[RE-wrenches] 4/0 GEC

[russ at solarray.com]

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.
russ at solarray.com



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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