Uh oh...what's this?!

[Highbeam]

What's the deal with you folks only loading 30-50# loads of wood in this furnace? It's 4.1 or maybe 4.6 CF right? Heck, I load 45# of low density softwood into my 2.8 cubic foot firebox every time. Is it because of that silly metal curtain thing that hangs down blocking half of the loading door? Does that thing prevent a full fill of the firebox?

 

[maple1]

What's the deal with you folks only loading 30-50# loads of wood in this furnace? It's 4.1 or maybe 4.6 CF right? Heck, I load 45# of low density softwood into my 2.8 cubic foot firebox every time. Is it because of that silly metal curtain thing that hangs down blocking half of the loading door? Does that thing prevent a full fill of the firebox?

I'm not one of these furnace folks, but I'm guessing it is all about timing.

Say if you load it right up with wood in the afternoon, and you want to load again on the way to bed, you might open the door to half a load of fire. So instead, you only load in the afternoon enough to get you to bedtime so you are loading on coals.

 

[JRHAWK9]

What's the deal with you folks only loading 30-50# loads of wood in this furnace? It's 4.1 or maybe 4.6 CF right? Heck, I load 45# of low density softwood into my 2.8 cubic foot firebox every time. Is it because of that silly metal curtain thing that hangs down blocking half of the loading door? Does that thing prevent a full fill of the firebox?

When you don't need 10+ hours of heat at 10-15,000 BTU's/hr. I've loaded 10-15lbs numerous times in the shoulder season just to give a little boost.

 

[JRHAWK9]

I'm not one of these furnace folks, but I'm guessing it is all about timing.

Say if you load it right up with wood in the afternoon, and you want to load again on the way to bed, you might open the door to half a load of fire. So instead, you only load in the afternoon enough to get you to bedtime so you are loading on coals.

that too, if the outside temps are cold enough.

 

[brenndatomu]

What's the deal with you folks only loading 30-50# loads of wood in this furnace? It's 4.1 or maybe 4.6 CF right? Heck, I load 45# of low density softwood into my 2.8 cubic foot firebox every time. Is it because of that silly metal curtain thing that hangs down blocking half of the loading door? Does that thing prevent a full fill of the firebox?

I burn 99.9% hardwood...a full load is waaaaaaaayyy overkill in all but the coldest temps...you apparently don't run your stove like most people do...because that is just about the only control you have to set the house temp where you want it, vary load size. Yeah you can change the air setting, but you can only go so low on modern stoves so load size means more often times.
Yes, on the Kuuma the computer can be changed to vary burn time, but low only goes so low...it is still gonna give the fire enough air to be at xxxx degrees (and burn clean) so you still need to load for the weather. @JRHAWK9 got me started checking the weight of a load...and I have to agree, its handy. I found that I often misjudge how much wood I am putting in, weight wise.
And no, the "silly metal curtain" doesn't prevent a full load...but it does help prevent even more smoke in the house, especially when loading on lots of hot coals.

 

[maple1]

The smoke curtain on my old POS didn't prevent a full load - but it most times made it more difficult.

 

[brenndatomu]

The smoke curtain on my old POS didn't prevent a full load - but it most times made it more difficult.

Yeah, I will agree that it doesn't make a full load any easier...

 

[sloeffle]

@brenndatomu or @JRHAWK9

You guys are always talking about setting the computer on your Lamborghini's ( Kuuma ) to low, medium or high. Can you explain what these settings mean to us Chevy and Toyota drivers ?

 

[brenndatomu]

@brenndatomu or @JRHAWK9

You guys are always talking about setting the computer on your Lamborghini's ( Kuuma ) to low, medium or high. Can you explain what these settings mean to us Chevy and Toyota drivers ?

It just adjusts the rate of the burn...basically what the computer is looking for as far as the firebox temperature.
Lamppa says that the burn rate is as such...
Low = 3-4 lbs per hr
Medium = 5-7 lbs per hour
High = 8-9 lbs per hour

Obviously this is just a general guide, as what type of wood (and how dry it is) you are burning, and what your chimney draft (baro) is set at can and will affect how much wood you are really burning in an hours time.
Also, it doesn't just have "low, medium, high", it has a dial, so it is infinitely adjustable to anything in between L/M/H too...

 

[TCaldwell]

I’ll take a schmedium please

 

[Highbeam]

I burn 99.9% hardwood...a full load is waaaaaaaayyy overkill in all but the coldest temps...you apparently don't run your stove like most people do...because that is just about the only control you have to set the house temp where you want it, vary load size. Yeah you can change the air setting, but you can only go so low on modern stoves so load size means more often times.
Yes, on the Kuuma the computer can be changed to vary burn time, but low only goes so low...it is still gonna give the fire enough air to be at xxxx degrees (and burn clean) so you still need to load for the weather. @JRHAWK9 got me started checking the weight of a load...and I have to agree, its handy. I found that I often misjudge how much wood I am putting in, weight wise.
And no, the "silly metal curtain" doesn't prevent a full load...but it does help prevent even more smoke in the house, especially when loading on lots of hot coals.

