Hi Drake,
The NEC says that "The size of the grounding electrode conductor for a
dc system shall be as specified in 250.166(A) and (B), except as
permitted by 250.166(C) through (E)."
The "except as permitted by" is what allows us to not run a 4/0 GEC.
250.166(C) says that the GEC doesn't have to be larger than #6 copper
for connection to a rod, pipe, or plate electrode. (I don't think
pipe-as-part-of-the-plumbing-system is what is meant by "pipe" there,
since 250.52(A)(5) and (A)(7) are referenced, and 250.52(A)(1) deals
separately with metal water pipes that come up from underground.)
250.166(D) says that the GEC doesn't have to be larger than #4 copper
for connection to a concrete encased electrode.
No mention is made of the maximum size of GEC connected to the plumbing
system in section 250.166, so the size of the GEC in that case might
have to comply with (A) and be way larger than necessary.
That's how I see it, at least.
Russ
Russell Mueller
SolarRay Inc.
[email protected]
Drake Chamberlin wrote:
Hello Wrenches,
Revisiting the grounding requirements for DC systems, the grounding
electrode conductor is still required to be as large as the "largest
conductor supplied by the system" (250.166(B). When we run a GEC to a
piping system, or the re bar cage embedded in the concrete foundation
of a building, it still reads like we need to meet this requirement.
If the system is a 24 volt, battery connected, VFX 3524, it still
seems that we would need to run a 4/0 GEC. Inspectors backed off
making us do this a dozen years ago. Why are we not being required to
do this now?
Thanks,
Drake Chamberlin
Athens Electric
OH License 44810
CO License 3773
740-448-7328
740-856-9648
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