# Walltherm Zebru Gasification Fireplace experiences.



## scooby074 (Sep 30, 2012)

I searched the forums for any mention of this company and debated between fireplaces and wood boilers on where to put this, hopefully this is the right place.

Does anyone have any experience with the Walltherm  Zebru gasification FIREPLACES? http://www.wallnoefer.it/cgi/sdcgi....action=&fname=&ebene=005&mkrecno=14&iklasse=1 I saw one today for the first time and am VERY impressed. It's something i"m considering for my next house as a retrofit in my current place would not be cost effective. Hopefully this is within 5 years, so Im doing some very basic planning now.I intend on having infloor heat and incorporating other energy saving techniques like thermal storage and passive solar, maybe even adding a PV or wind system generation system. My already too high power bill can only go up, so planing ways of saving money on my next place is a prudent idea.

The unit is a gasification fireplace which to me is the best of both worlds (fireplace and boiler).I was unaware a product like this even existed until today. When I thought "gasification boiler" i pictured a large, ugly, likely gray unit plugging away locked in the basement or outside, not something like this:







This company also markets solar collectors and can integrate them into a whole house system as well.

Now this unit isnt huge, only 51000 BTU if I remember right, but the fellow I talked to says he heats his house with one (he also has their solar collectors) and only burns 1.5 cord/ year, heating a house approximately the same size as mine, 1700 sqft. I burn almost 8 cord.  The savings in wood alone would go a long way to pay for the unit, let alone the savings in labour.

Cost IIRC was around $6500 for the stove, $800 for the circ pump and i cant remember how much the storage tank was, but overall not too bad. Plus there are some significant rebates from the government to the tune of $3500 on a complete system (I think).

So, bearing in mind that im at the VERY preliminary stages of planning my next place, are the Walltherm units a good investment?


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## Frozen Canuck (Sep 30, 2012)

AFA investment goes your probably the best one to pencil that out. Yes cheaper than many boiler setups for sure. I remember these units from a previous thread. IIRC the only downside mentioned was having to deal with the ash in your living area much like a stove. To be honest these IMO make alot of sense in a newer home that is not a drafty old..........nice appearance, benefit of dhw, the possibility to use this for radiant heating as well. Cant hurt to sit down & run the numbers for your situation. In a well insulated home this is all one would likely need. & yes they look great without breaking the bank.


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## maple1 (Sep 30, 2012)

Depends on the situation. It would also require that all the wood being burned, and all the dirt from cleaning & maintenance, passes through the room it is in. If it fit my space & plans, I'd consider it definitely.


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## velvetfoot (Sep 30, 2012)

Did you look at the length of wood it takes?  I recall it being very short, from what I read, but they might have other models.
I don't recall a thread on it.


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## willyswagon (Sep 30, 2012)

I looked at them very hard for about a year. I just didn't feel in the end that I could make my old house tight enough to make it work. I could never get it to the point that 51000 btu would cut it.

I'm assuming you are dealing with the rep out of Cape Breton.
If so keep in mind that his house is supper effeicent, and he has a large solar system( i think he said $12,000), with a 1000 gal storage tank that was around $3500.
His system works well do to the stratification that can be achieved in the storage system.

It is a great looking unit, and from some of the reviews i've read from Europe, it seems to work well.

It just didn't fit my needs, and like most newer products to Canada, you won't find many people with any experience operating it.

PS It has a very small fire bax


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## velvetfoot (Sep 30, 2012)

I can see how you could use the wood stove aspect to heat the downstairs and use the hydronic heat for upstairs and domestic hot water.


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## scooby074 (Sep 30, 2012)

willyswagon said:


> I looked at them very hard for about a year. I just didn't feel in the end that I could make my old house tight enough to make it work. I could never get it to the point that 51000 btu would cut it.
> 
> I'm assuming you are dealing with the rep out of Cape Breton.
> If so keep in mind that his house is supper effeicent, and he has a large solar system( i think he said $12,000), with a 1000 gal storage tank that was around $3500.
> ...


 
Thanks for the comments guys.

Yes it was the guy from CB, Nice guy, Seemed pretty passionate about alt energy and his product.

