Anyone else using old BT cable trays for solar panel mounting?

Mate, I've been eyeing up those BT cable trays for months and I keep bottling it because my inner sparky is screaming "it's not for that" — but then again, neither was half the aluminium extrusion I've bodged onto my van roof.

The galvanised ones are genuinely beefy stuff, designed to sit on rooftops and take British weather for decades, so structurally I reckon you're onto something. My concern would be the mounting points — are you drilling into the tray itself or using the pre-punched holes? Because if you're relying on those pressed slots for any real load, I'd want some decent stainless M8 bolts and big penny washers in there, not just whatever rattled out of a recycling skip.

Also worth thinking about wind loading if you're tilting the panels at all. A flat-mounted 400W panel is one thing, but angle it up and suddenly you've got a sail on your roof.

• What gauge are you using?
• Roof mount or ground array?
• Bonding the tray to your earth?

That last one matters more than people think — a big floating metal structure and a Victron MPPT don't always play nicely together if something goes wrong.

Done right though, this could be genuinely clever budget engineering rather than dangerous penny-pinching, and there's a difference. Curious whether anyone's had these up through a proper UK winter yet — we all know a sunny YouTube install video filmed in August tells you absolutely nothing useful.

@NaeClue your inner sparky needs to pipe down for a sec 😄

The actual question is load rating and corrosion resistance — and BT tray is typically galvanised steel, so it's actually better than a lot of cheap aluminium extrusion for outdoor use once you've sorted any cut edges with cold galv spray.

I've bodged together panel mounts from stranger things on the narrowboat. What matters is:

• Can it handle the wind loading?
• Are your fixings stainless or at minimum galvanised?
• Have you got adequate bonding to earth?

That last one is where DIY metalwork mounting gets people — your panels need proper earthing regardless of what they're sitting on.

Post some photos of what you're working with — someone here will have done something similar and can sanity-check it before you commit.

@NaeClue mate my garden office roof is basically held together by repurposed BT tray, three bungee cords, and sheer optimism — six months in and the Renogy panels haven't moved yet

@NaeClue I've been running four 400W panels on repurposed BT tray for about 18 months now up in the Brecon Beacons — so proper exposed conditions. The galvanised stuff has held up surprisingly well, though I did hit every cut edge with cold galv spray before installation which I'd strongly recommend.

Main thing I'd say that nobody's mentioned yet is the fixings — don't cheap out there even if you're skimping on the tray itself. A305 stainless M8 bolts throughout, no exceptions. The tray itself flexing slightly in wind is actually fine, it's the fixing points that'll let you down first if you've used anything less.

Also check the gauge — some of the thinner residential stuff is noticeably floppier than the heavier commercial tray. Worth weighing a metre length if you can before committing. 😊

@NaeClue Running three 200W panels on repurposed BT tray on the roof of my narrowboat for going on two years now. The main consideration nobody's mentioned yet is the perforated vs solid base — perforated drains but loses structural rigidity faster once the galv starts going, especially in anything near salt air or persistent Welsh rain like @ValleyAmy will know.

Key practical points:

• Degrease thoroughly before any bonding or self-tappers, the factory coating resists adhesion
• Earth the tray properly — it's conductive, it's near your array, don't skip this
• Stainless M6 hardware only, the supplied fittings are mild steel and will weep rust stains within months on a boat

The load rating concern is mostly irrelevant for static panel mounting — you're not asking it to flex under dynamic load, just sit there.

@NaeClue Your inner sparky isn't wrong to flag it, but the concern isn't really what it's for — it's whether you've thought through the specifics. Main things I'd want to know: what gauge is the tray, how are you bonding it all together electrically, and what's your earthing arrangement for the panels themselves? BT tray is generally decent aluminium but the joins between sections can be a weak point both structurally and for continuity.

@ValleyAmy 18 months in the Beacons is genuinely reassuring — that's proper weather up there. Curious how you've handled the section joints for structural rigidity?

The "not designed for it" anxiety is valid but manageable with a bit of planning. I've seen far sketchier setups using purpose-built kit installed carelessly. Document what you've done and why — keeps your head straight if you ever revisit it.