Real World Burns and Quality..? Anyone...? Anyone...? Bueller... Bueller?

MovingOffGrid · Feb 18, 2009

Solar+Wood -

Here's my 2 cents on using my new PE Summit over the last few weeks.
2500 sq ft 2 story basement entry home - R20 walls - R40 ceilings, double glazed windows - stove on basement entry level. 30' Brick chimney in center of home for storing radiant heat.

I have yet to pack the Summit full for an overnight burn at -6 celcius. With half loads, I still have some glowing coals 4, 5, 6 7 and 8 hours later, and my gas boiler heat hasn't had to come on at night.

This stove seems to be able to move a lot of warm convection air throughout the house when cranked up and the house stays pleasantly warm, but I'm still learning to find the sweetspot to get mileage out of my wood for sustained, long, non-fiddling burns. (using Birch, Alder and Maple).

I was going to buy a BK Princess but went Summit because I wanted to store chimney exhaust heat in our large brick central chimney (the cat stoves send less heat up the flue).

If I had no backup furnace and 2500 sq. ft, I would have bought the biggest Blaze King, for the Thermostat, for the extra long controlled burns and 'set and forget' capacity, without a hesitation! My dealer (a decent guy) did a 30 hour burn test themselves with their demo stove and swears by the large BK.

I enjoy the ability to watch the dancing secondary burn on my Summit (evidently the window on a cat stove is less picturesque), the Summit's ability to pound out the heat when you need it, and it's reasonably large firebox and decent looks ... but a 5 - 6 hour real world hot to medium to low burn time seems a more realistic expectation on my wood, and does not compare to the thermostatically controlled, BKing behemoth, capable of chugging along for a couple of dozen hours as your only heat source!

IMO, if you only have one heat source and you live in an area where it stays below freezing for days on end, and you're not willing to baby sit a stove, then and you need loooonnnnggggg burn times, and the cat stoves are the proven performers there.

Solar+Wood · Feb 19, 2009

north of 60 said:
Solar+wood get your mind to open up and not to narrow it down on steel thickness's when it comes to stove costs. If you take new boilers, wood or gas for instance, they all have less metal in them and are more efficient, have better warranties and yes cost more. You pay money for design and quality. The BKs have an auto t-stat mechanism, Dual positive discharge/displacement prop fans, An expensive cat combuster that gives outrageous burn times when you match it up with the auto damper. It has a reliable mechanical working bypass damper. Look at the welds on these suckers. There perfect continuous penetrating beads that go on and on. All wich requires labour in manufacturing. They have quite a bit of assembly time on these units. That labour costs. It comes with doors that are not prone to leek when you take your stove out of the box and fire it for the first time. I have a fire lit no less than 250 days a year 24/7. Lots of 25 to 15 yr old stoves around here, non cat and cat with the same metal thickness's. Still juggin away.
Iam headin outa town in the AM and will return a reply on the weekend if you have more to rant about. :coolsmile:
Cheers N of 60

Ok... I'm back, but it's really warm outside here in Hawaii

No stove to fool with today.

As always, I appreciate your input as well as others here.... esp when you are talking first hand.

As for BK....
My family has a line up of prof welders, machinists and tradesmen in one form or another. I know what they pay or lack thereof for welders and other trades nowadays, etc. Combine that with steel costs I posted and you can see that it's not difficult to build one more stout at a fair price. If it's not for the thermal properties, then it's for the profit properties to use thinner steel ----and this isn't a boiler transferring heat to a better thermal mass storage medium like water (one of the best). The efficiency ratings should be high there.

What I am getting at is that I would guess they would create better design for the price and their reputation. I would guess that more mass to store energy would be better than less mass. Unlike soapstone that has to stay relitively cool, steel can get hotter and a fan could be used to tranfer larger amounts of heat which would cool down the steel and allow heat to transfer back into the steel, so on and so on. From my layman's perspective, that's about what everyone is doing to some degree. But I am not an engineer captain.... I am a doctor; something like that.

