DC Runs in the Attic [RE-wrenches]

[Dean T. Newberry]

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Hi Mark,
The next electrician or handyman who works on the house will turn off 
the main breaker to be sure there are no live wires in the house when he 
begins to remodel. (Actually he will probably just shut off  the solar 
AC disconnect, it looks like it will do the job.) Your emt run through 
the attic is still hot. He may just cut through the emt with a sawzall 
so he can make a change. Zap, and he can't shut it off zzzzzzzzzzz...!
I basically agree with the building inspector on this one, and only 
violate this rule  occasionally. When we put a power plant of the roof, 
we incur an obligation to make it safe for workmen who will follow us.
cul  deant


Mark Byington wrote:

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>A local inspector in CA is interpreting 230.70 to mean we cannot run the DC line from a roof mounted PV array through the attic of a residence to the DC disco mounted on an exterior wall.  His justification is that the DC run is a service entrance conductor.  He is worried about fire hazard.  The code does say it is up to the local jurisdiction.  We have tried to convince him with the following points:  1) Unlike power from the utility, a PV array is inherently current limited.  The short circuit current, even with 25% derating per 690.8(A)(1), is much less than half the wire's ampacity at 90C.  2) We use metallic conduit with no J-boxes or splices in the run.  The wire is continuous and therefore very unlikely to fail or overheat, plus it is in metallic conduit - double protection.  3) The utility already runs the service entrance wire through the residence (although a shorter distance) if the service entrance panel is flush mounted (of course, this is in rigid conduit).  4) PV installations will be much less aesthetic with EMT on the roof and exterior walls.
>
>We even got John Wiles involved to talk to him, but so far no dice.  I plan to elevate it to the building official but I thought I would ask you all - do you run the DC through the attic?  Do your local jurisdictions allow this?  Do you have any other good arguments to help convince him?  By the way, DC runs through the residence will likely be explicitly allowed in the 2005 code.
>
>Thanks
>Mark
>Cobalt Power Systems
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-- 
*Quantum Energy Group*
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	Dean T. Newberry
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430 D Street
Davis,  CA   95616
T:  (530) 758-6064
F:  (530) 758-3684
deant at dcn.org <mailto:deant at dcn.org>

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