Originally posted by RShackleford
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mounting panels to treated-wood frame
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9 kW solar, 42kWh LFP storage. EV owner since 2012 -
Originally posted by Ampster View Post
I think it depends on what is upwind of the prevailing winds. I installed a system on a 3rd story roof at the peak of a small hill and if I remember the calcs there may have been a venturi effect.on that installation. You will always be safe by assuming the worst cast.
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If you two want to do this in a professional manner and get serious rather than all the blather and hearsay, consult ASCE 7- 05, ASCE 7-10, et seq. Neither of you has a clue what's required.Comment
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Originally posted by J.P.M. View PostIf you two want to do this in a professional manner and get serious rather than all the blather and hearsay, consult ASCE 7- 05, ASCE 7-10, et seq. Neither of you has a clue what's required.9 kW solar, 42kWh LFP storage. EV owner since 2012Comment
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Originally posted by Ampster View PostDoes it matter if he exceeds what is required? His goal is to get a permit.
Neither of you has a clue what's required.
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Originally posted by RShackleford View Post......... and for those, he spec'd Simpson H1 (good for 480lb uplift).Last edited by Ampster; 03-27-2020, 01:12 AM.9 kW solar, 42kWh LFP storage. EV owner since 2012Comment
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Originally posted by Ampster View PostIt is not too difficult to get several opinions about the pullout strength of a lag bolt in various species of lumber.
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Originally posted by RShackleford View PostYes, in fact, there's a tome called the Timber Construction Manual that has extensive tables.Last edited by Ampster; 03-27-2020, 12:45 PM.9 kW solar, 42kWh LFP storage. EV owner since 2012Comment
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Originally posted by RShackleford View PostWell that's a point. Even though I'm exposed to more wind by virtue of being ground-mount, I'll be much closer to the ground than any roof (about 8ft at the high end). Also, the max design wind here is 115mph, whereas the XR1000 rail is allowed to span 8ft even with 160mph winds (see attached). I'll run their design tool with 160mph and see what it wants for rail attachments.
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I once phoned Ironridge and their engineer was happy to talk to me. It couldn't hurt to give it a try.7kW Roof PV, APsystems QS1 micros, Nissan Leaf EVComment
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Originally posted by bob-n View PostI once phoned Ironridge and their engineer was happy to talk to me. It couldn't hurt to give it a try.
With ASCE 7-10, 120mph wind (exposure B), 20psf snow, 25-degree roof slope, a 4x4 array (of 60 cell panels), and XR1000 rails w/ attachments about 8ft apart, it computes 733 lb of uplift at the "zone 3" points of attachment - yet it specs a single L-foot (for each point of attachment).
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Originally posted by RShackleford View Post
I did, and they suggested using the "pitched roof" tool, since that uses the L-foot attachment. Yes, wind uplift is gonna be higher on ground-mount than an equivalent roof-mount. However, the pitched-roof tool tells you what the uplift force is at each point of attachment.
With ASCE 7-10, 120mph wind (exposure B), 20psf snow, 25-degree roof slope, a 4x4 array (of 60 cell panels), and XR1000 rails w/ attachments about 8ft apart, it computes 733 lb of uplift at the "zone 3" points of attachment - yet it specs a single L-foot (for each point of attachment).
Another question: What is the pullout strength at the point of attachment between the fasteners you're using and what they're attached to, and how are you calcing that number ?
Hopefully, the pullout strength of such connections will be > the pullout load.Comment
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Originally posted by J.P.M. View PostHow did you come the conclusion that the uplift on a ground mounted array will be greater than an equivalent roof mount ?
Another question: What is the pullout strength at the point of attachment between the fasteners you're using and what they're attached to, and how are you calcing that number ?
Hopefully, the pullout strength of such connections will be > the pullout load.
I'm a little bemused that IronRidge is happily concatenating aluminum with stainless steel (the UFO connectors as well as the bolts which join the L-foot to the rails), which is a bad match for galvanic corrosion. I guess the answer is that the aluminum is anodized.
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Originally posted by RShackleford View Post.......
With ASCE 7-10, 120mph wind (exposure B), 20psf snow, 25-degree roof slope, a 4x4 array (of 60 cell panels), and XR1000 rails w/ attachments about 8ft apart, it computes 733 lb of uplift at the "zone 3" points of attachment - yet it specs a single L-foot (for each point of attachment).
To be clear, I am not an expert, but common sense can provide some insight to test assumptions.Last edited by Ampster; 04-02-2020, 03:37 PM.9 kW solar, 42kWh LFP storage. EV owner since 2012Comment
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Originally posted by Ampster View PostThat would be a long lag bolt. I presume that if you use two L feet at each end you could figure. 375lb of uplift?
I could always fabricate my own extra brackets from hanger strap, wrap it over the top of the rails (there'll be no UFOs near the 2x12s) and nail it into the side of the 2x12. Kinda kludgy.
The worst wind weather event to ever strike my area (Hurricane Hazel, 60+ years ago, since records kept) sported 75mph sustained winds and 90mph gusts. My installation will never see winds anything like that, due to surrounding trees; and if winds that heavy ever do hit the area, it will be demolished by falling trees well before there's a risk of it suffering wind damage.Last edited by RShackleford; 04-02-2020, 07:08 PM.Comment
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