My particular modern woodstove is a lot like your kuuma. Costs a bit more to than the rest but offers performance unlike the rest. The blaze King stoves have a mechanical thermostat that holds stove output at a constant rate for the whole burn just like the kuuma. We’re talking 30 hours from 2.8 cubic feet and over 80% efficiency. The firebox is just a fuel tank, more wood means a longer burn but not a hotter burn.

I would have expected the kuuma to work the same way. After all 15000 btu is very low output. Your house in the cold north should lose it faster than that. So it follows that max fill just gets you max burn time.

The short loads make more sense in terms of scheduling but you can always just top it off can’t you?

Why is smoke leaking? Does that silly metal door blocker swing in, out, or both ways and how can it not limit how high you stack wood in there?

 

[woodey]

You can also extend your burn times in milder temps ( per manual) by switching off the computer when the 3 appears on the screen and let the remaining coals burn via pilot mode- I just did that as it is 55 degrees warmer here now than It was yesterday AM.

 

[brenndatomu]

You can also extend your burn times in milder temps ( per manual) by switching off the computer when when the 3 appears on the screen and let the remaining coals burn via pilot mode- I just did that as it is 55 degrees warmer here now than It was yesterday AM.

Yes! Just what I told Mr Hawk last winter...on warmer days, shut 'er off, low heat for an extra few hours...he has finally come around to my way of thinking this winter...

 

[brenndatomu]

The short loads make more sense in terms of scheduling but you can always just top it off can’t you?

Not really...loading on an "already in process" burn can result in the firebox "going nuclear"
I did it the other day and got away with it...but only because the fire was 2/3 done, and I loaded 3 LARGE splits (10# each)

Why is smoke leaking? Does that silly metal door blocker swing in, out, or both ways and how can it not limit how high you stack wood in there?

It just does sometimes...every furnace I've ever had does it...all the stoves too, at least sometimes.
The flapper thing is about even with the top of the usable part of the firebox when folded in flat, so it really doesn't stop a full load.

 

[woodey]

Does that silly metal door blocker swing in, out, or both ways and how can it not limit how high you stack wood in there?

The silly metal door (flap) only swings in and does not impede the ability to put on a full load if you have shorter splits (16-17") for the top tier.

 

[Highbeam]

Not really...loading on an "already in process" burn can result in the firebox "going nuclear"
I did it the other day and got away with it...but only because the fire was 2/3 done, and I loaded 3 LARGE splits (10# each)

It just does sometimes...every furnace I've ever had does it...all the stoves too, at least sometimes.
The flapper thing is about even with the top of the usable part of the firebox when folded in flat, so it really doesn't stop a full load.

Oh so you just shove the flap in and it ends up laying on top of full fuel load? I can see that working since there is no airwash for the window.

Is there not a “roof” inside like a regular tundra style firebox?

There are very few firebox photos of the kuuma on the inter webs.

 

[brenndatomu]

Oh so you just shove the flap in and it ends up laying on top of full fuel load? I can see that working since there is no airwash for the window.

Yeah...that or you can use shorter splits like woodey said...or do some creative stacking...which is not practical at all.

Is there not a “roof” inside like a regular tundra style firebox?

There is in the back.

There are very few firebox photos of the kuuma on the inter webs.

Right...I personally think its because the firebox design is part of their "secret sauce" and most Kuuma owners respect Lamppa Mfg enough to not make it even easier for "monkey see, monkey do" to happen...

 

[Highbeam]

Yeah...that or you can use shorter splits like woodey said...or do some creative stacking...which is not practical at all.

There is in the back.

Right...I personally think its because the firebox design is part of their "secret sauce" and most Kuuma owners respect Lamppa Mfg enough to not make it even easier for "monkey see, monkey do" to happen...

Got it. It’s an extremely expensive furnace and you can’t go look at one in person so pictures on the net are all we have.

Independent of low emissions, the control system of the kuuma also makes it a better furnace.

 

[brenndatomu]

It’s an extremely expensive furnace

I wouldn't say extremely...but yeah, not cheap...and I would bet that with what has happened with steel prices in recent times, they will not get any cheaper either. I'm grateful to have found this one at a price we could manage. (and got to meet some pretty cool people in the process...including @DoubleB and family...thanks again guys! )
FYI, you can wrap up almost as much into a Caddy, with some options...or even more easily, the Max Caddy!
Now if you want to get into stuff that is extremely expensive...start pricing out the better boilers...and then add up everything for a full install...now that, is extremely expensive!