Back to enjoying God's natural heat.... the sun and bikinis ;p

solar+Wood... and bikinis

Solar+Wood · Feb 19, 2009

go figure.... drizzle.............but I did see a bikini :cheese:

Hopefully the sun will come out tomorrow..... Oh hell, I sound like that song now.

Solar+Wood

karri0n · Feb 20, 2009

If you want looks, don't mind shorter burns, and are uncomfortable about steel thickness(personally I wouldn't buy a steel stove to begin with, *FUGLY*), then go with the Isle Royale. I just know there are people on this site who are completely happy with their Blaze Kings and heat their house to 75 degrees in -75 degree weather. I love my Isle Royale, but I'm quite certain it cannot do that. That being said, you and I don't live in Alaska, and I'm perfectly happy with my Isle Royale in a similar climate to you. Just be prepared that you're paying more since it's discontinued or at least temporarily not in production. Because it's a cast beast, even before the discontinuation it does cost more than a heater of equal heating ability, and if you just want BTUS for your buck a cat stove will always be better.

North of 60 · Feb 20, 2009

Solar+Wood said:
north of 60 said:

Solar+wood get your mind to open up and not to narrow it down on steel thickness's when it comes to stove costs. If you take new boilers, wood or gas for instance, they all have less metal in them and are more efficient, have better warranties and yes cost more. You pay money for design and quality. The BKs have an auto t-stat mechanism, Dual positive discharge/displacement prop fans, An expensive cat combuster that gives outrageous burn times when you match it up with the auto damper. It has a reliable mechanical working bypass damper. Look at the welds on these suckers. There perfect continuous penetrating beads that go on and on. All wich requires labour in manufacturing. They have quite a bit of assembly time on these units. That labour costs. It comes with doors that are not prone to leek when you take your stove out of the box and fire it for the first time. I have a fire lit no less than 250 days a year 24/7. Lots of 25 to 15 yr old stoves around here, non cat and cat with the same metal thickness's. Still juggin away.
Iam headin outa town in the AM and will return a reply on the weekend if you have more to rant about. :coolsmile:
Cheers N of 60

Click to expand...

Ok... I'm back, but it's really warm outside here in Hawaii No stove to fool with today.

As always, I appreciate your input as well as others here.... esp when you are talking first hand.

As for BK....
My family has a line up of prof welders, machinists and tradesmen in one form or another. I know what they pay or lack thereof for welders and other trades nowadays, etc. Combine that with steel costs I posted and you can see that it's not difficult to build one more stout at a fair price. If it's not for the thermal properties, then it's for the profit properties to use thinner steel ----and this isn't a boiler transferring heat to a better thermal mass storage medium like water (one of the best). The efficiency ratings should be high there.

What I am getting at is that I would guess they would create better design for the price and their reputation. I would guess that more mass to store energy would be better than less mass. Unlike soapstone that has to stay relitively cool, steel can get hotter and a fan could be used to tranfer larger amounts of heat which would cool down the steel and allow heat to transfer back into the steel, so on and so on. From my layman's perspective, that's about what everyone is doing to some degree. But I am not an engineer captain.... I am a doctor; something like that.

Back to enjoying God's natural heat.... the sun and bikinis ;p

solar+Wood... and bikinis

Uhhh OK , their design and performance is what has given there reputation. Why use thicker steel if it does not benefit any thing.
Seems to me that you only see what you want to read. Here, Ill keep it simple for ya. Take my previous stove for example.
It was comparable in ratings for house size etc... as my new stove. My previous stove was $800 less and got 2.5yrs out of it until I got sick of relighting fires every morning and every evening when I got home from work and listening to my furnace cycle on with my wood piles disappearing. ( good thing it had thicker steel,such a deal) I tried to burn 24/7 and had oil bills over a grand a year. Was going to stick my old fisher back in. After lots of info gathering I stuck my neck out one more time to get on the EPA bandwagon. Bingo I had great success. I might only relight my new stove once or twice a year and never had an oil bill at the end of the heating season over $300. Now it may be only me but I see value here. The only thing I got out of my cheaper stove which still cost lots of money for a poor tradesman, :-S that had thicker steel is that I now have heat in my Quad shed to pr-heat before I go plow at -30. For what its worth.

