Confusion over table 7.1(i) OSG

And herein lies the rub, pick a few corner cases - slow MCB, low mains voltage, hot live cable, so higher resistance,  then wonder should the earth path also be hot - probably in T and E on its own, but not if the earth path is assisted by trunking, plumbing  or conduit perhaps, add a bit of rounding up or down, and you will get a whole slew of similar, but not identical answers.

I'm aware of the 10% volt drop being pessimistic .but it compensates for my resistance figures not being ‘hot’ .

You could plug the loop impedance meter in at the far end after you have built it of course but then its a bit late to change it if the numbers come up a bit short.

The tables are good, so long as you realize that they apply only loosely to any specific  real case.

In many ways the last digit is a bit fruit machine - especially when it gives apparently precise answers like 118m or something.

Mike

And herein lies the rub, pick a few corner cases - slow MCB, low mains voltage, hot live cable, so higher resistance,  then wonder should the earth path also be hot - probably in T and E on its own, but not if the earth path is assisted by trunking, plumbing  or conduit perhaps, add a bit of rounding up or down, and you will get a whole slew of similar, but not identical answers.

I'm aware of the 10% volt drop being pessimistic .but it compensates for my resistance figures not being ‘hot’ .

You could plug the loop impedance meter in at the far end after you have built it of course but then its a bit late to change it if the numbers come up a bit short.

The tables are good, so long as you realize that they apply only loosely to any specific  real case.

In many ways the last digit is a bit fruit machine - especially when it gives apparently precise answers like 118m or something.

Mike