Kuuma VF100 hummin' along in sub-zero weather

[JRHAWK9]

We are having a bit of a cold snap here and I recently did some tweaks to my cold air setup. I think I'm getting things figured out for my situation.

Our house is a log cabin style house with a walk-out half exposed basement (see attached photo). It's a typical log cabin, very high ceilings in main area with a loft and then two individual rooms and bathroom underneath the loft area. It has no attic and only has whatever insulation which will fit in between the ~1' of space in the roof trusses. I don't feel it's very well insulated at all, as back when we used LP for our sole heat we'd use 1,300-1,500 gallons a year. We have very noticeable cold spots in a few areas in a couple rooms. To the point where there will literally be some FROST built up on the interior wall corners in those areas when it gets real cold out. The south end also has lots of glass area and two patio doors (see photo). Some windows are drafty and the front closet is not insulated (sucks pulling out a cold coat to put on in winter). It has footprint of 32'x42'. So figure 30'x40' inside. The basement is heated by the radiant heat off the Kuuma. So we are heating a 1,200sf half exposed walk-out basement, 1,200sf main area and the air space of at least another 800sf including the loft and above the main area, as the loft area has 15'+ tall ceiling. So we are probably heating an equivalent air space of a typical ~3,200sf house.

Anyway, I loaded Friday night around the typical 10pm. I waited until there were hardly any coals left as the house was plenty warm and I didn't want a lot of off-gassing, I just wanted a nice slow, low heat burn Friday night. I left the computer on low. Temps were going to start to drop Sat during the day. I re-loaded Sat morning at 10am (12 hours after the Friday night load). It was 72° in the house and 15° outside. Sat at 5:30pm I did a partial load. It was 6° outside, 77° in the house, 76° in the downstairs furnace area and 72° in the rest of the basement. It got much warmer than I thought it would. I then loaded for Sat night at 10:50pm. It was -4° outside, 76° in the house, 76° in the furnace area and 71° in the rest of the basement. I got up Sunday morning. It was -10° outside (with a -39° windchill), it was 69° in the main part of the house and 71° in the area of where the individual rooms are, 72° in the furnace area and 68° in the rest of the basement. It's now 1:30pm and it's currently -2° with -20 windchill and it's 70° in the main house, 71° in the individual bedroom area, 72° in the furnace area and 68° in the rest of the basement. It's supposed to be even colder tonight than last night.

Even letting the Kuuma eat as much as it possibly can, I'm still getting 8+ hours out of my 4cf firebox, heating a so-so insulated A-frame in sub-zero temps. The blower (on high speed and low limit currently set at 110°) never stops blowing, even towards the end of the burn, thanks to my cold air tweaks.

edit: Sunday night at 7pm. Been below zero all day with double digit negative wind chills. Currently it's -6° with a wind chill of -19°. It's 70° in the main house, 71° in the individual bedroom area, 73° in the furnace area and 68° in the rest of the basement.

 

[garmford]

Jr, always fun to read your posts! Being that we live less than a few hours apart, it's easier to compare my outcome to yours since we are dealing with nearly the same outside temperatures. The only difference is the homes that we are heating.
My house is 12 years old, built by yours truly, 2300 sq' ranch with 9' walls with some tray and cathedral ceilings. The basement is 13 coarse block walls that are equivalent to 9'. I figure the basement to be nearly 21000 cubic feet they stays mildly warm due to the radiant heat from the Kuuma. The main floor is probably pushing 22000 cubic feet if you would add the cathedral and tray ceilings. That being said, this is what my experience has been like during this weekends cold snap.
The house was 70* Saturday morning at 5:30 in the morning. I just kept small fires going all day with the computer on high. At one point I saw 78* inside the house near dinner time. I purposely tried to get the house hot knowing that Saturday into Sunday, the outside temperature was going to crash into the negatives. I loaded the furnace around 10:30 Saturday night before the end of the Packer game. It was 75* in the house at that time. I woke up around 5 Sunday morning and the house was 70*. I loaded the furnace with a smaller load so I would be able to load it again by 10:30 when we had to leave for my sons basketball games. Them temperature in the house continued to fall during the morning hours. Once it hit 67* my lp furnace had to kick in for a short while. The blower has been on high since sometime early Sunday morning when the house cooled to about 70*.
I loaded the furnace heavy right at 10:30 before we left. The house came back up to 68* by that time. We got home at 5:30 and it was up to 69*, I loaded a small load again and it's up to 70* and now at 8:30. I have -5 outside right now.
We'll see how it fares tomorrow. Like you said it's supposed to be even colder and I won't be able to babysit it all day like on Saturday.
I do want to clarify, you do not need to babysit a Kuuma!! When it's ready to be loaded, you rake the ash into the ash pan, rake the hot coals to the front, fill with wood, close the door,and walk away. No need to return until the wood is gone. 4-12 hours later depending on the amount of wood you put in and the setting on the computer. No need to go back 15 minutes later to open this or close that! Set and forget it!

