Can't get much over 400 degrees

[wahoowad]

Last night was my final break-in fire in my Jotul 3CB. I took it to 400 for about an hour, then let it cool. I had the primary air control all the way open and temps stabilized right around 400. It makes me wonder what I would do to get it burning hotter since the manual says optimum burn is between 400 and 600? I would like to shoot for midrange of 500.

Would partially closing the air control make it burn a little hotter? I felt like I was burning through the wood quicker than expected (same as with my open air fireplace) so it seems I will still burn quickly to run the stove at 500?

Thanks!

Oh, and I have my stove thermometer where Jotul says it should be. I will also calibrate it against another known good thermometer I have. I suspect it is OK and just my burn technique.

 

[elkimmeg]

Fully open air makes it burn hotter, but also more air enhances pushing heat with the exhaust up the chimney. Once you get it going 30 minutes cut it back 50% then 15 minutes later 1/ 4. This is a slow process do not rush it to get there quickly. Another concern is the moisture content in the wood. too much moisture you may never get it over 400. You might try splitting the wood pieces in half and see if that makes a difference. Once you establish 500 550. then add pieces as needed not filling up the box completely. There is a learning curb here, where you have to experiment to find the working formular. I have heard it takes 30 hours to fully cure a stove. especially with refactory and it being just manufactured and installed. Fresh refactory hold quite a bit of moisture and should be cured easilly, lest it could crack and crumble. Point being take it easy for a while longer.

 

[pmac]

The hottest I've gotten my Jotul F400 is 500 degrees, and that was with the air wide open, using smaller pieces of dry wood. It's hard for me to maintain the minimum recommended temp of 400 deg without leaving the air wide open - and I'm reading here that other folks seem to not typically leave the air wide open.

Then again, we've always had chimney/draft issues; previous owner built his own cinder block chimney with a 6" round clay lining (outside the house), didn't raise it high enough where it should be beyond the roof. We just had it extended a couple feet last year, which helps a bit, but we still get smoke coming in when I open the doors to feed more wood, and temperatures that I think should be hotter...

Are you sure you're getting enough draft? I guess you would be if you're burning wood as quickly as when it was just a fireplace...

 

[carpniels]

Hi Pmac (and wahoowad),

It is soooooo good to read you post. I thought I was the only one that had that problem. My Castine (F400) has the same issue. Hard to get up to 400 and over was very difficult. I have been playing with the air control and different loading capacities. I can get it higher now if needed.

The good thing is that it is also difficult to get it below 400. Once it is going, it is hard to mess it up. I have found that full air from cold to 500+ works fine. Then I tune it down (sort of like Elk, but not that detailed). I mostly watch to see if I can see the blue secondary brun flames. If they are there, things are good.

Yesterday, I had the stove at 350 and full loaded it up. It seemed to die so I left it alone and went to the computer. After 30 minutes I smelled a burn. I went to the stove and it was on. Hot glowing bright red embers and the fire was not roaring but going. The thermometer on the stove said 875!! Man it was HOT in that room. Crazy. I had never had the temp that high before. The wife loved it. I used decent size splits of black cherry (well dried) and stacked it so that the box was almost completely full.

Hope this helps.

Carpniels

PS. I am going to try Elks strategy and see if it works as well as I hope.

PPS. Good advice from Elk about curing. That is very important.

 

[pmac]

Yesterday, I had the stove at 350 and full loaded it up. It seemed to die so I left it alone and went to the computer. After 30 minutes I smelled a burn. I went to the stove and it was on. Hot glowing bright red embers and the fire was not roaring but going. The thermometer on the stove said 875!! Man it was HOT in that room. Crazy. I had never had the temp that high before. The wife loved it. I used decent size splits of black cherry (well dried) and stacked it so that the box was almost completely full.

875?!?! Did you turn out the lights in the room to see if the stove was glowing a bit? ;-)

I need to experiment more... maybe some of the splits I'm using at lower temperatures are too big... I also get too impatient, I think - if I throw more wood on and it doesn't perk up within 10 or 15 minutes, I go back and and tinker with the arrangement... I should probably just let it go for a while like you did...

Thanks for the input!

 

[carpniels]

Hi Pmac,

Yes, 875. I could not believe it either. It was so hot in the room I ran to the stove, closed the air control quite a bit and left the room. Within 10 ft of the stove was unbearable. No, it was not glowing.

I have noticed that most stove stores I go to have only 2 or 3 splits in the stoves. And the stoves are hot (500 or so). I noticed that these splits (actually quarters) are large (maybe 6 inch across). All my splits are small and short, because they were cut for my VC INtrepid II which can only take 16" (skinny) splits. So when I load my Castine, I have to add a lot of splits, and some are so short I add them pointing straight back so I can load the stove as much as possible. But I have to leave the air fully open and wait about 30 minutes until it really goes.

