Wood stove temperature question

[KarynAnne]

I'm trying to figure out what "normal" looks like for an overnight burn. I have a Jotul Oslo. The draft is fine, the wood is a mix of seasoned hardwood splits from last winter. I rake the coals to the front, load the stove up and put a small igniter split at the very front. I'm getting better about leaving the stove alone with the air open all the way for about 45 minutes or longer to try to get a bit of flame going. But there's not much room in the firebox to let much heat happen anyway, just get the flames started. The stove is not over 300 (and usually less) at this point and I don't think it goes over that all night. This is not enough to get the house warm. During the day I've found that if I want HEAT out of it that I need to load a piece or 2 at a time on top of mostly burned logs to trick up the temperature to around 600 or so. I don't think I could get it much higher than that if I tried. Not that it needs to click along at 700 all day, but I thought I'd get more heat than I'm getting. The stove seems to like hovering around 350 when you aren't paying attention to it. Back to the nighttime quesiton...I don't think that my secondary burners are even working since the temp seems to be so low. I cut the air back gradually to about slightly under 1/4 open. I think that if I left it more open than that I not only wouldn't get an overnight bed of coals but it wouldn't add that much heat anyway. Any suggestions? Thanks.

 

[DiscoInferno]

I find that the real heat doesn't come until the secondary burn kicks in, and for me that seems to take temps above 500 F. 300 is more of an idling temp, where I just have coals but am waiting for the house to cool down before I add more wood. When I'm loading for overnight, I start with a good base of coals, pack as many splits as I can, and then open the primary air and "air boost" (direct air at the bottom center) until it hits 650-700. Depending on the wood, this takes 5-15 minutes. At this point the fire looks to be about to run away, and I close the air down. This leaves me with a ton of secondary combustion, and the temperature will stay above 500 for hours, then slowly drop as the wood turns to coals. I find that a lot of wood makes for a hotter fire (more fuel, after all), so I'm not sure why you're seeing the opposite. If I left my air wide open with a full load like that for 45 minutes I think my stove would melt. Are you starting with a thick bed of coals? Are you leaving some under all the splits, or really raking them all to the front?

 

[KarynAnne]

There are a few coals left underneath of the back splits, but most are raked towards the front. My stove only has one air lever - at the front below the door. Now, I do open the side stove door a hair to tease the heat up, but I'm not getting anywhere near 500 before I shut it down. It WON'T go that high. I would have thought that the more wood the more heat too, but it's not happening. I just went to check the stove and it's riding at 250. I know it's not a draft problem. I'm not sure what to try next...but I know that I have to fool with it and leave lots of air room in there during the day to get it up to a high temp. The wood seems dry - it doesn't hiss when I put it in. I don't get it.

 

[KarynAnne]

I just went and tricked open the side door and got the stove to around 500. I added another piece of wood since it would fit now and that should be enough to keep the temperature up for a bit too. I have a nice rolling boil in there now, but I have a feeling that there won't be any wood left by morning. I really think that my expectations for my stove may be out of kilter. I really want to figure this out, but I'm getting frustrated. Any help is appreciated. Thanks.

 

[webbie]

KA, it sounds like you might be a bit short on draft. Can you tell us more about your chimney situation.

Draft is EVERYTHING. In other words, the chimney provides the pull which allows the fire to burn hot. You can have the best stove made (and you have a good one!) and a poor or mediocre chimney, and you will have problems getting heat.

So tell us more about the install and chimney.

Why do you say you know it is not a draft problem? Draft can be a funny thing.....for instance, a stove might have no startup problems, but still have draft problems. If you add additional wood and open the air control fully - and the stove does not react in a fairly quick manner, then I would suspect draft (or wood).

Another thing - overnight burns are usually not heat-producing burns. You are getting less heat, but for a longer period. Also, I have found that having a large bed of coals before loading for the night is very helpful - as opposed to your method which seems to have only a small bed. With a small bed of coal, adding a large load of wood cools the firebox way down....