 

[JRHAWK9]

very cool!! It is nice to compare similar climates. After reading your volume I had to go compute mine....lol We are at about 30,000 cf. total Kinda shows you how poorly insulated this place is.

We are currently at -7°. Edit, just dropped to -8°.

 

[JRHAWK9]

Loading it for the night. House is 70°, furnace area 73° and rest of basement 68°.

I have the LP furnace set to kick on at 67°. My guess it will end up running a cycle or two in the morning before I get up. We'll see. I usually re-load between 7 - 7:30am

 

[garmford]

I just loaded mine as well. 69* in the house. -6 outside. We'll see what it looks like tomorrow morning at 4.

 

[STIHLY DAN]

That's some serious BTU's you to are using. What type of wood is getting turned into heat?

 

[dogwood]

Great looking house you've got there JRHAWK9. Looks well built in spite of being cold in spots. I don't know much about log built homes, but I thought the logs themselves had a significant R-value. Is that not so? Is it air infiltration between the logs causing cold spots?

 

[garmford]

Well it did drop down to 67* in the house. I know I heard the lp furnace kick on at least once. That's where I have the thermostat set to anyway. -9 outside right now.
Mixed hardwoods. Elm, ash, oak, etc.

 

[JRHAWK9]

That's some serious BTU's you two are using. What type of wood is getting turned into heat?

Tell me about it. Mostly, if not all, red oak.

Great looking house you've got there JRHAWK9. Looks well built in spite of being cold in spots. I don't know much about log built homes, but I thought the logs themselves had a significant R-value. Is that not so? Is it air infiltration between the logs causing cold spots?

Thanks, it's actually just a "log sided" sided house. It's a normal A-frame with just log "slivers" for siding. It was built by my GF and her ex-husband and friends back in 2000. They started out great, as the basement has those styofoam lined poured walls, where the foam acts as the form. It has TGI trusses spaced 12" apart. She admitted they were in a hurry getting towards the end I think insulation was the last thing they were concerned with :-(. I am pretty sure they never even put a vapor barrier (Tyvek) on before siding it. There are a handful of areas on walls which are ice cold. Almost all the windows and both patio doors you can feel cold air. Couple all that with the inherit A frame design which are terribly inefficient to begin with. Think about it, 1,300-1,500 gallons of LP a year to heat just 1,200SF (the basement was not heated back then and would be ~55° all winter. I contacted a place to insulate the roof area better, but one has to rip the roof and all sheeting off in order to do so and we just had a new metal rood put on. The house seems to heat fine when the temps are above 10° or so. When it drops below that is when it's like someone leaves a window open based on the BTU requirement.

Well it did drop down to 67* in the house. I know I heard the lp furnace kick on at least once. That's where I have the thermostat set to anyway. -9 outside right now.
Mixed hardwoods. Elm, ash, oak, etc.

I got up at 6:15am, almost 9 hours after loading the night before. The Kuuma blower was still going on high with plenty of coals, plenum temp was 98° I believe. It was -11° outside at 6:15am. The house was also 67°. The furnace had run for only 12 minutes (according to my minute counter) and had just shut off when I got down stairs. So it ran for one 12 minute cycle at about 6am, as it too is set at 67°. The furnace room was 68° and the rest of the basement was 65°. I raked the coals forward and kicked the LP back on to run while I took a shower and ate. Both furnaces were running for about 50 minutes while I got ready. I loaded the Kuuma and shut off the LP and the house was still at 67° when I left at 7:15am when the outside temp was -10°.

garmford, out of curiosity, what was your yearly fossil fuel consumption before heating with wood? I used our records from 2005-2009 to average our LP consumption, which was about 1,300 gal per year with a max of 1,550 gal in 2008.

I have the feeling when I get home I'll probably have to kick the LP on and run both for an hour or two in order to get some BTU's built back up in the house. With how much the basement cooled off overnight, this extended cold streak will make it tough for the ole' wood furnace to recover the house temp during the day when it's not supposed to get much warmer than 0°.

Temps are closing schools this morning...........lol You'd think living in WI we'd know how to deal with this weather I'm about center on the photo, at -28° wind chill this morning.



