Wittus or xeeos Twinfire

[denjohn]

I've been lurking on this site for quite a while, trying to learn for when the time comes that I get a woodstove.
Some friends are considering a Wittus or xeeos Twinfire woodstove, told them I'd see what folks here had to say about them.
A title search came up w no results.
Anyone have an an opinion about this stove?
Thanks

 

[precaud]

Clean contemporary looks. Some very clever thinking, using modern materials and engineering, at work here. I love it. I want one. Probably expensive, though.

http://www.wittus.com/wpwoodtwinfiremain.htm

This is the sort of design I've been hoping we'd start to see. We used to get this from the big player in the industry. But now they shun innovation and let marketing determine their direction.

It appears to be an updraft that switches into downdraft mode.

Thanks for bringing this to our attention.

 

[precaud]

Here's the catch (from the users manual):

"ALSO NEVER ADD MORE THAN 3-4 POUNDS (1.5-2 KG) OF WOOD (ABOUT 1-2 LOGS). OTHERWISE THE STOVE COULD GET OVERHEATED, WHICH CAN CAUSE IRREPARABLE DAMAGE. THIS KIND OF DAMAGE IS NOT COVERED BY WARRANTY."

So the downside is the small amount of fuel that can be loaded into it per burn cycle: only 3 to 4 pounds. That means this stove can basically take one split at a time, which means you'll be reloading it every hour. This is going to be impractical for most users. And the realistic heat output will be more in the 25k btus/hr range.

I think we might need to wait until their next product release and hopefully they will address this limitation. It IS a very intriguing design, however. I'd love to have one on my hearth...

 

[begreen]

Fascinating stove, that is serious secondary burning. It reminds me of a gasifier boiler which makes me curious if it is noisy. I suspect it is sized appropriately for contemporary European homes and condos with smaller, well-insulated rooms being heated. Wonder how much it goes for?

 

[precaud]

Yes, it's definitely designed for a smaller, well-insulated space. Here in the US, I'd be surprised if it went for less than $4k. Probably $5k and up.

In my opinion, the market for this sort of stove will definitely grow, though slowly. Homes that implement more solar heat sources and maximum energy-efficient construction don't need big round-the-clock burners. They need stoves that fill in the gaps. Functionally, that means stoves that light easily and warm up quickly. The home construction does the heat-holding, not the stove.

Actually, I've been preaching that even for normal homes. Get the thermal mass off of the stove and into the home's thermal envelope.

 

[precaud]

Answer found:
"The Twinfire, a German fireplace, which is 93 percent efficient, the highest in the market, will cost between $5,500 and $9,000, depending on the size and model."

 

[begreen]

Well there ya go, get the big one, and a second mortgage.

 

[precaud]

Guess we'll have to wait for Corie to get the bug and design one we can afford.

 

[begreen]

Hmm, next gen Oakwood? I'm wondering if they tested with a refractory lined lower chamber for even greater efficiency.

 

[precaud]

Is he at Harman now?

The Twinfire lower chamber is vermiculite, you can see it in the pic.

 

[begreen]

Yes, last I heard. I was thinking of eliminating the front glass and the heat loss from it.

 

[precaud]

Perhaps, but the glass is a better insulator than steel. I wouldn't want the secondary visuals covered up on mine. And remember, that is the ash chamber too, so you'd still need access to it...

 

[denjohn]

Thanks for the comebacks.

 

[fjord]

Expensive pretty stoves. You have to love the decor, first.
With the small fireboxes your splits have to be +/- 14" . The Rais stoves are $$$$, small fireboxes, little real BTU's.
The Rais stoves are well into the higher 5 figures.
Morso has similar stoves for much less, with high quality.

 

[vvvv]

4lbs wood @ 8000btu/lb= 32000btu/load & unit can output 41000btu/hr?

 

[precaud]

4lbs wood @ 8000btu/lb= 32000btu/load & unit can output 41000btu/hr?

41k btus/hr is a rate of output, not an absolute output number. It may only do that rate for a few minutes. If the EPA wants to do something useful in upgrading the standards, they could change the ratings so they reflect actual output over a given period of time.

That's why I said, it's more realistically a 25k stove max.

 

[precaud]

Expensive pretty stoves. You have to love the decor, first.

Huh? They're not selling the room - just the stove.

With the small fireboxes your splits have to be +/- 14" .

No biggy - that's what I currently cut for the Quad, 14"-15"

Morso has similar stoves for much less, with high quality.

Similar, in that you put wood in and heat comes out, yeah. Beyond that, they are quite different. Morso doesn't make a downdraft stove, and nothing with 93% efficiency...

 

[vvvv]

4lbs wood @ 8000btu/lb= 32000btu/load & unit can output 41000btu/hr?

