Yup.. I'm on board with the bolted vs clamp notion for this app.. I also agree with a wider spacing for panel attachments...
As for racking manufacturers and design oopsies, anyone have anything nice to say about Iron Ridge roof mounts? Personally, I kinda like the rail design, but the slide in bolt set up seriously sucks.. or Am I missing something.. again? db
Dan Brown
Foxfire Energy Corp.
Renewable Energy Systems
(802)-483-2564
www.Foxfire-Energy.com
NABCEP #092907-44
-------- Original Message --------
Subject: Re: [RE-wrenches] Rail concerns (was: Top of POST mount)
From: August Goers <aug...@luminalt.com>
Date: Wed, March 23, 2011 10:09 am
To: RE-wrenches <re-wrenches@lists.re-wrenches.org>
You definitely have a point from a basic engineering point of view that bolts through the module bottom holes is technically the most robust option. However, the main racking companies have been selling top down clamps for a very long time and the two big ones, Unirac and Pro Solar, haven't changed their design for a long long time as far as I can tell. I tend to like Pro Solar's clamps, especially the end clamps, a bit better than Unirac's but I have to believe that if there was a problem that these companies would be the first to change their design. Modules flying off the rack or roof is a very bad thing. Some of you may recall the modified hex bolts that Unirac was shipping for a little while a couple of years ago. They definitely weren't good but Unirac got right on it and we had to switch out each and every one that we had installed... That said, if you're talking about pole mounts and other types of racking where you can get underneath easily then why not just use the bottom holes.-AugustFrom: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of Jason Szumlanski
Sent: Wednesday, March 23, 2011 4:40 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] Rail concerns (was: Top of POST mount)I tend to agree about the clamps, and in a case like this where there is little risk of an expensive mistake with a voided warranty, I would actually drill holes in the frame and use bottom clamps in addition to top clamping.Jason SzumlanskiFafco SolarFrom: re-wrenches-boun...@lists.re-wrenches.org [mailto:re-wrenches-boun...@lists.re-wrenches.org] On Behalf Of William Miller
Sent: Tuesday, March 22, 2011 5:48 PM
To: RE-wrenches
Subject: [RE-wrenches] Rail concerns (was: Top of POST mount)Friends:
When installing modules on extruded rail systems, I worry that any vibration or motion could loosen top-down clamps. Unlike bottom-up systems that install with tried-and-true bolts and lock washers through captive holes, clamp systems seem less "positive" in holding capability. If one rail in the proposed design moves in relation to the other, the clamps could loosen and the modules could eventually slide right off the rail. It appears that wind turbulence could rock the modules in the proposed design, there is a lot of leverage for that. This might loosen clamps.
I hesitate to design my own racking. Small business management is all about controlling risk. I do not want to be responsible for damaged modules if my design fails.
At least one local AHJ forbids home-brew racks for a permitted system. I'm not sure I support that restrictive approach. I might suggest allowing them for owner-builder systems where the home owner assumes the liability. For myself, the remaining tasks associated with installing a system properly have enough pitfalls without me playing structural engineer.
And lastly, it is my understanding that Solar World had temporarily abandoned mounting holes in the back rails of their new "Plus" modules (my quotes) and even abandoned the flanges altogether. According to what I heard, industry pressure forced them to add them back in, but as an option. This is third-hand knowledge, but I do know that removing the option to mount panels with through bolts would be a big mistake.
William MillerHere is my “cobulated” idea, admittedly done this way to take advantage of parts in stock:
http://www.fafcosolar.com/download/402/Cobulate.pdf
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