Scared of getting too many BTU’s

[bholler]

I'm comparing two units that extend into the room, 1) the Blaze King Ashford 25 (the Princess is a tad too tall for my firebox) and it is a catalytic unit and 2) the Quadra Burn 5100i which is non-catalytic. I'm checking the EPA database for Heat Output, and it appears that the non-cat has far greater heat output.

QB 5100i (3.0 cu ft capacity) -49,900 BTU, Ashford 25 (2.3 cu ft capacity) - 26,290 BTU.

Am I missing something?

Here's the list
https://www.epa.gov/sites/production/files/2017-08/usepa-certified-wood-heater-list.xlsx

Those are peak outputs. So yes non cats absolutly have higher peak outputs but cat stoves put out lower levels more evenly. And yes good cat stoves are a little more efficent than non cats but not as much as many claim.

 

[jotul8e2]

I'm comparing two units that extend into the room, 1) the Blaze King Ashford 25 (the Princess is a tad too tall for my firebox) and it is a catalytic unit and 2) the Quadra Burn 5100i which is non-catalytic. I'm checking the EPA database for Heat Output, and it appears that the non-cat has far greater heat output.

QB 5100i (3.0 cu ft capacity) -49,900 BTU, Ashford 25 (2.3 cu ft capacity) - 26,290 BTU.

Am I missing something?

Yes. You are comparing two stoves of vastly different sizes while also concentrating on the maximum heat output. The Quad is more than 30% larger in capacity. A larger stove is capable of holding a lot more fuel and throwing off a lot more heat. This has nothing to do with cat vs. non-cat.

The burn cycle for any stove is the same - load, ignition, operating temperature, coaling. You cannot keep feeding firewood into a stove to keep the maximum output going; the stove will simply fill up with coals after just a few hours. A tube burn stove must get an internal temperature of over 1,000 deg. f. to burn off the volatile gases. A cat stove ignites these gases at something in the 500 deg. range. A given load of wood has only so many btus available as fuel - about 6500 btu/lb. A 3 cu. ft. stove will hold maybe 60 pounds of hardwood as a practical matter. So the total btus available are, call it 400 k btu. A 75% efficient stove will generate 300 k btus from that. And the normal cycle for a stove that size might be six hours - so 50 k btu per hour. This is quite a bit of heat.

BUT!! A tube burn stove in the 3 cu. ft. range will burn at perhaps 80% of its maximum btu output for somewhere between 90 and 120 minutes. This value will fall to maybe 20% on average for the remaining two or three hours of the cycle. A cat stove can be run pretty much the same way if you wish - but with a catalyst you have the option to throttle back so that it runs at 30% or 40% or 50% of the maximum output for virtually the entire burn cycle. This ability translates into very long burn times at low heat, or shorter times at higher heat; it is your choice.

Imagine two natural gas furnaces. Furnace one puts out 200 k btu. Furnace two puts out 50 k btu. Now, further suppose we have two identical houses, each requiring 25 k btu per hour to maintain an average 68 deg. temperature. Furnace one does this by running at full bore 15 minutes once every two hours. Furnace two runs 15 minutes, is off 15 minutes, and is on again. Which house is going to be more comfortable? The house with furnace one is going to swing from 80 deg. to 55 deg. (give or take). The house with furnace two is going to swing only one deg. or so each way.

This issue is even more critical when you are dealing with a point source heating appliance (wood burning stove). The heat losses at the extreme - back bedrooms, upstairs, etc. - are usually in excess of what can be supplied in a relatively brief high heat session. If you can keep the heat output more nearly continuous you can more nearly even out the temperatures within the envelope.

 

[begreen]

BUT!! A tube burn stove in the 3 cu. ft. range will burn at perhaps 80% of its maximum btu output for somewhere between 90 and 120 minutes. This value will fall to maybe 20% on average for the remaining two or three hours of the cycle. A cat stove can be run pretty much the same way if you wish - but with a catalyst you have the option to throttle back so that it runs at 30% or 40% or 50% of the maximum output for virtually the entire burn cycle. This ability translates into very long burn times at low heat, or shorter times at higher heat; it is your choice.

In general this may be correct for some stoves, but not all 3 cu ft non-cats. For example, we burn on an average 10-12 hr cycle. Today our stove was reloaded at 7:30am, it hit a peak stove top temp of 650F and stayed close to that for about 3 hrs. It's now 2pm (6.5hrs later) and the stove top is at 450º. I would guesstimate that there is still about a 40% mass of charcoal to be burned. It will get reloaded at this rate at around 6pm. This is with somewhat loose packed, thick split doug fir. It I switch to tightly packed hardwood I can add 2-3 hrs to the burn time.

 

[jetsam]

I'm comparing two units that extend into the room, 1) the Blaze King Ashford 25 (the Princess is a tad too tall for my firebox) and it is a catalytic unit and 2) the Quadra Burn 5100i which is non-catalytic. I'm checking the EPA database for Heat Output, and it appears that the non-cat has far greater heat output.

