GSE Integration

[Worcester]

Having used various other in-roof systems, we've just done our first of 3 GSE Integrations that we have to do on new builds.

The technical training put on by GSE through Segen, was little more than a marketing exercise and what was published as a three hour technical training session was actually a 1 1/2 hr marketing talk

Anyway my post and question is:
Has anyone else done the wind loading and pull out calcs on the panel mounting system? Or have you just followed the (badly translated) installation instructions.

They advise that in a zone 4 (high wind / exposed area) that with rafters or trusses spaced at 600mm or less, then a "batten" 27mm thick x 110 wide would be adequate and that 6 fixings (3 each side) should be used. My calculations suggest though that even using 40mm battens that you need to double that (i.e. 6 fixings) between panels (mid clamps) and that sometimes 9 end clamp fixings may be needed just to meet the pull out strength requirements of the screws, with 15mm x 240 wide batten (which they also suggest is acceptable) you are in severe likelihood of catastrophic failure of the clamping system in high winds.

Or have I missed something?

 

[Gavin A]

your calculations using which wind loading calcs?

the old BRE or the new ones?

I assume you're aware, but the new bre calcs have massively lower wind loading for the mid sections of the roof - or to put it another way, BRE cocked it right up in the old calcs and have been making people using their calcs add far more brackets etc than necessary for years.

Can't answer your calcs query, I'm not sure we've used it anywhere that windy.

 

[BruceB]

I am about to do my first GSE system on a new build. I had the same issues with the 'training'. One Frenchman with good English who was a salesman who could not answer technical questions and another Frenchman who did know his stuff but needed a translator to be sure he was being accurate.
I cannot see the underlying logic in all their tables of sizes and struggle to see how 15 mm will work. It does claim to have got mcs012 approval at some stage though. At least my first is in zone1, near Oxford, and unlikely to fly off the roof.

Is is there a simple ready reckoned available that can give pull out forces for screws?

 

[solarsavings]

I don't like their top flashing it's a nightmare to get it right

 

[Worcester]

I don't like their top flashing it's a nightmare to get it right

There are alternatives for the top flashing, with a good roofer, in some circumstances none is actually needed, or you can use wakaflex, same as they use at the bottom.

The reason why it's so popular in france? -- The get a MUCH higher fit if it's an in-roof system as opposed to on-roof!

Screw pullout: BS5268 Part 2 (Should really use EC5 now..)

The pull-out force in C16 timber is given by the tables and formulae is: (Table 67 p 93)
For Grade C16, 5.5mm dia screw - 17.1 from the table, 30mm penetration - the 1.25 is for short and very short term loads - i.e wind loading
17.1 x 1.25 x 30 = 641N.

Simples

 

[The Solar King]

Have used GSE. This was before any training was available. You can see one of ours in the 'Show Us Your Work' on the public forum. Its the most recent post. I had concern due to four story buildings to one side of the array (to the north). They could have caused vectoring and spiralling above the array increasing uplift. We put in extra clamps on the long landscape side. (Can be seen in the photos)The is a Scottish roof with sarking board as well as battens so fixings are in to around 47mm of material.

I do not anticipate a failure due to uplift.

We didn't use their metal top flashing. it is not really necessary.

Will be doing something similar with customised GSE trays on my own roof which is slate with no battens, just sarking.

 

[BruceB]

Did first GSE last week. Not a particularly smooth installation because it is a new build small retirement house and we are trying to put as much pv on as possible which puts it tight against velux flashings. Sequencing roofing work, pv work, velux work was tricky. We also made it harder than it had to be because client/architect wanted slate flush with top of panels which requires extra counter-battening and sealing. Some observations:

- Laid out battens to support trays, put trays on, then roofing battens went on around them. Some trays had to be lifted again to allow roofing battens to reach under to attic trusses rather than flap. It would have been quicker to just batten the whole roof as normal and then add extra battens for the trays if some were missing from critical areas.

- Used the phonosolar panels with built-in solar edge optimisers. A cheap and quick way of doing it, but they do not fit on the gse trays the 'right' way up in portrait format. The optimiser hits part of the tray. You have to mount them upside down (optimiser at lower end).

- With panels being mounted on the trays 'upside down', the routeing of the cables means the cables are too short to go from one panel to the one above it. You need to fabricate an extension.

-Agree with The Solar King that top flashing is not really necessary. We did put it in but it does not really show because slates reach almost to top of panels. The top flashing clips onto top panels which I do not think is helpful. Beter to be able to put all frames and flashing in place, then all slates and then panels.

But I think it willl look ok. Certainly economical, apart from my time co-ordinating it.

 

[Worcester]

Will post photo's of the new build install from above as finished later this weekend.

We installed right to the ridge, and had a good roofer to work with - no flashing at the top - he is installing a batten between the joints in the panels and putting his ventilated ridge flashing over so no way way water can even get blown up (this is zone 4 )and then screwed down ridge tiles - note all new builds need positively fixed ridges, hips and edges so that makes this a bit easier.

Roofer is really please with the end result (Oh so is the client )

Got another to next week with plain tiles (100mm pitch) so asked then NOT to install any battens yet and will work with them on site.

 

[Gavin A]

we find it much simpler just to get the roofers to fit the battens, but ask them to leave us a few lengths to add extra as required.

cable routing can be an issue, particularly so with lanscape mounting.

 

[Worcester]

we find it much simpler just to get the roofers to fit the battens, but ask them to leave us a few lengths to add extra as required.

So are you just screwing into 19/25mm battens ?

 

[Gavin A]

yes, I'm not sure how else it could be done, though all the battens we've installed on have been 25mm

 

[solarsavings]

Things we learned the hard way. You need extra battens and a 60cm length of conduit so you feed a lead made up with an mc4 to make it easier to get the leads from the modules under the trays.

 

[BruceB]

I thought I would add a couple of photos of it almost completed:

 

[BruceB]

........
Screw pullout: BS5268 Part 2 (Should really use EC5 now..)

The pull-out force in C16 timber is given by the tables and formulae is: (Table 67 p 93)
For Grade C16, 5.5mm dia screw - 17.1 from the table, 30mm penetration - the 1.25 is for short and very short term loads - i.e wind loading
17.1 x 1.25 x 30 = 641N.

Simples

Just been to look that up for my education.
What a useful little table.
I found a pdf of the BS is actually sitting on the internet at the top of a google search if your morals will allow you to download a copyright document. Alternatively Eurocode 5 as Worcester says.