Burn Time Problem?

[wiscmonte]

Hey all!
I've been lurking on this site for a while as I was building my new house and picking out my zero clearance fireplace. I went with the Montecito because of the efficiency and long burn times. As I've been burning, I've noticed shorter than expected burn times, even when using oak. I'm able to adjust the air intake, but at best I get about 3 hours even on the lowest setting. So I'm wondering if anybody has experience with this and could offer advice and their burn times? I'm worried that something is wrong with my air intake and it isn't closing properly. I might have to contact my vendor, but I thought id check here first. Thanks everyone!

 

[TedyOH]

At first I thought my "burn" times were low as well, thinking "burn" meant actual logs burning with flame - the actual "burn" time manufactures mean is from solid logs to extinguished coals.

 

[firefighterjake]

Common issue here . . . the real problem for most folks is when they read the slick brochures and see the good looking websites list out "burn times" of X to Y hours they typically think "Those numbers look impressive."

The issue that no one thinks to ever ask the manufacturer or salesman is . . . drum roll please . . . "What is the definition of burn time?"

The problem is . . . no one seems to really have a real handle on what the definition is. Even us folks here at hearth.com have had debates on what the definition is . . . and when there really is no one definition for a term like "burn time" the manufacturers can all come up with their own definition.

I suspect most of us start off thinking "burn time" means seeing big, flames and having that heat pump out of the woodstove for hours on end. The reality for most folks is that you will get flames for 3-4 hours and then a mass of hot coals . . . which is less impressive to watch . . . but still pumps out the heat.

Who really knows how the manufacturer's define "burn time?" Is it from when the first is first lit to when the last coal is no longer glowing? Is it from when the stove reaches X degrees of heat to when it falls below Y degrees of heat? Is it from when the stove produces meaningful heat of say Z degrees to when it falls below that level?

I suspect that most of us here if pressed would say we consider "burn time" from when the stove starts producing meaningful heat (at say X degrees) to when the stove stops producing meaningful heat when it falls below X degrees. However, even then . . . what I may consider normal -- say 450 degrees on my stove -- another person may find too low or perhaps even too high.

 

[kennyp2339]

I've had (2) stoves for the past 4 seasons, I'm heating around 1800 sq ft raised ranch with non insulated block foundation. My1st stove was a US Stove 2500 (tractor supply epa rated reburn tube stove) The burn times on that unit were advertised of up to 12 hours, When the stove was upstairs in the living space I had average burn times of 10 hours between reloads, I did have a severe temp spike problem, during the peak burn cycle on a full load the stove would bake me out of the house.
I moved my whole setup into the basement (block wall foundation, non insulated) my burn times changed, I went from 10 hours to 6 hours, during the peak cycle the upstairs got warm but I was always chasing the heat curve and it was a job to keep the upstairs warm with reloads.
I was persuaded by this forum that my only answer to my heat problems was to change out the stove to a BK, I bought one last season, The advertised burn times were 30 hrs on low setting, my burn times have averaged around 18 hours (useable heat) but the stove could easily hit 24 hours, I just wouldn't see the heat upstairs.
I know my problem in lack of insulation on the foundation, I think I lose something along the lines of 30% heat produced to the walls.
My take on this in relation to burn times is perhaps when stove manufactures test these units they test them in ideal environments. Fully insulated rooms where the stove could hit a temp and maintain that stove temp for longer periods than the average home. Smaller stoves at full peak my be able to heat 1800sq ft at peak temp, but we all know that peak temps only last a few hours so the user is trying to maintain those temps by either reloading more frequently or burning the stove at a higher air setting and creating a faster burn cycle than what the unit was tested at. Thanks for reading my rant.

 

[CentralVAWoodHeat]

My stove, with a bed of hot coals, packed with dry hardwood will give me no more than 2-3 hours of good live flame. This is with the air supply properly managed. I then get heating coals for another 2 hours and embers for maybe another 2. My stove manufacturer says it has an 8 hour burn time so this would roughly make sense from loading time to the time when you can no longer create another fire from the embers.

Truthfully, I like having to reload my stove every 3-4 hours during the cold as I enjoy the process of heating with wood. If I wanted a super long burn time I would have bought a different stove.

 

[begreen]

Some of the reasons for shorter burn times:
1) reloading on too hot and large of a coal bed (burn it down some more with the air half open)
2) splits are small (load larger, thicker splits)
3) too much air (turn it down more and sooner)
4) too large gaps between the splits (pack it tighter and put small splits in to fill the gaps)
5) too strong draft (add a draft damper if possible or restrict some of the intake air or boost air)
6) too dry wood (mix in some harder wood or some with a bit higher moisture content)
7) leaky door or ashpan door gasket (fix)

 

[jophysx]

The brochures for my Hampton HI-300 insert claim an 8hr burn time. This is a 2.3cubic foot fire box. If I get the stove up and running well on one load, then reload when the stove is down to 250-350F (so the firebox is still hot, but mostly empty so I can get a lot of wood in there), I can pretty easily get 8 hrs of "burn-time". Meaning 8hrs later the blower will still be running (on Auto), and the unit will still be above 250F. I have to use big splits and pack it full, and keep the air supply on the low side - still getting secondaries, but avoiding a run up to 700F+.
So I don't think all the brochure numbers are totally unrealistic. In my case I would call 8hrs a realistic best case. I am satisfied.