QB 5100i (3.0 cu ft capacity) -49,900 BTU, Ashford 25 (2.3 cu ft capacity) - 26,290 BTU.

Am I missing something?

Here's the list
https://www.epa.gov/sites/production/files/2017-08/usepa-certified-wood-heater-list.xlsx

If you're going to consider non-cats as an option (bear in mind, they are not going to burn nearly as low as a similar quality cat stove), the Kuma Sequoia would be on my shortlist. It's 22.5" high, which is 1/4" shorter than the Princess.

You could also tell the wife that since the Princess won't fit, you are going to need to extend the hearth and put in a freestanding stove. That would even give you the option of stepping up to the BK King, which is maybe a better fit for you based on the size of the house. Needs an 8" flue, though.

 

[Zack R]

If you plan to live in the house for a while and don't want to mess around I'd say a freestanding stove, which will require a hearth build out. You'll get a lot of heat from a freestanding stove without a blower.

A big house in Minnesota = perfect place for a wood stove!

 

[allan5oh]

In your picture where is the middle of the house? Is it the area where the child is sitting? if so if you put a freestanding stove there you will have better more even heating as opposed to what looks like a room in the corner of the house with low ceilings and lools like it would be pointed towards windows.

 

[MN Mike]

In your picture where is the middle of the house? Is it the area where the child is sitting? if so if you put a freestanding stove there you will have better more even heating as opposed to what looks like a room in the corner of the house with low ceilings and lools like it would be pointed towards windows.

The center of the house is actually in the center of the photo, where the door hinges are. From right to left in the image are 1) kitchen, 2) dining room (where the fireplace is) then the center support wall, 3) family/great room/vaulted ceiling and 4) TV/room. I generally refer to the vaulted space and the TV space as the "family room" but for this discussion they are separate. Each of the 4 "rooms" are approximately the same width from left to right. The dining and vaulted room have an opening about 6ft wide x 7 ft tall connecting them. That is the opening where the center of the pano photo was taken from. You can see the stairway in the vaulted room, and that leads to the foyer/entry way where the front door is. That entry space connects around to the kitchen (again, far right in this photo).

Does that make sense?

Also, a free-standing stove is not something I'm considering at this time. I understand from a thermal standpoint, the vaulted space would be better for the localized heat source. However, it's just not practical from a space/usability standpoint or aesthetic standpoint, i.e. I've got a stovepipe running in the middle of the room to the ceiling and what do I do with the old fireplace? Believe me, I've thought about the same kind of thing.

I'm expecting the heat to flow out of the fireplace, and then through the 6x7ft opening up to the vaulted space. I have a ceiling fan in that space that should help to mix the air, but to what extent it gets around I have no idea.

 

[begreen]

Sounds like you've thought this through pretty carefully. Very few homes have perfect heat distribution. You work with what you've got.

 

[MN Mike]

Yes. You are comparing two stoves of vastly different sizes while also concentrating on the maximum heat output. The Quad is more than 30% larger in capacity. A larger stove is capable of holding a lot more fuel and throwing off a lot more heat. This has nothing to do with cat vs. non-cat.

Are you aware of a cat stove that's close to 3.0 cu ft that is less than 21.5" tall? BK does not have one.

 

[begreen]

Not offhand.

 

[jetsam]

Also, a free-standing stove is not something I'm considering at this time. I understand from a thermal standpoint, the vaulted space would be better for the localized heat source. However, it's just not practical from a space/usability standpoint or aesthetic standpoint, i.e. I've got a stovepipe running in the middle of the room to the ceiling and what do I do with the old fireplace?

You extend the hearth, drop a liner down the old chimney, and vent the stove through the old fireplace. It's pretty common but it would probably rule out BK for you, come to think of it (they're all top-venting).

The guy in the picture missed the point of taking the stove out of the stone box and bought a stove that IS a stone box, but you get the idea.

 

[MN Mike]

Alright so I ran some numbers on two simple BTU calculators and output is 60k to 75k BTU. See images and links. I and starting to think that the benefit of the catalyst units being able to go low and slow for a longer time will not be of value to me.

(broken link removed to https://www.simplex.ca/en-CA/tips-advice/btu-calculator)

https://www.alpinehomeair.com/hc/calculator/heating_estimator.cfm

 

[MN Mike]

Sorry - I screwed up and didn't attached the images.

 

[MN Mike]

I'm now learning about hybrid units that combine secondary-air and cats. Does anyone have experience with these? Do they combine the best of both worlds?

Here's one from Fireplace Xtrordinair, which sounds like it's the same as from Lopi (both owned by Travis)

(broken link removed to http://www.fireplacex.com/productguide/productdetail.aspx?modelsku=99800604#Dimensions)
(broken link removed to http://www.lopistoves.com/product-detail.aspx?model=422#dim-tab)

Here's the Xtrordanair brochure, see page 15
http://www.fireplacex.com/TravisDocs/98800725.pdf

 

[jetsam]

I and starting to think that the benefit of the catalyst units being able to go low and slow for a longer time will not be of value to me.

