Advertised max burn times? Likelihood of achieving it?

[Paulywalnut]

My old Fisher Grandma Bear averages 10 -12 hour burn times.

Yea they were good. Used to have one also. I could jam a wheelbarrow full of wood in it.

 

[Paulywalnut]

I get about 6 hrs of good burn time with my jotul castine. They claim 8 hrs but
I don't know how.

 

[Huntindog1]

I loaded big chunks in my stove the other night on really hot coals. It took off fast but was controllable since the split sizes were like 8" or larger.

I got the advertised 12 hour. I had lots of hot coals left for a reload startup.

I am beginning to like big splits loaded on hot coals and fast starts for a long burn times.

 

[DanCorcoran]

I loaded big chunks in my stove the other night on really hot coals. It took off fast but was controllable since the split sizes were like 8" or larger.

I got the advertised 12 hour. I had lots of hot coals left for a reload startup.

I am beginning to like big splits loaded on hot coals and fast starts for a long burn times.

Don't forget dry wood...that's the other requirement.

 

[clemsonfor]

fill that box up. I cut my wood shorter and on cold nights I put wood EW infront of the NS stack to fill that front gap, I also stuff it in all the crevices. I have little to no insulation in any room but the stove room and my bedroom is the farthest from the stove and I can maintain 65ish in the bedroom in the mourn and still have plenty of coals to burn for a few more hours till I reload on the weekends. I can get 20+ hour burns out of my 3.5cuft cat stove. If I pack oak in it I can get those times a bit less with elm and elm/pine, but way less heat. My stove room will be 82 when I go to bed and the close bedrooms will be in the mid to upper 70s and low 70s in the am and the stove room in mid 70s at lowest and my bedroom like I said abouve. THis was around Christmas when we had those upper 20s nights and wind.

 

[MnDave]

I think that Quad is talking about the time from the start of the fire until die down with some hot coals for the restart. With proper loading and turning down of the stove, In that case I would expect 14-16 hrs to be possible with the 5700, but haven't actually tried it. I do know I can do this with the T6.

begreen,
I believe that you modified your stove so maybe you should start qualifying your T6 as a modified T6.

MnDave

 

[btuser]

The other day I was raking a cold bed of ash and found a nice burning red cinder. I moved it to the side and refilled the stove, then placed the spark on a bed of newspapers. Poof!

I can get 48 hour burn cycles. No heat, but it's a pretty long burn cycle.

 

[begreen]

begreen,
I believe that you modified your stove so maybe you should start qualifying your T6 as a modified T6.

MnDave

PE has also modified the design since this model. I would love to switch it to the newer EBT design which could be even more efficient. In the meantime, all I have done is disable the factory EPA afterburner, which most stoves of this size do not have.

 

[HotCoals]

That gives me hope and motivation.

All this is making me rethink my comments in several old posts about fan usage affecting the burn rate.

I know that combustion engines are more fuel efficient when the engine is kept hot. Maybe this is the missing link. Maybe QF is wrapping their stoves in insulation to get the burn times up.

Hot Coal's is going to lose faith in me if I switch my opinion on "The Fan Effect".

Back to the drawing board. Ok. E=MC2.....

MnDave

lol

Look I still believe that the fans should cool the stove making the box less hot if anything..and that should make it burn longer...maybe more efficient in a way because you are capturing some heat that would have went up the flue because with the fans on the transfer has to be better.

That said I have found that because of the twin fans on my Bk that it does create a suction ..or a pull of air behind the stove and the intake is effected by it..I know it for a fact because I had my cover off the t-stat and with the blowers on it really blew the piece of tissue that i had over the opening where the cover would have been..kinda hard to explain.

The only way you are going to get longer burn times is to slow the rate of air coming into the stove..you have already slowed the draft some with your key damper...the only other way or I should say another thing that will help is really good seasoned dense hardwood,such as oak.

I'm not familiar your stove at all..is there a way to see just how big the opening is for air when you are shut down all the way?

 

[DanCorcoran]

I can't discuss physics theory, but when I'm running the blower on my stove, it burns down faster.

