Help size my future BK

[ironglen]

Hello Hearth Members! I recently joined the forum after reading dozens of posts since I hope to become a new wood stove owner/user. I hope to obtain guidance on the sizing for my home. I have a nearby friend with a Woodstock Fireview that primarily burns local spruce in his similarly sized home here in South Central CO at 8000' and loves it. Woodstock stoves look terrific but price and shipping make it rather prohibitive. The nearby Kuma dealer said their Aberdeen would not last the night with spruce. I plan to have a straight 6" double wall flue 18-19' high from the stovetop to account for altitude and a 4" PVC fresh air intake routed to the base. I have attached a sketch of my home with natural gas use by month. The heaviest winter heating is between 6 pm to 10 am as we benefit from a little solar heating, except for the few cloudy days here. I would like to avoid cold starts and reload once a day if possible, hence the BK choice. I have a local dealer with less than knowledgeable staff and being my first stove decided to ask the pros!

My thoughts about the models:

20 Chinook + might be correct output - too small firebox for extended burn times with spruce?
BX24 + has the lowest minimum output, mid-size firebox, best ash drawer? , looks - lacking fresh air input? , smaller splits? , damper hook/tool inconvenience?
30 Chinook + larger firebox, looks - too high output?
PE32 Princess + larger firebox, max output, possibly best value at my dealer - too high output?

 

[Highbeam]

24 hours with spruce. Skip the 20 boxes or any of the inserts like the boxer. Go bigger.

I do 24 hour cycles, barely, with Douglas fir which is actually a spruce but a bit denser.

 

[Nealm66]

I’d recommend the princess. Just a great, proven design in my opinion. You just have to look a little further ahead on the weather and plan accordingly. We’ve been blessed with pretty consistent colder weather here since November but I’ve definitely had some episodes of bad planning and opening windows. My princess has no mercy if I don’t see warmer weather ahead of time

 

[ironglen]

24 hours with spruce. Skip the 20 boxes or any of the inserts like the boxer. Go bigger.

I do 24 hour cycles, barely, with Douglas fir which is actually a spruce but a bit denser.

Hello Highbeam, I suspected you would provide that suggestion based on a previous response I read elsewhere. Appearance isn't a big issue, nor size since I'm placing it in the home addition. I'm very concerned about having too much output as this is a huge purchase for us and I have to get it sized right the first time. I should have mentioned that the 200ft2 area was a carport that was enclosed and insulated but has a small 1'x1' opening window that could possibly vent excess heat without affecting the living space, if that would make a difference. A neighbor has the same home minus the 200ft2 enclosed carport area and burns spruce in an old BK Princess circa 1980 which is probably much less efficient: his flue puffs a lot but his home stays warm!

 

[ironglen]

I’d recommend the princess. Just a great, proven design in my opinion. You just have to look a little further ahead on the weather and plan accordingly. We’ve been blessed with pretty consistent colder weather here since November but I’ve definitely had some episodes of bad planning and opening windows. My princess has no mercy if I don’t see warmer weather ahead of time

Hello Nealm66, I was thinking the same thing: proven design should have been a + for it. The PE32 also has a terrific base of knowledge on this forum since it has a strong following. I'll definitely have to plan ahead as we can get warm days here in the 40's this time of year after highs in the 20's. We usually watch the forecast since we go outside every day and the NOAA forecast is usually spot-on.

 

[ironglen]

Is there any significant difference between a Chinook 30 and the Princess other than aesthetics? I couldn't check out a Chinook, but the controls appear to be of the same type and location. The local dealer has the Princess in stock with an ultra pedestal, ash box, and blower kit, and is checking the price and availability of a Chinook 30. I'm curious about what price the 30-box comes in at.
The only shortcoming I noted on the pedestal BK models I checked out (Princess, Sirocco 20) was the ash box didn't slide smoothly since it doesn't have ball-bearing rails: is that something that could be safely modified? The tray really didn't rest on any rails of any kind that I could tell

 

[Ashful]

So, you're a numbers guy. Let's talk numbers:

My 2.8'ish cubic foot Ashford 30's hold about 80 lb. of red oak. Extrapolate that to 2805/3570 = 63 lb. of your Doug Fir.

Doug fir runs 17.4M BTU per 2805 lb. cord, so you're looking at about 391k BTU per load by weight calculation. Double-checking this by volumetric calculation, we get 17.4M BTU * 2.8 cu.ft. / 128 cu.ft. = 381k BTU per load. Let's call it an average 386k BTU.

