Kuuma VF 100 burn time

woodey

Burning Hunk
Feb 8, 2018
176
ST. Lawrence Valley N.Y.
Love this furnace, I loaded the furnace about 3/4 full last night at 11:00 temps in the mid 20's ( Stacking the pieces as tight as I could) and as of this posting the house is still 69 with outside temps at 36. While the temps are not extreme it's quite impressive to me considering I am heating a large mid 1860's Victorian with 9ft. ceilings. Heading down now to load on a nice bed of coals.
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,823
NE Ohio
I've not completely packed mine clear full yet...on its 3rd season here now...and I have never had to run it on anything above medium, and that has historically been only for a day or 2 in January or February, whenever we get our short blast of "real winter" here in NEO.
I generally load twice per day, 3 times per is reserved for colder weather...I'd say my average is about 50 lbs of wood per day (maybe just a bit more) that's heating just shy of 2000 sq ft, plus the 1200 sq ft basement stays about 68-70*. This is a brick cape cod built in 1940 with average insulation levels, although I have been working on beefing that up some, mainly due to the upstairs being so much warmer than the rest of the house in the summer.

Since you started this thread, if you don't mind @woodey , I was thinking of starting a similar thread and asking the same question, and in addition, how much and how often most people load, and how much area is being heated.
Also, how many people always try to load on a nice pile of hot coals, as is recommended, or do you just get a fire going, load it up and call it good?
 
Last edited:

docsj125

Member
Dec 25, 2016
15
Wolcott Ct
I load mine twice a day. Around 7am when I leave home and between 7-9pm when I return. Never weighed the load but usually fill as much to the top as I can.
Heating a 1500 sqft ranch Between 70 - 75deg depending on outside temp.
It keeps the basement around 68-70 deg. also.
Love this thing ,to do but load it up.
I try to clean it last week but there was about a cup of ash.
I burn about 1 1/2 cord of wood so far.
 
  • Like
Reactions: woodey

brenndatomu

Minister of Fire
Aug 21, 2013
5,823
NE Ohio

JRHAWK9

Minister of Fire
Jan 8, 2014
1,549
Wisconsin Dells, WI
Since you started this thread, if you don't mind @woodey , I was thinking of starting a similar thread and asking the same question, and in addition, how much and how often most people load, and how much area is being heated.
Also, how many people always try to load on a nice pile of hot coals, as is recommended, or do you just get a fire going, load it up and call it good
Or you could just run with this thread...? :)
 
  • Like
Reactions: brenndatomu

brenndatomu

Minister of Fire
Aug 21, 2013
5,823
NE Ohio
  • Like
Reactions: woodey

JRHAWK9

Minister of Fire
Jan 8, 2014
1,549
Wisconsin Dells, WI
I know, for me, it seems as my wood supply gets older it's almost like I'm finding it easier to heat the house. I'm burning 5-6 year old red oak mostly right now. As time goes by that wood I burn will be getting older though, up to about 10-12 years old. I just need to stop putting up more wood than I burn every year.

Also for me, burn times and if I load on coals or not and on how many coals I load on depends on the outside temps and what the inside temp is. Burn times are hard to quantify though, as they can vary by a couple hours depending on what state of coals one loads on.....or even more if you happen to find a few buried embers in which one can do a matchless relight with and include that time as "burn time". I don't have any issues loading a 40-45lb load at night and still having plenty of coals to load on 10.5 hours later in order to just load and go. The blower still running. 40-45 lbs is probably about 2/3rds full. I can do about 60-65lbs of good red oak in a full firebox. Now in colder weather I will be loading sooner on more coals or loading more wood the night before. I have done as long as a 21.5 hour "burn time" on almost 100lbs of Black locust in the past.


