If you are finding pinholes in the copper piping near or touching a iron
rebar/mesh it is dissimilar metals doing the deed. The alkalinity of the
concrete that drives the iron-copper cell. All copper systems in my neck of the
woods have to have these junctions prevented.Especially now that we have a lot
of steel studs used in commercial work. (Here in NW WA we export trees and
import steel to make studs. Whats wrong with this picture?) Up here we have a
lot of galvanized water piping in 70's and 80"s houses. They rust pinholes from
the inside out in about 15 years or so. Surprisingly the earlier ones aren't as
bad. All interior piping must be grounded to service for electrical safety.
Rebar is only allowed to be used as a grounding electrode when fully encased
in concrete. Otherwise you must use a 3/4 or large galvanized pipe 10 feet long
or a galvanized ground rod 5/8 solid or better or copper/copper-clad ground
rod. Rods are to be 8 foot or longer. Currently 2 are considered minimum but
local jurisdictions may require more. Of course the approved connectors must be
used, especially with the dissimilar metal connections.
The NEC wants to have all your grounding tied together but doesn't address
your radial system with it's insulated wire.
I'm glad to see that all are not forgetting the rather large dc component of
lightning and the effects of plasma if the strike chooses to jump even the
smallest gap. The plasma is such a different animal form dc and rf that it's
parameters are still an unknown.
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