EPA Compliant Wood Stove + (Firebox > 3.5 cuft) = 8" Flu?

[Renovation]

I think the rule is that if you build a jumb0 stove that holds 80 lbs of wood, the flue must be large enough to handle the exhaust flow generated by an 80-lb load, or you will soon be sued out of existence. Doh!

Maybe yes, maybe no, Homer.

Exhaust flow depends on burn rate, no? The Princess, rated at 40KBTU has a 6", while the King, rated at 47KBTU. Maybe that is the reason, but it seems a relatively small difference, with the firebox size difference being greater.

Riddle me this--wouldn't connecting a stove to an undersized, but otherwise well designed and drawing flue, have the exact same effect as closing a flue damper at high burn rates, simply limiting maximum burn rate, with no other negative consequences?

I can see why a company would not authorize under-flue-ing on basic principles--why take liability when there is no upside--but would there be any effect other than limiting maximum burn? If there were, wouldn't the same negative effect occur with flue dampers?

 

[Renovation]

FWIW, the Buck 80 is only 2.6 cu ft, and uses an 8" flue.

I always wondered why that was. Makes sense that all the 4 cu ft stoves have bigger flue openings, but why does this stove. The fact that it's a cat may have something to do with it - what do you suppose?

What's it maximum BTU rating? Could it be a really fast burning stove with relative large air requirements for it's firebox size? If not, it's something else.

 

[Renovation]

p.s. Fire Cat is a good name, but already used by Applied Ceramics for their combustors. Doh!

Thanks. No fame and wealth this time. I suppose if I were serious I should have at least Googled it first.

 

[ddddddden]

". . .depends on the burn rate." Exactly what BK will tell you when you call. "47k" is clearly padded down. Why? Why, IDK. Why are humans like they are? Mfrs pad specs all the time for a variety of reasons. The 2.6 cu-ft Buck specs @ 40k.

 

[ddddddden]

". . .depends on the burn rate." Exactly what BK will tell you when you call. "47k" is clearly padded down. Why? Why, IDK. Why are humans like they are? Mfrs pad specs all the time for a variety of reasons. The 2.6 cu-ft Buck specs @ 40k.

 

[Renovation]

". . .depends on the burn rate." Exactly what BK will tell you when you call. "47k" is clearly padded down. Why? Why, IDK. Why are humans like they are? Mfrs pad specs all the time for a variety of reasons. The 2.6 cu-ft Buck specs @ 40k.

Hi Den,

Thanks for your helpful replies. I'm not quite sure what you are saying here? What depends on the burn rate?

Yeah, I too thought 47K was amazingly low, considering that Hearthstone specs the Equinox at 120K, almost three times the burn rate! So I was only using the 47K King and 40K Princess specs as relative ratings for comparison with each other, since they are from the same manufacturer. I suppose BK could pad the Kings rating down relative to the Princess, but that would be even more mysterious.

 

[ddddddden]

Hearthstone doesn't claim 40-hr burns. Maybe that's the difference. . .or maybe it means you can fire the piss out of soapstone.

 

[ddddddden]

Hearthstone doesn't claim 40-hr burns. Maybe that's the difference. . .or maybe it means you can fire the piss out of soapstone.

 

[SolarAndWood]

Yeah, I too thought 47K was amazingly low, considering that Hearthstone specs the Equinox at 120K, almost three times the burn rate!

The 47 is a real world high burn rate vs running it hard. I think I read in the BK literature that the King can produce 90K if you are willing to feed it. That would be a full load of something in the Locust range burning in 8 hours. That would be quite a feat as I have to work real hard to get a load like that to burn in 12 hours at the highest burn I run the stove at with the blowers wide open. Might be more easily done with a softwood so you don't have to worry about coals.

 

[webby3650]

Hearthstone doesn't claim 40-hr burns. Maybe that's the difference. . .or maybe it means you can fire the piss out of soapstone.

Den, why do all of your posts come up 3 times?

 

[Renovation]

Hearthstone doesn't claim 40-hr burns. Maybe that's the difference. . .or maybe it means you can fire the piss out of soapstone.

Den, why do all of your posts come up 3 times?

I'm not sure it's his fault, but an interaction between his particular personal confuser and the servers here, which the moderators have reported are overloaded and being upgraded. The Ashcan is/was closed to try to take the load off the servers in the meantime.

I apologize--the overload is probably my fault.

 

[Renovation]

Yeah, I too thought 47K was amazingly low, considering that Hearthstone specs the Equinox at 120K, almost three times the burn rate!

The 47 is a real world high burn rate vs running it hard. I think I read in the BK literature that the King can produce 90K if you are willing to feed it. That would be a full load of something in the Locust range burning in 8 hours. That would be quite a feat as I have to work real hard to get a load like that to burn in 12 hours at the highest burn I run the stove at with the blowers wide open. Might be more easily done with a softwood so you don't have to worry about coals.

Thanks Solar,

I nosed around the BK site and found that info, which explains the difference and seems considerately conservative on their part. They say the 47K figure is for average output over a full burn with a full firebox, rather than the peak output if one were constantly stoking the firebox. Quite a difference.

