EKO flue gasification during startup

[Nofossil]

I'm burning REALLY dry wood this year, mostly pretty small pieces. I had to close my primary inlets to 6mm, and it seems that 5 might be even better. Last night, I had a bizzare situation that's never happened before. Keep in mind that this is my 5th season with the EKO.

I was starting the fire. Bottom door and bypass damper open, top door closed, fan off. After about three minutes, I got a big 'whoosh' and a flash of flame (and ashes) out the bottom door, followed by a very familiar and loud gasification roar. In this case, though, the gasification was happening in the flue. It was being fed by fresh air being drawn through the bottom chamber and up the HX tubes. My EKO had spontaneously become an updraft gasifier.

Flue temperature jumped instantly to 'quite impressive'.

I closed the damper and bottom door and kicked on the blower. It immediately settled down into normal gasification.

Has anyone seen this? Any thoughts on how to prevent it?

 

[sdrobertson]

I haven't heard this...3 minutes is pretty fast so that wood must be really dry...Don't tell your Brother-In-Law or he'll want to build the first combination updraft/downdraft boiler

 

[twitch]

Something similar happens with my Tarm if I leave the damper open and the bottom door open too long. I get the flame and ashes out the bottom door. I haven't noticed the sound of gassification in the flue, probably because the poof, sparks, and ashes startles me and I'm not paying attention to anything besides getting the door and then the bypass closed.

 

[twofer]

Kinda ironic but something like this happened to me yesterday. Now I'm not sure if gasification was occuring or not because I didn't look but it sounded exactly like what you are describing with the loud gasification roar. I should have looked but it freaked me out so bad that I slammed everything shut and started the controller.

 

[DaveBP]

Do you have turbulators in the fire tubes? If the boiler was cool (cold start, kindled fire) and turbulators in place it doesn't sound like your 'secondary air' coming up the tubes could have been very hot when it hit the gases coming off the wood. Makes such gassification even more peculiar.

Maybe while starting with such small dry stuff you should open the bottom door less widely in order to limit the amount of pyrolytics coming off the wood. As you had to reduce the primary air for the rest of the burn. The nozzle apparently isn't choking it down enough by itself. I think you could do the same by not opening the damper as much but it would be harder to do it consistently because you can't see it.

Maybe it was a brief gravitational singularity. You may have witnessed a Not-so-Big Bang phenomenon. Noticed any new galaxies floating around the place?

 

[taxidermist]

I had this happen last year and I was spitting hot ash out the top of my chimney. Closed it all down and it settled down.


Rob

 

[twitch]

Last night as I was reloading the Tarm that had just a bed of coals, I had the bypass and lower door open to get it going. I heard the 'poof', but it wasn't a big one. I left the door open and went to listen to the flue, and as it 'poofed' again I could hear the sound of gasification. It sounded like it was coming from the smoke box above the heat exchange tubes.

 

[dzook]

I had this happen a few times as well with my eko60. It also came during the lighting phase but I thought it was because I let the fire burn too long with lower door open and bypass open and the parts at the rear got too hot.

Sometimes if I let the fire gather too much momentum before shutting the bypass the fire would be was burning on top of the wood stack rather than at the bottom. I burned a lot of small kiln dried wood prices on a regular basis so the fire would crawl to the top quickly and I noticed if I waited too long to shut bypass damper it was a problem to get proper lower chamber gasification. I believed it was because the fire was burning from the top of the stack rather than a coal bed starting at the bottom.