Number of roof fixings?

[TJLinks]

can anyone tell me of a quick way to calculate the number of roof fixing required for an above roof array? I have had a quote from my suppliers and they have included 52 roof hooks for a 2Kwp set up ( 2 rows of 5 panels)
is there a formula or a chart available????
cheers

 

[SolarCity]

Depends on many factors.

However, the roof structure itself should dictate how many roof hooks you need. The distance between the joists and wind/snow loads dictate which mounting rail to use and you go from there. 52 roof hooks for a 2kwp? Doesn't sound right to me.

 

[Markc]

That's one at under 400mm apart. Thing they may of got that a bit wrong.

Not knowing your location, roof structure, height etc can't say if it is correct or not. To many factors affect numbers of hooks and there isn't a straight forward X times Y calculation. May be speak to your installer again and ask for clarification. For all we know you could live at the top of Ben Nevis!

 

[TJLinks]

Location = Shropshire
Slated roof, only ten years old
roof timbers are approx 4" x 3" and 600mm apart

 

[TJLinks]

what would a average Number be for a good /sound roof? one every meter? one every joist?

 

[SolarCity]

It depends on the mounting system that you are using. Haven't the suppliers given you mounting data? Some mounting kits will allow you to use brackets at every 1200mm.

 

[TJLinks]

only to say it is made by Schuco, what manufacturer allows 1200 spacings?

 

[SolarCity]

Schuco do under the right conditions and with the right mounting rail. Who is your supplier?

 

[TJLinks]

Segen, not sure what the rail profile is that they are offering tho. do you know what profile rail will allow 1200? I presume there are thicker / stronger ranges and lightweight ones too

 

[Markc]

Don't know if this helps?

 

[TJLinks]

Thats a great help, thanks

 

[goodwilld]

i do every other joist but not exceed 1200mm

 

[TJLinks]

i do every other joist but not exceed 1200mm

what is your reasoning for this spacing? Do you use a formulae? also what make of rails do you use??

 

[goodwilld]

Various-Hilti and Shuco, no math on spacing just seemed strong with fixing every other one.

 

[SolarCity]

what is your reasoning for this spacing? Do you use a formulae? also what make of rails do you use??

Get hold of the Schuco documentation and it explains the maximum distance between fixings. I'd be very careful about guessing - Some rails will accept 1200 spacings and some won't.