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Wood gasification boiler


Wood gasification boiler

Posted 12 Jun '17 08:43 PM

Is there anyone in this forum who is using an ATTACK wood gasification boiler for the central heating and warm water? Central Heating NZ in CHCH is the agent for this brand and it is made in Slovakia.
We are looking at installing one in our new house combined with a buffer tank. That way I only need to light the fire once a day when it is very cold and when it is not so cold only every third or fourth day.
Gasification boilers appear to be most efficient if they are going full throttle rather than slow burning.

RE: Wood gasification boiler

Posted 12 Jun '17 08:46 PM

The link is http://www.attack.sk/en/wood-gasifying-boilers/

RE: Wood gasification boiler

Posted 13 Jun '17 05:29 PM

Dont know anything about them sorry, but would be interested to know if you have compared the capital cost vs heatpump equivalent.

RE: Wood gasification boiler

Posted 13 Jun '17 09:41 PM

hi dys. that product range looks great! if you don't mind me asking, out of interest: will you accommodate it in a service space on the ground floor, or will you have a cellar? and: european style radiators in each room, or underfloor heating throughout? thanks! tobias




RE: Wood gasification boiler

Posted 13 Jun '17 11:11 PM

A cellar would be great but I am not sure whether we can afford that.
Anyway, I would not put it there as they do in Europe. The purpose of the cellar would be a cool place for food storage with ceiling well insulated.
The boiler would be in a service space near the laundry together with the hot water storage, water pump, filters, water distribution, ventilation.......
Radiators and/or underfloor heating is something we have to work out yet.
The concept is a combination of a boiler and solar feeding a large storage tank. If there is not enough sun the boiler will be used to top up. For heating, I like to get up in the morning to a warm house without having to light the fire first.
Hot water is drawn out of the storage tank through a heat exchanger.
Although we will have European standard (passive) of insulation and triple glazing, we have decided to have a good capacity to heat as Temperatures can drop to below -10 Celsius where we are building and we have been in passive houses in Europe which are great but we found a few degrees too cold.
The storage tank will allow us to draw only as much heat as required without lighting the fire every time.
If the boiler turns out to be too much output for our requirements, we have also the option of a heating stove in the kitchen.
http://www.pertinger.com/eng/categories/8/Heating_stoves
The disadvantage is the dust and the dirt that comes with the firewood into the kitchen.
While the CLT structure and house envelope, windows and glazing are straight forward, the finer details give me lots to research yet and think about without losing sight of costs.
We could never afford to do these things without importing materials where possible at wholesale prices.

RE: Wood gasification boiler

Posted 14 Jun '17 10:58 AM

Thanks a lot for the extensive reply! I'm with you on the cellar, I think it's a wise decision to put the money towards other details for the budget. I've been to a friend's place in Germanh over Christmas who also went against a cellar, for budget reasons. An unusual move back home. All heating, ventilation etc. fit nicely in a 4 sqm or so service room on the ground floor, very impressive. The detail I liked best was a pellet burner that was fed from a pipe/chute hidden in the wall, going over three floors, accessible up in the roof, where the pellets get filled up once a year or so. A very clever birdfeeder principle. Your setup sounds very thought through, I'm sure you'll have plenty more heat than ever needed ( much better than the other way around, of course ). I was asking about the type of central heating just out of curiosity what your preference was: the ( quite inflexible ) comfortable warmth of underfloor, or the more flexible adjustments from radiators. Either way, you'll probably only need one of the smaller ones of the heaters to keep your place at a cost 21 degrees year round...

RE: Wood gasification boiler

Posted 14 Jun '17 11:35 AM

We will probably end up with a small cellar as we need some cool place to store food.
What is the point to have gardens, fruit trees and other stuff if you don't have a place to store it properly?
The heating is a tricky question. The feedback I got here in NZ was that a 15 KW boiler is not enough to heat the house and workshop. This is advice from people who would put a 15, 20 KW or even 30 KW fireplace in the lounge and think this is normal.
The final calculation of the heating requirements, I will have to get done by someone in Germany based on the final plan as it is more realistic.