If you want to take the edge off the heating bill in the winter, maybe not. If you want to heat full time with wood, including in the spring and fall, it's pretty great to be able to dial it down to cruise through a 55° day.

 

[bholler]

If you want to take the edge off the heating bill in the winter, maybe not. If you want to heat full time with wood, including in the spring and fall, it's pretty great to be able to dial it down to cruise through a 55° day.

Many of us heat with noncats full time with no issues at all. And most of us do it without opening windows or any of the other things people claim needs to be done.

 

[tadmaz]

If you're going to consider non-cats as an option (bear in mind, they are not going to burn nearly as low as a similar quality cat stove), the Kuma Sequoia would be on my shortlist. It's 22.5" high, which is 1/4" shorter than the Princess.

You could also tell the wife that since the Princess won't fit, you are going to need to extend the hearth and put in a freestanding stove. That would even give you the option of stepping up to the BK King, which is maybe a better fit for you based on the size of the house. Needs an 8" flue, though.

I'm being a little nitpicky, but the Sequoia IS a cat stove, also requires 8" liner.

 

[jetsam]

Many of us heat with noncats full time with no issues at all. And most of us do it without opening windows or any of the other things people claim needs to be done.

Yeah, but it's a bit disingenuous to suggest that any stove can burn 24/7 through 50-60 degree weather.

You are managing your temperature with smaller fires and letting the fire go out. The stove is not doing that for you.

I'm not saying that anything is wrong with your methods, but it's like saying that a car that only has 4th and 5th gear as just as good because you can just turn it off if you want to go slower.

Whether it's of value to each person to be able to keep a fire going all the way through most of shoulder season is up to them... I think it's super convenient, personally.

 

[jotul8e2]

Yeah, but it's a bit disingenuous to suggest that any stove can burn 24/7 through 50-60 degree weather.

You are managing your temperature with smaller fires and letting the fire go out. The stove is not doing that for you.

If you substitute "40 degree" for "50-60" weather, that is what I do. I'm not sure I could burn a couple of decorative candles without overheating the place at 60 deg. I commonly burn only two loads a day for much of the heating season. And this works pretty well if you have enough insulation to keep the temperatures reasonable (I do) and can accept six or seven degree swings in the temperature. Since we are away most of the day and in bed over night this is not really a problem for us.

However, it is my opinion that the OP's house will lose heat more rapidly than he would like once a tube burn stove comes off its early high output phase and that a higher output but more even heating cat stove would be more satisfactory. The problem with that appears to be that larger capacity cat stoves will not fit the available space. Sometimes you have to do just what you can do.

 

[bholler]

Yeah, but it's a bit disingenuous to suggest that any stove can burn 24/7 through 50-60 degree weather.

When did I ever say that?

 

[jetsam]

I'm being a little nitpicky, but the Sequoia IS a cat stove, also requires 8" liner.

Woop, my bad. That's extra embarrassing because I researched that stove in some depth because I was thinking about buying it.

 

[jetsam]

When did I ever say that?

Many of us heat with noncats full time with no issues at all. And most of us do it without opening windows or any of the other things people claim needs to be done.

Because you understand exactly what the differences are between all these stoves, you see a difference between the statements "we heat fine with noncats" and "cats and noncats can do the same things". A new prospective stove owner is not going to know that. I'm breaking it out for them, not you. I know that you know.

 

[begreen]

Because you understand exactly what the differences are between all these stoves, you see a difference between the statements "we heat fine with noncats" and "cats and noncats can do the same things". A new prospective stove owner is not going to know that. I'm breaking it out for them, not you. I know that you know.

There is a tendency for some cat fanboys to sometimes forgo or forget to mention this fact.

 

[jetsam]

There is a tendency for some cat fanboys to sometimes forgo or forget to mention this fact.

Meh, I grew up in houses that only had smoke dragons and open fireplaces for heat. We did fine. I'm still a cat fanboy, though hopefully not a cat snob.

 

[blueridgerider]

I live in what used to be a barn. I am using a Buck Stove Model 91 (cat stove) as the primary heat for 2700 square feet. I have cathedral ceilings in living room. The floor plan is open for approximately 3/4 of the home. Our bedroom is in the old dairy part of the barn, it is 600 square feet with a bit of a roundabout access. The house is insulated well as I did it myself with the max I could in each area - BUT has lots of windows running floor to ceiling in some rooms. The Buck is in the center of the house and in the fireplace like an insert. 40 degrees and above it heats the whole house with it being in the mid to upper 70's in main portion to mid 60's in our bedroom. Much below 40 and my gas heat in our bedroom (An Empire vented insert rated about 73% efficient kicks in - I lined the fire glass tray of the insert with 1 1/2 inch slabs of Soapstone so it heats long after gas cuts off - can tell it actually changed how much heat it outputs into house).

I used a couple of space heaters when we had the two week arctic front this year (Temps in single digits to -10) in the outlying areas of the house and stayed just as toasty.

I load my stove generally twice to 2 1/2 times a day (once in awhile I will need to throw another couple pieces to top it off for a cold night).