Obviously I know little about OWBs or gassification units. I read references to both but I am unclear what the distinction is between the two. Can someone please explain the differences in how they operate, how they are installed, wood consumption, cost, pros/cons. I know this likely has been discussed elsewhere, but my slow dial-up makes it a chore to search through all these postings. Would either of these units be worthwhile in SW Missouri where the average coldest temp is 42 for the high, and 21 for the low? Appreciate your comments.
Difference between OWB and a gassification unit
- Thread starter Cold Mo
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It's good that gasification boilers are starting to come into the public conciousness, giving them a choice of what they should be doing and what they should not be doing.
The state of the art in gasification boilers use two stage combustion, usually downdraft design (except for the Garn) where the flue gasses are pulled down through the coal bed, then to a secondary ceramic burn tunnel where the flue gasses are raised up over 1200 deg F in the presence of excess O2, for complete clean combustion of the smoke components. All that remains after that is mostly H2O and very fine light non combustible fly ash. No soot or creosote is produced when operated correctly.
A gasificaton boiler compared to the typical OWB should cut fuel consumption by more than half, burn cleaner, and last longer.
If you have natural gas (methane) available, that is the best fuel choice. If you do not have your own free cordwood, the modern European type pellet boiler is probably a go to solution, especially in milder climates.
A good quality install does have an expensive price tag.
The state of the art in gasification boilers use two stage combustion, usually downdraft design (except for the Garn) where the flue gasses are pulled down through the coal bed, then to a secondary ceramic burn tunnel where the flue gasses are raised up over 1200 deg F in the presence of excess O2, for complete clean combustion of the smoke components. All that remains after that is mostly H2O and very fine light non combustible fly ash. No soot or creosote is produced when operated correctly.
A gasificaton boiler compared to the typical OWB should cut fuel consumption by more than half, burn cleaner, and last longer.
If you have natural gas (methane) available, that is the best fuel choice. If you do not have your own free cordwood, the modern European type pellet boiler is probably a go to solution, especially in milder climates.
A good quality install does have an expensive price tag.
maple1
Minister of Fire
'Worthwhile' depends on a whole lot of situation specific variables - you'll have to decide that part.
You need to factor in heat load, local fuel situation, budget, current heating system design, house size & layout, your preference/tolerance for preparing & feeding wood, inside/outside, on it goes...
You need to factor in heat load, local fuel situation, budget, current heating system design, house size & layout, your preference/tolerance for preparing & feeding wood, inside/outside, on it goes...
BoilerMan
Minister of Fire
What maple said. Personally, I like processing wood..........but not that much! So I went with the most efficient way possible, gasser inside with thermal storage all inside the building envelope. That is just me, I'm a wood scrounger and end up with some time involved in that wood. So I don't want to do more than I can keep up with and I'm in a significant heating climate.
TS
TS
I'm still unclear how an OWB and a "gasser" differ in doing such things as moving the heat from the unit to the house, installation, and maintenance. I assume both use wood to provide the heat and the gasser is more efficient in producing heat from the wood (and causing less emissions). Is efficiency the only real difference between the two? Do both have water jackets? Do both use cycled water to provide the heat to the house? Is installation basically the same? Does only the gasser use water storage tanks? Do all gassers use such tanks? Must gassers be inside an insulated structure? I live in a rural area with unlimited, free wood available to me. I use about 1000 gallons of propane a year at a cost of $1.65-$3.00/gallon. Does either a OWB or gasser make economical sense? Does it make sense where winter temps vary wildly--60s to 0, with most days 40s-around 20? I notice most posters live in cold climates. I read the "Can't decide between regular OWB or outdoor wood gasser" and I'm still not sure what the distinctions are between these units and whether they are beneficial in areas not consistently cold.
Good questions Cold Mo.
It might make more sense to consider a wood stove for your home, since you would only need to fire it on days when its truly cold. Even if it cuts your propane bill in half, thats a shorter payback, and there is nothing like wood stove heat....
- Both boilers move heat to the house the same way, through buried insulated piping.
- Both boilers have a water jacket.
- In simplest terms, gasification boilers "burn the smoke", resulting in higher efficiency. Since water doesnt burn, you need dry wood. While a regular OWB can "burn" green wood, you lose a lot of your heat output boiling the water out of the wood before it provides you any useful heat.
- The OWB doesnt cycle water, the outdoor loop pump runs continuously to prevent freeze-up in your lines or boiler. The pumps in your house then cycle based on your thermostat.
- Installation is the same between the two units.
- Some indoor gasification boilers require storage tanks. Most outdoor units combine storage into the unit itself. You can add additional storage which can help reduce cycling of the boiler, depending on your setup. Most outdoor boilers (gasser or OWB) do not require separate storage tanks.
- Only an indoor boiler needs to be inside an insulated structure. Outdoor rated units are freestanding, but you will want something to keep your wood supply dry.
It might make more sense to consider a wood stove for your home, since you would only need to fire it on days when its truly cold. Even if it cuts your propane bill in half, thats a shorter payback, and there is nothing like wood stove heat....
why don't you go with an inside wood stove? your weather is about same as Tulsa .. almost zero OWB around here
OWB are notorious wood eaters but good if you are heating huge sq ft.
OWB are notorious wood eaters but good if you are heating huge sq ft.
Thanks for the responses. I wanted to avoid an inside wood stove. I presently have two inserts (on different living levels) I use during power outages, but I have experienced more smoke in the house than I want due to lack of a good flue draft and/or failure to timely open the catalytic converter. Also, I am personally unable to get on our steep roof to clean the flue regularly which would be needed if I used an inside wood stove. For these and other reasons (e.g. no SS flue lining,flue fire risks, insurance concerns, frequency of loading the stoves, etc), I wanted to avoid frequent wood stove use in the house. On the other hand, I don't want to spend several $ on a heating system that would be overkill for this area and provide little if any payback. Anyone in warmer areas with OWB (gasser or not) available to share their experience with their OWB?
jeffesonm
Minister of Fire
Best bang for your buck would be to drop an insulated liner down your chimney, make sure your wood is dry and burn the insert cleanly. You can clean from the inside using a SootEater.
I can understand your hesitation here, but Jeff makes some good points. Getting dry wood (seasoned a few years ahead), an insulated liner, and a soot eater can make your life pretty easy without risking life and limb on your roof. Throw in a non-cat stove, and you have eliminated most of the issues that you had mentioned.
I only say it because you can get an Englander 30 stove, insulated liner, and the soot eater for probably $4k or less. The base price for a regular OWB, without any of the other install work is probably going to be at least $6k. I would think you are looking at a 10k investment, depending on how much you do yourself and your particular installation.
Personally, I like the idea of a Garn if I had the space (boiler and storage in one unit, can take larger chunks of wood) to put it. Not cheap, but you get a nice unit for your money.
Another option you might want to look into is a nice pellet boiler, since they are much more easily able to modulate to handle the varying loads you experience. I know pellets arent as cheap and easy to come by, but you might save yourself a lot of trouble with smoke and trying to match a mild day.
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