OK, what am I doing wrong?

[jtcedinburgh]

OK folks, I'm confused. What am I doing wrong?

In another topic I posted that I'm having difficulty in maintaining a decent temperature, and that I can go from full flame down to red glow in around two hours. This is making it quite difficult to leave the stove for any length of time and maintain a heat.

OK, the facts:

I am using seasoned mixed hardwood, have a stainless steel lined 12m chimney and as far as I can tell a good draft (it is always easy to start the fire). The stove is a 7kW, clean burning Morso Owl, and I maintain a reasonable bed of ash wherever possible. The stove has three air controls - one at the back (which is factory set and therefore can't be adjusted), and two at the front (the left one brings air from below, and the right one is the airwash).

What I do:

I get the stove up to temperature, which is normally between 400F and 500F depending on the amount of wood I put in it. I keep both air inlets fairly open until I have reached these temperatures, and progressively close them down - generally trying to close the left hand inlet down more than the right hand one (so that the airwash keeps the glass clean). I find that the temperature then drops over approximately an hour down to around 220F, and I have to put more wood in. I have found that the more wood I add, generally the hotter the stove temperature but no general increase in burn time is seen.

What I don't do:

I never close down both front inlets fully - I have found that what can happen when I close the inlets too far is that the flame firstly changes colour to a red/purple colour, and then eventually appears to go out (but is quickly reinstated by opening the lower air (left inlet).

Taking for example my most recent burn, on Sunday night: I managed to get a stack temperature of 520F, using five moderately sized splits (12" mainly) but having reached that temperature and closed down the air intakes most of the way, that dropped back to a red glow and ~250F in less than two hours.

Bearing in mind that I am still a relative beginner to all of this, and bearing in mind that my Owl is a 7kW stove (and therefore not huge) how should I be using it (assume I have the stove up to temperature). How many splits should I add when reloading, and how do I maximise the burn without ending up with a sooty window? How does my technique compare to that of you seasoned wood-burning types? Am I doing something wrong?

Any and all help *much* appreciated.

John

 

[bruce56bb]

hello john, i have a totally different stove so i'm not sure of it's relevance.
the handle on my stove for the low air intake is labeled "for start up only, must close completely after start up or over firing can occur". granted it's a different stove but the air intake design sounds very similar.
bruce

 

[Roospike]

What size fire box is the Morsø Owl in cf ?
Cast or steel or both ?
What does the stove weigh ?
What is the stoves max BTU rating?
Cat or non cat?
How big is the stove room? 8' ceilings?
Total home size?

 

[jtcedinburgh]

OK, don't know the exact specs, but the firebox is approximately 18" wide, firebricks, 12" ish deep, and being a tertiary burner, it has a sloping baffle being perhaps 15" tall at the front but down to perhaps 12" at the back. All estimates.

Cast iron, 120Kg.
Not sure of the BTU, but it's rated at 7kW.
Non Cat.
Room has max 11' ceilings, and is a slightly open planned area comprising three apartments, 16'x14' adjoining 12'x8' adjoining 11'x11'. I reckon around 3750 cubic feet. Total home size is perhaps three times that area in total, maybe four tops.

 

[Roospike]

Here is one thread one stoves and stove size.

https://www.hearth.com/talk/threads/4202/

 

[begreen]

John, best to keep experimenting. This is a multifuel correct? My guess it that the left air is for coal burning, not wood. After the first 15 minutes or when the fire starts to burn well, I'd try closing that control completely and just regulating with the right control (airwash). Leave the right control open about 3/4 until the wood is fully burning and has started to char. Then move it to 1/4 to 1/2. The flames should go blue or purple and just waft above the logs. There may be a decrease in stove temp at that point, but it should burn a bit longer.

FWIW,his stove sounds similar in capacity to the Jotul 3CB. I normally would only get 3-4 hrs. burn time with that stove unless I really stoked it and then dampered down as soon as was reeasonable. By doing this I had to accept decreased temperature output from the stove (~300-400F). This was fine for late night burns, when one doesn't mind the house cooling down. But only once did I have coals leftover in the morning.

 

[Roospike]

Sounds like the stove is about 1.4-1.5 cf fire box and around 280-320 lbs ?

