Solar layout advice

2nd_time_buyer

We are due to get solar panels installed on Tuesday. The proposed layout of the panels is below. The scaffolding was put up today and I have now being able to get an accurate measurement.

I have two options for the portrait panels on the side roof:

1) 1.85m (395w) panels. Which would result in eaving a 0.17m gap to the gutter and ridge (0.35m total)

2) 1.7m (350w) panels in the same range. Resulting in a 0.25m to the ridge and gutter (0.5m total)

The cost is the same for both options. So if I go for the first option I will be losing 315w (7x45w) of power but paying the same.

The question is, is the 17cm enough?

Thanks

Verdigris

If I recall correctly, option 1 would be too close to the ridge for wind-loading.

2nd_time_buyer

I am wondering if I can pinch a bit from the gutter side. As long as the water isn't shooting over the side. 

Verdigris

I'm assuming this is an "on-roof" installation ie. on rails. I think the same applies at eaves as ridge. "In-roof" installations, where you remove the slates/tiles so the panels are flush with the rest of the roof, can go right to the edge. It is quite a bit dearer, though.

The other option is to look for higher efficiency panels, if available, on the smaller footprint.

2nd_time_buyer

Yes, it is "on roof". We are in the South of England in not a particularly windy place. 

Verdigris

It's not what it is like on average. It is the 10/50/100 year events that will rip the roof off. The insurers won't pay out if the panels are incorrectly installed, even if you could persuade the installer to do that.

2nd_time_buyer

Good point about extreme events. Thanks

I have done a bit more research looking at fixing systems installation guides. From what I can see they do not explicitly include the gutter as a roof edge although they do explicitly mention the distance to the ridge.

Thinking about it, I can't think of a reason why the wind loading will be significantly affected by the proximity to the bottom edge of the roof.

It is discussed in fair account of detail here:

www.solarquotes.com.au/blog/solar-panel-exclusion-zones/amp/

The main problem of getting too close to the gutter, seems to be that there is a chance of water over shooting the gutter. I have done some experiments with a sheet of glass under a tap and have convinced myself that 15 cm gap at the bottom will be sufficient. This leaves the recommended 200mm to the ridge.

Verdigris

Thinking about it, I can't think of a reason why the wind loading will be significantly affected by the proximity to the bottom edge of the roof

I imagine it is to do with turbulence. Most modern aircraft have "winglets", those vertical extensions at the tips, to direct turbulent flows upward to prevent them creeping to the underside of the wing and reducing lift. However, getting rain into the gutter may well be a factor with rail mounted PV panels.

Spies

I'm not sure if roof orientation matters with wind loading, on my west facing roof (one gable south facing) there is a big gap between the highest panel and the ridge, lowest panel edge is maybe 15cm from the gutter. 

On the south facing roof (gable ends west and east) , the panels are close but not over the ridge - this may be more due to them under estimating the space, but if they're MCS certified and something happens, buildings insurance should surely cover any damages?

I've seen plenty of Installs around here with no regard for the 30cm no go area around the edges of the roof. 

2nd_time_buyer

Spies said:

I'm not sure if roof orientation matters with wind loading, on my west facing roof (one gable south facing) there is a big gap between the highest panel and the ridge, lowest panel edge is maybe 15cm from the gutter. 

On the south facing roof (gable ends west and east) , the panels are close but not over the ridge - this may be more due to them under estimating the space, but if they're MCS certified and something happens, buildings insurance should surely cover any damages?

I've seen plenty of Installs around here with no regard for the 30cm no go area around the edges of the roof. 

Thanks. That is reassuring.

jimjames

Is there a reason for not putting the panels across the roof or is there not space?