I also noticed that they use fir as the fuel for their 47K figure! Isn't fir relatively low BTU, making the estimate even more conservative?

At the risk of hijacking my own thread, do you monitor flue temps, and can you tell me the flue temp at full burn? I think you're one of the folks with the heating load to run full out at times?

 

[Treacherous]

I also noticed that they use fir as the fuel for their 47K figure! Isn't fir relatively low BTU, making the estimate even more conservative??

Probably more middle of the road at around 21M BTU IIRC.

 

[BrotherBart]

Hearthstone doesn't claim 40-hr burns. Maybe that's the difference. . .or maybe it means you can fire the piss out of soapstone.

Den, why do all of your posts come up 3 times?

I'm not sure it's his fault, but an interaction between his particular personal confuser and the servers here, which the moderators have reported are overloaded and being upgraded. The Ashcan is/was closed to try to take the load off the servers in the meantime.

I apologize--the overload is probably my fault.

It happens when the server is running slow and instead of waiting for the post to update a person keeps clicking on the "Submit" button thinking it will speed up the posting.

 

[ddddddden]

I'm not hitting the button multiple times. Seems to be something my phone sometimes does. OTOH, for some time now, I can't reply, quote, or edit without a Key Characters Disallowed error trashing it when I try to submit. Only Fast Reply works anymore. . .problem on my end?

 

[BrotherBart]

I'm not hitting the button multiple times. Seems to be something my phone sometimes does. OTOH, for some time now, I can't reply, quote, or edit without a Key Characters Disallowed error trashing it when I try to submit. Only Fast Reply works anymore. . .problem on my end?

As noted in this thread Craig has discovered the way to clear up some of the problems people have had the last week. But from the response time I am seeing right now posting I would be surprised if this sucker crashed before the night is over.

https://www.hearth.com/econtent/index.php/forums/viewthread/55236/P45/

But Craig has the handle on the controls. The mods just sweep up the bar.

 

[ddddddden]

I'm not clicking multiple times. Could be something related to my phone/browser/Sprint, but it started in the past few weeks. Also, Reply, Quote, and Edit now malfunction for me. Fast Reply is the only thing still working. . .

 

[ddddddden]

. . .and that was a repost because I got an error on the first one. Anyhow, BB, that quip about EPA not caring how clean your house burns. . .lmao.

 

[ddddddden]

soo. . .lessee. . .no idea why Buck would put an 8" flue on the 80. Maybe the draft was weak with a 6" flue? There was a thread a month or two back reporting improved performance with a VC running into an 8" flue instead of 6".

 

[ddddddden]

Another interesting example that's been discussed is the Vogelzang Boxwood. 6" flue, 1.0 cu ft, "96K" BTU. Perhaps if reloaded hourly. BK prefers to highlight long burn times over high output. A 6" flue might be adequate for this, but they still have to allow for Homer jamming the thermostat open and burning 80 lbs of wood ASAP in an attempt to make it throw heat like his old smoke dragon.

 

[ddddddden]

Oh yeah, back when I was looking at the Princess, I called BK with similar questions. They basically said that you could get 60k out of it if you want to burn that much wood.

 

[SolarAndWood]

Yeah, I too thought 47K was amazingly low, considering that Hearthstone specs the Equinox at 120K, almost three times the burn rate!

The 47 is a real world high burn rate vs running it hard. I think I read in the BK literature that the King can produce 90K if you are willing to feed it. That would be a full load of something in the Locust range burning in 8 hours. That would be quite a feat as I have to work real hard to get a load like that to burn in 12 hours at the highest burn I run the stove at with the blowers wide open. Might be more easily done with a softwood so you don't have to worry about coals.

Thanks Solar,

I nosed around the BK site and found that info, which explains the difference and seems considerately conservative on their part. They say the 47K figure is for average output over a full burn with a full firebox, rather than the peak output if one were constantly stoking the firebox. Quite a difference.

I also noticed that they use fir as the fuel for their 47K figure! Isn't fir relatively low BTU, making the estimate even more conservative?

At the risk of hijacking my own thread, do you monitor flue temps, and can you tell me the flue temp at full burn? I think you're one of the folks with the heating load to run full out at times?

No probe in the stack but I can tell you I don't get 24 hr burns when its cold or blowing out even with the good stuff. Pretty sure you wouldn't be able to put your hand in their either. Hopefully when I get the shell of the house done I won't have to run it wide open as often.

 

[ddddddden]

. . .and another oh yeah, Douglas fir is the official wood of the EPA. Maybe the spec is from the EPA test, or maybe BK uses fir to keep their testing consistent with EPA testing.

 

[ddddddden]

. . .and another oh yeah, Douglas fir is the official wood of the EPA. Maybe the spec is from the EPA test, or maybe BK uses fir to keep their testing consistent with EPA testing.

 

[Renovation]

. . .and another oh yeah, Douglas fir is the official wood of the EPA. Maybe the spec is from the EPA test, or maybe BK uses fir to keep their testing consistent with EPA testing.

Fair enough. And they're in Washington state, which is doug fir central, true?