I'm installing a 4kW ground mount solar panel with a wood base, it's a 4X4 solar array of Talesun TP660P. The plan is to have four concrete piers as the base, they'll support 2 two-ply beams with purlins supported between the beams. I'm thinking about using 20ft MCA treated wood, the purlins will be perpendicular on the long side of the panel. Each purlin will intersect the panel frame at 2 mandated clamping zones, which are around 4" long and centered 12" from the panel corner. Now, for the details of attaching panels to the purlins, I plan to use 5/16" stainless lag screws with washers.
Need insights to decide these dilemmas:
> Which one should I use, the 304 or 316 stainless steel? Which one is more resistant to galvanic corrosion at the interface with the aluminum panel frame. I put my money on the 316, but I'm not sure. Talesun doesn't seem to be worried cause they set down stainless steel. IronRidge says that high quality SS in their UFO clamp doesn't cause galvanic corrosion, but is it for the 316 or 304? My environment is not really extreme, by the way.
> Is using spacers around the bolt between two neighboring panels necessary? Yeah, spacers are really expensive, but I can get some SS tubing at the nearest scrap metal yard, I think I can make spacers myself using the abrasive wheel on a miter saw. It must be a hassle, so I wonder if it's really necessary?
> Is 4" purlin enough? I think it will bury about 2.5 bolts. Maybe less will be stronger, but 4" is cheaper and simpler.
> Has anyone ever used washers as clamps? How did it go? The manual says that clamps should be 2" long, but the UFO bolt just clamps the panels down with a washer, and it's a bit smaller than the one I would use.
> Is it a good idea to try grounding the panels with washers? Suppose I can put together the washers and the top or bottom edge of the frame. In that case, I'd only need to run ground wire along the top or bottom edge to connect four panels. I don't know yet where to get the washers I need (that looks like the one on the IronRidge UFO). If I can't find any, I have to buy 16 grounding clamps, like the $4 grounding clip (Tyco 1954381-2), Talesun recommends, and a lot more wire.
> The PE who approved the drawings of my frame told me to make sure that I painted the wood so it wouldn't bend and damage the panels bolted to it. I agree, but we need to make sure that the treated wood is dry before painting, and you know, it warps when it dries. I'm thinking about building the frame, letting it dry out, then painting it and mounting the panels.
Need insights to decide these dilemmas:
> Which one should I use, the 304 or 316 stainless steel? Which one is more resistant to galvanic corrosion at the interface with the aluminum panel frame. I put my money on the 316, but I'm not sure. Talesun doesn't seem to be worried cause they set down stainless steel. IronRidge says that high quality SS in their UFO clamp doesn't cause galvanic corrosion, but is it for the 316 or 304? My environment is not really extreme, by the way.
> Is using spacers around the bolt between two neighboring panels necessary? Yeah, spacers are really expensive, but I can get some SS tubing at the nearest scrap metal yard, I think I can make spacers myself using the abrasive wheel on a miter saw. It must be a hassle, so I wonder if it's really necessary?
> Is 4" purlin enough? I think it will bury about 2.5 bolts. Maybe less will be stronger, but 4" is cheaper and simpler.
> Has anyone ever used washers as clamps? How did it go? The manual says that clamps should be 2" long, but the UFO bolt just clamps the panels down with a washer, and it's a bit smaller than the one I would use.
> Is it a good idea to try grounding the panels with washers? Suppose I can put together the washers and the top or bottom edge of the frame. In that case, I'd only need to run ground wire along the top or bottom edge to connect four panels. I don't know yet where to get the washers I need (that looks like the one on the IronRidge UFO). If I can't find any, I have to buy 16 grounding clamps, like the $4 grounding clip (Tyco 1954381-2), Talesun recommends, and a lot more wire.
> The PE who approved the drawings of my frame told me to make sure that I painted the wood so it wouldn't bend and damage the panels bolted to it. I agree, but we need to make sure that the treated wood is dry before painting, and you know, it warps when it dries. I'm thinking about building the frame, letting it dry out, then painting it and mounting the panels.
