Jotul Castine Temp Control

Ski-Patroller · Jan 5, 2015

I had an interesting experience Friday night. We got to our cabin about 9:30pm and fired up the stove (Castine) as hard as we could, mostly on Presto Logs. It was running in the 500-700 range, just fine. About 11:30 with a good bed, I put on 3 more Presto Logs. We watched as the temp kept climbing all the way to 900 (Stove top on the right side) Shutting the primary air seemed to have very little effect. Even with the primary shut down, there was plenty of fire down at the bed area, and the secondaries were going gang busters. I slipped a piece of aluminum plate over the air intake the the back bottom of the stove and finally got it down to 700 about 1:30 am. I was afraid to go to bed until I got the temp down to a dull roar.

Any thoughts about what went on here, and what to do about it in the future? Jotul says ideal temp is 400-600F and not to go much over 600. My stove has the heat shield installed on the bottom so the air intake is not quite as accessible as I might like, but I'm going to make an aluminum plate device to close it off more easily in the future.

As a side of all of this, I really like the Presto Logs. It is much easier to have a bed of coals in the morning with them than with Doug Fir splits. 3 Presto logs is close to 28# so it is a lot more wood than I would normally get in the fire box. They put out a lot of heat and last a long time, but I am worried if 3 logs get the stove to 900 degs. on a normal basis.

Tenn Dave · Jan 5, 2015

Ski-Patroller said:
I had an interesting experience Friday night. We got to our cabin about 9:30pm and fired up the stove (Castine) as hard as we could, mostly on Presto Logs. It was running in the 500-700 range, just fine. About 11:30 with a good bed, I put on 3 more Presto Logs. We watched as the temp kept climbing all the way to 900 (Stove top on the right side) Shutting the primary air seemed to have very little effect. Even with the primary shut down, there was plenty of fire down at the bed area, and the secondaries were going gang busters. I slipped a piece of aluminum plate over the air intake the the back bottom of the stove and finally got it down to 700 about 1:30 am. I was afraid to go to bed until I got the temp down to a dull roar.

Any thoughts about what went on here, and what to do about it in the future? Jotul says ideal temp is 400-600F and not to go much over 600. My stove has the heat shield installed on the bottom so the air intake is not quite as accessible as I might like, but I'm going to make an aluminum plate device to close it off more easily in the future.

As a side of all of this, I really like the Presto Logs. It is much easier to have a bed of coals in the morning with them than with Doug Fir splits. 3 Presto logs is close to 28# so it is a lot more wood than I would normally get in the fire box. They put out a lot of heat and last a long time, but I am worried if 3 logs get the stove to 900 degs. on a normal basis.

Perhaps your coal bed was too big & hot for a reload. Next time try to burn it down more before reloading. Good luck.

begreen · Jan 5, 2015

Presto logs are not the best of the compressed logs. You can't burn them like regular wood. Putting three more logs on a fire only 2 hrs old caused the new logs to heat up and release their heat and flue gases very rapidly because these logs are not highly compressed. Let the original load burn down further before reloading and you will avoid this drama.

Ski-Patroller · Jan 5, 2015

begreen said:
Presto logs are not the best of the compressed logs. You can't burn them like regular wood. Putting three more logs on a fire only 2 hrs old caused the new logs to heat up and release their heat and flue gases very rapidly because these logs are not highly compressed. Let the original load burn down further before reloading and you will avoid this drama.

These are actually Northern Idaho 8# Logs. I can't imagine denser compressed logs. I will be more careful about putting them on such a hot bed of coals. I really like how they hold a fire all night in the Castine.

I was surprised by how little effect the primary air control had on the fire when it was this hot. It sure kept the glass clean though.

Toploader · Jan 6, 2015

Ski-Patroller said:
These are actually Northern Idaho 8# Logs. I can't imagine denser compressed logs. I will be more careful about putting them on such a hot bed of coals. I really like how they hold a fire all night in the Castine.

I was surprised by how little effect the primary air control had on the fire when it was this hot. It sure kept the glass clean though.

