Grounding garage roof panels through PVC conduit to combiner

[echoth]

Hi all, finalizing install of a 3.6kw system being installed on my garage roof and have this grounding question. 

For adequate grounding would there be an issue with running the ground wire from the panels through PVC conduit to the ground busbar of my MNPV6 combiner, then on through more PVC to end up at the ground rod?  I currently have 8awg from the panels to the combiner ground bus in the garage and all component EGC connected to the common ground bus in the combiner, but have not yet connected the combiner ground bus to the ground rod.  In effect, a lightning strike will run through the combiner, through the SPD and then on to the ground rod.  All panel wiring, including this 8awg ground, is routed from the roof through 1-inch PVC to the combiner.

For routing and visual reasons I don't want to run a separate conduit down the side of the house to the ground rod but safety is more important of course if the above has concerns. I have some 4awg insulated stranded thhn I can run in emt along and down the sloped roof if necessary if the above will pose issues.

Thanks
Tim

[zoneblue]

This is a kind of complicated topic. The primary purpose of the module frame bonding is to to remove shock hazards from the frames in the event of a earth fault. Thus the method you propose achieves that. However lightening is where things get interesting. The above bonding tends to paint a bit of a 'hit me' sign on the array. In lightening prone areas, its good to have something taller than the array in the immediate vicinity. And/or, use a second rod directly at the array which is in turn bonded to the main rod with smallish gauge wire, to get the energy to earth as direct as possible without dragging it all over the show. Of course SPDs at both end of the array homerun is advisable if you get much in the way of sky sparks.

Thats the short version! HTH.

[echoth]

Thanks. I hadn't even thought of the other option for secondary lightning rod near array.  My garage has a cupola for venting with a steel top within 2 feet of the array.  I could attach 4awg GEC (which I have alot of) to the steel cupola top inside and run along the inside of the roof  and out the soffit just above the ground rod on the other side of the garage (left in picture).  See attachment.  On the property maybe 200 ft away is a wind generator tower (28 ft) which I think attracts most of the lightning we've gotten.  50 ft away from the tower is the other large solar array (48x64w unisolars). I've heard some very close strikes over the last 16 years and think that's where they've hit at times (the tower or other array).  Of course the garage array has a lot more metal in it than the cupola.  Lightning is so unpredictable. It may go for the array instead but this can't hurt. 

[mike90045]

I could attach 4awg GEC (which I have alot of) to the steel cupola top inside and run along the inside of the roof  and out the soffit

I would not want to invite a lightning strike to the inside of my attic, and hope it will exit where the wire goes out.

[echoth]

Yeah I have abandoned that idea.  I'll be running EMT with 4 or 6awg along the roof straight to ground rod below.

[tecnodave]

echoth,


Check with your local code on use of PVC conduit in a solar system, as far as I know it is forbidden to use PVC for solar on a house even though your AC system can be in PVC!   EMT is legal for use in solar system from panels / combiner to the inverter or solar controllers.  In any case no PVC in the attic.

On the frame bonding I suggest a direct as possible route to a real good earth ground....I.e. A 8' standard ground rod which is connected to the main house ground Rod with 4 ga. copper wire with no splices, preferably buried in soil.

Lighting is weird stuff......a million volts will jump only 10 feet in normal air but when ionizastion happens things get real crazy!

dave

[CDN-VT]

I can see using a main Ground from the top steeple to ground as posted above , THEN grab the the panels & Y the second ground drop .
Face it , steeple is higher , but sky sparks have a destination of there own .

Thats the way I would try to grab the power spark.

VT