Secondary Burn??

[Valhalla]

I just experienced this "backdraft" combustion event writ large.

My VC Dutchwest was running hot in bypass mode with primary air wide open (starting from banked coals with dry wood).

I catalyzed it and slammed the primary shut. The flame went from roaring to out in about 4 seconds. I thought better of it, and popped the primary back wide open. I heard a sucking inhale, and then there was a bright flash and a BOOWWWOOOSH! Flames shot out of both the front primary air intakes, and rich, organic, fuelly smelling vapors hissed out of every crack for about the count of "son of a...!"

And so ends my cautionary tale.

Most unusual! Weather / storm related? Winds, barometer...UFO?

Seriously now, there is a physical cause for this. Did any wood
fall in the firebox? Is your fuel seasoned? Was the fuel a mix of
many species? How clean is the flue?

It seems as the burn stalled momentairly or the flue was blocked
by a downdraft.

 

[Bill F.]

Still air outside.
Seasoned wood.
A mixture of wood species... yes.
Cleanish flue.
UFOs -- haven't hovered around lately since I de-chipped myself.

One thing I forgot to mention. I did a no-no and opened the ash-drawer door briefly a few seconds before. Of course, there was quite an updraft that stirred up the thick ash bed. My best guess is that it stirred up some hot charcoal dust, too, that flashed in the oxygen-rich inrush. So it was sort of a miniature grain-silo explosion. I believe the military calls them FAEs or thermobaric weapons.

 

[Valhalla]

More like a flashover!

Still very strange, but your ash drawer may be the best clue.
Along with shutting the primary at the same time.

Otherwise, it burns well? Enjoy it and... no more tricks! LOL

 

[Bill F.]

Burns great, as a rule. I heart my Dutchwest.

This is the first and only time it has physically menaced me. Otherwise, nothing but love.

Bill