RE: Wood gasification boiler

Posted 14 Jun '17 12:10 PM

Understood, yes. I looked at the calculations at my friend's place, and was just very convinced by the sheer savings they put to better use.
The whole "bang for buck" ratio is quite insane, mind you: they put up three floors, including an attic fully used as master bedroom, small bathroom and wardrobe, for a budget of around 320000 NZD ( impossible to achieve here, of course, but still: they essentially swopped a "full-sized cellar" with an entire third floor, budget-wise ). A small cellar will incur a lot less cost, of course...

The calculations: yes, absolutely. I'm just suspecting ( I realize you know a lot more about this than me ) that given your specs in insulation,
you might be positively surprised at your heating needs, and might save on budget. And the people you'd ask in NZ are simply not used to
well insulated houses, and will give you very high kw recommendations...




RE: Wood gasification boiler

Posted 15 Jun '17 10:26 PM

If I wanted to heat the house only, I would definitely be ok with the heating stove in the kitchen. But I am also looking at heating the workshop with radiators (insulated) and if technically possible an outside spa pool.
Firewood is no issue luckily and we have plenty of land to plant more if we needed.
The other aspect I have to consider in the planning of the whole concept is that we are most likely to stay off the grid as the power connection from the power box to the house would be about 40 K.

RE: Wood gasification boiler

Posted 15 Jun '17 10:32 PM

wow, that all sounds like a very nice setup. and, yes, of course, in that case one of the bigger ATTACKs should do the trick...

RE: Wood gasification boiler

Posted 20 Jun '17 11:57 AM

Hi there
How did you get on with the wood gasification heater and buffer Dys?
We are making plans to install one in our yet to be built 150-200m2 rammed earth house.
Cheers Jay

RE: Wood gasification boiler

Posted 21 Jun '17 10:03 AM

Hi Houseonthehill,

I have yet to determine the required KW output to heat the house (150-200m2), the workshop (100m2) and if technically possible a spa pool. So I assume we will either use the 15 KW Attack boiler or the alternatively the Pertinger central heating kitchen stove with 10 Kw output.
In what part of the country are you going to build?

RE: Wood gasification boiler

Posted 24 Jun '18 09:25 PM

Hi. I have just come across this thread and wondered whether you have installed your boiler. I have an Attack boiler (45kw) in our home linked to an underfloor pad and radiators. The house is 160sqm so not large. It is very important that you have it installed by someone who knows what they are doing. Ours has been problematic in that it hasn't been plumbed well enough. It actually struggles to heat the place really well on very cold nights. We live in the South. Finding someone to assess and fix what is happening has not been easy. I would be interested to hear what you have done with yours if in fact you have installed it.

RE: Wood gasification boiler

Posted 24 Jun '18 11:42 PM

Hi Dilemma,

still stuck at resource consent stage. However we are leaning towards a wood gasification stove in the kitchen which also heats the water for radiators and shower in combination with solar. https://www.pertinger.com/en/heating-stoves/heating-stoves-reverse-flame/19-7.htmlThe reason is that a dedicated wood gasification boiler is simply too big for our energy requirements. With triple glazing and good insulation not much heating is required, even in the high country.
What puzzles me is that you have a 45KW :-0 ??? boiler and your house is not heating well. It must be either completely wrong plumbed, your thermal envelope so bad (4x2 standard walls and aluminium windows and maybe even single glass????) or loose massive amounts of heat somewhere.
In Europe (colder climate than anywhere in NZ) houses of your size are heated with 7-11 KW boilers Including warm water. Many modern houses there require even much less than that.
Eager to read more about this....

