Another help me choose add on furnace

[Gbawol42]

I believe most of the big manufacturers where/are trying to milk every last drop out of the old tech before investing in cleaner burning stoves.

This is pretty much what I was thinking, why come out with a new and/or more efficient truck design when the old one is still selling so well.

 

[woodey]

. Looking for some real world people to tell me what they are really getting for burn times.

I am heating my house with the Vapor Fire 100. The house is a 2 story 2700 sq/ft home built in 1866. With temps in the mid 20's I am able to achieve 12 hours between loads without house temps dropping below 68-70* by the end of the burn cycle.Radiant heat from the furnace and ducts also helps keep the chill out of 1200 sq/ft of basement.

 

[Highbeam]

If I was purchasing a wood stove I would most certainly want a window, as it would be almost a piece of furniture in my main living quarters. However a furnace will be in my basement only seen by me most of the time. I don't really see the need for a window, except to see exactly what your fire is doing without opening the door. But it sounds as though Kuuma took this guess work out, so I shouldn't have to worry about what the fire is doing for the most part.

It’s nice to check on fuel remaining with a window too. I’d bet that omitting the window and associated air wash system makes the construction simpler. Less gaskets to fail.

It’s a tough call. I really like to see the fire.

 

[JRHAWK9]

It’s nice to check on fuel remaining with a window too.

I use the computer's display of the damper position tell me that. Now that I added a firebox temp gauge (reading the OEM thermocouple used by the computer) I can also go by that if I wanted to......or the other temps I also monitor.

Waiting to light a fire for the night. BBQ thermometer on top right displays stack and plenum temps, which has a wireless remote unit which I place on the night stand next to the bed so I can glance at it when I roll over in the middle of the night. Top left is the MyPIN which I use just to monitor firebox temps.

I’d bet that omitting the window and associated air wash system makes the construction simpler. Less gaskets to fail.

IIRC, Daryl said they tried a window but they could not keep the burn as clean. I'm guessing it cools things down too much. Just a guess though.

 

[woodey]

It’s a tough call. I really like to see the fire.

It is nice to see the fire, but if its in the basement like mine all you have to do to see the time remaining for burn times is look at the computer, when it turns to 3 you have @ 2hrs of heat left.

 

[Case1030]

It is nice to see the fire, but if its in the basement like mine all you have to do to see the time remaining for burn times is look at the computer, when it turns to 3 you have @ 2hrs of heat left.

Well I got my tundra furnace in the sunroom so the window is a very nice addition.

 

[NoobTube]

I am heating my house with the Vapor Fire 100. The house is a 2 story 2700 sq/ft home built in 1866. With temps in the mid 20's I am able to achieve 12 hours between loads without house temps dropping below 68-70* by the end of the burn cycle.Radiant heat from the furnace and ducts also helps keep the chill out of 1200 sq/ft of basement.

Question,

Do you only have the ducting on the first floor and just let the heat rise to the second?

 

[woodey]

Question,

Do you only have the ducting on the first floor and just let the heat rise to the second?

I have warm air ducts to all the rooms upstairs but leave them shut unless the temps fall well below zero- the only one I leave open is the one to the bathroom.

 

[lampmfg]

Same here didn't realize that ether. I thought the Vapor Fire would have had at least a 10% if not more efficency advantage over the Tundra.

I honestly believe the only way Sbi will come close to meeting the 2020 emissions will be removing the fire picture window and insulating the door to increase firebox temps.

I know this might be off topic for this thread but when it comes to emission standpoint, remember when the new DEF systems first came out... burn more diesel to burn cleaner exhaust.

The Kuuma Vapor-Fire 100 was certified by the EPA test lab to provide a 79% efficiency based on the current test criteria. The current test "only measures" heat produced while the "blower" is running. So any heat generated when the blower isn't running does not get counted. So you can do the math. In real world the VF100 would be generating in the mid to upper 80% efficiency ranges. It is also 2020 certified. It actually tested 40% cleaner than the 2020 phase 2 mandate.