41k btus/hr is a rate of output, not an absolute output number. It may only do that rate for a few minutes. If the EPA wants to do something useful in upgrading the standards, they could change the ratings so they reflect actual output over a given period of time.

That's why I said, it's more realistically a 25k stove max.

@ 25k its gonna eat 3lbs/hr. + only 60% of wood energy comes from pyrogas & the rest from the coals. lovely video but i'd like to see full burn to the point where stove is cold again

 

[precaud]

@ 25k its gonna eat 3lbs/hr. + only 60% of wood energy comes from pyrogas & the rest from the coals. lovely video but i'd like to see full burn to the point where stove is cold again

There's nothing unrealistic at all about 3 lbs/hr . Gas and coals contribution are not separate, they overlap. With these batch heaters, who cares what they do after the last flame dies. It's a zone heater used only part of the day. It's a different mindset than a 24-hour burner is accustomed to. I operate that way every day during the burning season. You end up starting alot of fires from scratch. That's why I say, ease of lighting is one of the primary criteria. And these "fireplace" stoves tend to be very easy to get going.

I think it's safe to say, these stoves probably work better with softwoods. That's certainly what they're using in the video.

The one question I have, which is related to your comments, is - how does one deal with coaling in a geometry like this?

 

[vvvv]

@ 25k its gonna eat 3lbs/hr. + only 60% of wood energy comes from pyrogas & the rest from the coals. lovely video but i'd like to see full burn to the point where stove is cold again

There's nothing unrealistic at all about 3 lbs/hr . Gas and coals contribution are not separate, they overlap. With these batch heaters, who cares what they do after the last flame dies. It's a zone heater used only part of the day. It's a different mindset than a 24-hour burner is accustomed to. I operate that way every day during the burning season. You end up starting alot of fires from scratch. That's why I say, ease of lighting is one of the primary criteria. And these "fireplace" stoves tend to be very easy to get going.

I think it's safe to say, these stoves probably work better with softwoods. That's certainly what they're using in the video.

The one question I have, which is related to your comments, is - how does one deal with coaling in a geometry like this?

dunno, thats why i wanna see full burn cycle. i'd guess when adding wood the fire has to be reestablished be4 the downdraft mode is used or otherwise the upper chamber would fill up with gas & go boom?

 

[precaud]

i'd guess when adding wood the fire has to be reestablished be4 the downdraft mode is used or otherwise the upper chamber would fill up with gas & go boom?

yes, that is what the manual says. And it makes sense.

 

[vvvv]

i'd guess when adding wood the fire has to be reestablished be4 the downdraft mode is used or otherwise the upper chamber would fill up with gas & go boom?

yes, that is what the manual says. And it makes sense.

i'd guess that while the fire is establishing, stove is gonna be as efficient as non-epa stove?

 

[precaud]

i'd guess that while the fire is establishing, stove is gonna be as efficient as non-epa stove?

I'd guess more so. That's a really long uninsulated path the exhaust gasses take before they hit the flue outlet...

 

[fjord]

Expensive pretty stoves. You have to love the decor, first.

Huh? They're not selling the room - just the stove.

With the small fireboxes your splits have to be +/- 14" .

No biggy - that's what I currently cut for the Quad, 14"-15"

Morso has similar stoves for much less, with high quality.

Similar, in that you put wood in and heat comes out, yeah. Beyond that, they are quite different. Morso doesn't make a downdraft stove, and nothing with 93% efficiency...

Seeing and feeling the actual stoves in use here ( 3 ), and their extreme cost compared to others, yes, they are "decor" rather than a heater. Some were not EPA rated since they are technically "cook stoves".

As for "93% efficiency" , "I will love you in the morning" and "the check is in the mail" are closer to reality. In the Rais (Wittus) literature: " these stoves burn so clean, there is no ash". "I will love you in the morning". :lol: The most efficient gas furnaces are rated at +90% efficiency at 100% specified maintenance when new. Natural gas and LP have near NO emission particulates, such as any wood species wooood have.

Have you seen the stoves in home use for heating ? They are quite elegant and meld with any modern decor. For most wood burners, a small firebox ,and the need for tiny splits is a negative for any kind of real wood heating. Entertainment fires, romance perhaps. They are pretty decor.

 

[precaud]

fjord, you seem to think that everyone else has the same heating needs that you do.

I own and use a stove every day in the heating season that is much like these stoves. I could care less what "most" woodburners want. It fits my needs, and better than anything else I've used in that space. Apparently it doesn't fit any of yours, so I wonder what is the basis for your interest in this topic, except to lend your unexperienced opinion to it.

If you examine how the Twinfire works, compared to more common stove geometries, you would see that there is good basis for their test results of 93%.