(broken link removed to http://www.channel3000.com/news/Bitterly-cold-temperatures-close-schools/37491838)

 

[garmford]

Got home today at 3:30. 67* in the house which I fugured it would be. I last loaded the stove at 4:30 this morning. I loaded it heavy and turned the computer to a few notches below high and I still came home to a nice bed of coals. So I reloaded it for a good four hour burn so I can reload it again before bed and cranked up the lp to get the house up to 70* quick, then I'll let the Kuuma maintain for the rest of the night!

 

[JRHAWK9]

I got home about 4:30, 1° outside. It was 68° in the house, 70° in the furnace area and 66° in the rest of the basement. To my surprise the LP furnace did NOT run at all! Like you I re-loaded for a 5 hour burn. I too kicked the LP furnace on for an hour and let both furnaces bring it up to 70°....lol Seeing I have a 75K LP furnace, it uses pretty much a gallon for every hour it runs. So it cost me $2 today.

 

[JRHAWK9]

It was -12° this morning here and was already -8° when we went to bed at 9:30pm. Today looks to be the last day for these colder temps though before we get back to normal.

As far as the heating. Pretty much identical to yesterday morning.

 

[STIHLY DAN]

Thats running great. When I purchased mine, all I wanted was at 0* outside temps an 8 hr burn. Anything more was a bonus. Soooooo much better than dealing with the wood stove.

 

[JRHAWK9]

Thats running great. When I purchased mine, all I wanted was at 0* outside temps an 8 hr burn. Anything more was a bonus. Soooooo much better than dealing with the wood stove.

yeah, I think things are pretty much in place now. It takes a good cold snap to get things dialed in. The biggest issue is this house, and it irritates me knowing how much heat I am wasting. Anything below 10° and I swear I have someone opening windows on me....lol
My parents have a much larger house up in Green Bay, but it's tight and well insulated. They only have a 60,000 BTU NG furnace. I compared our BTU useage to theirs going off of past bills and this Kuuma would completely heat them out of their home if need be.

The thing I find awesome, is I can run this thing balls out and still see 8-9 hour burn times on a full load. Nothing would irritate me more than having to get up at 2-3am to load a furnace. Well that having to monitor and adjust things in order to guess at achieving optimum burn. All I have to do is turn a single knob ;-)

 

[Highbeam]

Like you said it's supposed to be even colder and I won't be able to babysit it all day like on Saturday.
I do want to clarify, you do not need to babysit a Kuuma!!

I admit, that's the first thing I thought of when I read your words about babysitting. I thought, what? these things are supposed to run themselves.

 

[garmford]

I wondered if I would catch anybody's attention with that comment! Lol
I do chuckle when I read the other Tundra post, those fellas have to set timers and alarms so they can get back to the furnace to set this and adjust that. I'd be ready to climb Mount Everest after a winter of burning with having to go up and down the stairs 20 times a day.

 

[3fordasho]

I wondered if I would catch anybody's attention with that comment! Lol
I do chuckle when I read the other Tundra post, those fellas have to set timers and alarms so they can get back to the furnace to set this and adjust that. I'd be ready to climb Mount Everest after a winter of burning with having to go up and down the stairs 20 times a day.

Nah, the purpose of the alarms and timers is so you don't have to babysit. The timer sets the air inlet open time to char a new load of wood on reload or cold start, the alarms (really temp control) close or open the air inlet based on flue temp. Actually the timer isn't really necessary - the flue temp control can care of that too. The only adjustment is deciding how much wood to throw in the thing based upon outside conditions.

Morning reload routine is - remove one scoop of ash if necessary, rake coals to front, load wood, shut door, set timer to 15-30mns depending on coal bed, go to work. The timer is nice because it allows the furnace to get hotter for quicker secondary burn action. The temp control will do the same thing but will take a bit longer and more cycling of the air inlet.

Way easier and quicker than operating either my Woodstock PH or Englander NC30.

 

[brenndatomu]

Nah, the purpose of the alarms and timers is so you don't have to babysit.

Yup, load n go with the timer and controller on it. I agree, wouldn't hafta have the timer, tsat works too, but having the timer is handy and works well...only $10

 

[garmford]

There is definitely a science to all of our furnaces!!

 

[STIHLY DAN]

Put a little wood in at 5 oclock to get me to 10 oclock for the overnight load. Its 11:15 and still waiting for it to burn down. May have to give it pre-mature wood cause I got to get up early.

 

[JRHAWK9]

Put a little wood in at 5 oclock to get me to 10 oclock for the overnight load. Its 11:15 and still waiting for it to burn down. May have to give it pre-mature wood cause I got to get up early.

pull the coals forward, draft up and crack the ashpan door