 

[Highbeam]

The Kuuma Vapor-Fire 100 was certified by the EPA test lab to provide a 79% efficiency based on the current test criteria. The current test "only measures" heat produced while the "blower" is running. So any heat generated when the blower isn't running does not get counted. So you can do the math. In real world the VF100 would be generating in the mid to upper 80% efficiency ranges. It is also 2020 certified. It actually tested 40% cleaner than the 2020 phase 2 mandate.

It appears then that the efficiency ratings of wood furnaces can not be compared to the efficiency ratings of woodstoves or fossil fuel furnaces. Similarly, the EPA emissions rating system for wood furnaces uses an incompatible metric instead of the standard GPH.

Is the entire 4.6 cubic feet of the VF100 usable or does that include secondary chamber volume?

 

[JRHAWK9]

Similarly, the EPA emissions rating system for wood furnaces uses an incompatible metric instead of the standard GPH.

Is the entire 4.6 cubic feet of the VF100 usable or does that include secondary chamber volume?

You always seem to bring this up but they do show both:


It also has a 4.1CF firebox, according to the dimensions of the box shown in the owners manual. If IIRC, those dimensions in the manual agree with when I measured mine and it's all fully usable.

 

[Highbeam]

You always seem to bring this up but they do show both:
View attachment 236133

It also has a 4.1CF firebox, according to the dimensions of the box shown in the owners manual. If IIRC, those dimensions in the manual agree with when I measured mine and it's all fully usable.

Thanks JR. I don't recall ever seeing that published anywhere important like on their EPA label or the owner's manual. Imagine me trying to prove that the furnace is under 2.5 gph to some enforcement guy.

Thanks for the firebox verification. There's a lot to like about the VF100.

 

[JRHAWK9]

Thanks JR. I don't recall ever seeing that published anywhere important like on their EPA label or the owner's manual. Imagine me trying to prove that the furnace is under 2.5 gph to some enforcement guy.

Thanks for the firebox verification. There's a lot to like about the VF100.

The GPH actually came right from Intertek's EPA test results, page 8: (broken link removed)

Also on Page 26 of the owners manual. Pretty sure they HAD to add it per EPA requirements: (broken link removed)

The Kuuma Vapor-Fire 100 was certified by the EPA test lab to provide a 79% efficiency based on the current test criteria. The current test "only measures" heat produced while the "blower" is running. So any heat generated when the blower isn't running does not get counted. So you can do the math. In real world the VF100 would be generating in the mid to upper 80% efficiency ranges. It is also 2020 certified. It actually tested 40% cleaner than the 2020 phase 2 mandate.

To be fair though, then all wood furnaces tested using the same method would see higher real world efficiencies.

I believe what you are referring to is stack loss efficiency? I believe this number is the more accurate of the numbers as it takes 100% minus the percentage of BTU's lost up the stack.

Definitely gives wood stoves an advantage on paper when comparing numbers.

 

[Highbeam]

The GPH actually came right from Intertek's EPA test results, page 8: (broken link removed)

Also on Page 26 of the owners manual. Pretty sure they HAD to add it per EPA requirements: (broken link removed)







To be fair though, then all wood furnaces tested using the same method would see higher real world efficiencies.

I believe what you are referring to is stack loss efficiency? I believe this number is the more accurate of the numbers as it takes 100% minus the percentage of BTU's lost up the stack.

Definitely gives wood stoves an advantage on paper when comparing numbers.

I was drooling over the kuuma website and they DO list GPH now! Hot dog.

 

[Gbawol42]

So after reading a lot of your comments and doing my own research I am leaning hard to the VF100. I believe I now see what the extra 3k will get me, and it seems worth it. Also looking at longevity of the appliance, I believe that the Vf100 will last many years more than the tundra, so looking at it in an investment point of view, the VF100 is the way to go.

The biggest selling point is if I tell my wife she has to fill the furnace because I got stuck at work. She should be able to load wood, shut the door, and walk away. That piece of mind is worth a lot to me.

 

[brenndatomu]

I want something that is controlled by a computer ( lambda ) and that is smarter than what I am when it comes to burning the cleanest.

