Jotul F600 air leak?

[branchburner]

I have been running some bigger fires in my new-to-me F600, with which the previous owners experienced high temps. Pretty obvious to me there was an excess of air inflow in the first full load, as it chewed right through the wood without secondaries lighting off. Even with primary air fully shut, the splits coaled and turned to ash way too quickly.

Smoke, light, and dollar-bill testing revealed some gasket issues in ash pan and front doors that I think I have fixed, so I got some good secondaries with last night's longer burn, but the burn was still seeming too short. The smoke test revealed air being pulled in at the base of the primary air control lever, regardless of the lever's position, so I know air continues to enter at that point.

Although not huge amount of air can enter the stove there, it seems there is nothing to impede air flowing in there? (I did pull the doghouse cover, and the slider seems to work fine.)

Further testing shows the fire can continue to burn with foil covering the rear air inlet and with primary air shut. With the incense test, I cannot see any smoke being pulled into the stove anywhere besides the rear inlet and at the air lever.

Since this is my first experience with my own burn tube stove, I'm not certain how the fire is supposed to behave compared to my downdraft stove, where closing the bypass damper forces the smoke (and much of the flame) into the rear burn chamber. But with the Jotul I see not much difference in the fire when adjusting the air control through the full range, making me think there is a source of uncontrolled air entering the firebox that is overwhelming the controlled source.

I saw another thread regarding secondary air leaking in to the base of the firebox, apparently through a small gap that was then sealed with cement. Would this be behind the rear burn plate?

Any thoughts and comments are welcome.

 

[begreen]

Ash pan gasket is where I would start. If that is good and tight pull the ashpan and check behind it with a strong flashlight and poker. Ash can build up behind it and get packed in there . This can push the ashpan forward slightly preventing the door from closing snug. Scrape with poker to see if there is impacted ash buildup.

The other things to check are the air control lever itself. Pull the doghouse and make sure the lever is working the air slider valve correctly. If so, with a robust fire, secondary air will be pulled in as the air control is closed down. You should see good secondary burn (fountain of fire from the tubes) at that point.

Another place to check is for cracks in the base around the edges of the grate. This requires the area to be completely clean and wiped down well with a damp rag.

 

[branchburner]

Thanks begreen.

And thanks to your many previous posts, I had already investigated these areas. No visible cracks, and the slider seems fine. With a light inside the stove, I did find a few problem spots in the ashpan door, which I corrected. Still wondering about the air that enters through the air control.

But my suspicions regarding the diversion of secondary air seem to be confirmed, as I just removed the single-bolt center burn plate in the rear of the firebox. Behind it is the channel for air going upward from the inlet, up to what I assume must channel the air to the burn tubes. I don't see any evidence of cement or gasket on this plate, but as it's secured with only a bolt it seems at least some air must be getting through those unsealed seams, and diluting the amount that flows to the tubes. Does this assumption makes sense? Is that piece suppose to have cement/gasket to seal it tight and prevent air from entering directly into the firebox?

 

[begreen]

Sorry, can't answer that question. I have not taken one apart. You might try @stovelark.

Are you closing the air all the way off or close to it once the fire gets burning strongly?

 

[branchburner]

Well, I think I found my answer... I replaced the rear plate with cement and an hour later fired the stove. It is now behaving very differently than before, with great secondaries and throwing great heat, with lower flue temps. Instead of a bright red-orange roaring fire filling the whole box, I have more restrained blue-orange flames mostly at the top of the box. The burn has definitely slowed considerably. So far so good.