RE: Wood gasification boiler

Posted 25 Jun '18 10:37 AM

Hi Dys,
Our house is very well insulated. Mostly triple glazed and some double glazing in an older part of the building. Well insulated and the pad is fully enclosed in polystyrene in rib raft form. The boiler is sited separate from the house in a stand alone garage which is still quite close, 7 or 8 metres away. The boiler has been plumbed to feed water to a concrete pad of 85sqm (new build) and 4 radiators (old build). It has been plumbed to heat the pad and radiators first then any excess feeds into 2 buffer tanks (total 1600 litres) for later use at night when the fire goes out. Initially the boiler was unable to heat both circuits at once pouring all the heat into 4 radiators and would only heat the pad if the radiator circuit was turned off. That has been resolved but it still struggles to heat the place when really cold. We have a Rayburn wood stove that helps. The boiler itself burns really well keeping the water temperature at 65 to 70 degrees.
Basically you have to be very careful as to who installs your system. I was trusting of who did ours, thinking he knew what he was doing. He didn't. It then becomes a problem finding someone who is prepared to analyse and solve your problem.I feel central heating systems are not well understood in this country.

RE: Wood gasification boiler

Posted 25 Jun '18 11:56 AM

Hi Dilemma,

I am still puzzled where your 45 KW go without turning the house into a baking oven?
No, central heating is not well understood in this country, like many other aspects of energy efficient construction.
What you need is a specialist to look at your system. If it is all running well, you should be able to heat at least two houses !!
Do your plumber do a proper plan and calcs. ?

RE: Wood gasification boiler

Posted 25 Jun '18 11:56 AM

Hi Dilemma,

I am still puzzled where your 45 KW go without turning the house into a baking oven?
No, central heating is not well understood in this country, like many other aspects of energy efficient construction.
What you need is a specialist to look at your system. If it is all running well, you should be able to heat at least two houses !!
Do your plumber do a proper plan and calcs. ?

RE: Wood gasification boiler

Posted 25 Jun '18 12:40 PM

I'm not sure what plan and calculations the plumber did. We were out of town for a lot of the build and installation so had assumed the people we contracted knew what they were doing. Big mistake.
As I said it is not easy finding a specialist in the South. Had we known what we know now, back then, it may have been avoidable. Anyway just make sure you get someone well versed in central heating as our story is not pleasant and may or may not be fixable. We deliberately over spec'ed the design in all aspects of the build to make sure it all functioned well enough.
Good luck.

RE: Wood gasification boiler

Posted 25 Jun '18 01:06 PM

We are building in the South too and after reading your story I think to get the design done overseas (material supply deal with plans ;-)) I plan to install it myself but I need a plan. Without plan it would be beyond me. I might know someone who could look at your system but know whether he is still in the South Island.
I'll post again.

RE: Wood gasification boiler

Posted 25 Jun '18 02:35 PM

Thanks Dys, We are just out of Dunedin and I have approached a couple of fellows. Target Heating in Dunedin found my first issue which did improve things and he may well help further. Also Israel Win from South Otago is very good but he didn't want to fix someone elses mess which I can relate to. I have been on the phone to Central Heating NZ and they have been very happy to help over the phone but without being here it is hard to analyse the issues. I have no problem with the boiler itself.
You are right to go overseas for plans and design as long as you have the contacts you can trust. I will be interested to hear how you go.

