Jotul Castine overfire

[sparksalot]

I have a question or a couple of questions about my Jotul...if anyone can answer let me know.....O.k here is what happend we had been burning the stove all day and i was about to go to bed and had one sizeable fir log in the stove with the temperature at 575 about...well i see that it is supposed to get down to -20 tonight (look out east coast it is comming) so i decide to through in some hard wood for overnight so i take a heavy piece of elm open the damper throw it in...hmmm i say...then i shut the damper down completly...i got a little nervous so i went to this site to look up overfires and 10 minutes later i smell the stove and run in and i am at 750 then 800. Luckily for this site the overwhelming statements on overfireing is don't panic and learn from your mistake...Well i didn't panic but i have not really learned from my mistake...why couldn't the stove handle it and why did the temp run so high so quick? i don't think i was starving the fire originally i had it about half open....before i put the elm in and the stove still had about 4 inches to the top of it....i guess i just should have let the fir burn down before i added the elm....

 

[Mike Wilson]

Its a little difficult to parse out exactly what you did from the above, however rest assured 800 degrees is fairly common, and you did not overfire the stove. Sometimes if you put in a nice sized piece of dry hardwood on an already good-fueled and burning fire, such as a half burned piece of fir, you'll start off-gassing the new wood very quickly. The stove is hot, so she'll fire on secondary combustion almost immediately, and your temperature will swing up. Also, remember that air damper controls only control the primary air (the air coming into the stove from the doghouse on the bottom), not the secondary air controls. When you close down the primary air control, the secondary air will increase as a result of the negative draft pressure in your stack. You cannot control secondary air, period. Keep in mind that normal fires have temperature cycles, and 750-800, while on the hot side, isn't destructive. I've had mine at 900, and a call to Jotul tech support in Maine taught me that these things can easily handle temps of 900+ for fairly decent periods of time. Just don't let it glow... which I believe starts at around 1100 or so. For comparison, if I am trying to get decent heat out of my Jotul, and putting in more frequent loads of "good" wood, I''ll see the temperature swing to 750 or 800 for periods, I don't worry about it anymore. Its been 3 seasons, and after a partial disassembly and cleaning last spring there's nothing wrong here.

YMMV,

-- Mike

 

[sparksalot]

Thanks mike that puts me at ease...i did remember a previous post where you did mention that you called Jotul...to find about the high temperatures....but let me ask you this should i not have closed the damper so quick after i loaded the stove up...i thought this would control the load better?

 

[Mike Wilson]

There's no real easy answer to that. What I find is that sometimes shutting the damper will cut combustion, and thus heat. Other times I find that cutting the damper causes, as expected, an increase in secondary combustion, which creates hotter flames, and raises stove temperature. Sometimes leaving the damper open all the way creates a lot of flame, but its all primary combustion, which is a cooler fire, and thus sometimes that results in keeping stove temperature down. I really can't think of a perfect answer for you... the best I can say is, it depends. The other way to handle it is to wait before you add new wood... let the cycle of the previous burn finish, so that all you have are coals, then reload.

-- Mike

 

[Highbeam]

As a newer burner I had pretty much the same experience. Putting in a good load of wood to get an overnight burn and then not being able to slow down the temperature rise. It is not a good feeling watching the appliance get hotter and hotter while the load of wood you put in is not shrinking. It seems like it will go to the moon.

I don't stoke very much now for the night. I have become familiar with the amount of fuel that will provide decently long burns but not runaway. I do completely shut the primary air each night to try and get as long a burn as possible.

The good news is that the stove, my Lopi, is supposed to be able to handle 800 degree temps before being considered "overfired". This information is in my manual and confirmed here on this site by other folks' input.

The stove is humming along right now at 650. I saw 11 degrees F last night when I was adding wood at 3am.

 

[sparksalot]

yes i think you are right about letting the cycle end sometimes it is hard because i want to go to bed or head out for some errands..i really only have this problem when i have been burning all day....and then throw in some wood before it is time....yes i was up at 2.00 am putting wood on the fire to make it through -24 last night...

 

[BrotherBart]

yes i think you are right about letting the cycle end sometimes it is hard because i want to go to bed or head out for some errands..i really only have this problem when i have been burning all day....and then throw in some wood before it is time....yes i was up at 2.00 am putting wood on the fire to make it through -24 last night...

Another thing to watch out for doing that. Last night I had several splits about halfway through their burn when I wanted to start building up for the overnight without waiting for them to burn down. I tossed a sizable oak split on and gave it a minute to catch and closed the door. Just as the door latched the oak split, sitting on the hot coals, gave off a burst of gases and BOOM. The gases exploded all at once in the firebox. I could hear the liner expand and contract with the pressure. I had heard about it happening and last year Eric Johnson said that that is why you put the three screws in each pipe joint. I went outside to see if the cap was off in the woods somewhere but it was still up there.

I am just glad the door got closed or I would be missing some eyebrows and have a sunburn.

 

[begreen]

Funny you should mention that BB. I did a similar thing in the Castine two nights ago. The power of wood gas is impressive.

I put a couple big logs in for overnight on hot coals. But they smoldered a lot and weren't flaming quickly enough for me to shut her down and go to bed. So I opened the door for a bit and that got them burning better. When I closed the door, they started smoldering again, but this time with a vengeance. When that smoke caught fire, I got a mighty whoomph of a blowback that sent smoke out of every gasket and orfice it could find. Everyone in the house came into the livingroom to make sure I was ok. My only thought was, boy I am glad all the joints are triple screwed.

Thanks for the reminder. I need to check and be sure the cap is still on the stack.

 

[sparksalot]

The gases exploded all at once in the firebox. I could hear the liner expand and contract with the pressure. I had heard about it happening and last year Eric Johnson said that that is why you put the three screws in each pipe joint. I went outside to see if the cap was off in the woods somewhere but it was still up there.


what do you mean that is why you put three screws in each pipe joint? I thought they were friction fit?

 

[BrotherBart]

what do you mean that is why you put three screws in each pipe joint? I thought they were friction fit?

Nope. That is why on page four of the manual for that Castine of yours it says:

"• Secure all connector joints with three sheet metal screws."