maximum acceptable value for resistance of main equipotential bonding conductors? Is there a calculation with 0.05 or less as the answer? Or is the idea just to keep it as low as possible and this is an arbitrarily chosen low value? I've been through all the books - BS7671, GN3, GN8, OSG and some other texts but no joy.

Cheers

 

[WayneL]

Hi Mate,

It's what the 'powers that be' determine as a 'negligible' resistance - in other words it's that low it won't matter.

It's the same reason that they allow that value as the tollerance when measuring R1 + R2 at socket outlets - i.e. each socket outlet should be within that range of each other.

 

[Smugley]

Thanks for your reply - that was the conclusion I was coming to!