[RE-wrenches] Using Metal Roof as conductor

[R Ray Walters]

I've oft wondered why we didn't use this time tested automotive wiring method more in PV; especially at higher voltages.
An energized roof is a happy roof as they say.
You go Solar Guru.

R. Walters
ray at solarray.com
Solar Engineer




On Apr 1, 2010, at 10:53 AM, Jason Szumlanski wrote:

> I am installing a PV array at about 400Vdc on a metal roof. The inverter
> is located a very long way from the array. I am contemplating just
> running a positive conductor for most of the run. I was thinking about
> connecting the negative PV conductor to a lug solidly bonded to the
> metal roof material. Then at the bottom of the roof, near the eave, I
> would attach another lug and continue with a negative PV conductor. At
> junctions of the roof material, I would drive a self-tapping stainless
> steel screw for continuity (with sealant, of course). This would save
> lots of copper. And since the negative conductor is bonded to the module
> frame by way of the metal roof, the negative PV conductor would also
> serve as the ground wire.
> 
> What do you think? Would this pass inspection? What NEC sections would
> apply?
> 
> Thank you for your time,
> 
> Solar Guru
> 
> P.S. April Fools
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