Poplar

[Quirke]

Greetings.

TLDR: How well does a full load of poplar perform in a Princess 32 or King 40?

A year ago we moved into a log house (kit), that's primarily heated with by woodstove, in northeastern Ontario.

The stove is a Jotul F 600 non-catalytic that's rated for 13k-45k BTUs at 63% efficiency. It's fairly centrally located and the chimney is close to 30ft of mostly straight single wall pipe to the thimble in the ceiling - the house has high vaulted ceilings and a steep roof pitch. The exterior pipe is doube-wall stainless steel that's at least 6ft. As you can imagine, the draft is quite strong, but the seals were in reasonably good shape so shutting the damper all the way produced the slow moving, dancing flames of a well functioning secondary burn stove. Unfortunately, even when fully damped down and packed with high quality dry hardwood, the stove was effectively either on or off, and the burn time where appreciable heat was being emitted was about 4 hours. I'd load the stove twice a day (3 during the coldest weeks) and the house would bounce between too hot and too cold. We burned about 8 face cords of hardwood and another 2 of softwood and poplar.

One of my co-workers has a tree cutting side business and heats exclusively with a larger stove. He's been a great source of knowledge and advice about wood, but he has never owned a catalytic stove.

Last year I burned hardwood that was purchased from a local firewood producer and began harvesting from my property for future winters. I very much enjoy cutting, splitting, and burning wood.

My property has a lot of small (under 8") sugar maples and white birch, some large poplars/large tooth aspen (18-22"), and some small softwoods - balsam fir and spruce.

I'd like to prioritize harvesting the poplars as they're nearing end of life, block light to the maples, and yield the most wood. Yes I know that they have noticeably fewer BTUs per cord.

I've burned poplar in the stove, but only during the spring so I don't have a great feel for how it directly compares to hardwood. As I was burning at most once a day in a cold stove with less temperature/pressure gradient for the draft it obviously felt much less potent than hardwood and a lot of efficiency was lost getting the stove up to operating temperature.
I found that the poplar did not like having the damper close all of the way, but I'm not sure if that's due to its lower heat output or the less than optimal burning conditions.

We're building an addition this summer and one of the the changes will be removing the old stove and chimney (which is inaccessible for cleaning without a cherry-picker), and installing a BK in the addition where the chimney piping can be installed such that I can actually access it. I intend to get the King 40 for its large firebox and its long burn times.

Will packing the 40 with poplar give me half a day's heat and allow me to focus on harvesting them from my property? Does it do well with the damper on low, or is it prone to extinguishing, and requires more airflow?

Thanks!

 

[Highbeam]

I have burned many cords of cottonwood. Same genus as poplar and aspen. Some areas have nothing but cottonwood to burn and get along just fine. I found it to burn just fine so long as the splits were relatively large and well seasoned. This wood does make a lot of ash but it's light and fluffy.

The king is about the ideal stove for burning such a low density hardwood. If any stove can do it, the king can. The thermostat will prevent the fire from extinguishing itself by giving it air as needed to maintain combustion. The only question will be whether the chosen stove output rate to get at least a half day's heat is high enough to keep your home warm. These stoves can burn quite cool, long, and clean which is why they are great.

So you can figure out how many BTU will be contained in a full 4.3 cubic foot firebox of a certain species. If you release that stored energy in a set amount of time then you can calculate how much heat is being added to the home during that cycle. Or, just know that the king is the best stove there is for this particular job of longest burns with low btu wood.

I'm currently filling the shed with red alder, another pretty low BTU hardwood. The BK will love it.

 

[Quirke]

I have burned many cords of cottonwood. Same genus as poplar and aspen. Some areas have nothing but cottonwood to burn and get along just fine. I found it to burn just fine so long as the splits were relatively large and well seasoned. This wood does make a lot of ash but it's light and fluffy.

The king is about the ideal stove for burning such a low density hardwood. If any stove can do it, the king can. The thermostat will prevent the fire from extinguishing itself by giving it air as needed to maintain combustion. The only question will be whether the chosen stove output rate to get at least a half day's heat is high enough to keep your home warm. These stoves can burn quite cool, long, and clean which is why they are great.

So you can figure out how many BTU will be contained in a full 4.3 cubic foot firebox of a certain species. If you release that stored energy in a set amount of time then you can calculate how much heat is being added to the home during that cycle. Or, just know that the king is the best stove there is for this particular job of longest burns with low btu wood.

I'm currently filling the shed with red alder, another pretty low BTU hardwood. The BK will love it.

Thanks for the input!

I have run the BTU numbers comparing my current stove's firebox size and efficiency to the King's, and theoretically it should hold more BTUs in poplar than the Jotul holds in hard(er)wood. Add in the fact that the King's efficiency should be easier to achieve due to the catalyst vs secondary burn, and that the Jotul can never be completely packed with wood due to the shape of the firebox, need for airflow, and side door loading, the difference should be significantly in favour of the King.

BUT, I know BTUs per cord don't always tell the full story.
Ex. Red Oak and Sugar Maple have similar BTU/cord, but the Oak burns down to just a few coals in 8 hours whereas the Maple leaves behind a lot of coals in the same time frame. A difference that becomes significant during the coldest days when burning too much Maple results in a bed of coals so thick that it limits how much wood can be added to the stove.

Great to hear that this stove excels with low BTU wood, I was concerned that the low heat density would make it prone to extinguishing itself. I'm very much looking forward to the upgrade.

Thanks again.

 

[Highbeam]

I burned 100% maple (bigleaf I think) this year and next and it does offer more coals and ash than douglas fir softwood. This allows for a slower possible burn if that's what you want. At all burn rates the thermostat does a lot of the thinking for you. Just set it for the desired burn rate and let it work. Unlike your jotul, the BK will automatically open up the intakes as the load is reduced to coals in an effort to maintain the burn rate or close down pretty dang tight to reduce the burn rate and extend the burn plus everything in between.

A full stove of coals indicates an undersized stove. You're asking too much of the appliance.

Note that there is a draft specification for this, well all, stoves. You may have to deal with a damper or two if your stack is very tall.

 

[Quirke]

The thermostat is a big selling point for me given what it does for evening out the heat production and extending burn times. It's high capacity firebox will increase the number of weeks I can comfortably burn the plentiful poplar, and reduce my reliance on big "all nighter" chunks of hardwood that are more scare.

I didn't feel that the Jotul was working hard - once it was up to temperature and all the wood was burning well I'd dampen it all the way down and it would produce plenty of heat, always increasing the temperature in the house. Unfortunately that burn time was limited and it wouldn't release much heat when down to just coals. My thermometer nicely shows the on/off nature of its heat production.

The maple coals weren't obscene, but the firebox was only just tall enough for two layers of "good" sized pieces so when a few inches were lost to coals it made refilling more challenging. When needing three loads per day (-25C to -30C) I'd switch to Oak and the excess coals disappeared. My co-worker made the recommendation when I complained about the coals, without even knowing what I was burning, as he's noticed the same issue.

I've been reading the manual for pipe/draft requirements. The BK will be in the new added space which will have standard ceilings. We don't have final drawings yet so I don't know how the pipe will be situated, but I don't foresee being forced into having too much height and requiring dampers. I want cleaning to be as easy as possible so that I don't risk skimping on that chore.

 

[Tron]

We usually burn pine and I sometimes too have the issue with excessive coals. But turning the thermostat to WOT burns them down pretty fast, obviously not with the same output as with a stove full of wood. We usually don't have that much of a heat requirement, to YMMV.
But I think that a double-walled pipe from the stove all the way up will help you out as well.