Unistrut racking roof mount best practices

[Richiep]

Hey All,
I'm starting to design my system and I think I'd like to use Unistrut on the roof. I'd like to build it so I can change the tilt angle a few times a year.

I'm a general contractor but have never worked with Unistrut before but based on my reading it looks pretty straight forward and super strong. I've done some googling and youtubing on this but most of what I've found has been for free standing ground mount setups.

I'm looking for advice on best practices when using unistrut on roof mount solar.

One question at the top of my list is connecting to the trusses. Should I look for something solar specific like this
http://www.quickmountpv.com/products...lag.html?cur=0

Or is there a cheaper unistrut equivalent?

Any and all advice is appreciated.
Thanks
Rich

[sensij]

Before you get too far into it, make sure you won't have problems with fire code. Some locations (San Diego for example) will require the array to meet a Class A rating. That can only be achieved when tested as an assembly, and you'd have to use engineered racking like Iron Ridge or Unirac to have the needed certification.

[Richiep]

I'm in rural Michigan and permitting shouldn't be an issue.

[ButchDeal]

I would defiantly use solar flashed attachements.
your snow load is likely an issue and adding weight with unistrut will not help. The cost of racking has come down so you might try costing it out.
also would forget variable tilt on the roof, add more sola for the same fixed effect but lower cost.

[littleharbor]

Home depot used to install BP Solar systems on Unistrut. They used stainless steel machine bolts and oversized washers as hold downs. For the end of row hold downs they had a short section of EMT tubing cut just short of the panel frame thickness slid on the machine bolts, under the washer, to keep the washer from rocking sideways.

[J.P.M.]

Home depot used to install BP Solar systems on Unistrut. They used stainless steel machine bolts and oversized washers as hold downs. For the end of row hold downs they had a short section of EMT tubing cut just short of the panel frame thickness slid on the machine bolts, under the washer, to keep the washer from rocking sideways.

Long as non stainless nuts are used, and proper consider is given to galvanic action, and strength requirements are addressed, I'd say bolting is good to go.

[GRickard]

The problem you will find with Unistrut is that in a few years the galvanized will give way to rust and you'll have rusty streaks running down your roof. You can get strut in aluminum or SS, but it will be alot more expensive than using Iron Ridge or Unirac.

[bcroe]

My experience is that the consumer products out there are not designed for convenient tilting, and that
is especially true on roof mounts. I ask, but nothing I've seen really works. The actual mechanism
of tilting is a problem, again how to on a roof? Ground mount helps mechanically and permit wise. I
have standardized on 6061 aluminum and 18-8 SS bolts that works today and into the future. Bruce Roe

[AzRoute66]

Don't forget that when tilting on a roof you need to have spacing between the rows to prevent self shading. On my 22 degree roof, if I want to add just 13 degrees tilt to the landscape orientation rows, I need 8" of extra space between the rows for shade avoidance. That is why the extra row of panels and higher panel density makes more sense on my roof.

[Richiep]

I think I'm gonna pass on the tilt function for this installation.

[Mike90250]

If your zoning requirements require an Mech Engineering Cert, DIY unistrut won't pass.

[J.P.M.]

If your zoning requirements require an Mech Engineering Cert, DIY unistrut won't pass.

At least not w/out P.E. review, w/perhaps some design mods. and then stamp.