 

[Kevin Dolan]

I get about 6 hrs of good burn time with my jotul castine. They claim 8 hrs but
I don't know how.

Pauly,
I can get 8 hrs with my castine with three large splits of dry ash, 6-8 inches in diameter wiggled in. When I get up in the morning play with ash bed and coals and load up with small stuff get fire back up to around 500 stove top then feed some larger splits throttle back air to 2/3 s and am set for the day. Of course my day burns are different than at night as I tend to use less splits and not as full as night time. I find a HUGE difference with dry seasoned wood and my burn times.
Kevin

 

[MnDave]

I find a HUGE difference with dry seasoned wood and my burn times.

I agree. However, I believe that my best wood vs really primo wood might account for 3 hours of burn time at the most. That would bring me to between 11-12 hrs of honest "real world" burn time. That would put my QF 5700 in the same ballpark as other 3 cf non-cat stoves.

That is still 6-7 hrs less than what Quadra Fire advertises as the average max burn. (15+21)/2 = 18 hrs

The more and more I think about it, begreen probably nailed it when he mentioned that QF may be stating usable/meaningful heat. I also believe that they must be using factory conditions that are favorable to keeping the stove from cooling off and stopping the time clock.

I believe that Quadra Fire must be including time that the stove is cooling off in their advertised burn time.

Think of that Florida Bungalow. Outside temp 60F, now burn the stove using "special wood" that burns super slow and long. Now keep the clock running until the stove temp equals room temp marking the end of useable/meaningful heat. IMO that must be where QF's max burn times are coming from.

Yep. And I bought it. I imagined myself loading it at night and waking up leisurely to a warm home even when it was 0F outside. I figured that with an average max burn time of 18hrs, that scenario would have been a piece of cake. I believe that I mentioned this to the salesman as I talked openly to him about what I expected to accomplish by replacing my Kent Tile Fire.

Well, the best thing I can do now is gather top quality hardwood, cut it 22 inches, split it on the big side, and get it drying for 3 years minimum. I have a lot of work cut out for me next spring but it will be worth it.

MnDave

 

[MnDave]

I can't discuss physics theory, but when I'm running the blower on my stove, it burns down faster.

I still wonder myself. I know that when I asserted that running the fan would not cause the burn rate to increase, I was assuming that the process of heat generation could be approximated as constant. The thermodynamic term for this is isentropic (keyword entropy) and it involves the second law of thermodynamics. A simple more common definition of isentropic would be " No change in entropy".

Well, for wood burning in a fire the change in entropy is significant. The ash will never be a log again.

Either way I want the heat in the room, not up the chimney. If running the fan reduces the burn time then I will still run the fan. The net, I believe is still more BTU's in the house.

I will continue to search for an answer to this. It will probably take me a good 6-10 hours of research to determine how the 2nd law of thermodynamics applies here. I learned this stuff in the late 70's. Once I read it I will probably understand it better now than I did then.

MnDave

 

[HotCoals]

Either way I want the heat in the room, not up the chimney. If running the fan reduces the burn time then I will still run the fan. The net, I believe is still more BTU's in the house.

I concur.

No matter if the fans make the fire last longer or shorter you will end up with more heat in the house with the fans..transfer is better imo.
Thing is I hate the fans..on low it's not to bad though.

Here's one for you.
The other night I left the fans on low all night.
The house was warmer in the morning.
But..
The stove had basically stalled out.
I think the fans cooled the stove and flue so much that I lost draft,but I had way more wood left over in the morning.
I had a stove top temp of only around 200 where normally it would be around 300.
I cranked the air because the lazy t-stat had barley opened up any..I had it set when I went to bed to be just shut...burned for another 4 hours then coals for another 2.
It was only a 1/2 to 2/3 load to being with.

I do like cat stoves and the only way for a long cycle is to have that cat and a huge firebox..I have that and to me that's the only magic this stove really has.
Really great in the shoulder.
But when it's cold it takes wood..plenty of wood.
And if it's really cold I bet a tube stove will get the job done as good if not better ..but I like the benefits in the shoulder with a cat to much to go to a tube.
Now having both a cat and tubes would be interesting for me to have a chance to run one.