-Jim

 

[jophysx]

For troubleshooting your short burn times, I would check the following:
1. Wood quality: You need low moisture content to get long burn times. Are you below 20% on the fresh face of a resplit split? 15% is even better. Are you using large splits? Big splits=Big burn times, but it needs to be dry.

2. Do you have good control over the air supply? - Gasket seal is tight all the way around? Do the air controls make a noticeable difference in burn characteristics? If you are getting a high consumption rate of the wood, there must be a lot of air to support the burn. You have to get that under control to get a long burn time.

3. Heat loss: Do you have a blockoff plate and insulation around the insert/chimney? If not you may be losing a lot of heat (up the chimney, into the surrounding masonry). If you are losing heat then you need a higher burn rate to keep the firebox hot enough to support secondary combustion. The trick to long burn times is to keep the burn rate just barely high enough to support secondary combustion. That way you get the extra efficiency of the secondary combustion, but at the lowest burn rate. It's like a positive-feedback effect - If the secondaries kick in, the heat they generate will heat up the firebox and they will sustain themselves. You can even reduce the air supply a little after secondaries are well-established and rely on the "positive feedback" to keep you in the zone.

-Jim

 

[tinman100863]

My stove, with a bed of hot coals, packed with dry hardwood will give me no more than 2-3 hours of good live flame. This is with the air supply properly managed. I then get heating coals for another 2 hours and embers for maybe another 2. My stove manufacturer says it has an 8 hour burn time so this would roughly make sense from loading time to the time when you can no longer create another fire from the embers.

Truthfully, I like having to reload my stove every 3-4 hours during the cold as I enjoy the process of heating with wood. If I wanted a super long burn time I would have bought a different stove.

this funny because I also get the same heating results as you do ,and also like to reload every 3- 4 hours! it makes it fun for me !!

 

[CentralVAWoodHeat]

this funny because I also get the same heating results as you do ,and also like to reload every 3- 4 hours! it makes it fun for me !!

Glad to hear it's not just me! I've tweaked my burning/air/stacking/wood techniques and it all produces the same result. There has never been such thing as a full 8 hours of good heat coming from that stove. Only getting to play with your stove every 8 hours would be very boring.

 

[tinman100863]

Glad to hear it's not just me! I've tweaked my burning/air/stacking/wood techniques and it all produces the same result. There has never been such thing as a full 8 hours of good heat coming from that stove. Only getting to play with your stove every 8 hours would be very boring.

a Big firebox is needed for long burn times

 

[begreen]

There has never been such thing as a full 8 hours of good heat coming from that stove. .

True for the Castine. It has a medium small firebox. OTOH the BK Princess is rated at 40K btus for 10 hrs.

 

[CentralVAWoodHeat]

True for the Castine. It has a medium small firebox. OTOH the BK Princess is rated at 40K btus for 10 hrs.

Thanks for the feedback. This was the first EPA stove I have ever owned and it was recommended for our square footage and house layout. However, we have 10 foot ceilings instead of the standard 7-8. This extra space really eats up a lot of heat and so getting the Castine to heat most of the house is a serious challenge. I run it at full bore anytime it is in the 30's or below, along with all our ceiling fans to push the layer of hot air down. The feature I have working to my advantage is our floor to ceiling soapstone hearth, along with the straight pipe that runs exposed, all the way up to the ceiling. I try to convince myself that these add up to the additional heat the Oslo would have produced.

 

[rdust]

Only getting to play with your stove every 8 hours would be very boring.

I can only assume you're new to burning wood or retired! I have no interest in all that fiddling! If winter ever gets here I'll load twice a day, until that happens the BK goes 24 hrs at a time.

 

[CentralVAWoodHeat]

I can only assume you're new to burning wood or retired! I have no interest in all that fiddling! If winter ever gets here I'll load twice a day, until that happens the BK goes 24 hrs at a time.

Hahaha! Not new to burning wood at all but definitely new to burning in an EPA stove. You caught me

We have used non EPA stoves for decades and this is my first experience with an EPA stove that seems to make wood disappear without a trace, or smoke. I'm fascinated to say the least.

I'm used to stuffing a stove full of wood, turning all dampers and air supplies down, and 12 hours later, coming back to redo it all over again. This at the cost of cleaning a stove pipe once or twice a season. Now, I don't have to clean it at all!

 

[ToltingColtAcres]

Is it from when the first is first lit to when the last coal is no longer glowing?

By that definition, my F55 can have a "burn time" of DAYS, as often I've let the fire die out and gone back to restart it several days later, only to find small coal embers still glowing!

 

[jebatty]

Seems to me that the right question is how long will the stove burn at the rate of heat output needed to provide the desired comfort? About 1000 or so possible answers here. Take your pick.

 

[dyerkutn]

Seems to me that the right question is how long will the stove burn at the rate of heat output needed to provide the desired comfort? About 1000 or so possible answers here. Take your pick.

I did not see anyone mention size of stove. I have an ALderlea T5 and cannot fit as much wood in it as some of the bigger stoves. So less burn time. Despite its smaller size, until the temp gets really cold I cannot fill it or I would have to live in shorts and tank top. So also less burn time.