DIY Ground Rack

[jovial_cynic]

So... after getting a lot of constructive feedback on this site, I've decided to pursue permits to make sure that I'm doing everything by the book. Additionally, something about PG&E turning the lights off at my house if I hook up without their permission concerns me a little bit as well. That said, I won't be going rogue - I'm going to do this by the book.

One minor problem is that I went out and built the rack and installed my panels *before* I decided to get a permit. It's a custom rack... so now I have to pay an engineer to put a stamp on it and say it's good.

Here are some pictures of what I've put up. The engineer is currently going over my drawing and photos, so hopefully I don't need to make any significant/costly changes. Any thoughts?

[SunEagle]

That looks like a really well done ground mount system. I hope you get a clean bill of help from the PE.

[jovial_cynic]

That looks like a really well done ground mount system. I hope you get a clean bill of help from the PE.

What's a PE? Project Engineer?

[DanS26]

Wow, no weeds growing under your array. Turning the top row of panels 180 degrees will probably result in less wire management. A good engineer will probably question the shear strength of the bolts used on the pylons......and composition of metals used...ie SS vs Al vs Iron.

Good DIY project.

[SunEagle]

What's a PE? Project Engineer?

No. Actually I am a Project Engineer.

A PE is a Professional Engineer and has a license that is recognized by state officials as having the ability to approve and sign off on engineering drawings.

[J.P.M.]

1.) Like Dan, I'm wondering about the bolting, size and quantity overall.
2.) Any footings to the slab ?
3.) Seismic zone ?
4.) Assuming the P.E. doesn't find too much, if/when you paint the C.Stl. structural members, and if it's a spray job, I'd suggest you consider covering the panels, top, sides and bottom during the spraying. Overspray can get in places you wouldn't think of quite easily and cause performance problems.

FWIW: You are paying an engineer to examine the design to see if it conforms to engineering and code standards - not a stamp as in buying an admission ticket. If, after examining the design and calcing it out, the P.E. deems that the design is safe, and conforms to those engineering and code standards, the engineer will stamp the design. If it doesn't conform - no stamp. The engineer may then contract with you for remedial work, or do it gratis. In any case, the stamp is not a slam dunk.

[jovial_cynic]

Replies below.

1.) Like Dan, I'm wondering about the bolting, size and quantity overall. The panels are held down with four 1/4" bolts each, and then the purlins are held to the upright posts with 9/16" bolts.
2.) Any footings to the slab? The slab is 4" thick, but there is a 1x50' footing in the front and back of the slab that is 6" deep, and that's where the upright posts are.
3.) Seismic zone? Zone 3. Central Valley California.
4.) Assuming the P.E. doesn't find too much, if/when you paint the C.Stl. structural members, and if it's a spray job, I'd suggest you consider covering the panels, top, sides and bottom during the spraying. Overspray can get in places you wouldn't think of quite easily and cause performance problems. The purlins are galvanized, but the upright posts and x-bracing will need to be painted. There's actually not too much to paint, so I'll probably manually paint it.

FWIW: You are paying an engineer to examine the design to see if it conforms to engineering and code standards - not a stamp as in buying an admission ticket. If, after examining the design and calcing it out, the P.E. deems that the design is safe, and conforms to those engineering and code standards, the engineer will stamp the design. If it doesn't conform - no stamp. The engineer may then contract with you for remedial work, or do it gratis. In any case, the stamp is not a slam dunk. I understand this. I was saying it based on the assumption that it DOES confirm, and that in the end, I just paid a guy to stamp something for me. Obviously, if I missed something, I'll be glad that I paid an engineer to address those issues.

[eugenek]

It is a nice looking system, but I have doubts that you'd get them to sign off on it without a good look at the bottom of the slab. For all they know, you might have 2" of concrete with no rebar, it'll fracture at the first earthquake and then pieces will be blown away by the next strong windstorm. A project like that generally requires an inspection after you excavate and lay rebar, but before you pour concrete.
There's nothing you can do about showing to them that you have reinforcement, but, if they are willing to let it fly, I'd expect them at least to ask you to dig down around the perimeter so they can see how thick the slab is.

[jovial_cynic]

I thought about that. If it comes up, i can do random drill samples so they can measure thickness at locations of their choosing.

[Wy_White_Wolf]

Looks good but I'm wondering what you did to prevent galvanic corrosion between the aluminum and steel? That would be enough to prevent the PE approval.

WWW

[bcroe]

It is a nice looking system, but I have doubts that you'd get them to sign off on it without a good look at the bottom of the slab. For all they know, you might have 2" of concrete with no rebar, it'll fracture at the first earthquake and then pieces will be blown away by the next strong windstorm. A project like that generally requires an inspection after you excavate and lay rebar, but before you pour concrete.
There's nothing you can do about showing to them that you have reinforcement, but, if they are willing to let it fly, I'd expect them at least to ask you to dig down around the perimeter so they can see how thick the slab is.

I took pictures of the rebar before pouring the guy wire anchors of my radio tower, and after it was poured. 2' X 4' X 8',
4' deep. Here in the "wild west" zoned AG, no permits or inspections are needed for anything short of a building, but
documentation might be useful some day. Bruce Roe

[jovial_cynic]

When you say steel, are you differentiating between regular steel and galvanized steel? The panels are only touching galvanized steel.

I'm doing research on galvanic corrosion now, so I'm trying to figure this out. Is this just a matter of rubber washers between the panels and the purlins?

[bcroe]

When you say steel, are you differentiating between regular steel and galvanized steel? The panels are only touching galvanized steel.

I'm doing research on galvanic corrosion now, so I'm trying to figure this out. Is this just a matter of rubber washers between the panels and the purlins?

Where there is an issue here (aluminum & treated wood), I have used squares of linoleum flooring with 18-8 SS bolts passing thru. Bruce Roe

[J.P.M.]

When you say steel, are you differentiating between regular steel and galvanized steel? The panels are only touching galvanized steel.

I'm doing research on galvanic corrosion now, so I'm trying to figure this out. Is this just a matter of rubber washers between the panels and the purlins?

It is about more than just the panels and their fasteners.

Galvanized steel and aluminum are quite close to one another in in the galvanic series, indicating less potential for problems. Still, such things are considered and checked in a good design. BTW, galvanized steel and mild steel are farther apart on the galvanic series than galv'ed steel and aluminum, indicating some potential for deterioration of the plating on the galv'ed material when those two materials are in contact.

Washers or spacers of a non conducting nature can mitigate the galvanic action - perhaps more of a concern here for the non galv'ed steel to the galv'ed steel, again, those two being farther apart on the galvanic series. In any case, such additions (in this case, spacers of easily compressed material) to a bolted joint will change its load handling characteristics, similar to the way a bolted joint using a gasket needs gasket information. The design should take this into account, as should the P.E. if galvanic corrosion is a consideration and spacers are used or deemed needed.

This is not an exact science.

Take what you want of the above. Scrap the rest.

[Mike90250]

9/16 bolts from home sespot are junk. you need to use certified fasteners with a grade (5 or 9) or structural graded fasteners, before an engineer can sign off.