The Ashford 30 can rip thru a load as quick as 4-6 hours for most of us, or stretch it as long as 30 hours. This gives you a BTU/hr range of 13k - 77k BTU/hour, time-averaged over the full load. This will always be warmer in the first 2 hours and less in the last hour or two, but the giant capacitor that is your house helps to level that curve.

Scale all of these weight and max burn time numbers by 2/3 for BK20, or by 4/3 for a BK40 (King), to get their available ranges. Bottom end is probably similar for all, top end will vary more with size.

 

[Jedi]

So, you're a numbers guy. Let's talk numbers:

My 2.8'ish cubic foot Ashford 30's hold about 80 lb. of red oak. Extrapolate that to 2805/3570 = 63 lb. of your Doug Fir.

Doug fir runs 17.4M BTU per 2805 lb. cord, so you're looking at about 391k BTU per load by weight calculation. Double-checking this by volumetric calculation, we get 17.4M BTU * 2.8 cu.ft. / 128 cu.ft. = 381k BTU per load. Let's call it an average 386k BTU.

The Ashford 30 can rip thru a load as quick as 4-6 hours for most of us, or stretch it as long as 30 hours. This gives you a BTU/hr range of 13k - 77k BTU/hour, time-averaged over the full load. This will always be warmer in the first 2 hours and less in the last hour or two, but the giant capacitor that is your house helps to level that curve.

Scale all of these weight and max burn time numbers by 2/3 for BK20, or by 4/3 for a BK40 (King), to get their available ranges. Bottom end is probably similar for all, top end will vary more with size.

Don't you have to multiply that final BTU average by the stove's efficiency rating?

 

[Ashful]

Don't you have to multiply that final BTU average by the stove's efficiency rating?

Yes. Sorry for the omission. Was doing this in the background while working on something else, and got distracted.

 

[Nealm66]

I hear a lot of guys like the looks of the chinook better. I prefer the princess. It’s purpose built and to me it looks more classic. I also hardly ever read anyone having problems with the princess.

 

[Ashful]

Excepting the very small inserts, you really can't go wrong with any of them. I think the Princess and King are ugly, so I went Ashford, because I like the classic looks. But if I didn't have to look at it, and heating was my only goal, I'd surely own a King (or two).

I asked before @BKVP, why not an Ashford 40?

 

[BKVP]

The reason provided by many Princess owners for their choice is the deeper firebox, translating to less frequent cleaning out of ashes. I have the King and I can tell you the deeper firebox is also safer when bashing coals or raking them forward to burn them down.

The ash drawer modification on the Princess is not something you'd want to tackle. The Chinook does have the ball=bearing slide ash drawer, but you may only empty the Princess once or twice a month if burning softwoods. Also, the Princess ash drawer volume is more than enough to get most accumulated ashes out in a single load.

AS for the Ashford 40, not on the near horizon....sorry @Ashful.

 

[Highbeam]

The reason provided by many Princess owners for their choice is the deeper firebox, translating to less frequent cleaning out of ashes.

you may only empty the Princess once or twice a month if burning softwoods. Also, the Princess ash drawer volume is more than enough to get most accumulated ashes out in a single load.

AS for the Ashford 40, not on the near horizon....sorry @Ashful.

The deeper firebox meaning the amount of firebox below the bottom of the loading door, or the belly of the stove. It's a great 6" on the princess and adds a lot of value to operation.

Burning softwoods is almost ashless. I haven't emptied ashes at all this year yet. The ash bed is only about 1" thick after just under half of the burn season by burning 100% seasoned doug fir. 1/2" per cord or so. It's almost problematic not having enough ash since it takes about a half inch of ash before the stove behaves really well.

I do use the ash pan on the princess and I've never missed having ball bearing slides. It's not a heavy ash pan and slides out just fine.