I think most of you already know what I'm heating. It's not very efficient and I lose a bunch of heat out the peak....which I have posted photos of in the past. In real cold weather there will also be some frost buildup on some corners in a couple rooms. Before I was in the picture, she kept the house at 68° all the time and averaged 1,300 gallons of LP a year from 2005 through 2009 (max of 1,500 gallons in 2008). This was NOT heating the basement. ~125 gallons of that went to the water heater and dryer a year (based on my records), using an average of 1,175 gallons of LP in a 92% efficient LP furnace equates to about using 4.9 cord of red oak in an 82% efficient wood furnace. Over the past 5 years since I've had the Kuuma and kept records, I have burned an average of 4.5 cords a year. House is kept between 70° and 74° and the basement IS heated by way of radiant off the Kuuma. So I'm heating more area to a warmer temp.


As far as usage this winter so far:

October: 705 HDD's, 0.28 cord, averaged 33.5 lbs wood used per day
November: 755 HDD's, 0.34 cord, averaged 41.2 lbs wood used per day
December: 1,262 HDD's, 0.72 cord, averaged 85.2 lbs wood used per day

I'm using 3,650 lbs/cord for red oak. I'm in the process of checking this, and of right now I used 0.67 cord by way of physically measuring the row. This same row came out to be 0.62 cord by way of weight....159 lbs short. I have another 1 3/4 cords to go though, so we'll see where I am at once it all gets burned. A couple years I checked it and 3,650 was pretty much right on. I'm guessing I'm going to have to lower it some now due to how old the wood is with less moisture in it. I'd think by now it has reached equilibrium state though and will just fluctuate from here on out based on weather conditions.
 
Last edited:

JRHAWK9

Minister of Fire
Jan 8, 2014
1,549
Wisconsin Dells, WI
Here's this morning's 25lb load. I loaded on a coffee -CUP- amount of coals. I loaded the 25lbs at 9am (11+ hours after the previous night's 44lb load). The blower shut off at 3:40ish. Over 6.5 hours.

Red is flue temp, blue is supply temp. Spike in supply temp at around 9am is when I shut the blower off to reload, bump up at around 3:40pm is when the blower shut off on it's own.

Outside temp this morning at 9am re-load was 18° & cloudy. House was 72°.
Outside temp when blower shut off at 3:40pm was 21° & cloudy. House was up to 76° at that time. I knew I shouldn't have reloaded, but I was heading outside for a couple hours and figured I'd take advantage of the coals that were there.

House is now 72°-73° (depends on which one I look at) at a little after 5pm and 19° outside. Will be relighting once house temp drops a bit more or when we start to feel chilled.

1609721030701.png


1609721089482.png
 
Last edited:
  • Like
Reactions: Indianawood

brenndatomu

Minister of Fire
Aug 21, 2013
5,823
NE Ohio
Here's this morning's 25lb load. I loaded on a coffee -CUP- amount of coals. I loaded the 25lbs at 9am (11+ hours after the previous night's 44lb load). The blower shut off at 3:40ish. Over 6.5 hours.
About the same here...25 lbs (~1/3 full?) loaded on minimal coals, house temp went from 69 to 72.5 and the blower ran 10 hours + (speed controlled)
Has been about 35* ish outside day and night here recently.
Just reloaded, house at 69.7, again on minimal coals, 25 lbs...I'm sure the blower will still be running, and the house will be somewhere 70-71 when I reload at 6:30 am.
I normally don't let the house drop below 70, but with the mild weather we have been having so far for most of this winter, the house still doesn't feel cold at all, so meh...
 
Last edited:

JRHAWK9

Minister of Fire
Jan 8, 2014
1,549
Wisconsin Dells, WI
About the same here...25 lbs loaded on minimal coals, house temp went from 69 to 72.5 and the blower ran 10 hours + (speed controlled)
Has been about 35* ish outside day and night here recently.
Just reloaded, house at 69.7, again on minimal coals, 25 lbs...I'm sure the blower will still be running, and the house will be somewhere 70-71 when I reload at 6:30 am.
I normally don't let the house drop below 70, but with the mild weather we have been having so far for most of this winter, the house still doesn't feel cold at all, so meh...
You are cheating by cutting power to the computer soon after it goes to '3'. :p This will make a difference in extending blower run time. It decreases BTU output/hour, but it also extends it's runtime for more efficient handling of the coals. I should really be taking advantage of that too more than I do. If I am down there at that time and think of it, I will turn the computer off. I just don't make it a point nor do I have it setup to do it automatically like you do.