N of 60

BrotherBart · Feb 21, 2009

I keep seeing this "thicker steel" thing in this thread. That Blaze King has to be at least 3/16" steel to even be called a plate steel stove. 99% of the stoves out there today, including the 30-NC, are 3/16" fire boxes.

herbert · Feb 21, 2009

BrotherBart said:
I keep seeing this "thicker steel" thing in this thread. That Blaze King has to be at least 3/16" steel to even be called a plate steel stove. 99% of the stoves out there today, including the 30-NC, are 3/16" fire boxes.

Are you talking stand alone wood stoves or OWB fireboxes ?

BrotherBart · Feb 21, 2009

herbert said:
BrotherBart said:

I keep seeing this "thicker steel" thing in this thread. That Blaze King has to be at least 3/16" steel to even be called a plate steel stove. 99% of the stoves out there today, including the 30-NC, are 3/16" fire boxes.

Click to expand...

Are you talking stand alone wood stoves or OWB fireboxes ?

Stove.

herbert · Feb 21, 2009

BrotherBart said:
herbert said:

BrotherBart said:

I keep seeing this "thicker steel" thing in this thread. That Blaze King has to be at least 3/16" steel to even be called a plate steel stove. 99% of the stoves out there today, including the 30-NC, are 3/16" fire boxes.

Click to expand...

Are you talking stand alone wood stoves or OWB fireboxes ?

Click to expand...

Stove.

what thickness is being used in fireboxes in owb 's

Solar+Wood · Feb 2, 2011

north of 60 said:
Solar+wood get your mind to open up and not to narrow it down on steel thickness's when it comes to stove costs. If you take new boilers, wood or gas for instance, they all have less metal in them and are more efficient, have better warranties and yes cost more. You pay money for design and quality. The BKs have an auto t-stat mechanism, Dual positive discharge/displacement prop fans, An expensive cat combuster that gives outrageous burn times when you match it up with the auto damper. It has a reliable mechanical working bypass damper. Look at the welds on these suckers. There perfect continuous penetrating beads that go on and on. All wich requires labour in manufacturing. They have quite a bit of assembly time on these units. That labour costs. It comes with doors that are not prone to leek when you take your stove out of the box and fire it for the first time. I have a fire lit no less than 250 days a year 24/7. Lots of 25 to 15 yr old stoves around here, non cat and cat with the same metal thickness's. Still juggin away.
Iam headin outa town in the AM and will return a reply on the weekend if you have more to rant about. :coolsmile:
Cheers N of 60

I wanted to say thanks to all of you who put up with my closed mind, narrow view and poor attempt at humor while I ranted last year. I really appreciate the patience and guidance I received.

I guess an apology is due to all.

Thanks

Beetle-Kill · Feb 2, 2011

Dude, everyone that posted in '09 are now dead. While it's a nice gesture, you're slackin' on the response time. BTW, what stove are you burning? :cheese:

Solar+Wood · Feb 2, 2011

Ya.... maybe some of those brain cells are dead, but many are probably still plugging away cutting wood..... and ya gotta call a spade a spade. After looking at how I approached and digested things here combined with my poor attempt at humor, I thought it only best to man up and wipe the slate clean... move on. In the end, I really do appreciate the advice and points I got from everyone. It helped a lot.

As far as this thread...
After personally measuring all those boxes to what I think makes sense (space you can actually put/use a log) I still feel that the advertised volumes are very deceiving..... but what the heck do I know.

This is probably more than you want to know, but you asked and so here we go.
In the end I got a good deal on a NC30 up in Boulder (I see that you are from CO too). It has worked great for us so far. The POORLY insulated 30x40 cabin I live in is just about at 9,000 ft. I think it may be considered "steppe" land with mostly shrubs and NO trees close by. Guess many would consider my land and area surrounding it not so desirable without any trees and the winds, but it pleases us just fine. With that picture painted you can get an idea what the 20 to 70 mph winds do in the winter with nothing to stop it but your house. Tonight I saw -20f with a wind chill of -40f.... yyyOUCH !!!