 

[DiscoInferno]

If it won't get above 500 then I would think there's a problem with some combination of wood, draft, and stove design. I'll assume Jotul knows how to make a stove. When you crack the door, do you get a good raging-fire wind-tunnel effect? Can you get it hot with a cris-crossed stack of your thinnest, driest splits (or even scrap untreated lumber)? If no, then it might be draft. If yes, then it's probably the wood. I know when I grab a less-than-fully-seasoned log or two it slows things down a lot, even if not so wet that it hisses.

 

[begreen]

Something's amok. I can get the next size down stove (F400) up to about 450 in about 30 minutes and never need the door open more than 15 minutes, usually only about 5-10 minutes. The F500 will need a bit more wood, but most are able to run the F500 and other Jotuls at 550-650. Either the wood is not as dry as is thought, or there is not enough wood to really get going, or perhaps the fire is getting too much air. That is what I was doing wrong. I was giving it too much air which was cooling the fire. Now I throttle the air down as soon as a robust blaze is going and the stove is over at about 300 deg. This encourages good secondary combustion.

How is the stove connected? Describe the flue in detail starting with the stove connection. What are you using for kindling? Describe the fire starting procedure including amount of wood, door opening, time and air control settings. Also, describe the house - is it modern or old? If new, try opening a window near the stove. Does the flame brighten and pick up burning?

 

[KarynAnne]

To clarify: my thermometer sits on the top back right of the stove. My house is a Cape Cod built in 1948. The stove has been installed in front of the basement fireplace. A hole was cut in the firebox and a piece of flexi-pipe runs from the back of the stove at about a 45 degree angle for about 5 - 6 feet to a short (1 ft) horizontal piece of straight stove pipe that connects to an elbow and then straight up the chimney for 3 stories. When I crack the side stove door I do get a great wind tunnel and LOTS of productive flame. When we installed the stove we noticed a tendency for a strong draft even before a fire was lit. A bit of loose ash wants to fly towards the flue even with a cold stove. I think I've mastered the criss-cross logs, bright, hot fire part. My first thing in the AM fires are great - inspiring even. If I happen to be in the house, near the stove and can spoon feed it all day, the heat is wonderful and the second floor is comfortable. If I have to pack the stove for leaving for any length of time though...splat. I want to think that it's me, but maybe it's the wood. If I can get a hot, bright fire going with the same wood in a criss-cross formation, wouldn't it burn fine packed? I have to say though...I had written in a few weeks ago, before we started using this batch of bought wood, with a question about a borderline runaway stove. We we burning 8 year old locust and I couldn't keep the stove at a reasonable temp in the other direction. It was scaring me...750 and climbing fast. I wish I had a whole shed full of that wood now! I was sort of relieved when we bought the new wood and the stove settled down into a very predictable routine - except that NOW I can't get as much heat as I'd like to have and I know that the stove can produce. My husband works away from home so I'm on my own to try to figure this out - I'm no boyscout, but I'm sure trying like hell.

 

[KarynAnne]

When I say that I can keep a hot fire going if I spoon feed the stove, I mean in the neighborhood of 600-650. The days are gone of getting it much past 700 - even if I wanted to, like I could with the locust.

 

[KarynAnne]

I just went to check on my first AM fire and it's running at a beautiful 600...but it will be downhill from here for the rest of the day unless I feed it a piece or two at a time before all of the old wood is burned even though all of the wood stove operating tips I can find say that you should NEVER just put a piece or two at a time in the stove.

 

[jtcedinburgh]

FWIW, KarynAnne, I have a similar situation with my Morso Owl stove. I can get the heat to stick at high temps (reading 450F on the fluewall therm, which probably translates to more than that on the top) if I 'spoonfeed' as you so cleverly put it, but if I don't do this it wants to drop down, and within an hour or so it's back down <300F.