Just a point of clarification...the Kuuma's are not lambda controlled...they just monitor firebox temps.

 

[JRHAWK9]

Just a point of clarification...the Kuuma's are not lambda controlled...they just monitor firebox temps.

by lambda, are they referring to having O2 sensors and having STRIMS and LTRIMS like on OBDII autos in order to get things really dialed in?

 

[brenndatomu]

Yeah, more or less...the air/fuel mixture is monitored and controlled to try to maintain stoichiometric (but I think with wood as a fuel, they might aim for the "excess air" side of stoi)

 

[brenndatomu]

Here is a little reading on lambda
https://www.hearth.com/talk/threads/lambda-controlled-boilers.82410/

 

[sloeffle]

Along with the lambda controlled wood furnace, can I have it feed itself also. Something similar to

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When I hit the lottery, I'll hire a bunch of people smarter than me and we'll build it.

 

[JRHAWK9]

Christmas day we left to go out of town again to go up by family for the holiday. I did a similar thing as last time in that I planned the loads out so that when we are walking out the door to leave the furnace was ready to be loaded (even though I would not have loaded if we were staying home). So I loaded the firebox full, leaving the computer on minimum burn. The whole point was to keep a nice slow and steady burn for as long as I could to keep the LP furnace from running. I didn't care how warm the house got seeing we were not going to be home. I knew it was going to get warm. The cats would enjoy it though.

We are heating ~31,000 CF of air volume (including basement, which is heated by radiant heat only off the Kuuma). No Attic, 12/12 pitch roof, ~25' ceiling at peak with a loft. Not efficient. No outside vapor barrier.


Below is what I calculated the heat loss to be at 70°, definitely not "careful new construction". Closer to the "leaky" side of things. Calculated it from here: https://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm




Anyway, it was a balmy 28-30° the whole time during the burn. I loaded 95.7lbs of black locust (nice and dry with NO bark, as it fell off) into the firebox at 11am on 12/25 with house temp 75°. I have a MyPIN wired into the factory TC now so I can view internal firebox temps and also have an IP camera setup so I can view all vitals remotely via my laptop.

Started monitoring and documenting temps around 10:30pm (11.5 hours after loading) while binge watching Homicide Hunter: Lt. Joe Kenda on ID while laying in bed....which I could not stop watching, hence the data points in the middle of the night. Good thing my other half sleeps good, as I sure didn't get much sleep.

Keep in mind, as a reference, the internal firebox temp at which the computer goes to pilot (when set to minimum burn) is ~1,080°.

- 0 - 11.5 hours. Guessing it spent a lot of time on pilot (while opening to '1' momentarily when needed) keeping firebox temps between 1,100° - 1,200°.
- 11.5 hours into the burn, firebox temps 1,020°, computer on '1' and house temp 77°.
- 12 hours into burn, firebox temps 1,003°, computer on '1' and house temp 77°.
- 13 hours into burn, firebox temps 925°, computer on '1' and house temp 78°
- 14 hours into burn, firebox temps 919°, computer on '1' and house temp 78°
- 15 hours into burn, firebox temps 907°, computer on '2' and house temp 79°, turned off TV and went to bed.
- 19 hours into burn (woke up to pee then went back to sleep), firebox temps 475°, computer on '3' and house temp 78°, blower was still running
- 22 hours into burn (got up), firebox temps 282°, computer on '3' and house temp 77°, blower was off.

When I first calculated out what my theoretical "burn time" should be on low with ~96lbs of wood, I came up with between 19-20 hours. Pretty much what I got. Going off memory here based on past experience, I am guessing blower turned off shortly before I got up when plenum temps reached ~98°......~21-22 hours of blower run time.

We got back home 27 hours after initial load and house temp had already dropped to 71°.....warmed up to 34° outside. The LP furnace never kicked in though so it was a success.

 

[Gbawol42]

Christmas day we left to go out of town again to go up by family for the holiday. I did a similar thing as last time in that I planned the loads out so that when we are walking out the door to leave the furnace was ready to be loaded (even though I would not have loaded if we were staying home). So I loaded the firebox full, leaving the computer on minimum burn. The whole point was to keep a nice slow and steady burn for as long as I could to keep the LP furnace from running. I didn't care how warm the house got seeing we were not going to be home. I knew it was going to get warm. The cats would enjoy it though.