I agree, 51000 seems small. In my current place I have an undersized stove.. I'm NEVER making that mistake again . However the the little bit of information I can find on the product seems to indicate that it punches above its weight... One thread I read was about a guy in Ireland, in an old, drafty farmhouse that heated it fine with this unit.  I couldn't find a single mention of the Walltherms here on Hearth. If anyone knows of such a thread, Id be interested.


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## goosegunner (Sep 30, 2012)

I would find out how many lbs of wood the firebox will hold. That would give you an idea of how often it would need attention.

Are you thinking that this would burn continuously or start a few fires a day and burn until out?


gg


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## scooby074 (Sep 30, 2012)

goosegunner said:


> I would find out how many lbs of wood the firebox will hold. That would give you an idea of how often it would need attention.
> 
> Are you thinking that this would burn continuously or start a few fires a day and burn until out?
> 
> ...


 
I dont know how it would work for burns. I think most people load it up and burn  allowing the thremal storage tank to store all the heat from the fire and release it though the day, then refire and repeat the procedure at night.

As to capacity, the firebox holds 25 kg of 13" wood which is supposed to give a burn time of 5 hrs.

Here is about the only video I could find for the unit in English. It describes the operation of the unit.


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## willyswagon (Sep 30, 2012)

As I said in the ealier post, they are very new to NA.
Here are two previous posts.
https://www.hearth.com/talk/threads/did-you-know-this-was-available-here.85844/ 

https://www.hearth.com/talk/threads/indoor-wood-stove-boilers.33239/#post-33239

You won't find much about them on the web, that's why I spent  another $ 1K more to get a gasifier that I knew would handle my needs.


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## scooby074 (Sep 30, 2012)

willyswagon said:


> As I said in the ealier post, they are very new to NA.
> Here are two previous posts.
> https://www.hearth.com/talk/threads/did-you-know-this-was-available-here.85844/
> 
> ...


 
Thanks for the links, especially the first. Neither thread came up when I searched.

I see you installed the Empyre, how do you like it? The North American style gasification units are significantly different than the Euros in capacity! The Empyre is what 125000 BTU and can take a 24" stick. I bet you could put the Walltherm inside it


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## willyswagon (Sep 30, 2012)

Time will tell what it is like in my place. I have talked to a couple of people that have the Empyre and they are happy with them. The long sticks sure make it easy and fast for blocking the wood.

It has only been in for a week, and the weather has been to warm to run it.


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## BoilerMan (Sep 30, 2012)

13" wood? Ouch.  I think it's a cool idea, as you'd have plenty of radiant heat from the glass alone.

Pros: Nice to see the fire, and know when to add more wood, fire in living room

Cons: Fire in living room, ash cleanup, 13" wood in living room etc.

TS


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## willyswagon (Oct 1, 2012)

One thing to remember is that you would need to have a battery back up to run the circ pump if you had a fire going and the power went out.

The boiler only holds 16 litres ( 4.25 USG) of water. This could lead to it over heating very quickly in a power failure as there is not much water there to absorb the heat, possibly causing it to blow of in your living area


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## BoilerMan (Oct 1, 2012)

Man, than is not much water......  and the 13" wood thing.......  Someone have some splainen to do.

TS


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## scooby074 (Oct 2, 2012)

Taylor Sutherland said:


> 13" wood? Ouch. I think it's a cool idea, as you'd have plenty of radiant heat from the glass alone.
> 
> Pros: Nice to see the fire, and know when to add more wood, fire in living room
> 
> ...


 
Yeah 13" wood doesnt sound that great does it. Seems like lots of extra cutting and waste in the form of sawdust.


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## scooby074 (Oct 2, 2012)

willyswagon said:


> One thing to remember is that you would need to have a battery back up to run the circ pump if you had a fire going and the power went out.
> 
> The boiler only holds 16 litres ( 4.25 USG) of water. This could lead to it over heating very quickly in a power failure as there is not much water there to absorb the heat, possibly causing it to blow of in your living area


 

Good point on the circ pump. I hadn't thought of that. Coming home to blow off in the living room would suck


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## PassionForFire&Water (Oct 2, 2012)