 

[ironglen]

Thanks for the terrific responses. Still waiting for the dealer pricing for the Chinook 30 to help make a decision. I don't understand why it takes over 24 hrs to obtain a price quote from a product line they have displayed. I'm not in retail but it has to result in some lost sales.
I have a couple more questions for all the experienced members.
Is there a notable difference in loading the fireboxes N-S, other than the difference in depth?
Regardless of choice, the front face and vent pipe will be the most noticeable since the stove will be installed flush with the nearby wall 10-11" to make the clearance spec. I would like to reduce that clearance if at all possible, but I do not see any listed reduction in the manual as I have for other manufacturers for reduced rear clearance. Could I install a custom metal heat shield an inch from the end wall to reduce clearance? If that is allowed and I can figure out a decent-looking design, I would do so. I have metal-working tools to cut, weld, etc. I've seen rear-clearance reductions using a free-floating heat shield of metal but would think a 'C' profile would provide the same protective effect in this instance using the design below.

 

[ironglen]

Yes. Sorry for the omission. Was doing this in the background while working on something else, and got distracted.

Quite alright! A full firebox of 386000 BTU/.75 esti. efficiency = 289500 BTU output
289000/24 hrs = 12063 BTU/hr
289000/12 hrs = 24125 BTU/hr
289500/8 hrs =36188 BTU/hr

Looks like a Chinook 30 or Princess run primarily on low or low/med would work as that output seems to match up well with my NG furnace that provides 26k BTU on 1st stage and 38k on 2nd stage and is slightly oversized for 99% design temperature, with the 2nd stage running almost consistently only on the coldest hour of the coldest day of the year. Is there a term for that? Perhaps Poindexter has one?

The furnace rarely heats from noon to 6 pm on our common winter sunny day reaching a high in the 30s F, which is the time period I'm most concerned about having too much heat with a constant 12k BTU output. Would loading smaller loads of spruce both morning and evening be the easiest and most compatible output for heating requirements rather than attempting 24 reloads? I guess opening a window or two for a few daytime hours is an option to prevent overheating if needed, it just seems wasteful.

 

[moresnow]

Quite alright! A full firebox of 386000 BTU/.75 esti. efficiency = 289500 BTU output
289000/24 hrs = 12063 BTU/hr
289000/12 hrs = 24125 BTU/hr
289500/8 hrs =36188 BTU/hr

Looks like a Chinook 30 or Princess run primarily on low or low/med would work as that output seems to match up well with my NG furnace that provides 26k BTU on 1st stage and 38k on 2nd stage and is slightly oversized for 99% design temperature, with the 2nd stage running almost consistently only on the coldest hour of the coldest day of the year. Is there a term for that? Perhaps Poindexter has one?

The furnace rarely heats from noon to 6 pm on our common winter sunny day reaching a high in the 30s F, which is the time period I'm most concerned about having too much heat with a constant 12k BTU output. Would loading smaller loads of spruce both morning and evening be the easiest and most compatible output for heating requirements rather than attempting 24 reloads? I guess opening a window or two for a few daytime hours is an option to prevent overheating if needed, it just seems wasteful.

Guessing your NG furnace is a forced air unit that delivers warm air throughout your home with ductwork? If so, that is different than heat dispersing from one location as a freestanding woodstove functions. Food for thought when comparing btu requirements.

 

[ironglen]

Guessing your NG furnace is a forced air unit that delivers warm air throughout your home with ductwork? If so, that is different than heat dispersing from one location as a freestanding woodstove functions. Food for thought when comparing btu requirements.

Yes, I'm not sure how it will compare, but the forced air installation was deficient in distribution, along with uninsulated ducts in the crawlspace that I'll have to address to a greater extent. The living room and dining areas are underheated, the kitchen and utility areas are severely underheated, and the bathroom is overheated along with the bedrooms. Having a warmer living room and kitchen will be appreciated along with cooler bedrooms. I'll add electric floor heating in the upcoming bath remodel.

 

[Highbeam]

The furnace rarely heats from noon to 6 pm on our common winter sunny day reaching a high in the 30s F, which is the time period I'm most concerned about having too much heat with a constant 12k BTU output. Would loading smaller loads of spruce both morning and evening be the easiest and most compatible output for heating requirements rather than attempting 24 reloads? I guess opening a window or two for a few daytime hours is an option to prevent overheating if needed, it just seems wasteful.

What I do is one large load in the evening, after 6pm, to match up with the coldest period of the day. That load lasts overnight and most of the way to 6 pm the next day. Dwindling near the end which aligns with your lower heating needs.

The other plus of a single large load after dark is that nobody sees my startup smoke. It's pretty embarrassing. Large loads on low are the most efficient and lowest emissions way to burn a BK cat stove.

During really cold times, I will chuck a few extra logs in the stove in the morning and sometimes run at a slightly higher output setting.