 

[etiger2007]

Last night was a cold one, 0F. I started at around 1 AM, the house was 70F. I let the coals die down. I pulled them to the front of the box. I loaded 2 splits E/W at the back of the stove. Then I put 7 in N/S. This filled the box to within 4 inches of the glass.

This was all the same wood which I believe is a hard wood due to its weight but it doesn't seem like red or white oak. This is my best quality and driest wood at 1.5 years c/s/s. I stuck around and watched the burn proceed.

Amazingly I was able to set the burn control on minimum and set the damper horizontal and the stovepipe temp held constant at 325F. The secondary burn was very stable.

At 9 AM it was 66F in the house and 7 F outside. I went down to check what I had for coals. I walked toward the stove with a big smile and two thumbs up. The stovepipe temp was 200F and I not only had a big mass of glowing coals in the middle of the box but those E/W splits were still intact!

Those coals could have gone another hour at least so I am going to say that was a 9 hr burn at 0F in an 1800 sf home with lots of windows!

I credit the drier wood for letting me turn the air down that much.

I was surprised that the 2 E/W splits were intact. They were covered with coals. I pulled back the coals and found them charred black. When I pulled them away from the back of the stove they did not fall apart. They were totally outgassed and not glowing. That is the first time I have ever seen that.

I plan to burn a totally E/W load of this same wood tonight.

One question I still have on the Quadra Fire 5700 advertised max burn time (15-21 hrs) is, "How do they run the stove that low?". It must be a trick they do with a few big blocks of kiln dried wood. I plan to call them and see what kind of answer they come up with.

MnDave

I have quit the raking the coals forward method because I feel the back two logs sit there and smolder causing a dirty burn, If I could make that go away Id be a happy camper. I use 20% and less moisture ash and still get it.

 

[HotCoals]

I still think the claims of any stove reaching 80% efficiency is pretty absurd.

Maybe at peak..I dunno..but it was not that long ago that forced air furnaces had a problem hitting that..lol.

My guess is maybe 50-60% avg over the entire burn.

 

[etiger2007]

I loaded big chunks in my stove the other night on really hot coals. It took off fast but was controllable since the split sizes were like 8" or larger.

I got the advertised 12 hour. I had lots of hot coals left for a reload startup.

I am beginning to like big splits loaded on hot coals and fast starts for a long burn times.

Thats what I have been doing, I level out the coal bed (no tunnel of love) load up three big ash splits and as you mentioned control the burn. Stove is between 550-650 as measured on the stove top. I have been doing this to burn cleaner, I did this last night at 12am and by 9am I still had good enough coals to start another fire and the stove top was around 200. My experience with the rake the coals forward method is the end of the burn is dirty and I dont want that, my stove is non-cat and cant chew up that smoke at the low temps.

 

[MnDave]

Here's one for you.
The other night I left the fans on low all night.
The house was warmer in the morning.
But..
The stove had basically stalled out.
I think the fans cooled the stove and flue so much that I lost draft,but I had way more wood left over in the morning.
I had a stove top temp of only around 200 where normally it would be around 300.

This is entirely possible. Draft is the driver. I have found on mine that stovepipe of 300F is the minimum to keep my secondary burn from dropping off.

Could it be that the fan affected the thermostatic control? Meaning that the fan created a slightly reduced pressure at the air control? You would think that the thermostat would sense a corresponding lower temperature and compensate by opening the air control a little more. Maybe that cooled your cat and made it go inactive.

MnDave

 

[MofoG23]

My Quadrafire 4100i is not too far off from factory specifications. They state "up to 12 hour burn time". My regular routine is to load up at 9:30pm and remove most air by 10pm'ish. By 6-6:30am I still have stove temps of around 300-350 and plenty of coals to start another load. I primarily burn seasoned (1-2 year) cherry, maple and oak. If I run a full load of seasoned oak (with a couple large splits), I've been very close to the 12 hour mark (200-300 temps with plenty of coals for a reload). Keep in mind, I make sure most of my coals are burned down so I can get a full load in at night.