Like a lot of stuff from Europe this indoor gasifier comes in a small but powerfull package.
The wood length needs to be max 12 - 13.5" for optimum burn.
The advantage of smaller/shorter wood is that you can cut back on years of drying.
A maximum of 18% Moisture content is crucial, but this is the same for any gasifier I would say.
It burns pine very well. This is the wood availalble in the area where this unit is manufactured.
The unit comes with a standard cupro-nickel cooling loop that handles the potential overheating. Unit comes with a Watts ST30, hooked up to the city water or well system.
The safety valve needs to be discharged to a safe location. This is typicaly not the living room.
We recommend a 120 gallon water storage tank.
Heat distribution of the unit: 36,000 BTU/hr to the water, 15,000 BTU/hr radiant heat into the room.
LK820 is standard availalble or pumpgroup PAW K36E is optional, this to prevent condensation.
3/4" piping will do.
You can use a DC pump of a battery charged by a solar panel. The pressure drop over the heat exchanger is minimal.
6" double wall chimney.
The unit sells very well in Germany, Austria, Switserland, Northern Italy and Japan.
The unit sells good in Canada.
The US will catch up, ... eventually.
More questions, more answers.


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## BoilerMan (Oct 2, 2012)

I do understand that the 13" wood will dry much faster due to the greater endgrain exposure, however...... Has anyone ever tried stacking 12-13" wood?  If it doesn't fall over your better than me.  I usually have about 1/4 cord of ends, uglies, etc that are in that length range and they are hard to stack to any height.

TS


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## PassionForFire&Water (Oct 3, 2012)

I have seen them in a double row, butted against each other, for 3 or 4 layers and then 1 row perpendicular. 5/6 feet high


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## scooby074 (Oct 6, 2012)

Thanks for the information Passion. I take it that your a retailer for Walltherm?

the local rep I talked to recommended the PAW circ pump. He said it was more money, but it had the hot water bypass to improve the life of the boiler. (Sorry, im still not up to speed on boiler technology and why some are better than others)


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## PassionForFire&Water (Oct 7, 2012)

scooby074 said:


> Thanks for the information Passion. I take it that your a retailer for Walltherm?
> 
> the local rep I talked to recommended the PAW circ pump. He said it was more money, but it had the hot water bypass to improve the life of the boiler. (Sorry, im still not up to speed on boiler technology and why some are better than others)


I'm the importer/distributor for the USA.
The PAW K36E pumpgroup is just a more elegant solution to a boiler return water temperature protection valve (like an LK820).
All is included in the package: circulator, bypass, valve .... and price.
The reason why Roland is recomedning this, is because the manufacturer recommends it in europe. But the PAW K36E pumpgroup it is significant less money in Europe.
The PAW is faster in bringing in bringing the boiler water up to temperature but not significantly faster to justify the money.
Key is that you have some sort of boiler return water temperature protection in your system setup to avoid condensation.


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## PassionForFire&Water (Oct 7, 2012)

Soem pictures of the safety cooling loop and PAW pump group.


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## tom dee (Feb 18, 2015)

looks like a lot of stuff to maintenance . valves  pumps etc o rings gaskets .. me thinks many would've issues with this.. copper piping . water heating interests me but I really don't use a lot of hot water.. and with our flailing econ. im away from house a lot more trying to make money/living.. water batterys etc a lot of stuff that's right now costly .. tanks etc 15K system or 3k progress heating house no hot  water .. I can add solar water in Nc pretty inexp.. say 3 grand for nice hot water or 6 ish K water and Pv I install so that's 9K water  pv and progress .. Vs thee 15K


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## gkingsley (Nov 23, 2015)

Just put one in my new house in Canada. Don't have it fully done yet but the initial light went well


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## gkingsley (Nov 23, 2015)

Built a thermal storage tank out of a propane tank


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## velvetfoot (Nov 24, 2015)

Looks like it came right out of a brochure!
I've been intrigued by those units.  You'll have to write of your experience after some time goes by.


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## Karl_northwind (Nov 24, 2015)

BoilerMan said:


> I do understand that the 13" wood will dry much faster due to the greater endgrain exposure, however...... Has anyone ever tried stacking 12-13" wood?  If it doesn't fall over your better than me.  I usually have about 1/4 cord of ends, uglies, etc that are in that length range and they are hard to stack to any height.
> 
> TS


all over germany and austria I saw wood stacks of 1 meter long wood.  I couldn't figure out what they were burning it in (knowing a bit about the euro gassifiers) but found out that they cut and split in 1M lengths, for easy stacking, handling etc, then buck it into 1/2m (19") or 1/3 M (13") lengths for inside storage and burning.


