Jotul insert and secondary combustion

myth83

New Member
Sep 20, 2019
41
Germany
Hello everyone,

Thank you so much for sharing your knowledge with me so far despite of my many newbie questions ;)

I have yet another subject that confuses me, probably because of the lack of knowledge:

Secondary burn/combustion in my Jutol (non-cat) insert.

I have that strip on the top back of the firebox, it has many holes on it, I know that part is the secondary combustion component, but I am unable to understand, when burning wood - when I have achieved secondary combustion or not (sure when I reach a good temp. The wood gases burn well and clean and no smoke is visible through the chimney, but anyway..)

I wanted to attach a short video shot of one burn (unfortunately unable to upload anything that is not a still photo) where I am sure I was not getting the secondary combustion to kick in, since the strip with the air holes in it was not active (one time I have had a good fire going on and I could see flames dancing around those holes..)

Can anyone try to explain to me, how can I identify that my firebox‘s secondary combustion is active? Any visual sight?

Any help will be much appreciated :)
 

ChevWood15

New Member
Apr 27, 2018
27
N.Y.
My stove with active secondaries. Visible flames will be coming out of the tubes. Doesn't happen right away. It needs to be hot. Also, primary air is almost closed so air can be drawn through the secondary.

8a887ef9f5b31b7335c60b88a71aa074.jpg
 
Last edited by a moderator:
  • Like
Reactions: myth83

myth83

New Member
Sep 20, 2019
41
Germany
My stove with active secondaries. Visible flames will be coming out of the tubes. Doesn't happen right away. It needs to be hot. Also, primary air is almost closed so air can be drawn through the secondary.

Sent from my SM-G950U using Tapatalk
Thank you for the photo, it helps!

Here is how the secondary combustion looks on mine for compare (it doesn’t look like a perforated tube like I’ve seen in many photos online):



Is it possible that I am not burning hot enough ?

I should probably find and buy one of those round thermometers, question is will it fit an insert (no top plate or steel pipe to attach it on)
 
Last edited by a moderator:

firefighterjake

Minister of Fire
Jul 22, 2008
19,349
Unity/Bangor, Maine
With my Jotul Oslo I don't tend to see the propane gas BBQ effect with flames shooting out of the tube's holes as some other folks with secondary burning stoves have reported.

When the secondary burning kicks in I sometimes get the "fireworks" where the combustible gases build up and then "burst" in a non-violent way into view and then a second or two later there is another burst.

More often I either get "ghost flames" where you will see the wood burning and there are these slow moving, wispy looking flames dancing about . . . or even more typical I get the "Portal to Hell" effect where there is little to no flames on the wood, but in the upper part of the firebox there is a fire raging as if someone has opened a door to hell.
 

charger4406

Burning Hunk
Dec 25, 2011
249
southern Quebec
With my Jotul Oslo I don't tend to see the propane gas BBQ effect with flames shooting out of the tube's holes as some other folks with secondary burning stoves have reported.

When the secondary burning kicks in I sometimes get the "fireworks" where the combustible gases build up and then "burst" in a non-violent way into view and then a second or two later there is another burst.

More often I either get "ghost flames" where you will see the wood burning and there are these slow moving, wispy looking flames dancing about . . . or even more typical I get the "Portal to Hell" effect where there is little to no flames on the wood, but in the upper part of the firebox there is a fire raging as if someone has opened a door to hell.
This is also how my F600 runs except I rarely get the "ghost flames" or the fireworks unless the firebox is really hot when I reload.
 

begreen

Mooderator
Staff member
Nov 18, 2005
86,546
South Puget Sound, WA
The F400 Harmony is more of a fireplace than an insert with a different design than the Jotul inserts sold in the US. The secondary ports appear to be just a the back of the baffle, is that correct? If so, the secondary burn may not be as robust. How much wood are you burning per load? What is the air control set to? What temperature does a thermometer on the upper face of the fireplace read?

Here is a lightened version of the secondaries on this fireplace.
0eecc8e47de34e723de37b0b99b9ed15.jpg
 

myth83

New Member
Sep 20, 2019
41
Germany
The I400 Harmony is more of a fireplace than an insert with a different design than the Jotul inserts sold in the US. The secondary ports appear to be just a the back of the baffle, is that correct? If so, the secondary burn may not be as robust. How much wood are you burning per load? What is the air control set to? What temperature does a thermometer on the upper face of the fireplace read?