Very surprised to see the 5700 advertised up to 21 hours. My 4100i has a 2.4 cuft box....not sure how an additional .6 cuft is going to give you an extra 8-9 hours??

 

[MnDave]

I still think the claims of any stove reaching 80% efficiency is pretty absurd.

Maybe at peak..I dunno..but it was not that long ago that forced air furnaces had a problem hitting that..lol.

My guess is maybe 50-60% avg over the entire burn.

I agree and until some truly independent standards lab does some "real world" testing, we are going to be subjected to cooked-up numbers driven by sloppy marketing practices.

MnDave

 

[MnDave]

By 6-6:30am I still have stove temps of around 300-350 and plenty of coals to start another load. I primarily burn seasoned (1-2 year) cherry, maple and oak.

Is that 300-350 a surface temp or a probe temp?

Congradulations on getting the kind of heat output you expected.

MnDave

 

[etiger2007]

I agree and until some truly independent standards lab does some "real world" testing, we are going to be subjected to cooked-up numbers driven by sloppy marketing practices.

MnDave

When I first bought an insert three years ago and before I found this site I bought a Dutchwest insert that had a 1.3 cf fire box and they claimed it could burn up to 8hrs on a load of wood so being a rookie I thought this would be ok so I bought it. Man was i pissed when I had to fill it every two hours. I sent Vermont Casting an e-mail about this and three months later I finally got a response and they said the stove has never been tested for the burn time ( so how could they advertise one????). So after learning this and finding hearth.com I looked for a new insert and the wife was not on board because I had just bought a new one. I learned from folks here your burn time is mostly based on fire box size so this was the main feature of my search. I ended up with the Osburn 2000 which is the absolute biggest unit i could fit in my fireplace and It was rated to heat 2100 sq ft. I have 1700 sq ft so I thought it should do the job because Im sure the manufactures pump their chest out on this stat to. This is my first season with this insert and the difference is night and day. Just wanted to throw out some more examples of misconstrued numbers by manufactures.

 

[MofoG23]

Is that 300-350 a surface temp or a probe temp?

Congradulations on getting the kind of heat output you expected.

MnDave

Surface temp (front of the stove, above the door). The biggest thing that helped my overall burn time at night was using very seasoned hardwood (oak) and a couple large splits in the center.

 

[etiger2007]

My Quadrafire 4100i is not too far off from factory specifications. They state "up to 12 hour burn time". My regular routine is to load up at 9:30pm and remove most air by 10pm'ish. By 6-6:30am I still have stove temps of around 300-350 and plenty of coals to start another load. I primarily burn seasoned (1-2 year) cherry, maple and oak. If I run a full load of seasoned oak (with a couple large splits), I've been very close to the 12 hour mark (200-300 temps with plenty of coals for a reload). Keep in mind, I make sure most of my coals are burned down so I can get a full load in at night.

Very surprised to see the 5700 advertised up to 21 hours. My 4100i has a 2.4 cuft box....not sure how an additional .6 cuft is going to give you an extra 8-9 hours??

What setting do you run your fan on for the all night burn? I never take mine off high.

 

[HotCoals]

This is entirely possible. Draft is the driver. I have found on mine that stovepipe of 300F is the minimum to keep my secondary burn from dropping off.

Could it be that the fan affected the thermostatic control? Meaning that the fan created a slightly reduced pressure at the air control? You would think that the thermostat would sense a corresponding lower temperature and compensate by opening the air control a little more. Maybe that cooled your cat and made it go inactive.

MnDave

I have the cover off my t-sat and the blowers don't seem to effect it because of that..with the cover on it does seem to some..not much..but the stove does seem to get more air then.
Since my cover is off I can see the operation of the t-stat..and trust me ..it is slow and lazy to react to temp change.
Anyways I had it turned as low as it can go and it will never open there..even if the stove was room temp.
I did not want the t-stat to have a role in that experiment and it didn't..good thought though!
Now I have to get my sleds and trailer from outback..we have over a foot of snow and dummy me never brought the trailer up.
Prolly have to take the sleds out then hope that I can drag it up with the apex..man I'm a bonehead at times.