RE: Wood gasification boiler

Posted 29 Jun '18 12:42 AM

Hi Dys, I'm a first time poster here and thanks for your post first. I am planning to move to Christchurch from North Island and am in the stage of planning the build and hope to keep the house warm all year round. From my recent search, aside from Central Heating NZ's Attack wood gasification boiler, Spark Energy has many models and it seems to serve the commercial market mainly, but its boilers seem to be very good. My build will be a 150m2 principal + 75m2 secondary dwelling, separate barn as workshop/garage, 140 stud external wall (R4.1), super insulate the ceiling (R6.6), MaxRaft (R4) as foundation, triple glazing (R1.5, optimal amount of windows in the optimal places only), simple rectangular shaped houses, underfloor heating and radiators and decentralised single room heat recovery ventilation. With such a well-insulated passive house configuration, would you think I still need a wood gasification boiler (20kW/30kW/40kW)? Or should I be better off with electric underfloor heating? Material cost for electric underfloor heating (far infrared heating film) is very low and I can save on installation cost. Complicated zoning and control for electric underfloor heating are also easily done to save on running cost and compensate for the cold south parts of the house where not so much sun can reach (7.2m deep, 22mm wide rectangular house). In addition a fully automatic and programmable system together with quick warm up time are very tempting compared to a boiler and hydronic system. But a supply of free wood is also very tempting for the wood boiler option (of course capital cost of installation is very high comparatively)! If I opt for wood gasification boiler, I plan to use it for domestic hot water and possible future spa/pool heating too. I am not sure if I should choose electric over hydronic for underfloor heating and radiator as if I go electric, I may use the solarZero service for solar panel and battery. However, I am a bit worried if that free solar panel is large enough to provide enough energy for the space heating, hot water heating as well as normal household power use. Wood gasification boiler seems to be sure to keep the whole house warm (might be overkill) as well as providing for hot water and future expansion need (e.g. spa/pool). But it is most expensive and requires a lot of manual input, e.g. wood preparation and loading. What's your thought? And if I get the plan and supply of material from Europe as what you do, will there be any issue with council for approval? Your link to the Pertinger Reverse Flame Heating Stove is also very interesting! Keep us informed of any progress of your build! Thanks again.

RE: Wood gasification boiler

Posted 29 Jun '18 11:35 AM

Hi daniel_c. and Dys, Two days ago I spent a day with a boiler specialist to see if I could sort out our heating problems. It took most of the day but essentially most of the problem came down to how I was running the boiler. I had been getting it up to running temperature (65 degree water jacket temperature) and running it at that temperature. However this basically had the boiler working at about half its potential. What we did was to totally fill the fire box as much as possible and have the fire burning with a lot more intensity. So instead of ticking over it was roaring. This allowed the heated water from the boiler to overcome the buffer tank back pressure and the whole system began to heat up i.e. radiators, pad, HWC, and buffer tanks. Never before had this happened. So yesterday I lit the boiler at 3PM and in 25 minutes it was up to temperature and began heating the house and buffer tanks. At 7Pm I stopped feeding the fire totally and the house was kept to temperature for the rest of the night and morning. This is how it should run. I believe.
So daniel_c your house build is very close to ours in concept. Older cottage double glazed well insulated attached to new build triple glazed rib raft pad etc etc. We chose the boiler as it meant free heating as all our firewood supplies are on site and free and less electricity use. There are downsides to gasification boilers.
1)You don't get instant heat if your house is cold, it takes about 35 minutes to get our boiler up to heating temperature.
2)you have to light a fire rather than flick a switch.
3)you have to provide firewood and a significant amount.
4)Boilers are normally sited away from the house (ours is in the garage) or in a dedicated room attached to the house.
5)Cost. Ours cost about $37000 installed. 3 years ago.
For instant heat, if we have been away for a couple of days, we have a woodburning Rayburn stove and a modern open fire place.We also have a 4.5KW solar array and I don't want to use electricity for heating. And we don't. Well rarely. Battery storage is next on the agenda.
I don't think you will need to buy your material from overseas unless it's cheaper but you would need to be careful and make sure it is planned and installed well. Be careful if you buy overseas as the model you buy may have to have council approval. Dunedin City Council had already approved our model Attack boiler for another project.
If you go the boiler way don't undersize it. You can calculate how many Kw you need by the size you need heated. Ours was calculated at 20Kw however Central Heating NZ only had 45Kw boilers and there was not much of a price difference between that and the next model down at 35Kw. Better to be too big than not big enough. Then size the buffer tanks well.
We would be happy to show you what we have done here if you are in the South at some point.


