Is the cause of Ikea fire Wembley known?

Sergio Fernandez said:

Does anyone know the cause of the fire?  

It's likely to take more than a couple of weeks to get that information ... sometimes months.

I guess some of the other questions could be answered, if the investigation becomes public, but it is regularly the case that there is insufficient information left after a fire to answer all of those questions satisfactorily.

We don't even know yet if the panels were the source of the blaze.. Flat(ish) roofed commercial buildings often support all sorts of kit...

   - Andy.

AJJewsbury said:

Flat(ish) roofed commercial buildings often support all sorts of kit...

Agreed.  I have seen many with air handling units/AC on roof.  Some roofs have communication equipment like antenna or parabolic dishes or the motors for the lifts.  

It does feel odd to have 100 panels catch fire at the same time - it seems unlikely they're on the same string so hard to see how a single simple electrical fault could have triggered it. How does a PV panel burn anyway? I thought they were mostly glass and aluminium - hardly the easiest things to ignite - and usually well spaced, so hard to see how a fire would naturally spread from one to another.

So far I can only imagine either some catastrophic invert fault that back fed mains to the panels (presuming it was one huge inverter for the lot, which feels unlikely), or perhaps arson?

    - Andy.

Anything is possible.  My thinking was maybe a Solar PV panel strike or some kind of power fluctuation that was enough to melt some cables which could then ark.  Maybe the PV system is just the ignition source and the fuel was provided by something else like the paint/coating of the roof.  Thus completing the fire triangle of

Spark/Flame + Fuel + Oxygen

You may not have seen what LFB have to say.

https://www.london-fire.gov.uk/incidents/2025/october/fire-at-store-wembley/

The last line is germane

"The fire is believed to have been caused by resistive heating"

Now I'm not sure resistive heating of what but on a roof some kind of frost heater or de-icer perhaps ?

Mike.

mapj1 said:

Now I'm not sure resistive heating of what but on a roof some kind of frost heater or de-icer perhaps ?

Or PV cables, connectors ... or panels themselves (forward or reverse current)?

Simply a very broad statement at this stage ....

I would be very surprised if the PV modules themselves were the case of the fire. They consist largely of glass and aluminum. Glass is non flammable, and aluminium burns only under extreme conditions,

I consider it likely that "resistive heating" occured in the DC cables from the modules to the load, or in the series connections between the modules. Such connections carry full load current for hours, often during conditions of high ambient temperatures. One the fire was started, the main fuel was probably bitumastic roofing material.

"The fire is believed to have been caused by resistive heating"

Or maybe, given usual description of the cause of the rash of CU fires, that's just become the FB's new stock phrase (as "electrical fault" used to be in years gone by when they couldn't attribute the cause to anything else).

Mid-morning on a gloomy October day isn't likely to see unusually high PV generated currents 

   - Andy.

Was it a mis-match of MC4 connector brands?  What cable was used between the Solar PV panels?