Patience pays off. Especially because it gives you time to think about what is wrong/right, and then act.

Good Luck

Niels

PS. I cannot wait to try to cut larger trees and keep the splits large and long. A lot less work and hopefully easier and warmer burns.

 

[Eric Johnson]

I've noticed that I get longer burns out of bigger chunks. The tradeoff is that you have to dry them longer. But if you can get a year ahead on your wood, there's no point in splitting pieces that will fit into your stove, unless splitting makes them easier to handle. It's nice, in any event, to have a variety of sizes to choose from, depending on the circumstances. In my case, smaller, split pieces make for a quicker, cleaner burn. The big stuff I save for the overnight burns and very cold weather.

Hey carpniels, what happened to winter in the Mohawk Valley? I thought we were in for another long, cold one. Not so far, but LOL, that can change overnight.

 

[pfmg]

I can get my castine up to around 600 with one or two big splits and 3-5 smaller ones. Once the temp is up, i close the airflow to half for a little while and then down to about 25% and the temp will lower to about 400-500 and stay there for a good 4 or 5 hours and then it will start to drop. If i left the airflow wide open, i have no doubt the stove would be glowing in a few hours, this baby wants to heat!

 

[wahoowad]

I will heed Elk's advice about continuing a gradual increase in temperature...although I'll have to figure out how to get the temp up! I did not have it full of wood because I didn't want it getting too hot. Next time I will try packing a few larger pieces than previous attempts and see how she does.

I have seen a few references to the blue flames but do not know anything about this. Should I be burning in such a fashion that I should see blue flames? Where should I see them?

 

[Rhone]

Though I don't have a stove thermometer (I have an insert) it sounds like your wood is wet. Do you hear any hissing, or popping, or see steam coming out the ends when you burn? Do your flames go out, and at max air wish you could give it even more? That's a sign, along with low heat, extra wood use, and short burn times. This year has been terrible for drying wood, I bought and stacked seasoned wood July 1st, piled it then, and covered just the very tops of my pile with plastic. That wood that was just under the plastic burns incredible, I can turn my insert down to 50% and on extremely rare occasions even that's too high and I get so much heat and the fire lasts an extremely long time. The rest of my wood I have to burn at either max air, or slightly below max just to keep a flame going and it hisses, it pops, it doesn't produce as much heat, and is over in 4 hours and I reload in 5. Nothing like the dry wood.

To help, I cleared off my open porch and moved a cord of wood there. Now, the sun hits it for a few hours a day, it's in the wind, and completely protected from snow/rain and lasts about a month before I move another cord there. I then made a cabinet that holds my wood inside near my insert, with screens & holes on both sides so air can flow through the wood before I use it. Each side holds 2 days worth (if it were dry wood, it would be more like 3 days). That has helped me get my fires started faster, burn them hotter, and I can usually turn down my air to about 80% now. A lot of work to get a small amount of help, as the wood is still wet but at least now I can burn it and get a fire going. When I started I used to take it from the piles in my yard and try to burn it on an as needed basis. I'd have it on max air and have a heck of a time trying to keep it going. Like Elkimmeg says, I learned when my units gets moving on max air I can't just cut it to 50%, the fire gets starved and dies out. When I want to turn it down, I have to go in steps. I turn it down a little, the fire struggles to stay lit, recovers and then I turn it down a little more, rinse, and repeat. I thought that was just my unit, glad to see I'm not the only one that can't just turn down the air from Max to say 25%. The blue flames in my unit are the secondary flames at the top before my unit gets very hot. Once the fire gets moving, and I've turned the air down, in a matter of time the secondary flames seem to happen much less if at all, and blue flames come off the wood & coals.

 

[wahoowad]

No, I do not think the wood I have used so far has been wet at all. I have been hand selecting my wood to ensure my break-in fires will go well. I have neard no hissing, seen excess smoke or heard popping. It starts quickly and fresh logs start up fast too.

 

[carpniels]

Hi Wahoo,

Looks like Elk is right, your furnace cement needs to cure properly and is giving of water. Also practice makes perfect.

Hi Eric,

I am happy as a clam!! No winter, no snow. I love the high temps. I have seen my woodpile decrease way to fast (this is the first year I am trying to heat exclusively with wood (24/7) so I cut as much as I could but it still does not seems to be enough. With the higher temps, I can slow the fire down more and save on wood.

Indeed the winter in the Mohawk Valley can change overnight. I am keeping my fingers crossed that the weather stays warm like this. Sorry for the snowmobiles, but I am selfish. Hurray for global warming!!

