Grounding and bonding a large solar array.

[electrofelon]

I just want to go over this and make sure I have it all correct. Say I have a large rooftop solar array where the array consists of a number of isolated sections. Lets also say there are a number of inverters, and each array section can have strings or part of strings from several inverters, thus we have "dc jumpers" crossing between the array sections which are run thru EMT and the EMT does no connect to the racking structure. The string conductors (2KV PV wire) leave the inverter thru a 6 foot piece of LFMC which is strapped to the racking structure. Remember that some of these string circuits will be routed through the array and jump over to another array section. Granted there is some ambiguity about whether all parts of the mounting structure and modules are listed for grounding per 690.43 (C thru E), but for the purpose of this discussion, lets assume all parts of the racking are listed for grounding to each other and to the modules.

Assuming the typical 15A string fuses at the inverter, I would just need a 14AWG minimum EGC from the inverter through the sealtite and bonded to the racking with an approved lug. If the EGC was not routed through the sealtite, I would need #6 per 250.120(C)

The EMT housing the DC jumpers is likely to become energized so That is bonded with a bonding bushing and #6 to the array structure. But the "remote" strings or part of the strings that are in another array section need to bonded back to the inverter they serve so I put a bonding bushing on the other end of the EMT to bond it to the other array section.

Does everyone agree with the above two paragraphs?

Also one final question: Can a water pipe bonding clamp be used to bond in the EMT instead of a bonding bushing? The crew has been using these and I have never seen them used this way.

Thanks.

 

[jaggedben]

I see nothing wrong with anything you've said.

As far as the pipe clamps, I've seen it quite a bit, although mostly on older systems. I can't answer the question, but your guys probably didn't make it up on their own. I'm a bit annoyed and surprised at the lack of an integrated lug and bushing product for bonding chases the way need in the solar industry.

 

[electrofelon]

I see nothing wrong with anything you've said.

As far as the pipe clamps, I've seen it quite a bit, although mostly on older systems. I can't answer the question, but your guys probably didn't make it up on their own. I'm a bit annoyed and surprised at the lack of an integrated lug and bushing product for bonding chases the way need in the solar industry.

Thanks for the response. Yes I am annoyed by a lot of stuff racking makers dont think of. Im half tempted to go into the racking business myself. I would like to see an angled end plate for this racking system (panel claw) that bolts to the ballast tray and you can punch it out for conduit entry/exits. The jumper pipes are a real pain and add so much time. I proposed using deep strut and just laying the conductors in the strut like a mini cable tray, but that idea got nixed.

 

[Zee]

Sounds fine.

Do you use the bonding bushings as they come or do you replace the aluminum body and zinc set screw lay in lug on them with a direct burial rated lay in lug? (heavier tin plated copper lugs with stainless steel set screws)

Technically the water pipe bonding clamp is rated for water pipe and not EMT...there MAY be an issue with inspection. Anyone have experience with this?

 

[jaggedben]

Technically the water pipe bonding clamp is rated for water pipe and not EMT...there MAY be an issue with inspection. Anyone have experience with this?

I've seen a few that must have passed inspection when solar was a relatively new thing. Your AHJ may vary.