RE: Wood gasification boiler

Posted 29 Jun '18 11:35 AM

Hi daniel_c. and Dys, Two days ago I spent a day with a boiler specialist to see if I could sort out our heating problems. It took most of the day but essentially most of the problem came down to how I was running the boiler. I had been getting it up to running temperature (65 degree water jacket temperature) and running it at that temperature. However this basically had the boiler working at about half its potential. What we did was to totally fill the fire box as much as possible and have the fire burning with a lot more intensity. So instead of ticking over it was roaring. This allowed the heated water from the boiler to overcome the buffer tank back pressure and the whole system began to heat up i.e. radiators, pad, HWC, and buffer tanks. Never before had this happened. So yesterday I lit the boiler at 3PM and in 25 minutes it was up to temperature and began heating the house and buffer tanks. At 7Pm I stopped feeding the fire totally and the house was kept to temperature for the rest of the night and morning. This is how it should run. I believe.
So daniel_c your house build is very close to ours in concept. Older cottage double glazed well insulated attached to new build triple glazed rib raft pad etc etc. We chose the boiler as it meant free heating as all our firewood supplies are on site and free and less electricity use. There are downsides to gasification boilers.
1)You don't get instant heat if your house is cold, it takes about 35 minutes to get our boiler up to heating temperature.
2)you have to light a fire rather than flick a switch.
3)you have to provide firewood and a significant amount.
4)Boilers are normally sited away from the house (ours is in the garage) or in a dedicated room attached to the house.
5)Cost. Ours cost about $37000 installed. 3 years ago.
For instant heat, if we have been away for a couple of days, we have a woodburning Rayburn stove and a modern open fire place.We also have a 4.5KW solar array and I don't want to use electricity for heating. And we don't. Well rarely. Battery storage is next on the agenda.
I don't think you will need to buy your material from overseas unless it's cheaper but you would need to be careful and make sure it is planned and installed well. Be careful if you buy overseas as the model you buy may have to have council approval. Dunedin City Council had already approved our model Attack boiler for another project.
If you go the boiler way don't undersize it. You can calculate how many Kw you need by the size you need heated. Ours was calculated at 20Kw however Central Heating NZ only had 45Kw boilers and there was not much of a price difference between that and the next model down at 35Kw. Better to be too big than not big enough. Then size the buffer tanks well.
We would be happy to show you what we have done here if you are in the South at some point.


RE: Wood gasification boiler

Posted 29 Jun '18 12:28 PM

Hi Dilemma,

Thank you for your detailed inputs! That's reassuring to me. On the Spark Energy website, it has more models to choose from, like 20/30/40/50/60kW (first three being clean air approved) and has RRP listed (from $22460 to $29960). Once daily loading is acceptable to me and once lit, it will stay on for the whole seasons unless I want it to stop. I'm more inclined to use wood opposed to electricity as I can easily oversize the system and keep the whole house warm day and night for at least half the year by continuously burning wood each day free.

The Pertinger Reverse Flame heating stove only has maximum of 15kW output and it's sited in the kitchen of the house (central position). That means all log loading would be done in the house on a continuous basis (smaller chamber, more manual input), creating a mess in the kitchen (wood storage, ash, creatures on wood, etc.). Besides, I am worried about how easy it is to keep the oven and cooktop at a set temperature compared to induction hob/electric oven. In contrast, wood gasification boiler can be sited in a separate barn/garage and have the hydronic underfloor heating/radiators system fed from that location to the separate major and minor dwellings. Siting the system away from the main house has another advantage of not creating another big hole in the house for the flue and possible back drafting from powerful rangehood fans in an airtight passive house.

RE: Wood gasification boiler

Posted 29 Jun '18 12:53 PM

Hi Dilemma and Daniel,

I do agree with concerns like having enough heat and fireplace in the kitchen etc.... but there are more aspects to it which to explain would exceed the time I have at the moment.
More on the weekend about that.
In the meantime have a look at this link wheter it is the same model you have.
Given the importers mark up on the price you should have got perfect technical support until it runs perfectly.

https://www.heizprofishop.at/Attack-Holzvergaser-SLX-Profi-35-14-35kw
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