Talk:Taking electricity outside
concrete resistance
"A concrete floor in a garage that has no extraneous metal parts in contact with earth and no other services like water pipes entering the building will offer a good isolation from earth,"
Experience with ufer earthing seems to indicate the opposite. NT 23:26, 4 June 2007 (BST)
Not been able to find much on this. Normal practice in new builds seems to suggest that a concrete floor is considered to pose no risk with a PME installation. Ufer earthing also seems to depend on quite a high rebar content in the foundation slab.
The conductivity of concrete also seems hard to pin down - but it is influenced by its moisture content. I have seen figures of 25K ohm / cm - which if true would place more than enough impedance in the earth reference to make this a non issue.
I might post another invitation to comment on the group since the first one seemed to generate somewhat less than the normal level of response.
--John Rumm 11:17, 7 June 2007 (BST)