 

[ChrisN]

HI karyneAnne, I have an Olso too and I find that mine likes to hang out between 300 and 450 degrees too, unless I fiddle with it to get the conditions right. A few things I've found to help: I know that both the manufacturer and common sense dictate otherwise, but instead of cracking the side door to encourage vigorous burning, I crack the ash door by leaving it on the latch, but not tightly dogged and keep a close eye on the burn until it is cranking, usually it only takes 5 minutes or so before the fire is really stoking. then dog the ash door tight and leave the front damper open a while longer until it is a solid burn. After it's been burning for 20 or 30 minutes this way, it should be up in the 450 to 500 range. I find then backing the damper to about 1/3 open increases the temp to the 550 to 650 range. Up to 700 isn't unusual. Also I've found that the stove really likes a deep bed of coals. When burning my stove hot I will let the splits burn down to a deep bed of coals, like 4 or 5 inches deep in the fire box, and then add splits to maintain. once it's going in this fashion I might add a large split every hour or so. Another thing i've noticed is that the stove burns much hotter when the ash can is emptied. If it is approaching 2/3 full or more you might experiment by emptying it. I agreee with Craig that overnight burns will be lower temp. Mine usually runs around 400 for most of the night and in the AM when I reload it might be down to about 250. I also keep my magnetic thermometer on the top back left corner. My last thought is the outdoor temp affects the burn temp significantly for me. If it's above about 40 or 45 degreees, the stove just doesn't want to burn as hot. Good luck!

Chris

 

[begreen]

Caveat - using the ash door to start fires is a potential warranty voider. It can damage the grate. But overall I agree with chris's observations.

KarynAnne, what do you set the air control to at each stage of a full wood burn? Can you describe the steps over say 2 hrs.? When making the AM fire, are you using small or large splits? When packing the stove full, are you using many smaller splits or a few large ones?

 

[KarynAnne]

Caveat - using the ash door to start fires is a potential warranty voider. It can damage the grate. But overall I agree with chris's observations.

KarynAnne, what do you set the air control to at each stage of a full wood burn? Can you describe the steps over say 2 hrs.? When making the AM fire, are you using small or large splits? When packing the stove full, are you using many smaller splits or a few large ones?

Well, last week after loading it I would fiddle with it (open side door, close side door, open ash door for a few seconds, close ash door - blah blah blah) and this would go on for about 25 minutes at a pop. I finally decided to stop fiddling with it so much - take a more "the hell with it" approach - and just leave the air lever open all the way and walk away from it until it catches and come back later to put the lever to around 1/2 or just below during the day. Now I'm between fiddling and "the hell with it". The AM fire uses small splits. Love that stuff. I wish they were all that size. What I would call "medium" splits for me measure about this: I took a tape measure to an average one - about 8 1/2" around the round side and about 5 1/2" down to the point. The "large" splits or chunks are about double that - maybe a bit less - but still a mass of wood.

So - the AM fire is small splits - perfect burning with the air lever all the way open until about 550 - 600 degrees on the top of the stove and then I shut it to about 1/2 and it goes just fine. I get some good coal going, start in with about 2 medium splits with some air room between them and open the stove up again - side door too - until it seems like the temp has maxed out at around 550 - 600 and then back it down in 2 -3 stages to about 1/2 open or 1/4 open if it's really behaving. Then I leave it alone until the stove is around 350 or maybe has dropped a bit more when I wasn't watching and I start the process over...more wood, more fiddling. It's like having a toddler in diapers.