 

[Highbeam]

I wouldn't say extremely...but yeah, not cheap...and I would bet that with what has happened with steel prices in recent times, they will not get any cheaper either. I'm grateful to have found this one at a price we could manage. (and got to meet some pretty cool people in the process...including @DoubleB and family...thanks again guys! )
FYI, you can wrap up almost as much into a Caddy, with some options...or even more easily, the Max Caddy!
Now if you want to get into stuff that is extremely expensive...start pricing out the better boilers...and then add up everything for a full install...now that, is extremely expensive!

The boilers and systems, all of them, are insanely expensive which is why my underslab tubes are dry. Even “simple” pellet boilers are very high.

 

[maple1]

The boilers and systems, all of them, are insanely expensive which is why my underslab tubes are dry. Even “simple” pellet boilers are very high.

I think a decent working boiler system could be put together for a pretty reasonable price.

It wouldn't likely include a new gasifier though. (Although there are some nice new leftover ones out there now at good pricing). And would be very heavy on the DIY aspect. Storage is the biggest game changer with a boiler - throw that together with a non-gasser that has tubes (there are good used ones out there) or otherwise decent HX ability & you're off.

 

[JRHAWK9]

My particular modern woodstove is a lot like your kuuma. Costs a bit more to than the rest but offers performance unlike the rest. The blaze King stoves have a mechanical thermostat that holds stove output at a constant rate for the whole burn just like the kuuma. We’re talking 30 hours from 2.8 cubic feet and over 80% efficiency. The firebox is just a fuel tank, more wood means a longer burn but not a hotter burn.

I would have expected the kuuma to work the same way. After all 15000 btu is very low output. Your house in the cold north should lose it faster than that. So it follows that max fill just gets you max burn time.

One very important piece you are missing though. Yours has a cat. You are able to smolder a fire and let the cat deal with the fuel before it exits the stove. The Kuuma doesn't have a cat, so it must actually burn the wood completely so it never reaches the point of smoldering.

Yes! Just what I told Mr Hawk last winter...on warmer days, shut 'er off, low heat for an extra few hours...he has finally come around to my way of thinking this winter...

I'm a little slow sometimes. Back when we were discussing this our weather was not such which would allow me to do this and not knowing what your weather was I was just assuming similar situations. We were after two different outcomes in two different situations. This spring is when I saw the light though. Like I said, a bit slow.

@brenndatomu or @JRHAWK9

You guys are always talking about setting the computer on your Lamborghini's ( Kuuma ) to low, medium or high. Can you explain what these settings mean to us Chevy and Toyota drivers ?

What Bren said, it just controls the level of burn. The higher to you turn the knob, the higher the BTU output per hour and faster the wood burns.

 

[Highbeam]

One very important piece you are missing though. Yours has a cat. You are able to smolder a fire and let the cat deal with the fuel before it exits the stove. The Kuuma doesn't have a cat, so it must actually burn the wood completely so it never reaches the point of smoldering.

What Bren said, it just controls the level of burn. The higher to you turn the knob, the higher the BTU output per hour and faster the wood burns.

No, not missing it at all and the cat makes zero difference. The only benefit of a cat is that I can choose a very low burn rate for really long burn times. The kuuma has a narrower range of output levels to choose from but works exactly the same way. This is a good thing. One of the best things about the BK stove is that thermostat which is what only the kuuma furnace has. After living with a thermostatically controlled woodstove I can't imagine why all furnaces are not similarly equipped.

 

[JRHAWK9]

No, not missing it at all and the cat makes zero difference. The only benefit of a cat is that I can choose a very low burn rate for really long burn times. The kuuma has a narrower range of output levels to choose from but works exactly the same way. This is a good thing. One of the best things about the BK stove is that thermostat which is what only the kuuma furnace has. After living with a thermostatically controlled woodstove I can't imagine why all furnaces are not similarly equipped.

sorry, I mis-understood what you were trying to get at. Thought you were comparing burn times/efficiencies between the two different sized fireboxes.

my bad, once again, I'm a bit slow.

 

[Highbeam]

sorry, I mis-understood what you were trying to get at. Thought you were comparing burn times/efficiencies between the two different sized fireboxes.

my bad, once again, I'm a bit slow.

They used to make cat furnaces and maybe will again. I don’t think they can do much better on emissions than what kuuma already accomplished, and the extra efficiency is probably not worth the extra cost/work of a catalyst.

Did I read right that “low” setting on a 4.6 kuuma is just 15000 btu per hour? Seems very low.