Kuma K-180 (Aspen LE) Short Burn Times

[Gravity]

I finally fulfilled my dream of getting a wood stove installed in my house to provide some supplemental heat on our first floor, but have been having issues with short burn times right off the bat.

The details:
- Kuma K-180 LE (Aspen) installed January 2024
- Approximately 24 ft tall chimney in an insulated chase after the first floor
- Blower fan installed usually running on low once the cat temp is in the active region

I think my first fire for paint curing may have been a little large, though the cat probe never went over 1/3 and I had the blower running the whole time. I did have to reload three times over a 4 hour total burn time, but was trying to keep the loads small. I think everything was fine, but with the stove turned all the way down I just wasn't getting the longevity I expected with only about a little over an hour per load of wood.

I burned another fire with a fairly full load the next night, slowly increasing the cat temp over 5 hours again. This time with the stove completely warmed up and air turned down, the cat temp was usually in the 1/2 to 3/4 mark in the "active" region. The 5 hours required two reloads, getting just under 2 hours per reload.

I was feeling a little frustrated and read a few things to try on the forum, so I ran the stove again last night, filling the firebox pretty much completely with three large splits N-S on the bottom, 3 medium sized splits E-W on the top, then my kindling and tinder to kick things off. The top-down fire lit quick, so I closed the door after about 3 minutes. The cat probe read just into the first set of hash marks after 10 minutes, so I closed the cat bypass. After another 5 minutes, the probe was in the active region and I closed the primary air down to ~75%. In another 5 minutes the cat probe was reading at about 1/2, so I closed the air down almost all the way, from there the cat probe read between 1/3 and 1/2 in the active region and I was down to smoldering coals with a couple larger red-hot chunks after a total time of 4.5 hours.

I have attached a picture of the load that I ran before starting and a picture of the fire when I turned the primary air almost the way down around 20 minutes into the burn, but definitely expected way more than 4.5 hours after all the reports of 10 hour burn times I've been seeing. I have no idea why I'm burning so fast, yet still maintaining lower active cat temps for the whole duration. I have no idea what to try next and am just at a loss as to how to get this stove to reach it's full potential. Given the lack of a run away fire (with the air closed down the flames go out, but the logs glow and secondary combustion lights up periodically) I can't imagine it's an air leak. My chimney doesn't seem too tall, and I live at ~7400 ft elevation, so that would mitigate the extra height a bit anyway, but could it be that my draft is too strong?

I could really use some advice from anyone who has it, as I love the stove, I just don't see how to get the burn times people (and Kuma) are reporting. As an aside, Kuma has been absolutely amazing from a customer service perspective, and I can't recommend them enough to anyone in the market for a wood stove.

 

[kennyp2339]

Where in the US are you located? The cris cross method actually speeds burns up since more surface area of wood splits are exposed to the fire.

 

[Gravity]

Located in the Rockies. After seeing someone else's post with a Blaze King crammed full N-S, I figured I'd try something similar. I filled the stove much fuller than I had before with less space between splits, generally larger splits, and just enough room to get the top lit. So far I've been burning for about 5 hours and 20 minutes, so it definitely yielded some results. I expect to get another hour at least on what's left of the logs (a few large charred chunks still lingering).

Still wondering if it's just a matter of filling it with more wood or if I have some other technique issue going on. I am using a mix of hard and soft wood currently, but Kuma told me all of their advertised burn times are based on soft woods. It seems like it's most likely a matter of confidence and skill when loading and starting the stove, but I'm definitely open to any more input.

 

[kennyp2339]

5-7hrs on a 1.9 cu ft firebox is pretty decent, don’t forget you loose space with ash / coal build up. Pack it tight N&S loads and let her rip.

 

[Wisco Shepherd]

I have an Aspen LE. Your burn times sound normal for a cold start as these breathe easily so you won't see your best burn on a cold start when compared to a tight packed reload on a bed of coals (you can definitely pack things tighter than your photo). Burn times in general can be a bit of a misleading term as the definition is a little loose and some companies will claim a few small coals is still considered a burn.

Other things to check would be door gasket, and if you have a tall flue you may want a key damper.

 

[kingofcreosote]

What kind of wood are you burning? What size are the pieces?