vaillant blew up! eco Tec plus 831

[Ted808]

custard rang last week, boiler is going out intermittently, he can't remember the fault code... so I take a look, stuck it on chimney sweep to see if anything is untoward. Nothing fires runs... then it went to F75... so I said I'll come back with the flow switch and recommend a drain down and flush out, fresh chemicals... one thing and another, planned to go Monday. Last night he rang to say the boiler had literally blown up, bit red flash of flames and conked, He turned off gas and electric- lucky sensible chap. F29 fault.
Has anyone had this before? Thought boilers failed to safe?

 

[ShaunCorbs]

Seen it with the old ones eg didn’t have the g10 gasket changed flames coming out of the front of the boiler etc

 

[Scott_D]

Could he have been fiddling with it?

 

[Last Plumber]

I've seen a couple with explosive ignition due to a faulty PCB.
They were running through the ignition sequence but not igniting due to lack of spark until the very last second. The chamber was filled with Gas air mixture when the spark finally appeared and they went with a bang. A scary bang too.

 

[Harvest Fields]

As above. I have only seen it on the old rubber combustion door seals.