I'm not sure about the Castine but on my Oslo it is possible to close the air control so hard that the plate which closes off the air slides up and out of the track it normally rests in. This can create, as it did for me a couple times, a situation where you think the air is completely closed but in reality it is the equivalent of about half open. If it happens again, to rule out this possibility, open the air up a bit and gently tap it closed until you feel it resist.

begreen · Jan 6, 2015

Ski-Patroller said:
These are actually Northern Idaho 8# Logs. I can't imagine denser compressed logs. I will be more careful about putting them on such a hot bed of coals. I really like how they hold a fire all night in the Castine.

I was surprised by how little effect the primary air control had on the fire when it was this hot. It sure kept the glass clean though.

That means even greater heat energy released suddenly. 3 NIELs will bring the Castine up to 650F easily. This video is with 3 NIEL logs burning, no wood.

In a couple hours these logs have only released maybe 1/4 of their total energy, so adding 3 more you had like 6 NIELS firing off for several hours. The fire was mostly secondary burn, not primary air. As you have learned don't do that. The energy potential of these logs needs to be respected. Adding one NIEL after a few hours would have been sufficient to maintain heat until morning.

Ski-Patroller · Jan 6, 2015

begreen said:
That means even greater heat energy released suddenly. 3 NIELs will bring the Castine up to 650F easily. This video is with 3 NIEL logs burning, no wood.

In a couple hours these logs have only released maybe 1/4 of their total energy, so adding 3 more you had like 6 NIELS firing off for several hours. The fire was mostly secondary burn, not primary air. As you have learned don't do that. The energy potential of these logs needs to be respected. Adding one NIEL after a few hours would have been sufficient to maintain heat until morning.

On Friday, my Castine had a lot more primary burn than what the video shows, even with the primary air shut down. In the past closing the primary air had a dramatic effect on the stove, but not on Friday night. The effect was noticeable but certainly not dramatic, and it had no noticeable effect on the temperature. Even restricting the main air inlet did not stop it, though it did reduce it a lot. With a stove this hot I would have had a lot of draft, and I could not close the main air intake completely because the heat shield restricted my access to it.

Is there a consensus on how hot you can run one of these stoves without causing damage. I have 12 ft of Double wall Duravent inside the house, and another 12 ft of Metalbestos above the ceiling. Did not look like anything suffered, but it sure made me nervous.

rijim · Jan 6, 2015

24' of stack will give you significant draft, you may need a damper in there to allow you to chock it down a bit.

Ski-Patroller · Jan 6, 2015

rijim said:
24' of stack will give you significant draft, you may need a damper in there to allow you to chock it down a bit.

I would consider that, if I could figure out how to clean a flue with a damper installed. With my Castine, I leave the flue connected to the stove when I clean it, and just remove the top of the stove to clean the smoke ledge.

Are Barometric dampers ever used on wood stoves? I have speced them for industrial boilers, and I think I recall seeing them on residential furnaces, but I've never seen one on a wood stove.

FYI a Barometric damper is a weight balanced damper that is installed in a tee on the flue. It opens to admit air to the flue to reduce the draft to maintain a specific maximum draft. They could have a tendency to leak smoke when starting a cold stove.

begreen · Jan 6, 2015

This does not sound like a draft issue. The F400 likes strong draft. The issue is too much high octane fuel at one time. This is why stove mfgs. say burn only wood.

Ski-Patroller · Jan 6, 2015

begreen said:
This does not sound like a draft issue. The F400 likes strong draft. The issue is too much high octane fuel at one time. This is why stove mfgs. say burn only wood.

The 400 does like a lot of draft. In normal operation the 24' stack is just adequate. We will continue to burn the NIELs but no more than 2 at a time. I had not considered how much fuel we were putting in the box with 3 logs and a bed of coals. I love how these things burn. They will maintain a bed of coals all night, so restarting in the morning is a piece of cake. That is important to me because often I don't have a lot of time between getting up and heading out the door on a patrol day.

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Jotul Castine Temp Control

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