Adapting 15kW Roof Mount to Ground Mount - Special Considerations

[ztrain727]

Hello folks -

Long story short, a neighbor had roof leaking issues with a 15kw system and gave it to us for free.

My primary concern/question is the racking. It is roof mount aluminum racking. See the images below.

My first thought was to add a section of angle iron that bolts to the racking, bracing the joints. I would then affix the angle iron/racking to the pipe with U-bolts. However, our solar guy said this could lead to issues with with modified racking no longer being UL certified.












We got a quote for all new racking at $10k. That's our budget for the whole installation. Any ideas how to get this thing racking to work and still get final approval? For the permit, I just said we are using the existing racking and didn't provide much detail, but I'm worried about the inspection.


Some background, if you care...

We didn't really have the budget for the install, but couldn't turn down such a good offer. I won't go into detail about the system - 100x BP 150w panels, 6x sunnyboy 600vdc grid-tie inverters.

I drew up the structural plans, got them approved by a structural engineer. Frame will be 1.5" ID galvanized steel, concrete piles. Had a solar electrician do the electrical drawings. After jumping through all the hoops, we finally have our permit in hand, and we've trenched from the house to the array and run all the conduit and wire to the inverters in the basement.

I'm happy to share all information including my drawings and photos of the install down the road to help other attempting similar installs.

[DanS26]

Almost all rail systems are dual purpose. Check with the OEM to see if the brackets for ground mount are available for those rails. Save yourself $10k.

[ztrain727]

Interesting... I was under the impression talking with the solar guy who did the drawings, looked at the racking etc. that ground mount racking was different. From what I've seen from other systems online, most ground-mount racking is double walled more like square tubing: 670_tt_rails.jpg

If most systems are in fact universal, that is excellent news. When you say OEM brackets, do you mean to hold the panels down, or connect the racking to the frame structural elements (pic 1 vs. 5 in my first post)? Only issue there is I can't find anything printed on the racking - no brand name, UL sticker, nothing. The system is 10 yrs old so not sure if this stuff is still manufactured. That said the bolts are standard 7/16.

[Samsolar]

An end view of the rail would help, but the end clamps and mid clamps are fairly similar to Ironridge products of today. Maybe it is an earlier version of their XRL light rail product?

Speaking of Ironridge, if you look around their website, you can see how they use a standard system of racking and make minor adaptations to allow it to be roof or rack mounted. With that concept in mind, it would seem that your existing racking may be able to be reused if you build a pipe frame that allows support at all of the former roof attachment points.

Good luck with your project and keep us posted on how it all turns out.

[inetdog]

FWIW, no racking system that I know of is UL listed, since except for the details of grounding the NEC and UL do not really care about the racking.
It needs to have sufficient mechanical strength to withstand expected snow and wind loading in addition to the weight of the panels, and the requirements for that vary with the installation site.

I would worry more about calculating the forces on the racking system correctly than "violating a listing".

[ztrain727]

This all sounds encouraging... My bad on the end view - I seem to have forgotten that photo. Just took another in the dark for clarity.





The weak point is the joint that connects the two sections. None of the single sections are long enough for my purposes. They seem to have all been joined in this way on the previous install, but they are pretty flimsy, so I added a second plate on the back so there is one bracing both sides and it seems solid. Interesting about the UL certification - I guess my solar guy isn't quite up to speed. I have other reasons to doubt him as he installed plastic conduit in our basement for DC even after I asked if it should be metal. He ended up having to come back and rip it all out and reinstall metal flextube. He is NABCEP certified, but I am wary...

It's not the end of the world to have to go back and reinforce the racking. What I want to avoid is building this whole thing and having the inspector inform me I have to rip it all out and buy new racking.

One thought was to make a trip down to the municipal office and show the inspector the racking. So long as he is flexible with adapting it as needed (or not at all), I'm covered.

[bcroe]

There are all kinds of ways to build a ground mount. Purpose built PV racking is probably the
most expensive, if convenient way. Here I see 6061 aluminum angle cut & drilled to fit.
Kee-Klamps (fencing) have been very economical. A treated wood frame might emulate
the roof it used to be on; cheapest & shortest life. Check
your local regs. Bruce Roe

[ztrain727]

Bruce - We are in NJ and as expected the regulations are through the roof. This system is totally over-engineered IMHO but we got the permit and that's what matters I suppose. Has to be metal, 110mph winds, snow load, etc. I am using Quik Clamps which appear to be the same thing as Kee clamps but half the cost (as long as you're using 1.5" or under.

Seem like angle iron affixed to the racking would be bomber, if necessary.

[Amy@altE]

For kicks and giggles I ran it through the IronRidge configurator (I guessed on snow load and tilt angle). They do a nice modular product that has you provide your own schedule 40 pipe, and they have the pieces to put it all together. It says you can do 5 high on a 14' rail. Not sure what the lengths are of the rail you have, if you could use the existing rail. Your rail seems awfully thin however, I'd be very nervous about using it in a ground mount. If you are interested, the IronRidge with new stronger rails would be about $6k, without the 600' of 2" schedule 40 piping you'd get locally. I attached the output for your enjoyment. Design Assistant _ Ground Mount _ IronRidge_BP150.pdf