We are heating ~31,000 CF of air volume. No Attic, 12/12 pitch roof, ~25' ceiling at peak with a loft. Not efficient. No outside vapor barrier.
View attachment 236680

Below is what I calculated the heat loss to be at 70°, definitely not "careful new construction". Closer to the "leaky" side of things. Calculated it from here: https://www.builditsolar.com/References/Calculators/HeatLoss/HeatLoss.htm

View attachment 236682


Anyway, it was a balmy 28-30° the whole time during the burn. I loaded 95.7lbs of black locust (nice and dry with NO bark, as it fell off) into the firebox at 11am on 12/25 with house temp 75°. I have a MyPIN wired into the factory TC now so I can view internal firebox temps and also have an IP camera setup so I can view all vitals remotely via my laptop.

Started monitoring and documenting temps around 10:30pm (11.5 hours after loading) while binge watching Homicide Hunter: Lt. Joe Kenda on ID while laying in bed....which I could not stop watching, hence the data points in the middle of the night. Good thing my other half sleeps good, as I sure didn't get much sleep.

Keep in mind, as a reference, the internal firebox temp at which the computer goes to pilot (when set to minimum burn) is ~1,080°.

- 0 - 11.5 hours. Guessing it spent a lot of time on pilot (while opening to '1' momentarily when needed) keeping firebox temps between 1,100° - 1,200°.
- 11.5 hours into the burn, firebox temps 1,020°, computer on '1' and house temp 77°.
- 12 hours into burn, firebox temps 1,003°, computer on '1' and house temp 77°.
- 13 hours into burn, firebox temps 925°, computer on '1' and house temp 78°
- 14 hours into burn, firebox temps 919°, computer on '1' and house temp 78°
- 15 hours into burn, firebox temps 907°, computer on '2' and house temp 79°, turned off TV and went to bed.
- 19 hours into burn (woke up to pee then went back to sleep), firebox temps 475°, computer on '3' and house temp 78°, blower was still running
- 22 hours into burn (got up), firebox temps 282°, computer on '3' and house temp 77°, blower was off.

When I first calculated out what my theoretical "burn time" should be on low with ~96lbs of wood, I came up with between 19-20 hours. Pretty much what I got. Going off memory here based on past experience, I am guessing blower turned off shortly before I got up when plenum temps reached ~98°......~21-22 hours of blower run time.

We got back home 27 hours after initial load and house temp had already dropped to 71°.....warmed up to 34° outside. The LP furnace never kicked in though so it was a success.

Wow I am so surprised that you heat that much space for so long on one load of wood. I am still used to the old wood stove at my parents that if not loaded every 6 hours the house will drop fast in temp.

 

[JRHAWK9]

Wow I am so surprised that you heat that much space for so long on one load of wood. I am still used to the old wood stove at my parents that if not loaded every 6 hours the house will drop fast in temp.

It wasn't very cold out though. When it drops below 0 for longer periods things change in a hurry in this house.

 

[Highbeam]

Wow I am so surprised that you heat that much space for so long on one load of wood. I am still used to the old wood stove at my parents that if not loaded every 6 hours the house will drop fast in temp.

Almost 100# of wood got him 22 hours. Good woodstoves can now run an easy 24+ hours on 50# of fuel if you can live with less output. Your parents old wood stove is not one of the good modern ones. This kuuma is also more advanced than the old furnaces.

When buying a woodstove or wood furnace you have some pretty big choices to make these days.

 

[JRHAWK9]

Good woodstoves can now run an easy 24+ hours on 50# of fuel if you can live with less output.

.....and are willing to deal with the idiosyncrasies of a cat stove. Some people prefer their appliance actually burn the wood completely and not smolder it; only to let the consumable cat deal with the fuel before it exits the flue. Kinda like with women, some guys like temperamental/higher maintenance women and some, well, umm, don't.