You'll just need to see how much heat you need and then formulate a loading schedule to match it. You really can't do much better for getting furnace like temperature control with wood heat than by using a BK.

The non princess 30 box is a tiny bit smaller, a tiny bit less efficient, a tiny bit more polluting, and has a very shallow ash belly but they look a lot better. I'm not sure why BK didn't just make a princess look better instead of inventing a whole new stove.

 

[ironglen]

What I do is one large load in the evening, after 6pm, to match up with the coldest period of the day. That load lasts overnight and most of the way to 6 pm the next day. Dwindling near the end which aligns with your lower heating needs.

The other plus of a single large load after dark is that nobody sees my startup smoke. It's pretty embarrassing. Large loads on low are the most efficient and lowest emissions way to burn a BK cat stove.

During really cold times, I will chuck a few extra logs in the stove in the morning and sometimes run at a slightly higher output setting.

You'll just need to see how much heat you need and then formulate a loading schedule to match it. You really can't do much better for getting furnace like temperature control with wood heat than by using a BK.

The non princess 30 box is a tiny bit smaller, a tiny bit less efficient, a tiny bit more polluting, and has a very shallow ash belly but they look a lot better. I'm not sure why BK didn't just make a princess look better instead of inventing a whole new stove.

Your schedule appears to mimic what I believe will be my heating needs, albeit with smaller loads. This will likely be the only clean stove in the hood: I almost called the fire dept when I first moved here and small huge plumes of smoke rising over rooftops.

It looks like a 30 box or princess will work well. I heard back from the dealer and the earliest availability would be May/June for a Chinook 30 and no price could be given. Guess prices will be going up for 2023! I won't install everything for some time, but should probably purchase a princess they have in stock at 2022 pricing sooner than later.

If I'm essentially resorting to 2x/day loads morning and evening, wouldn't my stove options increase to include other brands/models such as a Hearthstone, Woodstock, or other cat or hybrid stove? Or will they not last 12 hr+ with my spruce choice? I think a friend does that with his (small) Woodstock Fireview in a similar home. He mentioned easy access to the catalyst: will it need checking/cleaning that frequently to matter much?

 

[Highbeam]

Why would you load twice a day? Will one load in the evening not carry you through until the next evening?

If you choose to load twice a day then yes, some Woodstock stoves are well known to be capable of 12 hour reload times with eastern hardwoods but I haven’t read of experiences with spruce. The fireview is one of their larger stoves and is very ornate. The IS is another high performance Woodstock that looks different but is larger for more burn time.

Another “local” brand to consider is the kuma out of Idaho. High efficiency but none are terribly large. Close to fireview in size.

Cat access is not a problem for any of these stoves. Some other brands make it much harder.

 

[Poindexter]

9 million BTU for the 31 day month of January is a half cord of spruce. Doable in a size 30 box. 9 million/ 31 days ~290,322 BTU per day, ~ 12K BTU per hour.

On the one hand I can see @ironglen might be nervous about a Princess 12.5-37.7 K BTU/ hr, as it might be too much output on low.

On the other hand, the 30 boxes may look like a better fit, with a range for the Ashford at 11.9 -35K BTU/hr; and an identical BTU range for the Chinook. I hadn't poked around on the BK website in a while.

Kudo's for the OP for having done homework and come up with both utility data and a floor plan, that is awesome. I think it is also an indicator his learning curve as a new burner should be short and sweet.

No one has yet admonished the OP to get his wood split and stacked mui pronto. 60M BTU is about three cords of spruce that needs to be split, stacked off the ground and top covered before Saint Patrick's Day. Ideally, for planned ongoing 24 hour repetitive burns, I like fuel at 15-16% MC.

Fuel at 20% MC, I find, needs to be baked down to 0% MC with the combustor engaged and the throttle on wide open for a full 30 minutes before gradual reduction to cruise. Down around 13-15% I can engage the combustor, run on wide open throttle for 15-20 minutes and then chop to cruise throttle setting in one step. YMMV.

When I look at Oct and May I see about 3.5 M BTU/ month, divided by 31 days and 24 hours ~5K BTU hour, neither the 30 or princess box can turn down that low.

The Boxer 24 (sentimental favorite for me, I left fingerprints on serial #2 at my local BK dealer) range is 9.5 to 30K BTU/Hr. The Chinook 20.2 is listed at 11.3 to 28.3K BTU/ HR. Neither of these can turn down far enough to meet OP's heating needs in shoulder season in continuous operation, but trying to run a half cord of spruce through either in January is going to be a pain in the neck because of the small fireboxes.