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## dhaslam (Nov 25, 2015)

I have a  Walltherm stove for four years.   It is  quite difficult to  keep the stove burning properly and over the years it has become worse.  I think I have now identified the problem as being the rear flue passages.    The cleaning  brush will go to the bottom but  it doesn't clean them properly.   I have been using wood briquettes which makes it worse  because it leaves a harder coating on the  the sides of the flue passages and one is blocked completely.   The heat output to water is practically  non existent,  the fuel is just smoldering away  without producing  much heat and sometimes the flue gases explode..  I don't know how to  clean it properly  and I may have to  replace it with a more conventional stove.


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## velvetfoot (Nov 25, 2015)

Is there a vacuum involved as well?


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## dhaslam (Nov 25, 2015)

The draught is  generating by preheating the chimney.  The flue gases initially go  straight up the chimney  by setting the bypass lever.   When the  thermometer on the chimney goes to 300C  the  lever is changed to  the gasifying position and in theory the  warm chimney should then draw the flue gases down. to burn in the lower chamber and then up through the  flues at the back.   In practice it doesn't always keep the gas burning  and  also if the lever isn't changed in time the  fire gets hot enough to  burn paint on the flue pipes.


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## velvetfoot (Nov 25, 2015)

I'm sorry.  I meant do you use a vacuum when cleaning?


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## gkingsley (Nov 25, 2015)

What is your boiler return set at? I tryed to cheat and go with a 55 degree C (131F) mixing thermostat but it's too cold as the flue gas is too cold for a proper draft. I played with it with a ir gun to watch the jacket temperature and controlled it by turning the pump on and off. Average of 65-70 degree C seems to work so I've ordered a 70 degree thermostat for the boiler protection. I will see how that works when I get home from work in 2 weeks.


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## huffdawg (Nov 25, 2015)

scooby074 said:


> Good point on the circ pump. I hadn't thought of that. Coming home to blow off in the living room would suck


You would think you could run a discharge pipe off the pressure relief valve to the outdoors.


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## dhaslam (Nov 25, 2015)

The stove came with a faulty thermostat,  it   is 10 degrees out  so  I have to set it at the maximum 70C to  get a  return temperature of 60C.    It is probably part of the problem, another ten degrees might help but  part of the problem is that the flames  don't reach  the bottom of the  flue ways  as they would in a normal stove.


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## gkingsley (Nov 25, 2015)

dhaslam said:


> The stove came with a faulty thermostat,  it   is 10 degrees out  so  I have to set it at the maximum 70C to  get a  return temperature of 60C.    It is probably part of the problem, another ten degrees might help but  part of the problem is that the flames  don't reach  the bottom of the  flue ways  as they would in a normal stove.




How tall is your chimney? What is your flue gas temperature? The manual says that 60 degree return temp is absolute minimum and it also says to run in the 60-70 range. I have a 24 foot 6" chimney but since I put it under my stairs it has to go through two 90's and 18" of horizontal and form my understanding that significantly reduces draught. So running a hotter boiler temp produces a hotter flue gas which provides an adequate draught for my stove. Flue gas is around 145 and it's working good.


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## dhaslam (Nov 25, 2015)

The chimney is not very tall because it is a single storey building.   I extended the chimney  with a pipe on top but it didn't make much difference probably  because the house is in quite a windy position.


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## Aboveandbeyond (Mar 15, 2017)

Very interested to know how you are all making out with the Walltherm units.  Dhaslam you seem to be having trouble and are therefore not happy with your system. Gkingsley yours was new and you seemed enthusiastic about its potential.  Has it lived up to your expectations?  I am considering this unit to partner with a propane boiler to heat a new 6000 ft home in Ontario Canada.  I don't think that this unit is sufficient to heat the house alone but I want some sort of log burner in my basement and this seems like a useful alternative to an ordinary stove / fireplace.


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## unique3 (Jun 20, 2019)

PassionForFire&Water said:


> Soem pictures of the safety cooling loop and PAW pump group.



Passion do you still have access to the Walltherm units? 
I designed my house heating around one of these units. I just talked to PSES to order and they told me they are out of stock and no longer going to be carrying them and I haven't been able to find anyone else yet who sells them.


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