Recommendations on Furnace

JRHAWK9

Minister of Fire
Jan 8, 2014
1,501
Wisconsin Dells, WI
The option to idle the fire once it's gone to pyrolysis, that I've been campaigning for, I think would help
Some of us, in warmer weather, just turn the computer off when it hits '3' to preserve the coals for loading later. In fact I just got done doing that about 15 minutes ago. However, I personally, would not like it to automatically close the damper when the computer goes to '3' (wood in pyrolysis) without an option to turn that feature off. In real cold weather I need to burn the coals down ASAP in order to re-load.
 

RockyMtnGriz

Member
Apr 19, 2019
87
SW Montana
Some of us, in warmer weather, just turn the computer off when it hits '3' to preserve the coals for loading later. In fact I just got done doing that about 15 minutes ago. However, I personally, would not like it to automatically close the damper when the computer goes to '3' (wood in pyrolysis) without an option to turn that feature off. In real cold weather I need to burn the coals down ASAP in order to re-load.
Yes! Totally agree. In fact it's in my instructions to turn the computer off when it hits 3 to save the fire. With my particular stove, and the pine I mostly have to burn, I find that about 2 1/4 shutoff is about optimal for fire holding. I'd settle for 3 if it was automatic, though.

For example, right now, I'm burning two full loads a day. I've been posting and goofing off, and not watching, but I just passed by the stove and noted that it was getting cold. Draft at 3, a few small coals left, and a bunch of air cooling the stove on the way up the chimney. Checking the data on my Fireboard, I see that I should have shut the computer off about 2 hours ago. The day load went a little quicker than I expected. Had I been paying attention, it would have let me extend the reload time so I have a little more heat and a bigger buffer in the morning, and I wouldn't have had to coax a few small coals back to life in a lukewarm stove to reload. And, a longer, colder restart, I'm sure means more crud in the heat exchanger.

I'm currently pondering if there is some parameter I can set an alert on with the Fireboard that would let me know when, and only when, the fuel load is being exhausted. Most people could maybe use delivered air temp. I'm not sure if fan cycling would screw with that, but in my case, my water heating setup in the plenum definitely would.

So, I just wish I had the option for the draft to close automatically! With softwood, my only wood, the window between the draft going wide open and last call to reload, is only an hour or two on a full load. Small loads are even less. If I turn off the computer at the right time, it goes up to 6 or 8 hours. I'm sure it's completely different if you're burning hardwoods.

And, yes, it has to be optional! When it's 3 or more loads a day, my coals need to go too, and it's cold enough that if I'm home, I can sense the BTU output dropping as coal burning mode kicks in. I just dream of another little switch that says "fire hold mode" or something. I can activate or deactivate it according to my reload plans, or if I might not be home when reload time hits.

Part of what I was getting at (not very clearly) in the earlier reply to another post, is that thermostatic output control might be possible once the fuel load had mostly off-gassed, and entered a primarily pyrolysis phase. Maybe the stove could be put to idle, at least intermittently, if the thermostat wasn't calling for heat, rather than maintaining a near constant output. This would be before the 2-3-out thing starts happening. That would be nice for the cold morning transitioning into a sunny day thing. Basically a lower than "low" setting available to the thermostat, once the fire has burned off most of the nasties. It's pure speculation though, as the CO levels would have to be maintained.

For that matter, something that would do the equivalent of turning the control knob down would be great. Maybe the control goes down a notch for every 15 minutes there's not a call for heat. Maybe inches back up to the manual setpoint if the call for heat doesn't stop or lasts too long.. It'd be great if these parameters were programmable to adapt to different houses or climates. That would at least help in weather where I'm not already burning at about minimum. As it is, I don't use my thermostat, because it doesn't seem to do anything. Most of the time, I leave it max low for slow blower. If it's cold, and I'm burning in the upper settings, and I don't mind the little bit more fan noise, it's max high. High with lower output settings just leads to cycling.