Here is a lightened version of the secondaries on this fireplace.
View attachment 248184
Thank you for the reply :) yes as I understand this I400 model is not common in the US market (or not sold), yes the secondary combustion strip is like a flat perforated square steel block that is laying flat with the fire brick at the upper back of the firebox.

I am not sure about the burn temps, that’s why I have ordered a magnetic thermometer to stick on the front.

When I do a first load from cold, I open both primary and secondary air controls and fire it up.. then after about 20 minutes I close the primary air control and keep the secondary control in the middle.

For a first load from cold, I use the top-to-bottom method using 2 larger splits at the bottom, then on top of that at the opposite direction another pair of slightly smaller splits, on top of that kindling and a fire starter (made out of wood shavings and wax).

Today I have had a pretty good looking burn and I could notice that there were flames dancing on, up, down and around that perforated part. Go figure.. I must keep on learning
 
Last edited by a moderator:

begreen

Mooderator
Staff member
Nov 18, 2005
86,546
South Puget Sound, WA
You're doing ok from the sound of it. There is a learning curve with any new stove. The fire will burn a bit hotter and longer once a nice bed of ash develops. With a larger fire in the fireplace, try to experiment a little by closing down the top air control a little further. That may encourage more robust secondary combustion.
 
  • Like
Reactions: myth83

myth83

New Member
Sep 20, 2019
41
Germany
You're doing ok from the sound of it. There is a learning curve with any new stove. The fire will burn a bit hotter and longer once a nice bed of ash develops. With a larger fire in the fireplace, try to experiment a little by closing down the top air control a little further. That may encourage more robust secondary combustion.
Thank you for the input!

I did indeed notice once that when the fire is going strong and I restrict the secondary air control a bit further, the secondary combustion seem to become more permanent- but how does it work ? By restricting air it works better?

Maybe it is useful to add that I have my fireplace air supply from the outside using an external air supply pipe that goes through the wall and draw air from the outside.

BTW magnetic stove thermometers, is there any difference in quality/reliability/precision between the cheap unbranded products and the branded (e.g one from Jotul vs. Another from China) ?

There is sometimes a 50% difference in price and I was not sure if the extra premium is only for the brand name on the thermometer or do they make them better and/or more precise.
 

begreen

Mooderator
Staff member
Nov 18, 2005
86,546
South Puget Sound, WA
I did indeed notice once that when the fire is going strong and I restrict the secondary air control a bit further, the secondary combustion seem to become more permanent- but how does it work ? By restricting air it works better?
The terminology is wrong. The upper air is the primary air on this fireplace. The lower air control is boost or firestarting air. The secondary air supply is unrestricted. With the lower air control closed and a good fire burning, closing down the upper air control caused a vacuum to be created in the firebox due to draft. That vacuum pulls air through those secondary air ports.

A lot of stove thermometers are cheap junk. Even if they are accurate to start with some lose accuracy as time goes by, especially if they get too hot. I don't know what Jotul sells in Germany. That said, a friend has an inexpensive Chinese thermometer for about 7 yrs now and it seems to be doing ok. Ask around at some reputable stove shops in your area.
 

myth83

New Member
Sep 20, 2019
41
Germany
The terminology is wrong. The upper air is the primary air on this fireplace. The lower air control is boost or firestarting air. The secondary air supply is unrestricted. With the lower air control closed and a good fire burning, closing down the upper air control caused a vacuum to be created in the firebox due to draft. That vacuum pulls air through those secondary air ports.

A lot of stove thermometers are cheap junk. Even if they are accurate to start with some lose accuracy as time goes by, especially if they get too hot. I don't know what Jotul sells in Germany. That said, a friend has an inexpensive Chinese thermometer for about 7 yrs now and it seems to be doing ok. Ask around at some reputable stove shops in your area.
Thank you for the explanation about the air controls and secondary air operation, it was confusing for me to unterstand which air control is what even after going through the original printed Jotul guide that came with it.

So I will look around for a thermometer, as long as it is only about 10-15% off the real temp. it would be useful for me