Hope it froze every one of those darn prairie dogs up. Well, maybe leave a few for the hawks and eagles

With my NC30 downstairs and the new 2inch foam insulation against the poured cement basement walls, I would say that it is performing better than last winter (less wood burnt). Guess it's not the best burning stove as I do get a lot of coals if I don't watch how the girlfriend works it (other stove upstairs has fewer coals in the end). She doesn't watch the NC30 fire at times and smothers it a bit after a few hours, but under the same conditions the other stove has fewer coals.

Right now it's a good toasty 74f in the basement. Burning primarily lodge pole pine and some elm and some sawmill cuts/drops of oak. What I really like about the NC30 is being able to put a 19 to 20 inch log in that's about 6 to 9.5 across into the bugger with a few oak scraps and just walking away... AND watching the temps jump up in the house in short order. Can't do anything like that with the other stove. Both stoves 90 out and up with a vacu stack on each. Also put a pipe damper in for the NC30 to deal the crazy winds here.

The other stove:
Under warmer conditions, she/we don't really need to run the upstairs Phoenix, but we can accept 65f up there. The Phoenix is running now and is undersized for my little loft area and living space under normal conditions. Under current/tonight's freezing weather it has trouble keeping the upstairs warm unless I stay on top of it w/wood. Although I love the show the Phoenix gives.... so it will prob stay. Plus it's paid for. If I could come out w/out too much of a shellacking I may try and sell it next year and get something bigger. Maybe even a CAT if I win the lotto. Buck 91 or BKK??? Got a friend who may buy one soon; so, maybe I'll get some hands on time.

HMMMM....
Got any buds that run either stoves here in CO? Wonder how they do with it at the higher altitudes and soft woods. What troubles me about them, other than high cost, is that they show a much lower BTU output for their supposedly larger sized box (compared to the NC30). I think in one post here a dealer suggested to add an additional layer of firebrick to the base (I believe the BKK); thus, reducing the box volume further. Either way, here's what I found on-line for normal boxes under perfect conditions
BKK at 47,000/hr and 82.5% eff
Buck 91 @ 50,400/hr at 86% eff
NC30 @ 75,000/hr at I'm guessing 70 to 75% eff (didn't see any data)

I do see that they both get rave reviews for burning forever and saving fuel, but I'm still suspicious to see if either CAT can put out the heat like I need that I get from the Englander when it drops to -20 w/wind chills to -40 like tonight.... and the winds aren't even blowing that hard tonight. I also wonder how much fuel I would have to save to offset the higher acquisition and installation costs. I'd have to look it up, but I think I got the NC30 around $600 to $650 (normally in the $1,200 range).... but I do burn a lot of wood (house/insulation problem). I think those two CAT stoves run somewhere in the $2,600 to $3,400 range.

Wow... I still have almost 1400 characters left. Vanna..... I'd like to buy a vowel please.

Sorry to burn out your eyes <g>

Cheers!

webbie · Feb 2, 2011

Solar+Wood said:
I didnï¿½t sleep at a Holiday Inn Express last night, but I guess marketing isnï¿½t being as honest as they could when they advertise their specs.

Now someone is going to say Santa Clause and the Easter Bunny aren't real.... they all are liars ;>

Cheers,
Solar+Wood

Speaking of Holiday Inn Express, are you composing your posts in a word processor outside of the forum?
I ask because of strange characters showing up within your posts....

thanks!

Solar+Wood · Feb 3, 2011

Dunno. That was a bit ago.

I don't recall ANY of those goofy characters back then.

I could have used a couple computers at internet cafes overseas while traveling....??? I know they can create goofy characters, but they show up when previewing if not immediately.

Probably also used Word on a few posts.

