[RE-wrenches] Mounting system for array on a metal (delta-ribbed) roof

[David Brearley]

Bob,

For a top down anchor, check out Fab-Lok stainless steel fasteners. It looks
like these are made by Fabco Fastening Systems (Camcar/Textron). They are
described as "high clamp-up", "weather tight" fasteners. I'm not sure that
they are strong enough for this application. (Maybe someone will supersize
this fastener for the solar biz?) You need to order these in the right
length for the clamp up feature to work properly, taking care not to
over-torque. We used to purchase these through Dynamic Fastener, but it
looks like Fastenal also carries them.

David

On 3/13/09 12:40 AM, "Bob Clark" <bclark at solar-wind.us> wrote:

> RE-Wrenches:
> 
> I am certain some of you have dealt with this situation before and can offer
> some sage advice.  Sorry about the long-winded description, but when one is
> limited to plain text messages, one must use a 1000 (or more) words.
> 
> SITUATION - Metal building with delta-ribbed roof.  "Red" steel (the hard
> metal kind), C-beam purlins running parallel with the ridge of the roof on
> 5-foot centers.  Unirac mounting system with heavy duty rails running N-S
> from near the ridge to near the eave across the purlins (this means points
> of attachment are 5-ft. O.C. along the rails) and solar panels mounted
> across the rails in landscape mode.  The solar panels are 64.6" (1640 mm)
> long.  The array is to be mounted parallel to the roof (non-tilt).  It is
> inevitable that, if the array is to cover as much of the roof as possible
> (and also look good), that some of the attachments along the rails will fall
> on the crest of the metal roof ribs while others will fall in the valleys.
> When we mounted an array on a metal, delta-ribbed roof that was on a wood
> framed structure, we used Unirac hanger bolts to make the L-feet attachments
> come out on the same level regardless of whether it was on a rib or in a
> valley.  That way, the weight of the panel would not be resting on the rib
> (thereby forcing it flat), but on the face of the nut on the upper portion
> of the hanger bolt.  Obviously, we cannot use these hanger bolts that have
> threads on the bottom for screwing into wood beams.  WE CANNOT ACCESS THE
> UNDERSIDE OF THE ROOF, therefore, bolting the L-feet to the purlins is NOT
> an option.
> 
> What can be used that will attach securely, minimize the penetration area of
> the attachment device (after all, there will probably be 242 points of
> attachment, which could lead to one leaky roof if not cone correctly), and
> allow rails to be at the same level regardless of whether the attachment
> points fall on a rib or in a valley?
> 
> Furthermore, how can the L-feet be secured to the hardened steel, C-purlins
> when access to the underside of the roof is not possible?
> 
> Bob Clark
> SolarWind Energy Systems, LLC
> bclark at solar-wind.us
> 
> 
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David Brearley, Technical Editor
SolarPro magazine 
NABCEP Certified PV Installer 
david.brearley at solarprofessional.com
Direct: 541.261.6545
Fax:  541.512.0343

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