DC Runs in the Attic [RE-wrenches]

[Joe Felker]

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markb at cobaltpower.com wrote:
> 
> 
> 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
> 
> [Non-text portions of this message have been removed]
> 
********
For a recent install in NJ, the customer wanted us to drop right into 
the attic so he would not have to see any wiring conduit on the outside 
of his house.  It was a very large attic.  

I added a DC Disconnect in the attic to address the NEC Code.  The 
inspector however objected to the 20' of wire from the roof penetration 
to the disconnect.  He made us run the conduit outside of the house and 
then penetrate the attic space from the side right next to disconnect.



Joe Felker

Director of Field Operations
MAK Technologies
joe at MAKtechnologies.biz

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