An underground tt supply going into a meter cabinet on the outside of a garage, 16mm tails straight through the wall to henley blocks, 10mm earthing conductor to a rod with a Ze of 38ohms. From henley blocks a small gagage sub main with a 63A 100ma T rcd, main house feed from henley blocks (in 16/16/16 split concentric cable) back into the meter cabinet and through underground ducting feeding house cu where circuits are protected by 2 x 80A 40mA. House built approx 1980.
Asked about this at school yesterday where I was lent gn8. From my reading there could be two issues.
1) Lack of a 100mA T rcd protecting the house feed and
2) The house feed needs a cpc but this should not be connected (house cu end), instead a separate earth electrode should be provided.
So my confusion is that the logical, practical and most convenient place for this new rod is back through the ducting to roughly where the existing rod is but only in 10mm. Surely it makes sense to keep the existing 16mm earth rather than replace it with a 10mm one.
Am I misreading something? Don't worry, I am not the person doing this, just trying to learn!
Asked about this at school yesterday where I was lent gn8. From my reading there could be two issues.
1) Lack of a 100mA T rcd protecting the house feed and
2) The house feed needs a cpc but this should not be connected (house cu end), instead a separate earth electrode should be provided.
So my confusion is that the logical, practical and most convenient place for this new rod is back through the ducting to roughly where the existing rod is but only in 10mm. Surely it makes sense to keep the existing 16mm earth rather than replace it with a 10mm one.
Am I misreading something? Don't worry, I am not the person doing this, just trying to learn!