Just fantasizing, though I'm sure I'm not the only one. It'll be interesting to see how much of this stuff gets incorporated into the new furnaces that are coming soon.
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,529
NE Ohio
So, I just wish I had the option for the draft to close automatically!
I've considered doing something along these lines...haven't yet though.
Since we know that the Kuuma's are designed to burn 3-4 lbs per hour on low, 5-7 on medium, and 8-9 lbs on high, you can kinda figure out how long it is going to take to burn a load up to the point of coals (after some experimenting) so if you weigh your load going in, you can set an adjustable timer relay to cut 24V to the computer at the proper time.
It'll be interesting to see how much of this stuff gets incorporated into the new furnaces that are coming soon.
Its already so hard to pass the test that I don't think you'll see much, if any of your wish list incorporated into future models...IMO this last round of limits (2020) was meant to put as many wood stove (furnace) manufacturers out of business as possible...and to a large degree, it has worked.
Checking the data on my Fireboard, I see that I should have shut the computer off about 2 hours ago. The day load went a little quicker than I expected. Had I been paying attention, it would have let me extend the reload time so I have a little more heat and a bigger buffer in the morning, and I wouldn't have had to coax a few small coals back to life in a lukewarm stove to reload
The Maverick ET732 BBQ thermometer that I use to monitor things has a low and high temp alarm that can be programmed to any temp you wish...that could be used to alert you to go shut things off too.
thermostatic output control might be possible once the fuel load had mostly off-gassed, and entered a primarily pyrolysis phase.
From talking with Daryl about this one time, IIRC, after the firebox is up to operating temp, it goes pyrolysis phase first, (computer mostly on 1) then burning of the cellulose (computer mostly on 2) then the coals burn down (computer on 3)
 
Last edited:

JRHAWK9

Minister of Fire
Jan 8, 2014
1,501
Wisconsin Dells, WI
From talking with Daryl about this one time, IIRC, after the firebox is up to operating temp, it goes pyrolysis phase first, (computer mostly on 1) then burning of the cellulose (computer mostly on 2) then the coals burn down (computer on 3)
I guess I was incorrectly assuming the pyrolysis state was the coal state. ;em
 
  • Like
Reactions: brenndatomu

brenndatomu

Minister of Fire
Aug 21, 2013
5,529
NE Ohio
I guess I was incorrectly assuming the pyrolysis state was the coal state. ;em
Yeah, I guess you did start this, didn't you!? ;lol ;)
 

JRHAWK9

Minister of Fire
Jan 8, 2014
1,501
Wisconsin Dells, WI
Yeah, I guess you did start this, didn't you!? ;lol ;)
It appears I did. Below is what threw me off, as I assumed he was referring to closing the damper full time after going on '3'......so '3' = pyrolysis. I should have looked into it before opening my cake hole. ;lol

The option to idle the fire once it's gone to pyrolysis, that I've been campaigning for, I think would help,
 

RockyMtnGriz

Member
Apr 19, 2019
87
SW Montana
Yeah, hey, I'm guilty of being sloppy with my terminology. I probably should have used the term "pyrolyzed", or perhaps better, "well charred". Firefighters (at least some older ones) will use the term pyrolysis to describe a fire that has exhausted most of it's gaseous abilities, where the fire dies back from the raging combustion of gasses, to where the fire is limited to burning on the surface of the fuel, and this I believe is not technically correct, what they really mean is the fire is burning pyrolyzed fuel, but when somebody says it, we know what they mean. I drifted there, and I'm sorry.

Brenndatomu and JRHAWK9 - Thanks again for your help when I was setting this thing up a year and a half ago!

Brenndatomu - It's the right way, but I'm trying to stay away from the weighing thing, though I may get there. I just don't need anything else in my small furnace room. Plus with softwood, the firebox is a little small for the house I'm heating. I'm often selecting from a range of wood pieces to puzzle stack that thing FULL. I'd have to build a mock-up of the firebox to pre-stack it, with allowance for that load's coal height, or have a wood rack on a scale, and use the difference when I load it. But there's often a piece that I thought would fit, but won't quite let the smoke flap close, so I have to wrangle that back out. Pieces that have been in the firebox are required to self-quarantine in a metal can until they go back, so I would need a way to weigh those separately.... Complicated.

When you're weighing, how much of a factor is moisture content? I experimented with placing a "dry" split to toast in the warmth in front of my furnace for a few days, and was surprised to see that it lost more than a quarter of a pound over a few days. IIRC it was about an 8 lb split.