The Rack Materials

The rack is constructed out of slotted, galvanized, steel angle stock. This stock is available at most hardware stores. Our local store sells National Slotted Steel Angle (stock #180-109) for about $7.00 each retail. This stuff is 6 feet long, with two perpendicular sides each 1.5 inches wide. The stock is about 1/8 inch thick, with a heavy galvanized coating. Its entire length is covered with holes and slots that will accept 5/16 inch bolts. We have had no problems with corrosion or electrolysis with this galvanized stock after three years in the weather. We haven't yet tried this material on a seacoast, and would welcome feedback from anyone who has. To the left is a drawing of a typical length of this steel angle.

You can shop around locally, and may encounter different sizes and lengths. Six foot lengths are long enough to mount 4 of just about any type of module. We use this angle on Kyocera, Arco and Solec panels without having to drill any holes in either the angle or the PV modules. Working with this stock is like playing with a giant erector set. The only tools you really need are wrenches, a hacksaw (to cut the angle), and a drill for making holes in the surface holding the rack.

The amount of steel angle stock you need depends on the size & number of panels you wish to mount, the mounting location, and your particular environment. Let's consider the rack shown in the photoon the next page as an example. This rack holds four 48 Watt Kyocera PV modules and is bolted to the almost horizontal metal roof of a mobile home. Each PV module is 17.4 inches wide and 38.6 inches long. The mounting holes on the bottoms of the PV modules match the hole cadence in the slotted angle. This particular rack used 9 of the 6 foot lengths of the steel angle. Four lengths comprise the framework for the modules. Three lengths make up the legs and bracing, while two more lengths are used as skids on the roof. Strictly speaking, the skids are not essential, but do add rigidity and relieve stress on the mounting points on the sheet metal roof. We don't want any leaks. A rack could be built with the about half the materials. The top and bottom pieces of the rack holding the panels, the brace on the legs, and the skids could all be deleted. If this were done then the rack would be roughly equivalent to most commercial models. In our opinion, PV modules should be mounted as securely as possible. Many commercial racks use the PV modules' frames as a structural members in the whole module/rack assembly. This rack does not do this. Many commercial racks use 1/8 inch aluminum angle. This rack uses steel of the same thickness; it is much stronger.

This rack lives in snow country, with lots of high winds. Consider that the rack holds some $1,400. worth of PV modules. We figured that the additional $35. the extra bracing costs to be worth it in terms of security. It's comforting to be inside during a howling snow storm and know that when its all over the PVs will still be there. Don't skimp on materials for your rack. Use extra bracing to make it as strong as possible. Remember that it holds over a thousand dollars worth of PV modules. The 9 pieces of slotted angle cost us about $65., and are well worth it.

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