Why? Did I do something wrong or screw something up?
If it helps I am a bit goofy and that may have worn off in the posts <g>

rdust · Feb 3, 2011

Solar+Wood said:
What troubles me about them, other than high cost, is that they show a much lower BTU output for their supposedly larger sized box (compared to the NC30). I think in one post here a dealer suggested to add an additional layer of firebrick to the base (I believe the BKK); thus, reducing the box volume further. Either way, here's what I found on-line for normal boxes under perfect conditions
BKK at 47,000/hr and 82.5% eff
Buck 91 @ 50,400/hr at 86% eff
NC30 @ 75,000/hr at I'm guessing 70 to 75% eff (didn't see any data)

Don't get hung up on the BTU numbers, BK lists the average BTU numbers not their peak numbers. This is from their manual "If you were to stand in front of
your stove and frequently add fuel, burn the unit on high and have optimal conditions, the PEJ1006 could produce as
high as 87,500 btuâ€™s and the KEJ1107 could exceed 90,000 btuâ€™s! However, maximum btuâ€™s would only be achievable at
certain â€œpeakâ€ times during the burn. Blaze King does not wish to mislead you so we give you all the facts."

Solar+Wood said:
I do see that they both get rave reviews for burning forever and saving fuel, but I'm still suspicious to see if either CAT can put out the heat like I need that I get from the Englander when it drops to -20 w/wind chills to -40 like tonight.... and the winds aren't even blowing that hard tonight. I also wonder how much fuel I would have to save to offset the higher acquisition and installation costs. I'd have to look it up, but I think I got the NC30 around $600 to $650 (normally in the $1,200 range).... but I do burn a lot of wood (house/insulation problem). I think those two CAT stoves run somewhere in the $2,600 to $3,400 range.

Wow... I still have almost 1400 characters left. Vanna..... I'd like to buy a vowel please.

Sorry to burn out your eyes <g>

Cheers!

Plenty of members burning BK stoves in Alaska that are getting along just fine with long burn times. If you're really interested in speaking with someone who has burned a 30 and a BKK pm Hiram Maxim and ask him about both stoves. He had a 30 and is now burning a BKK,(actually he can still burn both stoves) he's in Michigan so he's not dealing with your climate but he'll give you some real world opinions.

jadm · Feb 3, 2011

I am in the 'low lands.' Only 5280ft above sea level here...I burn a 550 Jotul insert. I buy hardwoods from local tree companies because the hard wood burns longer than the pine and down here the cost of pine is the same as hard wood cost BUT I use far less hardwood due to the longer burns...For me hardwoods last twice as long as pine...

Right now it is -2Â° out. I am burning a load of red oak - large chunks. Temp. in insert room is 77Â°. I imagine the load will last well into the wee hours of the morning. Yesterday, with temps even lower than they were today, the coals were still putting out plenty of heat at 3AM though the temp. in the insert room dropped to about 70Â°. A load of red oak will burn and heat in my insert for a good 10 hours.

I save my red oak for these really blistery days. My regular hardwoods would probably burn for about 7 hours. This winter has been an unusual one here and I have only gone through about a cord of wood so far. Usually I burn at least 2 cords per winter...

My house is 1800sqft. Insert heats about 1/2 of that. Poor heat circulation due to doorways and halls but the rooms heated are where we spend most of our time. COld part of the house are the bedrooms which we like cool.

Supplemental heat is NG which I will turn on for about an hour each morning to help take the chill off....also helps off set cost of wood.

Was glad to hear what kind of stove you did end up purchasing...

Solar+Wood · Feb 4, 2011

Rdust:
Thanks for the info. That makes more sense with the larger box. Guess I'll tell my bud to consider the BKK or Princess... or the Buck 91 or 94NC.

Perplexed:
Can you tell me where you get you oak? PM if you like. Thanks

henkmeuzelaar · Feb 4, 2011

Solar+Wood,

I have lived the last 33 years at 7200 ft altitude (just moving to 5800 ft now) where air only contains 75 % (wt/vol) of oxygen at sea level. So when you try to burn anything you got one big strike against you already.

Now you (and I) also want long burn times, which simply means you'll have to skimp on air supply and will end up with a less hot fire and more products of incomplete combustion (CO, VOCs, creosote, soot; or if you want to be less technical: SMOKE) That is strike #2.

