Low cost ground mount idieas?

[Philip]

Is there a low cost way of mounting panels on ground. It seems from shopping around pressure treated wood for a "frame" then standard roof mounting for the actual panel mount might be a decent solution, though at least the Unirac stuff seems really expensive.

Has anyone done their own mounting without the commercial stuff?

[Naptown]

No the unirac and others are engineered to withstand the anticipated wind loads which are substantial on a ground mount. Example I did a system with two pole mounts. each pole was 9 Canadian solar 220 modules on a DPW pole mount. This required an 8" schedule 80 pipe buried 8 feet in the ground with about 4 yards of concrete and a bunch of rebar to keep it in place. Most wood ground mounts that are home built do not account for the wind loading particularly from the rear where it is mostly uplift. You do not want to find your expensive modules in the neighbors yard because you tried to save a few bucks on the mounting which is equally as important as the rest of the system.

[Philip]

Darn, I was hoping I wouldn't hear that! That's kind of why I was thinking about using the pressure treated 4x4/4x6 for the frame and the Unirac for the actual mounting rails, etc.

I did a design with their building tool and it quoted the up, down, and side loads. They were actually pretty tame at 90 mph, even at 120 mph. Oure site is 85. One can easily do 5x that with timber framing and appropriate tie downs., (had to learn a lot building my own house!).

I would NEVER do anthing on a pole up here! I'd be basically doing a "roof" frame on the ground.

The problem is, even doing it that way, with thier recommended Solar Mount I the estimate was almost $1/watt! That pretty much would kill any chance of a reasonable payback. Guess I'll have to check pricing around the net.

Any thoughts on Haticon mounting hardware?

[Naptown]

Take a look at the ULA system runs about $150 a module if I remember the last time I priced one. I wouldn't use 100 watt modules on it though. Use big honking high wattage ones to reduce the racking cost per watt.

[Philip]

Again, that's over a buck a watt! Yikes that's expensive!

One way the quote from their tool is flawed though, is that it only seems to allow landscape layout, which requires twice the rails and rail-roof attachments it needs in portrait.

I'll do a layout and submit it to them for feedback. I'll do the same for Haticon, their system looks much cleaner for ground mount.

[Paul54]

You may want to consider using Superstrut or Unistrut steel channel. It is sold at Lowes, Home Depot, and most electrical supply houses. A 12 foot section of the heavy duty stuff is about $18. If assembled and anchored properly it is much stronger and much cheaper than most aluminum systems. It helps if you have a metal bandsaw to cut it, but it can be done with a hacksaw. Use stainless steel hardware to attach the panels to it. If you want to make a tilting mount and have lots of heavy panels, try having the pivot point or axle in the center of the panels, much like a see saw. Use supports at top and bottom also. It is easy to tilt several hundred pounds of panels with one hand if you have them balanced.

[Naptown]

Again, that's over a buck a watt! Yikes that's expensive!

One way the quote from their tool is flawed though, is that it only seems to allow landscape layout, which requires twice the rails and rail-roof attachments it needs in portrait.

I'll do a layout and submit it to them for feedback. I'll do the same for Haticon, their system looks much cleaner for ground mount.

That is done to keep the overall height and therefore moment down. yes the rails run vertically but many modules are not designed to be mounted from the ends they need to be balanced over the rails or the loading from wind and snow is reduced by half or more. However the rail length per module is about half of what it would be running the other way ( basic module dimensions of 39 x65 with rails running across the module on the short dimension = 78" per module running the other way is 135"

[Naptown]

Again, that's over a buck a watt! Yikes that's expensive!

One way the quote from their tool is flawed though, is that it only seems to allow landscape layout, which requires twice the rails and rail-roof attachments it needs in portrait.

I'll do a layout and submit it to them for feedback. I'll do the same for Haticon, their system looks much cleaner for ground mount.

If you are looking at the pricing on Unirac's website that is list price. generally you can find it for about 35-40% off list.

[Philip]

I may have to break down and call in one of my mechanical engineer friends on Superstrut. We used it all the time so I'm sure they are familiar with it. ULA looks like it may do the trick though.

ULA does look much better, more like 70 cents/W list. If it is discounted enough, that could do the trick.

Thanks all, this is the help I was looking for. I'll still also follow up with Haticon when the time comes. There stuff looks very good as well.

[LeRoy]

Pressure treated lumber PV racks

I am considering using properly graded 4 x 4 or 4 x 6 pressure treated lumber for ground based racks for a 4.5 Kw system. The array will need to be two panels high (roughly 10' maximum height above ground). Has anyone had any experience with this idea?

[Naptown]

Pressure treated wood unless properly isolated from the aluminum will cause many problems with the aluminum frames of the modules due to galvanic corrosion.
Copper which is a primary ingredient in pressure treated lumber is about as far away on the galvanic scale from aluminum as one can get. Meaning of this is the aluminum will be sacrificial to the copper. Dissimilar metal when in the presence of moisture which will happen outdoors will create a battery. The aluminum in this case is the anode which will corrode.

[LeRoy]

spacers between panels and pressure treated wood

Thanks, Rich. How about nylon or fiberglass spacers between panels and pressure treated wood?

[Naptown]

That will work but how are you going to bolt them to the wood and you will need to bond each panel individully.

[LeRoy]

Since the spacers would not experience much force, would a small counter-sunk galvanized lag with washer be enough?

I'm not sure I know what you mean by: "you will need to bond each panel individually".

[inetdog]

Since the spacers would not experience much force, would a small counter-sunk galvanized lag with washer be enough?

I'm not sure I know what you mean by: "you will need to bond each panel individually".

Not sure how the galvanized lag and washer would react with the copper compounds either, but at least the aluminum would be protected.

Re bonding: If you fasten an aluminum panel frame to a metallic structure using the right fittings, you have bonded them together electrically and only one ground wire is needed. If you bolt them to a wood frame, you must run wire bonding jumpers to interconnect the frames so that you can ground them.