Explosion type in stove?

[griam01]

I had something I’ve never seen before happen. I was running the stove with cat engaged for about 2 hours and noticed the cat was still glowing orange but didn’t seem like anything was going on with the wood. No secondaries firing or flames at all. I had the air all the way closed down. I checked the cat temp with the probe monitor and it was 1350. I bumped the air control a bit to allow a bit more air and I heard a puff and then flames through the firebox. Immediately the cat probe temp dropped down to 1100 within 5 mins. Can anyone explain what happened? Thanks in advance for your time.

 

[Dieselhead]

Smoke is unburnt fuel, sounds like it reached its ignition temp and lit off. I, and many others on here have had it happen when conditions within the stove get just right.

 

[Sodbuster]

I've had the same thing happen in my PE Summit (non-cat)

 

[Ashful]

Classic “back-puff”. Your stove was running fine, before you turned the air up, doing exactly what a cat stove is designed to do on low burn. In essence, the wood was smoldering, giving off volatile “wood gas”. The cat was happily chewing this wood gas fuel, and producing heat. Perfect low burn, which is why folks love these cat stoves.

When you turned up the air, you momentarily upset the balance, providing enough combustion air to the mix for spontaneous combustion to occur in the firebox. Not a big deal, but sometimes a little alarming, and it can push smoke out thru the inlet if the pressure is high enough during the backpuff.

The subsequent drop in cat temp is not directly related to the backpuff. That occurred because increasing the inlet air allows more of the wood gas to burn in the firebox, leaving less fuel for the combustor. So, combustor temp drops, accordingly. All normal behavior.

 

[griam01]

Classic “back-puff”. Your stove was running fine, before you turned the air up, doing exactly what a cat stove is designed to do on low burn. In essence, the wood was smoldering, giving off volatile “wood gas”. The cat was happily chewing this wood gas fuel, and producing heat. Perfect low burn, which is why folks love these cat stoves.

When you turned up the air, you momentarily upset the balance, providing enough combustion air to the mix for spontaneous combustion to occur in the firebox. Not a big deal, but sometimes a little alarming, and it can push smoke out thru the inlet if the pressure is high enough during the backpuff.

The subsequent drop in cat temp is not directly related to the backpuff. That occurred because increasing the inlet air allows more of the wood gas to burn in the firebox, leaving less fuel for the combustor. So, combustor temp drops, accordingly. All normal behavior.

Thank you for the explanation! I get nervous when the temp goes above 1300 but I guess it is rated to go higher. I appreciate the help!

 

[toddnic]

Backpuff! It definitely can be scary if you've never experienced it. I've had the cook top lift off of my PH before. Lots of power in unburnt gas when it gets the right oxygen mixture!

 

[Ashful]

Thank you for the explanation! I get nervous when the temp goes above 1300 but I guess it is rated to go higher. I appreciate the help!

1300F is fine. You’re pretty good running long-term at temperatures up to 1700F. Above 1700F, the catalyst can begin to slowly delaminate from the combustor substrate, but even that is not instant death... it will just reduce combustor life.

I’ve had them hit 2000F for brief periods without serious damage before, as long as they’re not thermally shocked with a blast of cold air (eg. Opening the door) at those high temps.