[RE-wrenches] Using Metal Roof as conductor

[Dan Fink]

Very good idea for the cost-conscious consumer and installer! It could 
also lower PV module cleaning and maintenance costs by dramatically 
reducing pigeon, squirrel and other avian or rodent populations that 
foul PV arrays and chew wires.

My consulting client at our meeting this morning said he wants to 
install a large PV array to power his off-grid home; however he is 
located on a north-facing slope deep in a  canyon, so the array must be 
mounted over 1/2 mile from the house. We have decided to run all power 
at 600 volts from the array to house via the existing electric fence, 
saving money and also thus mitigating wildlife damage problems on the 
property, including bears, moose, and pumas.

DAN FINK
Bucvkille Energy Consulting LLC



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