In many of these nice mountain communities you will lose friends (no to mention pay fines) if this smoke comes out of your chimney. That is strike #3!

Perhaps your wood is occasionally not of the best quality and/or perfectly seasoned. That is strike #?? Wait, I forgot you struck out already!

So, one either has to lower one's expectations (e.g. no long burns) plus improve one's performance (e.g. burn only the most perfect and expensive wood) or one will need to get a stove with a catalytic afterburner......

Success

Henk

Solar+Wood · Feb 21, 2011

Someone here has probably already done this.... but what they hay anyway.

AVG BTU burns over the course of 8hrs. Based on a formula noted below.

I assume some will have issues with it, so have at it

It is my first draft and could use some help if I have something wrong.
so...Help me create a fair comparison since the industry has not.

Listed in order by size of firebox (smallest to largest)

Woodstock Fireview..... 31,530 AVG BTUs for 8hr burn..(72% eff)... 2.18cu ft
Herthstone Phoenix..... 33,145........................(75% eff)... 2.2cu ft
Regency 2400............ 35,576........................(77% eff)... 2.3cu ft
BKK Princess (CAT).... 46,403........................(82.5% eff). 2.8cu ft
Regency 3100............ 43,924........................(75.4% eff). 2.9cu ft
Harmon TL300........... 45,801........................(76% eff)... 3.0cu ft
PE Summit................ 48,392........................(80.3% eff). 3.0cu ft
Hearthtone Mansfield.. 49,754........................(77.4% eff). 3.2cu ft
Everzone 3.4............. 53,273........................(78% eff)... 3.4cu ft
QuadraFire 5700........ 52,518........................(76% eff)... 3.44cu ft
Englander 30-NC....... 53,434........................(76% eff)... 3.5cu ft
BKK King 1107 (CAT)..71,594........................(82.5% eff). 4.32cu ft
Buck 91 (CAT).......... 76,013........................(86% eff)... 4.4cu ft
Buck 94-NC.............. 64,523........................(73% eff)... 4.4cu ft

Add your own box by using the formula below.... Enjoy!

Look at the note below about the two Buck stoves for CAT vs. NC comparison.... interesting.
-------------------------------------------------------

Why I put the comparison together and how.
A friend asked me to give him a realistic comparisons on wood stoves and in doing so
I ran into the same marketing and sales gimmicks/confusion as before.
Even with that, it rekindled my thoughts of upgrading my NC stove to a large CAT while I continue
researching options for my true desire of solar heating.
.
.
So.....Here's something that I ran across that may help others on that journey to help cut
through all the sales hype.

Ran across a formula that one on-line salesman uses to try and make things equal when
looking at stoves. He seems genuine enough via e-mail.

Either way, it falls in line mathematically with what Blaze King uses for their 1107 BTU numbers; so, it
makes me think it may be useful since two different companies kind of match up.
Although Blaze King used 6,000 BTUs (Tamarack wood?) versus the following formula's
use of 6,200 BTUs (avg of all the woods in his list). FWIW... Over the phone BKK said their 1107 King model burns 2#s per hour at 12,000 BTUs avg for 45-hrs and at 10#s per hour at 60,000 BTUs avg for 8-hrs.

So again...I don't know if it really helps or hurts, but I think it helps in a big
picture kind of way.

Something to note is that it takes an 8hr burn as a given.

FWIW, I corrected a step he left out of the formula that was noted in his explanation.
It's using "1728" to convert cu ft back to cu inches (cu ft box x "1728").

---------------------------------------------------------

FORMULA HERE

To find the average burn in BTUs, the formula is:
Avg BTU Burn = (Fire box size in CU ft x 1728 x .015 x 6200 x EFF rating) / 8hr burn

* Fire box size in CU ft uses ADVERTISED box size
* 1728 gets in back to cubic INCH
* .015 takes into account how much wood can actually get stuffed in the advertised firebox dimensions (accounts for air spaces).
* The 6,200 is an average BTU for wood based on a cu inch (official BKK data uses 6,000, I/he used 6,200 in the example formula)
* EFF Rating is the manufacturer's LHV (EPA5H??)... optimum burn... whatever they publish as best.
* 8 hr burn Is what the on-line guy says most EPA stoves can do over the course of a fire's progression from peak to smoldering.

