Can someone explain to me the physics behind this? (woodstove)

[woods]

Getting ready for bed last night, I go stoke the woodstove. The few embers weren't really catching. Sometimes what I do is open the bottom ash tray to get air moving and it'll catch, then I'll close it. I did that last night, fire caught, closed the tray, fire went dim but was going. Go to plug my phone into the charger, BOOM! Giant puff of smoke and a big thump; blew the chimney cover right off!

Was it just the flammable gasses left behind in the stove that caught? Scared the freaking shit outta me. I thought the thump was my kiddo falling out of bed from the boom, but when the chimney cover landed on the back deck that answered that.

So, no more opening that freaking ashtray.

 

[bigun]

Getting ready for bed last night, I go stoke the woodstove. The few embers weren't really catching. Sometimes what I do is open the bottom ash tray to get air moving and it'll catch, then I'll close it. I did that last night, fire caught, closed the tray, fire went dim but was going. Go to plug my phone into the charger, BOOM! Giant puff of smoke and a big thump; blew the chimney cover right off!

Was it just the flammable gasses left behind in the stove that caught? Scared the freaking shit outta me. I thought the thump was my kiddo falling out of bed from the boom, but when the chimney cover landed on the back deck that answered that.

So, no more opening that freaking ashtray.

My homemade stove did that a couple of times late at night scared the crap out of me

 

[Kaptain]

Sounds like a large buildup of off-gassing from the wood but I'd expect that to draft out of your chimney before any type of explosion like that

How's your draft normally? Any creosote buildup in the chimney or cover?

 

[Pony_Driver]

Combustible gasses built up, oxygen level increased, ignition took place and turned your chimney into a pressure vessel.

for poops and grins you might want to check your chimney for buildup. One cold winter night years ago we were visiting family. I could not get the fire to light or draw for anything. Eventually it got going and we built up a bed of coals. About the time we were headed for bed we heard a chuff and saw a puff of smoke come out around the thimble. I ran to the stove and opened the door to see what was up. As soon as I opened it I heard a weird noise and slammed it shut. When they say a chimney fire sounds like a train building up speed they aren’t kidding.

I ran the dampers all the way down, kids were pulled from bed and we stood outside and watched the top of the chimney turn into a road flare as the creosote burned in the liner. Scary shit. There was a foot of snow on the ground and some of the responding firemen got stuck.

They ran the thermal imager around to make sure there was no fire in the walls and left.

The root cause of the fire was repeated burning of shitty green wood at low temps allowing the creosote to cool and condense on the flue.

 

[woods]

My homemade stove did that a couple of times late at night scared the crap out of me

I've had small puffs before, but only when I cracked open the bottom ashtray. Otherwise this doesn't happen. Just something about opening that tray. Like it allows all the oxygen in or something and it catches.

 

[Pony_Driver]

I've had small puffs before, but only when I cracked open the bottom ashtray. Otherwise this doesn't happen. Just something about opening that tray. Like it allows all the oxygen in or something and it catches.

Maybe it drafts weird and the combustible gasses pool down low? Like a separated vortex?

 

[woods]

Chimney is clean. No buildup on the cover, I can see it clearly from the upstair's window which I check regularly. I actually just cleaned out the entire stove itself. Looked to where the base of the chimney connects to the stove, that is fine.

Its only when I open that bottom tray. I only do it if the fire doesn't want to catch.

 

[Kaptain]

Chimney is clean. No buildup on the cover, I can see it clearly from the upstair's window which I check regularly. I actually just cleaned out the entire stove itself. Looked to where the base of the chimney connects to the stove, that is fine.

Its only when I open that bottom tray. I only do it if the fire doesn't want to catch.

Sounds like the tray is letting too much air\oxygen in then. Just crack the stove door slightly to get the fire to catch, that has always worked for me.

 

[87manche]

whens the last time the flue was cleaned?

you may have had a slow burning chimney fire and then you added air.

 

[woods]

Sounds like the tray is letting too much air\oxygen in then. Just crack the stove door slightly to get the fire to catch, that has always worked for me.

Yea, I'm all done with opening that freaking tray.