Carpniels (Rome, NY)

 

[begreen]

Last night was my final break-in fire in my Jotul 3CB. I took it to 400 for about an hour, then let it cool. I had the primary air control all the way open and temps stabilized right around 400. It makes me wonder what I would do to get it burning hotter since the manual says optimum burn is between 400 and 600? I would like to shoot for midrange of 500.

Would partially closing the air control make it burn a little hotter? I felt like I was burning through the wood quicker than expected (same as with my open air fireplace) so it seems I will still burn quickly to run the stove at 500?

Thanks!

Oh, and I have my stove thermometer where Jotul says it should be. I will also calibrate it against another known good thermometer I have. I suspect it is OK and just my burn technique.

This stove should comfortably burn in the range Jotul describes with dry wood. Damp wood will rarely burn in this stove over 400 deg. We normally run it at about 500-550 peak. Your burn temps will vary with the type and dryness of the wood burned. But assuming you have excellent firewood. It should get to 500 quite easily. If it runs too cool, try moving your stove thermometer to the other side. Is it hotter on the other side? I had this problem. It turned out that the top wasn't on perfectly and there was a small air leak that was messing up the secondary burn on one side. One I pulled the top, the soot train from the air leak showed the problem. Look at the stove side and make sure that the top is on perfectly parallel. If your issue is the same, here is the link to the what and how my problem was solved with the F3CB:
https://www.hearth.com/talk/threads/46/

PS: I have very good draft and my stove is happier with a stovepipe damper installed. Once it gets going well, I normally run it with the stovepipe damper almost all the way closed and the air intake about 50% closed. At night I stoke it up with a good load, let it char and then close the air intake all the way.

 

[wahoowad]

Well, I'm still having problems and i don't understand it. I'm around the 40-50 hour mark after my first dozen burns. I'm using good, dry wood and I have experimented with more/less wood and various air settings. I also calibrated my stovetop thermometer and learned it runs about 50 degrees high. This means I've been achieving even lower temps that I thought!

At least now I can initially get up to 475 (525 reading - 50) with full air and hold it until the logs burn down a good bit. But again, that is with full air. I've been trying to cut the air back (to slow, lazy flames) to get a longer burn out of my wood. The temp drops to maybe 350 (400 reading - 50) if I slow down the combustion.

Fortunately my living room gets right toasty regardless of what i am reporting here. I'm just focusing on the temps to ensure I am operating it for efficient use and ensuring it is performing like other Jotul 3CB's folk have here.

 

[precaud]

These stoves were not designed to be run with the air control full open except during the warmup phase. Typically, primary air controls on this type of stove would be in the range of 15% to 40% open during normal operation. If it doesn't cruising properly in that range, assuming your wood is dry as you say, then either you have insufficient draft or your stove has a construction defect. BeGreen has already outlined one thing to look out for; here's another.

Look at the exploded diagram in your manual. Part #26 is called an "air deflector". That's the primary air chamber and hood that guides it over the glass. The F3 does not significantly preheat it's primary air, so it's very dependent on a strong draft for good air velocity. The air enters through the slot by the control, into the said chamber, and into the firebox. But... if this chamber is not well sealed, it would pull some of the air intake right into the upper chamber, cooling it and completely bypassing the fire. It sounds to me like this might be what's happening. A bead of stove cement all around the air deflector would solve the problem.

My Jotul F602 had significant leaks everywhere due to sloppy assembly; excessive cement in some places, and absolutely no cement in others. Sealing the main joints all around the inside of the stove made a big difference in the way it burned.

 

[wahoowad]

thanks precaud.

Tonight i went for maximum heat. I let an intial load of kindling burn to coals, then filled the firebox with 3x4x16 pieces of dry pallet wood. It is burning like the gates of hell and went up to 550 before I backed the air supply back 25%. That wood is burning very fast and I can't imagine it getting any more air (as you seem to suggest some air was bypassing). In fact, I just backed the air down 25% and noticed the temps then slipped back down a bit. it is so hot around the stove I have to make an adjustment and back away. She keeps tinking.

 

[precaud]

Well wahoo, now you've experienced the opposite extreme in terms of load combustbility. Methinks you'll be living somewhere in the middle. I hardly ever fill the firebox with wood. Try this: spread your coals bed out not flat but into two gentle mounds, leaving a slight valley in the center of the stove, enough to allow some air to get under the front log. Load two or three logs, 3 to 4 inches across, with 1/2 inch space between the bottom ones and the third one on top corner-to-corner across the two below. Get them burning and char the outside of the logs, then lower the air control so the flames are streaming against the bottom of the secondary air chamber. That's where you want the mixing with the secondary air to occur.

