finding that optimum setting on the primary air ?

[deedub]

The problem is, i'm only getting 4 hrs burn time ( 35d outside temp ) with the stove 1-3/4 filled with dry ash and maple. With the primary air damper set to half to full, it plows thru wood with high temps 400-650d, and with the damper choked down, temps fall to 300d or less. I'm looking for optimal heat with max burn time on a jotul castine. I know the manuf say 8 hrs but that is under ideal conditions. Any thoughts ?

 

[deedub]

another thing, this is a new epa stove , but i have no flue damper, just the primary. is this most effective for the most efficient burn times w/o flue damper ?

 

[karl]

I've only got one season under my belt, but here goes.

I have found my stove will actually get hotter with the primary closed down than it does with it open. This happens because the secondary air ignites the smoke when it's closed down.

If you're dropping to 300 degrees it's probably closed too much. Try halfway, then a quarter way, and so forth. I run the Summit about 1 or 2 inches from completely closed in the winter. Right now, since it's warmer out and not drafting as well. I have been running 2-3 inches open. I'm guessing the slide is is 6-8 long.

 

[InTheRockies]

What size splits are you using? The smaller the splits, the shorter the burn time. If you do any of your own cutting, make sure to save some smaller diameter rounds for nighttime burning when you're cutting next season's wood. Good luck. I've got a new EPA stove this season, too. They do operate slightly differently than the old stoves, but I'm finding that the new stove seems much more efficient than my old one, which had a cavernous firebox that ate wood like crazy. (My old stove was much slower in casting off heat too when a fire was first started.)

 

[deedub]

What size splits are you using? The smaller the splits, the shorter the burn time. If you do any of your own cutting, make sure to save some smaller diameter rounds for nighttime burning when you're cutting next season's wood. Good luck. I've got a new EPA stove this season, too. They do operate slightly differently than the old stoves, but I'm finding that the new stove seems much more efficient than my old one, which had a cavernous firebox that ate wood like crazy. (My old stove was much slower in casting off heat too when a fire was first started.)

i put in some large "square" profile spilts that were about 8" x 8" x 18". i do have a lot of 3" round splits that i can try. thanks.

 

[karl]

wow 8 by 8 square. Dude, save those for when it gets cold.

A load of those would burn all night and half the next day in the Summit.

Are you sure they're dry? That's what might be your problem. At this point, probably is your problem.

 

[Corey]

A single 8"x8" chunk or multiple? Multiple chunks should be an all-nighter for sure. One way to estimate wood consumption is by looking at the stove rated BTU's. The other day we had a case of a stove rated for 76,000 btu/hr @70% efficiency which meant burning 106,000 btu's of wood per hour. Wood having about 7600 btus per pound meant roughly 14 pounds of wood per hour at full output. So that should give you some ballpark figure.

It would also be good to know how your flue is set up. Sometimes an extremely tall, well insulated flue will actually create too much draft and the stove burns like a blast furnace even with the primary air cut way back. Also, depending on the species, Ash and Maple aren't really the densest hardwoods. Check link in my sig and call in the peer review board, but red maple and green or black ash are actually somewhat low btu, though sugar maple and white ash can approach the btu of oak.

 

[deedub]

i'm burning several splits at 8"x8" and the stove is 1-1/2 full. flue is approximately 25' tall and insulated 76 flex liner. it drafts great, too great ?..dunno. i can choke it down to reduce the flames, but the temp seems to drop to 300d +/-. would i need a flue damper to increase burn times. all the suggestions given are good , but i still don't see how species or even size of splits will give me an extra 3 hours of burn time to equate to a total of 7-8 hours. i'm just not getting that long burn.

 

[Corey]

25' is a pretty tall liner, plus the insulation...I'm sure that is creating quite a draft. There is generally a 'sweet spot' of operation where reducing the air slightly will actually make the stove run hotter. The best way to think of it is the fire needs a certain amount of oxygen to burn, any extra air is just cooling the stove off from the inside. When you cut off the excess air, you get a hotter stove, but if you cut off too much, you start to decrease the burn rate which also cools things off. Also similar to a gas engine...if you feed it too much or too little air, it runs bad. With a very strong draft, this 'sweet spot' might fall into a very narrow range on the air control, whereas if you had a little less draft, the controls might not be as 'touchy'. Search around the forums for 'overdraft' and you can see what others have said of the situation.

I wasn't trying to imply that the wood was the total problem, but different woods can have a substantial impact on heat output and burn time. The link in my sig shows woods run from about 12 to 33 million btu per cord - so a cord of the highest btu wood is almost 3x the heat content of the lowest. This is not to say either one burns 'hotter', but there is more energy in the denser wood. Some of the species of the woods you quoted (black ash, red maple) are around 19 Mbtu per cord which are right at the bottom 1/3 of the list - compare to something like hickory or locust which have about 27-28 Mbtu per cord. So for every 2 logs of hickory, you'd need to throw in about 3 logs of red maple. This would also mean burned at the same rate of heat output, hickory would last 1/3 longer - ie 6 hours instead of 4.

Again, I'm not trying to say you 'have' to burn the higher btu wood, just trying to point out that the species can have some affect on burn time.

 

[deedub]

very good points cozy heat, that makes sense to me.
thanks.

 

[bokehman]

The problem is, i'm only getting 4 hrs burn time

What do you mean burn time? Do you mean you still have flame after 4 hours? If so you are doing well. Quoted burn time normally means there are a handful of coals left that would need kindling to get restarted and that the stove is making very little heat at all.

 

[cmonSTART]

Maybe I have yet to learn how to achieve both, but in my limited EPA stove experience, I usually have to make a choice of a HOT fire or an overnight fire. It also seems the slower I make the burn, the dirtier it gets.

 

[deedub]

The problem is, i'm only getting 4 hrs burn time

What do you mean burn time? Do you mean you still have flame after 4 hours? If so you are doing well. Quoted burn time normally means there are a handful of coals left that would need kindling to get restarted and that the stove is making very little heat at all.

i don't have any substantial coals after 4 hours, let alone coals to quickly ignite a new log.

 

[chad3]

I still feel that I can get better times on my stove (Oslo 500). I was getting overnights last year so its not that bad, and checking the chimney this fall, it wasn't even dirty other than right across from the outlet from the stove. I'm at about 1/3 open after going through about 2-3 steps to get there. I'd rather not have huge rolling flames before starting to hold it back as these seems to send the temps way up. I usually have it close to 600 at the start of the nighttime burn, then drop it down. It is usually about 200 or so when I wake up with plenty of coals to start with a few small splits.
Hope you find your happy place.
Chad

 

[bokehman]

i don't have any substantial coals after 4 hours, let alone coals to quickly ignite a new log.

That's not surprising if you are burning with the primary wide open, and anyway you're sending the majority of your energy up the flue. Try this: put some small/medium size pieces of hardwood in and burn them fast. When the flames start to die rake them out into a good coal bed. They should be really hot. Now really pack the firebox with as much wood as you can get in it. Get this flaming rapidly and with a good char on the wood. Should take about 10 or 15 minutes with plenty of primary air. Now gradually cut the air down so the primary is nearly closed (less than 1/4 open). Now you should have good secondary combustion that should last for at least 90 minutes. If the secondary combustion will not sustain itself then your wood is not ready to burn or there is something wrong with your install.