So there is the dilemma. If OPs air sealing is as good as his insulation this could easily be a 5 or possibly even a 6 star house on energy efficiency.

Dinner is ready. I shall ruminate and be back directly.

 

[ironglen]

Why would you load twice a day? Will one load in the evening not carry you through until the next evening?

If you choose to load twice a day then yes, some Woodstock stoves are well known to be capable of 12 hour reload times with eastern hardwoods but I haven’t read of experiences with spruce. The fireview is one of their larger stoves and is very ornate. The IS is another high performance Woodstock that looks different but is larger for more burn time.

Another “local” brand to consider is the kuma out of Idaho. High efficiency but none are terribly large. Close to fireview in size.

Cat access is not a problem for any of these stoves. Some other brands make it much harder.

I was thinking that higher output would be needed in the evening/overnight and a bump in the morning that would require additional fuel, but I guess an adjustment of the thermostat can account for the morning temperature increase. I was also thinking smaller loads overall would be needed to obtain the lowest output in the middle of the day, such as today when the furnace didn't run between 1 pm and 5 pm.

I spoke to a local Kuma dealer that said they won't provide heat overnight with the local spruce fuel and said locals use firebricks for 8 hr overnight burns. A friend says he loads spruce in his Fireview twice daily as his only heat source for his similar small home.

 

[Nealm66]

I still would just get the princess. Highbeams got his down to a science and it will probably take you a bit but I suspect you will as well. You can always run it hotter like a regular stove or just let it simmer and take up the slack of what you’re currently using. Like Highbeam said, you could stoke it full and then just a partial. Having the ability to turn the stove down is way better than one that’s going to burn a full load in 12 hours or less.

 

[ironglen]

I still would just get the princess. Highbeams got his down to a science and it will probably take you a bit but I suspect you will as well. You can always run it hotter like a regular stove or just let it simmer and take up the slack of what you’re currently using. Like Highbeam said, you could stoke it full and then just a partial. Having the ability to turn the stove down is way better than one that’s going to burn a full load in 12 hours or less.

The idea of filling a stove and allowing it to provide simmering heat is so appealing, but I can't help being nervous that the lower, steady heat will still be too much when accumulated during our ~300-day/year sunny afternoon hours (I'm fairly confident we have more, we only have ~15" rain and 50" snow/year). Even now at 9 pm and 18F, my furnace just ran for 15 minutes out of the last hour. That will increase dramatically as the night goes on, but my point is it's a really small home.

If I could count on utility service, NG pricing, technology (my furnace board has a bad gas valve relay I'm limping on with no parts available), and didn't live near the Rio Grande Forest (my neighbor delivers firewood), I wouldn't be considering a wood stove. Perhaps I should just plan to burn a decent load in a smaller BK, or possibly be looking at smaller, shorter (8-12 hr) burn-time stoves to burn overnight with a morning load when temps necessitate?

Kudo's for the OP for having done homework and come up with both utility data and a floor plan, that is awesome. I think it is also an indicator his learning curve as a new burner should be short and sweet.

No one has yet admonished the OP to get his wood split and stacked mui pronto. 60M BTU is about three cords of spruce that needs to be split, stacked off the ground and top covered before Saint Patrick's Day. Ideally, for planned ongoing 24 hour repetitive burns, I like fuel at 15-16% MC.

Thanks for the compliment Poindexter, my friend told me the 3-4 cords of standing dead spruce he gets in the spring are ready for his cat stove in the fall and my firewood biz neighbor gets his stock off the ground and sells it for the fall. I will have to check the moisture content for myself. What I'm wondering is if a metal covering over only the top of the stack will suffice. I have yet to see a neighbor with protected firewood, but they probably use non-cat stoves. It's so dry here that the snow evaporated in the shade behind my home but the pavers are frozen together and to the ground.

 

[Highbeam]

The fireview is a great stove. It’s really small though, measures less than 2 cubic feet with a weird shape that you can’t stuff as well as a princess. Anything a fireview can do, a princess can do for longer.

Good cat stoves use the firebox as a fuel tank and give the operator a wide range of burn rates to choose from. BK and Woodstock give a pretty wide range, kuma apparently not so much.