Only thing is, when I have to empty it out. Maybe open the stove door too while the tray is open?

 

[Kaptain]

Yea, I'm all done with opening that freaking tray.

Only thing is, when I have to empty it out. Maybe open the stove door too while the tray is open?

Just empty the tray during the coaling cycle, not right after you load it full of fuel

 

[woods]

whens the last time the flue was cleaned?

you may have had a slow burning chimney fire and then you added air.

September?

Hm. I guess I'll run the brush down again this weekend.

 

[87manche]

September?

Hm. I guess I'll run the brush down again this weekend.

well I can't imagine you generated enough builup in a few months unless you just don't run it right or you're burning the worlds most greenest shittiest wood.

 

[woods]

well I can't imagine you generated enough builup in a few months unless you just don't run it right or you're burning the worlds most greenest shittiest wood.

Wood has been covered and was split and stacked 2019.

 

[Texas97]

*laughs in the temperature was 72 degrees yesterday*

 

[woods]

*laughs in the temperature was 72 degrees yesterday*

We'll revisit this conversation in August when you feel like you're breathing through Gandhi's thong.

 

[Aggie06]

*laughs in the temperature was 72 degrees yesterday*

No kidding. We might get lows in the high 30s tomorrow night.

 

[Roktoy829]

With you saying the fire died down, then went boom. It sounds like a backdraft.

 

[woods]

Its been teens at night here. A year or two ago in January the high was -15º for about five days straight. That was pretty meh.

 

[woods]

With you saying the fire died down, then went boom. It sounds like a backdraft.

Yep. It was going alright, closed the door, pilfered out, and KABOOM.

 

[Firstram]

We'll revisit this conversation in August when you feel like you're breathing through Gandhi's thong.

I hope I can purge this mental image before next August

 

[Poke]

Mine used to blow like a 20gauge sometimes. The stove manufacturer told me it happens. Just gassed building and ignition

 

[Clb]

Not enough information on venting and "stove" to accurately assess this!
Details on install?

BUT
It sounds like the venting was depressed due to a low pressure front in the area, this is the cause of the odd times when ya open the door and the smoke comes into the house rather than going UP.
Also this is compounded by a cold vent on first startup.

That , combined with a dirty venting system.

 

[woods]

Its just an ordinary Jotul. Nothing fancy. Has two doors and an ashtray.

I'm thinking there was the flammable gasses inside that caught after ignition. A sudden rush of fresh Oxygen and kapoof.

No more opening the tray after the fire has dwindled out.

 

[TRINDU]

We'll revisit this conversation in August when you feel like you're breathing through Gandhi's thong.

I fucking love 100° heat and high humidity.

Concerning wood stoves, I've never had that happen. The wall of the ranch house IS the chimney, so theres no way to clean it. I have had flames coming out the top before though

 

[Tin Roof]

Our Vermont Castings stove would do that occasionally. I could never figure out a pattern of when/why it would. Sure would scare a guy though.

 

[evernoob]

Maybe it drafts weird and the combustible gasses pool down low? Like a separated vortex?

I bet the 'free radicals' went all the way up the chimney looking for O2. He introduced some and the reaction pulled more O2 with it, accelerating the whole process right up the chimney. I saw a documentary about this where a Fireman was setting oxygen-starved fires which then killed his fellow Firemen when they went to control it. A cagey and hard-bitten Fire Marshall Inspector caught the man, along with the son of another Fireman who was killed by him. It was very tragic and sad but they got the guy.

 

[nahmus]

as long as your stove was not playing a recording to evacuate your house you should be good.

 

[ThePanzerFuhrer]

Lol if you don’t know what happened you prolly shouldn’t be operating a wood stove in your house. You had a backdraft happen. Very common I just open doors slowly to keep it from happening.

 

[woods]

Lol if you don’t know what happened you prolly shouldn’t be operating a wood stove in your house. You had a backdraft happen. Very common I just open doors slowly to keep it from happening.

Ah. So first mishap in a few years and suddenly I should stop using it instead of doing the math and how to prevent it from happening again. :rolleyes:

Next time I smack my knuckles from a wrench, I guess I should stop using those too.