I have read about a lot of stoves in this size range and short burns seems common.

Burntime: To me , burn time is from when a log is first put into a stove and fired to then the point of the end being coal enough to relight a new fire. Might not be a huge coal bed but coal enough to put off some heat.
So if say i get a 10 hour burn time with my stove that does not mean the logs in my stove are looking like normal wood for 10 hours with flame from them. I could get say for example 3-5 hours of fire logs and then to 3-4 hours (or more depending on type of wood) of coal logs putting off blue flame and then hours of coal that has broke down but still putting of heat.

I have a few friends with wood stove of the 1.4 - 1.5 size fire box and considered to be a "small" size stove. The information I get from them is around 2 hour log(s) on fire and then maybe an hour or so of coal log putting off heat and then the stove is warm for a little wile after that.
So about 2 to maybe 3 hours of good heat and down hill fast on the last hour or so is what there are getting. Small stoves burn hot and dont hold a lot of wood nor do they normally hold a lot of heat after the fire goes out.

The normal rule of BTU heat for wood is that a log will only have so much or so many BTU per each log. How you control that BTU is up to the user and the stove. A few logs at xx amount of BTU and burned fast and hot will put off the logs heat all at once in a short time . Turn down the heat and you get a longer burn time but less BTU ( heat ) per hour.

So with said, the different size stove is going to change the heat. The bigger the fire box the more wood can be added. The more mass of stove the different the heat is going to be transferred and or stored in per stove.

 

[wg_bent]

My stove has a 1.8 cuft firebox, but stuffed and turned down it will produce good heat for about 6-7 hours. Depends on the wood big time. One additional factor is the size of the peice of wood. If I load a lot of small splits, even oak, elm, cherry etc...it burns very fast and hot, no matter what the air setting is. surface area of the wood is the issue. (This is part of the biobrick debate...putting neatly stacked bricks acts as a single huge chunk of wood...neatly stacking bricks in a hot stove = burned knuckles too ) But I digress... If I put in 2 very large peices of wood such as elm, or oak, I easily get burn times and usable heat up to 8 hours. A much more controlled and even burn too. I learned a lot about splitting wood and how big a chunk to throw into a stove. In my opinion, and in almost all cases, the larger the split, the better off you are. Sure it takes longer to season, but in the end, you'll get better results.

See if you can find a really big chunk of wood and put it in the stove to see what happens, and compare the burn times. What kind of wood do you burn there? I always thought you guys had similar species to the US Northeast...lots of hardwoods.

 

[Roospike]

My stove has a 1.8 cuft firebox, but stuffed and turned down it will produce good heat for about 6-7 hours. Depends on the wood big time. One additional factor is the size of the peice of wood. If I load a lot of small splits, even oak, elm, cherry etc...it burns very fast and hot, no matter what the air setting is. surface area of the wood is the issue. (This is part of the biobrick debate...putting neatly stacked bricks acts as a single huge chunk of wood...neatly stacking bricks in a hot stove = burned knuckles too ) But I digress... If I put in 2 very large peices of wood such as elm, or oak, I easily get burn times and usable heat up to 8 hours. A much more controlled and even burn too. I learned a lot about splitting wood and how big a chunk to throw into a stove. In my opinion, and in almost all cases, the larger the split, the better off you are. Sure it takes longer to season, but in the end, you'll get better results.

See if you can find a really big chunk of wood and put it in the stove to see what happens, and compare the burn times. What kind of wood do you burn there? I always thought you guys had similar species to the US Northeast...lots of hardwoods.

Great add on information about the wood size Warren. Right on target.

There is also the issue of trying to get max heat out of ones stove and not getting the long burn times. You could put the same exact stove in two different homes with the same square footage and burn the exact same wood and load and it might not wood well in both homes. This is another reason why the stove companies have a wide range of heating per sf of a home on 1 model of stove.

Example: Stove brand Y: , Model xx heats 1200-2000 sf , Model X heats 2000-3000 sf

jtcedinburgh also has this in his Signature: "1900 Victorian end-terraced townhouse, leaky old pile really, but we love it"

Max heating of the stove for the home equaling shorter burn times maybe ?

