Morning

Does anyone know what the typical maximum load is on the roof hooks you buy locally (like these -> https://pvstore.co.za/products/roof-hook-eco-basic-no-wood-screws?_pos=1&_sid=45d7279ed&_ss=r)

I am putting 7 x 550W Panels (27KG each) side by side in a portrait config (2 x 8m wide tracks, Trusses ~700mm apart, 17Deg Pitch) I was planning on using one roof hook on ~every second trusses (so 12 of them) BUT...

I used the Renosul Configurator (https://www.renusol.com/en/configurator/) to do a sanity check and it failed the Static load test (@190%) for the hooks (rails and clamps OK) even when putting a hook on every trusses. To make it worse it still failed with three tracks, only way I could get it to pass was to use 4 (so 40 hooks) which seems totally nuts.

Putting a hook on every trusses means 20 of them so each hook will be carrying ~10kg, this sounds reasonable but I am now I am paranoid

Any advice?

Hi PRP, I am on a roof most days doing exactly what you are attempting to do. The Renusol product has in my opinion the strongest & robust roof mount hooks available. The only issue I have with the product is that the Aluminium Profiles that the panels clamp to are a bit flimsy & not as strong as say other products like the Schletter or Valsa product. 

The Schletter & Valsa product however, win in the category of preparing a roof that needs an adjustable mounting bracket & the Aluminium Profiles are much stronger. 

What you describe as placing a hook on every second truss seems totally reasonable in my humble opinion. I think that placing one hook on every 4th truss so skip distance 700mm x 3 will be a massive problem as the rails will warp & bend into a Concave shape. 

You plan to place a hook on every second truss seems to pass my rough mental sanity check🤔 However, if the rail starts to bend then you will need more hooks as I have said above. Hence I prefer the Schletter & Valsa product, no rail bends. 

1 hour ago, Steve87 said:

Hi PRP, I am on a roof most days doing exactly what you are attempting to do. The Renusol product has in my opinion the strongest & robust roof mount hooks available. The only issue I have with the product is that the Aluminium Profiles that the panels clamp to are a bit flimsy & not as strong as say other products like the Schletter or Valsa product. 

The Schletter & Valsa product however, win in the category of preparing a roof that needs an adjustable mounting bracket & the Aluminium Profiles are much stronger. 

What you describe as placing a hook on every second truss seems totally reasonable in my humble opinion. I think that placing one hook on every 4th truss so skip distance 700mm x 3 will be a massive problem as the rails will warp & bend into a Concave shape. 

You plan to place a hook on every second truss seems to pass my rough mental sanity check🤔 However, if the rail starts to bend then you will need more hooks as I have said above. Hence I prefer the Schletter & Valsa product, no rail bends. 

Thanks Steve, appreciate the practical advice. Have sent you a DM. 

@PRP you can put in a brace between every second trusses and mount at around 1meter at center of each panel a bit of work tho or you can use the 12 hooked but maybe a 2mm or 3mm unistrut for strength.