------------------------------------------------------------

CAT vs NON-CAT

What is also interesting to see what appear to be TWO IDENTICAL fireboxes from Buck Stoves...
The CAT model produces about 8,000 more BTUs per their literature.
I have NOT seen either stove in person and ASSUME the boxes are identical other than
secondary tubes in the NC in the 94 and the CAT in the 91. I ASSUME the secondary tubes take
some area away from the two boxes reducing its ability to hold some fuel; thus, lower BTUs...???

Which leads me to....
I am more inclined to use my measurements instead of the advertised box dimensions when looking at heat capabilities.
I measure what you can actually use to set fuel/wood in. From what few boxes I've measured
the box drops in size a bit.

AGAIN....The cu ft box numbers listed above are ADVERTISED box dimensions and NOT my measurements.

The AVG BTU figures are created from a formula that seemed to make sense. *** It is NOT my formula. ***
The AVG BTU figures do not match the MFR's figures from those that I compared.

Cheers,
Solar+Wood

pyper · Feb 22, 2011

Solar+Wood said:
To find the average burn in BTUs, the formula is:
Avg BTU Burn = (Fire box size in CU ft x 1728 x .015 x 6200 x EFF rating) / 8hr burn

* Fire box size in CU ft uses ADVERTISED box size
* 1728 gets in back to cubic INCH
* .015 takes into account how much wood can actually get stuffed in the advertised firebox dimensions (accounts for air spaces).
* The 6,200 is an average BTU for wood based on a cu inch (official BKK data uses 6,000, I/he used 6,200 in the example formula)
* EFF Rating is the manufacturer's LHV (EPA5H??)... optimum burn... whatever they publish as best.
* 8 hr burn Is what the on-line guy says most EPA stoves can do over the course of a fire's progression from peak to smoldering.

0.015 = 1.5%

The results produced seem plausible, but I'm sure I can fill my stove to more than 1.5% of it's rated capacity.

When I multiply 1728 cu in per cu foot x 6200 Btu per cu in, I get 10,701,200 btu / cu ft, which is way too high. I guess the two wrongs are offsetting each other.

According to http://chimneysweeponline.com/howood.htm

there are approximately 20 million btu per cord in the average wood (middle of the chart, more or less). There are 128 cu foot per cord, so there are 156,250 btu per cu foot. Here's an alternate formula:

CUFT x 156,250 x EFF% x .85 (load factor) / 8.

So for the first stove in the chart, 26,057

If you burn white oak (24 mbtu = 187,500 btu / cuft) and load 95% of the available space, then 34,948

But maybe the "per cord" measure already accounts for the open space in the stack, and then you'd just have:

cuft x 156250 x eff% /8 = 30,656 for the first stove on average, or 36,787 for white oak.

kettensÃ¤ge · Feb 22, 2011

pyper said:
Solar+Wood said:

To find the average burn in BTUs, the formula is:
Avg BTU Burn = (Fire box size in CU ft x 1728 x .015 x 6200 x EFF rating) / 8hr burn

* Fire box size in CU ft uses ADVERTISED box size
* 1728 gets in back to cubic INCH
* .015 takes into account how much wood can actually get stuffed in the advertised firebox dimensions (accounts for air spaces).
* The 6,200 is an average BTU for wood based on a cu inch (official BKK data uses 6,000, I/he used 6,200 in the example formula)
* EFF Rating is the manufacturer's LHV (EPA5H??)... optimum burn... whatever they publish as best.
* 8 hr burn Is what the on-line guy says most EPA stoves can do over the course of a fire's progression from peak to smoldering.

Click to expand...

0.015 = 1.5%

The results produced seem plausible, but I'm sure I can fill my stove to more than 1.5% of it's rated capacity.

