Flat roof mounting

[solgen]

Hi,

Does anyone know how to calculate ballast requirements for the schueco flat roof mounting systems PV light 10, 20 or 30 angles. I have used the Schueco wind load software tool and it gives a value of 0.744Kn/M^2 so how do you turn this into Kg?

I also used the BRE guide for the same property and got an uplift force of 2211N and down force of 1701N. Any ideas how these figures correlate with figure I got from the Schueco software?

Other than getting a structural engineer to calculate if a roof can withstand the loading from ballast. Does anyone know any some simple methods to calculate this?

I would appreciate some help.

Thanks

 

[Markc]

Hi.

2211N equates to 255Kg-force. 0.744Kn = 744n or 75Kg-force. The newer Schuco flat roof system is interlocking and so less ballast weight is required. Structural engineer is the best option also.

Can you tell me where you got the Schuco wind load software?

 

[solgen]

Hi MarkC,

The wind loading software was from the Schueco website at ...

WindLoad - Software - Services*-*Schüco

You have to register then you can access the software.

I understand 2211N equates to 255Kg-force and that 0.744Kn = 744n or 75Kg-force.

So does this mean that one method of calculation is saying that I need 255Kg of ballast to hold the system on the roof and the other method is saying 75Kg?

Here's the scenario:

Flat roof 10M high. 7x8.6M.

Don't know what the roof construction is but the house is 5 years old. Based in London about 60Km from coast.

I've been looking at 2 mounting systems: Solion and Schueco both at 10 degrees as the owner doesn't want to see anything on the roof from the bottom of a long garden.

My questions are for each type of mounting system:

1. How far in from the edge of the building should the panels be placed?
2. How do you determine the ballast required if cannot penetrate roof. (I will then use a structural engineer to determine strength of roof).

 

[Markc]

I can't make out form your posts if the figures you have is per panel or for the array. Either way both seem to be out. 255Kg of ballast per panel I would walk away form the job! The newer mount system is inter lockable and so less ballast is required. May be something to look at. As for giving you a set figure I think more information is required.
Does the calculations you have consider the mass of the array on its own? I've seen systems with no more than a 400 x 400 paving slab on each mounting and one with cast concrete feet made to measure the mounting system. We have been involved with a flat roof design for a global heating manufacture on their office complex. They happen to manufacture their own panels in group so naturally they decided to us these. Their design showed 36Kg feet per mounting the crunch came when we discovered their panel is not MCS accredited so the project is on hold until the new year when they should achieve it. There panel size is 1595 x 809 x 50 and weigh 17.5Kg each. Mounted 8mts high and 35 miles inland. Don't know if this helps?
As for distance form edge we work to 600mm to 1000mm but also depends on customer requirements. Regardless there should be access for future maintenance.

 

[solgen]

OK - looks like I need to clarify a bit more.

Flat roof 10M high. 7x8.6M based in London (60Km from coats) so there is nothing particular extraordinary about it.

The panels I intend to use are 235W Sharp in Landscape (1652x994) so per panel I get a figure of 2211N uplift by following the BRE guide - unless I've done something terribly wrong?

Can you give me a reference to the new interlockable bracket please?

How do you determine the value 600mm to 1000mm for edge distances. Does it depend upon whether it is a ballast only system or if fixed to the roof? For example the Solion roof mount must be placed at a distance of (2 x height of building)/10 from the edge of the building. In my case this is 2M which doesn't leave very much room for PV. Am I being too strict and following guides too closely? I would love to get some answers on this?

Thank you

 

[Markc]

PM me your email address and I will copy you the Schuco newsletter article and manual.

Our determination on 600 to 1000 is practical rather than manufactures recommendations although Schuco give an equation for boundary. We found 2 meters from roof was unobtainable on the majority of systems. A perfect example of this was a six meter wide roof. It left a 2mts centre strip to work from which just wasn't workable. HSE suggest 2mts also but this is more defined for commercial properties. They will accept alternative arrangements as long as they are written into the companies H&S policy accordingly.

The trouble with the literature is its all in German but Id be happy to send you it via email. I haven't translated all of it yet (Goggle translator is good for this) but I think it gives some ballast calculations.