 

[jtcedinburgh]

OK, thanks for all of the advice.

It's hovering around 46F today, so not especially cold, but enough to get that stove going (bear in mind that it's a secondary heat source as due to Victorian construction every room is seperate (except the open plan bit that we did, so we generally are only using the stove for a bit of extra oomf in the colder part of the house). That said, I'll find some big splits and try running with the left lever (primary) off, and just use the right one (secondary) and report back...

If I knew my hardwoods better I would post what I've got, but to be honest I couldn't say. Maybe I'll take some photos of the various types and someone can id?

 

[JMF1]

I used a Lopi Answer last season, 1.5cu ft stove if I remember correctly. I had to play with split size and species alot to get it down.............it liked big splits and I filled the gaps all I could with smaller stuff....seemed to work for me. You almost need to experiment with it while you can be there to see how it reacts to the different things you try.......practice makes perfect! Also, you didn't mention whether or not you have a blower installed, maybe cooling the stove down too much? Just a thought............

 

[jtcedinburgh]

For JMF1: No, I don't have a blower.

Hi all. I fired up the stove last night and tried leaving that left lever alone - and things were somewhat better. I found that, if I loaded three splits up close together, and with the primary (left) air control closed down completely, and with only a small amount of secondary air (right) I could get a 1 hour burn at around 400F (flue temp) and an additional hour or so at 350F. After that I went to bed (~11pm) so I can't say at what point the fire went out, but at 6am the stove was completely out though I noticed a warmth in the ashes in the ashtray.

So, I'm guessing I must have managed another hour or perhaps more after retiring, but it's still not really enough. I think using some bigger splits and/or whole logs (up to 6in diameter) might extend that a bit further.

I'm sure there must be something else I can do, though?

 

[babalu87]

Have you tried leaving the air almost all the way off?
Once you get a REAL good fire going with well seasoned hardwoods you can just about shut the air off.

Bigger logs (rounds) are best for long burns and dont be afraid to pack that stove either.

 

[jtcedinburgh]

Have you tried leaving the air almost all the way off?

Yes, see my last post above. I backed the air as far as I could, but not completely (as the flames basically died). Maybe I need to pack more - there was a definite improvement in the burn temperature when loaded with more wood for a given air control setting.

Maybe I also need to face the possibility that a few hours is likely to be my maximum burn time...??

 

[babalu87]

Yes I saw the post but I was chatting with a fellow off line from the Mid-West and he finally realized how far down he could turn the air and still maintain combustion with the results he was looking for (longer burns from his 3610)

You dont have to have many flames to maintain stove temps and keep the fire going.
A flickering flame is enough.

You should be able to have some coals to get a fire going again after 4+ hours at the least.
Maybe you just need a bigger stove for what you are trying to do?

 

[jtcedinburgh]

I'm wondering about a bigger stove. Your stove is a 16kW, whereas mine is a lowly 7kW. However, we have two living areas - one with a living flame gas fire which we want to replace anyway. Maybe I'll move the Owl into that room - it's approx. 18'x16'x11' wbh and I think a 7kW stove in there would be more than enough. We have a lined chimney which may or may not be suitable for use with a wood burner, but if it is it could be an option. And as we have the chimney newly lined in the bigger room, I could get a bigger stove in there perhaps. Maybe a 3610 :D though the price is quite high having just spent 2/3 of that amount on the Owl already!

 

[webbie]

In MOST stoves, a few hours burn time is the best way to operate when the stove is attended. Longer burns are for overnight and when you leave for long periods. You are on the right track about picking out the best woods. There is a big difference between the "coaling qualities" of various species, meaning that in some the fire dies soon after the coal are formed and with others it can last hours.

Also, given as your stove is a multi-fuel, perhaps you have pressed briquettes of various types available that might burn longer?

 

[G-rott]

I found that my 2110 had a problem with too much draft. I installed an in line damper and it stays closed most of the time now and I can increase my bur time by half what it used t be. With small rounds 2 1/2 - 4" I can get 4-5 hours. Without the damper I was lucky to see 3.

I can't adjust my secondary air, it just draws what it needs.

Garett