I just relit at 8:30 and loaded 15lbs before I load for the night. House is 71°. It's 19° outside. Probably going to load 40lbs for the night load.
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,823
NE Ohio
You are cheating by cutting power to the computer soon after it goes to '3'.
'tis true...and it works great (for this house) in this milder weather we've had. Once cold weather hits (if it does :rolleyes:) then its back to factory settings...in the meantime, this new setup is saving me lots of matches, and some time. ::-)
 

brenndatomu

Minister of Fire
Aug 21, 2013
5,823
NE Ohio
I'm sure the blower will still be running, and the house will be somewhere 70-71 when I reload at 6:30 am.
Exactly as predicted...34* out, 70.3 inside, blower running...loaded another 25 ish lbs...looks like its gonna be about 35* all week here...blah.
 
  • Like
Reactions: JRHAWK9

JRHAWK9

Minister of Fire
Jan 8, 2014
1,549
Wisconsin Dells, WI
Exactly as predicted...34* out, 70.3 inside, blower running...loaded another 25 ish lbs...looks like its gonna be about 35* all week here...blah.
You are doing good if you can get away with those small loads w/o doing daily re-lights. I know I definitely can't do that while leaving the computer turned on 24/7.

I'm also waiting on winter to arrive. According to the average lows, we should be getting into the single digits consistently at night....the forecast is not even close to that.
 

woodey

Burning Hunk
Feb 8, 2018
176
ST. Lawrence Valley N.Y.
I am heating a circa 1865 Victorian , 2700 sq ft and 1200 sq ft of basement .The house is built on a slight grade with 2 doors exiting from the basement at ground level leaving about 1/3 of the basement above grade. The basement is warmed by radiant heat from the furnace and ducts. Insulating the rim joists is on my list of things to do. I let the coals do their thing and don't reload until about a shovel full of coals are left unless the outside temps are extremely cold. Both the Kuuma and a new propane unit were installed in the fall of 2016. With my set up the warm air ducts exit from the Kuuma with a 12x18 X22" duct run between the 2 plenums along with a damper. My cold air return for both units is fed by ducting from the first floor of the home with another damper just outside of the cold air return bonnet of the Kuuma. The thermostats for both units are wired into a relay switch at the Kuuma (both high and low) with the propane wired as the main furnace which allows it to kick in and disable the blower on the wood furnace ( if I am not home in time to load the wood on before the temp on the propane hits desired set temp), usually set at67. I don't weigh my wood but I am pretty good at gauging the amount I need before the next load by the weight of the pieces as I load. I got a good deal this summer on 5 face cord of(16") seasoned wood which is ideal for this milder winter as I am loading these shorter pieces on 3 at a time and saving the longer ones for night and the colder temps sure to arrive. I also shut off the computer at the coaling stage on the milder days. I rarely use the high side of the blower on the wood furnace as I like the more constant heat from the lower.
 
Last edited:

brenndatomu

Minister of Fire
Aug 21, 2013
5,823
NE Ohio
  • Like
Reactions: JRHAWK9

JRHAWK9

Minister of Fire
Jan 8, 2014
1,549
Wisconsin Dells, WI
Just yesterday we removed the wall thermostat that used to be used to control the Kuuma blower from low to high. This means I have a thermostat wire already ran to the Kuuma that is not being used. hmmmmmmmm May wire up a small microswitch so I can turn it off/on from upstairs.
 
  • Like
Reactions: Case1030

JRHAWK9

Minister of Fire
Jan 8, 2014
1,549
Wisconsin Dells, WI
That was easy. Moved a couple wires around at the transformer and put a switch on the other end of the wire. I need to buy a decent switch and wall plate to make it look decent yet, but for now it's just hanging.