When I multiply 1728 cu in per cu foot x 6200 Btu per cu in, I get 10,701,200 btu / cu ft, which is way too high. I guess the two wrongs are offsetting each other.

According to http://chimneysweeponline.com/howood.htm

there are approximately 20 million btu per cord in the average wood (middle of the chart, more or less). There are 128 cu foot per cord, so there are 156,250 btu per cu foot. Here's an alternate formula:

CUFT x 156,250 x EFF% x .85 (load factor) / 8.

So for the first stove in the chart, 26,057

If you burn white oak (24 mbtu = 187,500 btu / cuft) and load 95% of the available space, then 34,948

But maybe the "per cord" measure already accounts for the open space in the stack, and then you'd just have:

cuft x 156250 x eff% /8 = 30,656 for the first stove on average, or 36,787 for white oak.

Thanks for that alternate formula Pyper, It puts my pre cat insert at 80,936 BTU, right about where I figured, based on a heat loss calculation for my new heat pump a while back.

Solar+Wood · Feb 23, 2011

The gent sent me the following regarding the formula and the givens used in it. I think it explains what you are driving at about wood, how much one can stuff in their box and where he gets the BTUs. FWIW, I think using the ADVERTISED cu ft of a box is wrong since when measuring with your own tape measure, to where wood could actually fit, you get a bit different number. My 3.5 cu ft box is really 2.7, etc.... but I'm just a nut job. Excerpt pasted below.

Excerpt starts
Wood is measured and sold by the area it occupies, not by weight. According to a study done at Oregon State University a couple
of decades ago, a cord of wood, which occupies an area measuring 4' x 4' x 8' (128 cubic feet), only contains 85 cubic feet of
wood, due to the spaces between pieces. The airspaces between pieces don't weigh anything, so when we need to know the weight of a cord (or 128 cubic foot stack) of wood, we use the weight of 85 cubic feet of wood. This convention translates down to smaller
quantities as well.

For example, if we were to take the top 60 species from our firewood btu value chart at http://www.chimneysweeponline.com/howood.htm and average their weight per cord, we'd get 3327.54 lbs. If we were able to compress that cord of wood down to one solid mass with no airspaces, each cubic inch would weigh .023 lbs. We don't use that number in our formula, because in the real world, you can't get 3 cubic feet of firewood into a 3 cubic foot firebox.

For purposes of our formula, we recognize that we can only get 85 cubic feet of wood pieces into a 128 cubic foot firebox, so we
adjust the weight of a one cubic inch load to that exact scale, from .023 lbs to .015 lbs.

In other words, you can trust our formula: the adjustment for how much wood will actually fit into a 3 cubic foot firebox has
already been done for you.

Excerpt ends

Thanks for your post.

pyper said:
Solar+Wood said:

To find the average burn in BTUs, the formula is:
Avg BTU Burn = (Fire box size in CU ft x 1728 x .015 x 6200 x EFF rating) / 8hr burn

Click to expand...

0.015 = 1.5%

The results produced seem plausible, but I'm sure I can fill my stove to more than 1.5% of it's rated capacity.

When I multiply 1728 cu in per cu foot x 6200 Btu per cu in, I get 10,701,200 btu / cu ft, which is way too high. I guess the two wrongs are offsetting each other.

According to http://chimneysweeponline.com/howood.htm

there are approximately 20 million btu per cord in the average wood (middle of the chart, more or less). There are 128 cu foot per cord, so there are 156,250 btu per cu foot. Here's an alternate formula:

CUFT x 156,250 x EFF% x .85 (load factor) / 8.

So for the first stove in the chart, 26,057

If you burn white oak (24 mbtu = 187,500 btu / cuft) and load 95% of the available space, then 34,948

But maybe the "per cord" measure already accounts for the open space in the stack, and then you'd just have:

cuft x 156250 x eff% /8 = 30,656 for the first stove on average, or 36,787 for white oak.

Real World Burns and Quality..? Anyone...? Anyone...? Bueller... Bueller?

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