Nighttime shutdown - man is that frustrating. I rake most of the coals to the front, load in the largest chunks I've got starting in the back. It will hold about 3 pieces - large, a couple of large mediums and a really small igniter split for the very front on top of the coals. The stove plummets to about 250 and there is stays. If I can tease the temp up by fiddling (side door, ash door, much prayer) then I can get it to about 300 - 325 MAX. Then I want to cash it in and turn on the oil heater because I know that everything I just did for the whole day is SHOT and the stove will have lost the battle to the house temperature overnight. I'm in New Hampshire but I haven't turned on the furnace for weeks. I'm a stubborn one. It's just pretty nippy in the morning - and I spend the rest of the day playing with the stove so that the upstairs living room is about 64 degrees and then BAM - it's time for overnight. I know, I know - the stove's in the basement, what do I expect? But I have a really good method of getting warm air upstairs. It's working, just not good enough. My house is about 1400 sq feet, so the Oslo should be sized right.

I do have an upstairs fireplace in the living room. The damper is closed - but it's piped for a gas log set. The logs are pretty, but I'm wondering if I should be looking into a gas heater stove for the living room to augment the wood stove. I don't have the $$ for that, but it's a thought.

 

[KarynAnne]

Regarding the overnight burn paragraph above: - IF I can get the temp up to 300 - 325 with some active flame I back the air lever down in several stages to about 1/8 - 1/4 open. The temp is already dropping by that time, but it has to be fairly shut down, doesn't it? By morning I have enough coals to lay in kindling and get the thing going again and the top of the stove temp will be about 200 or so.

 

[begreen]

I think you might need a wood splitting maul or hire someone to split up the larger splits. It's possible that the large splits are not completely dry yet. Did you say what kind of wood this new load is? Do you know someone with a maul? If yes, take a couple big pieces and ask if he/she could split it for you. As soon as it is split, feel the new face of the split wood for moisture. It will be cooler to the touch.

My guess is that if you split those big pieces, they will burn a lot better. Also, try this. Don't rake the coals to the front. Instead, with a good glowing coal bed, add small splits, then medium to large ones on top of the small ones. The idea is to try get a hot fire started under the larger logs. This may not be the ideal front to back burn technique, but the idea is to get some heat going, then you can finesse it.

 

[ozarkjeep]

those sound like BIG splits to me too, if I am understanding your descriptions there.

Id call HALF of that a large 'overnighter' split!

I think you might need a wood splitting maul or hire someone to split up the larger splits. It's possible that the large splits are not completely dry yet. Did you say what kind of wood this new load is? Do you know someone with a maul. If yes take a couple big pieces and ask if he/she could split it for you. As soon as it is split, feel the new face of the split wood for moisture. It will be cooler to the touch.

My guess is that if you split those big pieces, they will burn a lot better. Also, try this. Don't rake the coals to the front. Instead, with a good glowing coal bed, add small splits, then medium to large ones on top of the small ones. The idea is to try get a hot fire started under the larger logs. This may not be the ideal front to back burn technique, but the idea is to get some heat going, then you can finesse it.

 

[DiscoInferno]

What I would call "medium" splits for me measure about this: I took a tape measure to an average one - about 8 1/2" around the round side and about 5 1/2" down to the point. The "large" splits or chunks are about double that - maybe a bit less - but still a mass of wood.

If I'm reading that right, your "medium" splits would be my largest splits, and your large splits I wouldn't be able to easily fit in my firebox. It's a lot harder to get a huge split up to temp; you might try packing the box with more, smaller splits and see if that helps. Large splits do tend to last longer because of the reduced surface area, but if you aren't able to maintain secondary burn for the first few hours then you are losing a lot of heat. It's a delicate balance; you need a high enough temperature to keep secondary burn going, and you need the secondary burn to keep the temperature up. Once the wood gasses are gone then temps will drop, as coals just don't burn as fast (unless you have the air wide open, or a soapstone stove).

 

[wahoowad]

After reading all this I was prepared to basically say what BeGreen says - reduce those larger splits. You've mastered the startup fire. I sometimes struggle getting my largest splits to get going good even when small and medium size splits from the same wood stock burn like crazy.

I think smaller splits are easier to get going and larger splits just take a bit more experience with the stove. Move up to mastering medium splits and play with larger splits. You'll figure it out.