 

[wahoowad]

precaud,

I do need to pokemy head in the firebox and look for any assembly issues or problems. I actually found about a 12" long thin piece of what I assume is stove mortar that had fallen out of wherever it was installed. Picture 4 pieces of spaghetti stuck together - that's about the thickness of this mortar I found. It probably fell from somewhere in the top of the firebox. I'll look around tomorrow.

 

[begreen]

precaud,

I do need to pokemy head in the firebox and look for any assembly issues or problems. I actually found about a 12" long thin piece of what I assume is stove mortar that had fallen out of wherever it was installed. Picture 4 pieces of spaghetti stuck together - that's about the thickness of this mortar I found. It probably fell from somewhere in the top of the firebox. I'll look around tomorrow.

Sounds like you are on the right track. When my stove had the air leak due to the mis-seated top, it had similar symptoms. Burned a lot of wood without much heat output (at least on that side of the stove) and it was harder to get burning well. These stoves are quite efficient, but rely on tightly controlled airflow. I noticed in your original pics that there was soot build up in the back corners. This may not mean anything, but I'll try pulling my top off (if the allen screws still come out) and will see if I have the same look. I'll take a pic if I am successful so that you have something to compare to.

 

[begreen]

OK, I pulled my top. Nothing really conclusive to report except that it was pretty evenly sooted up. The good news is that even after 3 months of running, the allen screws came out like they were new. That was a pleasant surprise. This leads me to wonder if the allen screws in your 3CB are possibly mis-tapped and mis-aligned from the factory? When they are right, they screw in an out of the aligned holes on the top inner flanges very easily.

It seems that perhaps you would benefit from a stove leak test? I read in another thread (on the Encore?) that there is is smoke pellet test. I'm not sure where one gets these, but perhaps Craig or other installers can chime in here. If you have a badly caulked seam I would think this would show it up pretty quickly.

Last, are you a long way from your dealer? It seems like they should be helping you out with a new stove. After Jotul tech support had no clue, my dealer was ready to consider coming out, in spite of the 45 mi + ferry ride distance.

 

[wahoowad]

precaud,

I checked that air chamber using a flashlight and could not see even a hint of light showing through any cracks. I think that area is OK. I did find where that piece of dried mortar fell out inside my stove. It came from the leading edge of where the Air distributor (#12) meets the Baffle plate (#11). In essence where my reburn chamber meets the top of the firebox. I'm not sure if this has an impact or not. I do see air coming out those baffle holes during reburn.

BeGreen - i took a small flashlight and manuevered it up on top of the firebox (the area you see if you remove the top). I shined it towards the back and sides and could see light by looking towards the back and sides of the firebox. It either is this way by design or it is missing lots of stove mortar. My gut says it is normal but curious if you have (or will) try this. On the diagram it is item #11 baffle plate that I see light shining past. Also, I sent you an email via this forum but not sure if you got it.

 

[BrotherBart]

Get the stove burning pretty well and light something like an incense stick. I smoke so I just use cigarette smoke. Pass it around the stove at all of the seams and you will find any leak real quick.

 

[begreen]

precaud,

BeGreen - i took a small flashlight and manuevered it up on top of the firebox (the area you see if you remove the top). I shined it towards the back and sides and could see light by looking towards the back and sides of the firebox. It either is this way by design or it is missing lots of stove mortar. My gut says it is normal but curious if you have (or will) try this. On the diagram it is item #11 baffle plate that I see light shining past. Also, I sent you an email via this forum but not sure if you got it.

So, let me be sure I understand this. If you shine the light towards the back corners of the stove, you see the light shining from the outside corners of the stove? I'll check it later, our stove is hot right now, but this does not at all sound correct. I would be very suprised to see any light at all. It might however, explain the sooty back corners in the pic you posted a while ago. I would take it up with the dealer. This really sounds like an assembly issue.

 

[wahoowad]

No no no! I guess I didn't explain myself very well. Sorry.

I took a small flashlight and put it inside the stove, sliding it up and into the upper portion of the stove where your stovepipe connects. This is the area you see when you remove the top. I pointed the light along the rear or the stove and along the sides. Then I looked into the stove, into the back of the firebox (where the logs go) and could see light shining down. I hope that was better.

 

[begreen]

Ah, ok. I got it. That is all on the interioro of the stove. I see a thin crack of light there as well. It should be ok. What you are looking for is exterior air coming into the stove via an unplanned path. Check ashpan door seal, top seal, and the corners with an incense stick while the stove is burning to see if the smoke is drawn into the stove at any of these areas. Also, you might want to try a pack of energy logs, (pressed sawdust type, not the wax duraflame type, you want no additives), just to eliminate the wood as a source of problems.