How close to a roof edge can panel corners/bottom be?

[ChrisJEvans]

How close to a pitched roof edge can panel corners/bottom be?

Googling and searching this forum give comments varying from 100mm to 500mm!

Officially I found: MIS 3002 The Solar PV Standard (Installation) PDF available from:
https://mcscertified.com/standards-tool ... #v-pills-0
Provides some detailed information but not on panel borders. It does say installations should comply with:
IET code of practice for grid connected solar photovoltaic systems
But that seems to only be available to buy on dead trees for £65+ Anyone know what it says there please?
and are they guidelines or requirements?

The roof in question is triangular and if I fit three rows of panels landscape with one in the top row, two in the middle and three in the bottom row the top corner of the bottom panels are going to be close to the roofs hip. I've measured up the roof where the panel edge will be and it is 1500mm, the panels are 1050 high so if I left 450mm gap to the roofs gutter edge the top corner would be just touching the hip line.
If I have 350mm to the gutter edge then it'd be about 70mm to the hip from the corners

The picture shows the roof in question on the right and omits the top (sixth) panel. The top panel and the middle row's two panels will be slightly further away from the hip.

Rain would have 3.15m of panels to run down in the centre. If water overshoots the gutter it would be landing on a flat roof.
The roof faces East so the left panel corner would be subject to the prevailing wind.

Any thoughts as to the best compromise please?

I've seen locally installations with the panels right at the bottom of the roof and other where the corner of panels just overhang the hip!

Also am I correct in thinking that on the trapezoidal south facing roof the panel corners can be close to the valley though I realise that means they will be more shaded after noon?

[nowty]

I don't think there are any actual hard rules, but there is guidance, use common sense is my advice.
Triangular roofs are obviously more difficult.

Page 74.
https://mcscertified.com/wp-content/upl ... TRONIC.pdf

"Unless specifically designed to do so, systems should be kept away from the roof perimeter. For a
domestic roof, a suitable minimum clearance zone is around 40-50cm.

The requirement to keep an arrays away from a the edge of a roof is suggested because: wind loads
are higher in the edge zones; keeping edge zones clear facilitates better access for maintenance
and fire services; taking arrays close to the roof edge may adversely affect rain drainage routes; and
when retrofitting systems, there is the potential for damage to ridge, hip, valley or eaves details.

Note – on many roofs a 50cm gap from the edge will still mean that PV modules are fitted in the
“Edge Zone” as defined in BS EN 1991-1 where higher pressure coefficients need to be implemented
due to the higher imposed wind loads."

[Mr Gus]

Chris / mods can we combine the other recent thread on the same !? question & thisone for continuity & ease of search please!?

Not dissing the additional info & reasoning mind

[Oldgreybeard]

Our panels (integrated in-roof) run right down to the gutters, with no roofing below them. It works OK, but we did have a problem with heavy rain overshooting the gutter, because of the additional height. This was fixed when we replaced all the gutters earlier this year with continuous aluminium ones that project out a bit further from the eaves.

[sharpener]

...It does say installations should comply with:
IET code of practice for grid connected solar photovoltaic systems
But that seems to only be available to buy on dead trees for £65+ Anyone know what it says there please?
and are they guidelines or requirements?

Members/fellows can borrow this from the IET library f.o.c., they even pay the outbound postage.

So I borrowed it earlier in the year, AFAIR there is nothing in it about margins for panels. The text is incorporated by reference in the MCS standard so all installers should be adhering to its provisions (though the requirement that the EESS inverter has its own RCD not shared with house loads is I suspect widely ignored).

The topic came up again a few days ago and I was told 300mm is ideal for the bottom edge, 200 minimum to avoid rain overshooting the typical gutter.

BTW the other odd thing about the IET publication is that there are no examples or guidance for wiring inverters that have separate AC-in and AC-out.

[AGT]

I think there is new guidance out at the end of the month, the last time I checked the online shop

[Swwils]

Didn't MCS recently-ish reduce the wind load guidances as it was proving to not be much of an issue?

[Tinbum]

If I recall correctly their is a dimension under planning regulations.

also look at wind loadings (BS6399:Part2:1997)

[AGT]

Wasn’t it 200mm from the ridge?

[ahas]

My installer wouldn't go less than 300mm from edges. Wind was the reason to keep 300mm from edges. The images look less than 300mm but on measuring they're not far off 300mm I'm sure.

We're on the corner so get awful wind impacts. Neighbouring properties have ridge tiles flying regularly.
So was happy to take fitters advice.

There's a house around ours with overhanging panels and they look a bit ridiculous imo.

We've had panels fitted on inset roof area. Not as much shade as you will get but might help guage.