Cast iron rookie looking for advice on operation - Jotul F3 TD

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New Member
Oct 5, 2016
Hello Hearth Gurus!

I'am checking in form Hungary, Central Europe, and I would appreciate your advice regarding the following a lot:

Our new wood stove has just been installed, which is a Jotul F3 TD.

I think this model is not sold in the USA, maybe never has been sold, so in case you are not familiar with that stove here is some info on it:

The CB version is also available here but we decided to go for the TD version for several reasons. If you are interested in it, I write you a summary about the "research" we made and decision with pleasure, but that is a different story, I don't want to bore you with that now.

Back to the F3 TD, it is not on the EPA list, has no secondary burn pipes, it can be rather considered as a traditional woodstove BUT it is very far away from the old and leaking, unefficient stoves often refered to as "traditional stove" (vs. EPA certified). At least this is what I think...
It has airwash, a combustion chamber of cast iron, with also a cast iron top baffle, which - as I learned - is important for radiating back heat and lenghtening the flame path for better combustion.
It is a very tight stove and very precisely controllable.
We have a very good chimney: insulated stainless steel in the middle of the house, with excellent draft,
and have superb firewood: different types of hardwood, seasoned at least 2 years, dry as the Sahara (it really astonishes me that burning dry wood needs to be a question, and people in U.S. forums are really talking about how forgiving their stove is with green wood...).
We give the fire the oxygen it needs, do not let it smoulder but burn with bright flames. (Although we need to conrol/reduce the air flow because if we let the stove go full tilt, the fire is so intense the load would bur down in 10 minutes, the stove would fly away, we would melt or someting similar would happen :) )

So summarized, the set up works very well, fire ignites at ones, no signs of smoke when lighting or burning the fire hot. I'am convinced that we burn very clean despite not having a stove with secondary burn, but we have a good set up, and use it properly.
(Yes maybe we use a bit more wood than with a secondary burn stove, but that is OK)

In our family we always had a fire burning - my father being a huge woodheat ethusiast has always heated with wood, but he almost always had a tile stove (here in Hungary this is the most traditional source for woddheat) Before the Jotul, we used a masonry heater which requires different operation, so cast iron is new to me and in some points I am unsure.
(my father has a cast iron stove but it is an antique collector's pieces which is in daily use but a dfferent story again).

So finally, after the long preamble we arrived to my questions, problems:

- I start the fire with the "2 logs..." technique, that seems to work best.
I also tried top-down but it did not convince me so far, it is somehow too slow. With the "2 logs..." we have a bright fire going in seconds. It burns really intense, but after the knidling is gone and the only 2 logs are burning, I am not satisfied with the result. The logs are not burning intensely but rather just glowing, and burning with silent flames. I have the feeling the problem is that the 2 logs just can't produce enough heat to burn optimally. You can feel this on the stove too. It gets nice warm but not really hot, in this period it doesn't really have much heat output I guess...
After the logs burned down to embers (in 40-60 minutes) and I add 2-4 logs depending on their size, they ignite immediately, we have a really intese fire going in a moment, this time (/from now on) with real, massive heat output. (I have no idea about the exact temperatures, we do not use flue or stove thermometers, so I have to trust my instincts :) )
My concern is that at one hand I dont think the "starter" logs burn optimally this way, and at the other hand in the first 40-60 minutes (sometimes more) we do not really have heat coming form the stove, or at least it is not intense enough that we can feel it immediately.
I have tried starting with more logs (3-4) in the beginnning, it helps a bit. More wood would is burning > higher temperatrures > there is more "fire mass" the stove gets a bit warmer, the wood burns a bit more complete but in the end the story is the same and the real heating starts when the first reload is added.
I thought of starting the fire with even more logs to reach better combustion and a faster heat up, but I am afraid that this would be too much for a cold start, and the too fast heating up could harm the stove.

Also I have noticed, that the inner log, which is closer to the back of the stove, does'nt really burn well. The one closer to the door burns completely but the back one only like 50-60%. If I rake it a bit towards the door, turn it a bi than it ingites, and burns, but I need to "touch it" it reach that. That is logical as the air flows colse to the doar, behind the glass, and later when there is a bigger fire, and the temperature in the whole box is higher/ more even, comustion of the back logs is also better, i think this only happens in case of a small fire.

So what is the secret? Is there one?
Maybe I do everything correctly, and that is just the way it works, my expectations are too high to get real heat in a shorter time. If that is the case I accept it, but maybe there is a way to get a bigger, hotter fire and better combustion in a shorter time but not hurting my stove.

- My second question is about fuel/air balance

What strategy is best to avoid overheating but still get the performance AND to burn clean and also get readonable burn times?
How much wood, how much air?

I have read it somwhere or maybe seen in a video that ones the fire is going, air can be/should reduced until the wood is burning with "calm flames", this way it is still burning clean but it gives a reasonable burn time.
What I have experienced during my few experiments:
- When the fire is really intese, the burn is - i suppose - really clean: no smoke, massive heat output.
- When I reduce the air to the level that just some calm flames are licking the logs, smoke appeares, the heat output is ok, maybe the burn is longer, but this is surely not the most clean and efficient way.
- If I pack the combustion chamber almost full (aiming for a longer burn) because of the quantityof the fuel and generated heat by that (in the beginnning) the fire is roaring even with the air completely shut down, so I guess it burns clean, but in this case I am affaraid the danger of overfiring appeares. So this will not be the way.

Yes I do not have secondary burn, so I have to play with the controls a bit more, and there will be some compromise somewhere: need to load more often, burn more wood, or produce more smoke etc. but I want to find a reasonable "package".

- My third one is rust...
As mentioned the burn plates inside the combustion chamber are cast iron.
I noticed that already after a few burns, a thin layer of rust has appeared on the surface of the burn plates and also on the inner side of the cast iron "body" of the stove.
I know that the huge teperature differences (stove heated up-cooling down) cause this corrosion, I have seen it on older stoves. But is it OK to appeare on a brand new one?
Can or should anyting be done to avoid it?

Thank you for your advice in advance, I really look forward to hear your opinions.

I know that this stove (the TD version) is not very common, but maybe some of you did have or still run one. I would be very much interested in your experience whith that exact stove.

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Hi everyone,

Are my questions that uninteresting, or that complex?
I know similar questions might have been discussed a million times, I did my homework and have read the "start here" section and also done my research before asking, but I didn't feel to have found the answers to my specific questions, thats why I asked...
I would really appreciate some thoughts..

Thank you & bye
The operation is the way pre-EPA F3 was run. In lieu of that follow the manual. I've only run the F3CB which burned pretty evenly. The front log will burn first because it is in the direct path of the airwash airflow, but the rear log should pick up speed and burn well unless the wood is poorly seasoned. I usually ran the stove with 3-4 splits in the fire and closed the door vent once the fire was burning well.

Oxidation is accelerated by heat. It's not uncommon to see a slight surface rust color in the firebox. Get a good stovetop thermometer to learn more about regulating the fire and avoiding overfire. Take the stove up to about 600-650F for a couple burns to bake in the paint. Once the fire is well established on a coal bed that should not take wide open air unless the wood is poorly seasoned.
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Thank you begreen!
It seems to me that the TD works almost the same as your CB did, de real difference will,be in wood consumption, and emission in some cases. (Regarding emissions , I have read a Norwegian study, they comare the F3 CB and F3 TD in lab tests, with interesting outcome..if interested I will try to find the study again and post is)

Regarding the thermometer, as talked about it in an other discussion, they don't sell them here, so I see where I can order one.
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