High Flue Temps and Difficult Cold Start with Jotul F602 V2

[AILDWarrior]

Greetings! I want to start by saying that I operated nuclear reactors on USN submarines, and this little stove is substantially more difficult to operate than a reactor. On a more serious note, I grew up around wood stoves, specifically a pre-EPA Scan, so I'm not unfamiliar with wood burning, though I'm certainly not an expert either.

I've frequented this site a lot and found a lot of valuable info from BG that has changed my burning habits, but I still have two primary questions I haven't been able to answer: (1) what are normal flue probe temps for these stoves when in the 400-600F stove top temp band? and (2) how on earth are you guys lighting these things to get a decent coal bed?

I'm burning Sitka spruce, with fresh splits ranging between 16-18% and my house is about 800 sqft. Double wall stove pipe (Excel), about 15 ft tall. At peak temps, the stove top is 450F between the flue adapter and the cook plate, while the Jotul logo on the front is about 580F. At that temp my flue probe typically reads between 800-900F, which seems absurdly high to me, though I'm wondering if I'm just inexperienced and this is actually normal. Flue probe is Condar, 18" above the stove top.

I typically light top down, starting with 2x 3-6" pieces, then 2 or 3 layers of 1" kindling and a fire starter at the top. I recently watched a Jotul video and tried two stacks of 2-3" fuel pieces on the bottom, separated by kindling for air flow, this second method is new to me but seems to be working slightly better. My main issue is that the kindling lights up great, and I progressively shut down the damper as flue temps approach 400F. By the time temps hit 600F, I'm all but shut down on the front damper, just a sliver open with a healthy blazing fire. 10 minutes later, the kindling is burned out and my bottom logs are smoldering. Then it's a 2 hour fight to cut the smoke and get enough flame to keep a sustaining fire. Very frustrating. To me, it seems like the major issue is no air flow under and between the bottom pieces of fuel when cold starting.

For additional info, I had a minor chimney fire with this stove last year due to a poorly positioned 45 elbow near the ceiling and wood that was very poorly seasoned and stored. Since then, I've learned a lot, especially from this site, and I have a proper shed for 6 cords of wood. Like I hinted at earlier, I'm mostly just frustrated because this stove seems so difficult to control compared to the Scan I grew up with. I've dialed in many of my issues, but the high flue temps are making me nervous and I'm convinced that my issues with cold starts are due exclusively to operator error. Once I've got a good coal bed, I feel like I have pretty good control over the stove.

Sorry for the long post, and thank you for taking the time to read it and provide any advice you might have!

 

[Todd]

Try starting off with just kindling to get a coal bed established then rake all the coals forward and add your splits. The 602 has a small firebox and all the combustion air comes from the front so it burns front to back. Top down fires are difficult with this stove in my opinion, just not enough room. Another technique is what I call the sandwich method. Lay two small splits side by side, small kindling on top front then another two small splits on top.

Sometimes these stoves burn too hot because the front air control doesn’t shut completely. This can be fixed by taking the air slide apart and grinding down the slide stop. There’s a video on YouTube somewhere on how to do this.

 

[EbS-P]

with fresh splits ranging between 16-18%

At room temp?

Things I’ve learned to get fires established quickly. Use Lots of kindling. Like 1/3 to 1/2 a fire box. I like pine for this. Use whatever you have and it split small. I have a bigger stove and sometimes only get 2 real splits in on a cold start. You might even crack the door a bit to help it take off but ALWAYS set a timer anytime you crack the door.

At 15’ you’re not tall but if it’s -40 and windy you might be overdrafting. A pipe damper is can help control flue gas temps.

 

[AILDWarrior]

At room temp?

Yes, I checked the moisture at room temp and split within the previous 24 hours. After my chimney fire last year, I found it helps to ease my anxiety by batch testing the moisture content on any wood I bring in. Saves me $200/hr by avoiding a therapist 😉

Thank you Todd and EbS-P for the advice. I took it and mashed it with Jotul's video and tried something different that seemed to work this morning. Two E-W pieces of kindling to elevate 2 small N-S splits followed by 3 stacks of kindling and a lighter between the top two stacks. Appeared to burn clean as intended and the elevated bottom splits ignited MUCH better, getting the fire hot and leaving a nice set of coals for refuel. I'll keep working at this, but I feel like I'm finally working toward a solution.

As far as the flue temps, I found another thread on this site that made me feel a bit better:

F

Thread 'Flue Temps - A bit confused. Clarify?'

Oct 25, 2021

I've been reading quite a bit on flue temps and am a bit confused, more so on the low end.

I've heard flue temps above 400deg are best. However, when researching things here I found several references to temps as low as 250deg in that above that is recommended for keeping creosote from condensing.

As for water vapor - being above the boiling point of water, at 212deg F, would seem to make sense and this lines up closer to the 250deg F temp - that 250 is hot enough for water vapor to flow right up and out rather easily.

Are the references to 250deg F in fact in reference to limiting...

• FlyFish'n
• Replies: 6
• Forum: The Hearth Room - Wood Stoves and Fireplaces

It sounds like I might be near the top end of the band, but that's not entirely unexpected with an EPA catless stove since these machines force higher flue temps and don't use the cat to strip additional heat before entering the pipe. Todd, I've come across your threads before regarding the damper modification. I'm tempted but I also haven't found myself overfiring the stove yet, at least based on stove top temperature. I haven't convinced myself yet to file down the stop tabs, though that day might come soon enough when I start burning birch.

 

[begreen]

I haven't run the v2 version, but would aim for flue temps once the stove is damped down to be approximately around the stove top temperature with a probe thermometer.

 

[Brian K]

I use a propane torch for a few minutes to light my Osburn stove. I used to do the kindling thing but now I just put in the logs (mostly spruce and poplar where I am) I want to burn, light the torch and aim it at the bottom of the log pile and close the door as much as possible to keep the smoke in the woodstove - and away it goes. Split logs are arranged north/south. My stove has a front shelf that I place the torch on and I watch that once the fire starts nicely, I remove it. My stove is, of course, different than yours and I was having a devil of a time getting it to light, then one suggestion was to remove or partially dislocate the cleanout which is on the bottom of the stove and that REALLY made it easier to get started as air would directly get at the bottom of the fire. Once going I replace the cleanout plug.

 

[NickW]

With some wood burners bigger pieces on a cold start need to be well charred before closing the air at all. My NC30 stove at the old house didn't need this too much, the Stratford 2 zc here in the new place absolutely does.