There is a lot of good information in here from wood boiler owners, particularly at WoodHeat.org.
You don't have to settle for a lot of smoke and creosote
— read on.
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Tips to reduce smoke/creosote cleamed from these comments:
1. Only reload when fire has died down and boiler temp is below 160F.
2. Burn seasoned dry wood. (cut and split early in the summer) 3. Burn hot chamber rather than slow burn. (Some people burn a hot chamber to heat up the water that is stored away from the boiler to 185-190F and then let the fire go out. A large water jacket usually surrounding the firebox is good for heating water, but it cools the escaping gases before combustion is complete.)
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TOP THREE CAUTIONS FOR OUTDOOR WOOD BOILERS 1. Incomplete combustion = smoke: Many outdoor wood boilers generate a lot of smoke! A large water jacket usually surrounds the firebox, which is good for heating water, but it cools the escaping gases before combustion is complete.
2. Intermittent heat demand is the second reason the units are smoky. There are long periods of time when the wood just smolders. During periods of low airflow, creosote collects on the water jacket walls. When the fire is rekindled, the creosote burns off and creates black soot.
3. Worst of all, often the exhaust stacks of these units are short. Smoke and soot are released close to the ground where it can drift into your neighbor’s yard.
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Outdoor Wood Boiler & Air Quality Fact Sheet
http://www.burningissues.org/pdfs/OWB_michigan%20Fact%20Sheet.pdfIf you’re still thinking about installing an Outdoor Wood Boiler, we recommend you:
? Look for a well-designed unit that utilizes secondary combustion.
They burn more efficiently and can be a good home heating option in rural areas. The Garn design is the only one that has demonstrated compliance with existing state particulate limits.
? Look for unit with a lot of firebrick which allows the unit to burn hotter with better combustion.
? Be a good neighbor. Make sure the stack is at least as high as high as the chimney on your home.
? Ask for proof if the unit’s performance claims seem exaggerated.
? Fuel right … ONLY dry, seasoned wood should ever be used in wood burning units.
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http://www.woodheat.org/technology/outboiler.htmDedicated to the responsible use of wood as a home heating fuel (includes two very informative article by two wood boiler owners - be sure to read Bob's in Pennsylvania's 2001 update) The big problem is they smoke. Boy, do they smoke. There are a couple of reasons why older outdoor boilers were such notorious smokers. First and most obvious is that the firebox of most units is fully surrounded by a water jacket. While this might be good from a heat transfer point of view, it makes complete combustion of the wood just about impossible.
Some outdoor boiler manufacturers compound the problem by running a series of water pipes right through the firebox so the exhaust has to sweep past them to reach the chimney. The flaming combustion of wood cannot occur below about 1000°F, so those steel surfaces backed up by water at 150°F chill and quench the flames well before combustion is complete.
Another reason for the smoke is the cyclical operating pattern. When the boiler’s water temperature falls below a set point, its combustion air damper opens and/or a small fan forces combustion air into the firebox. Once the water is heated back to the upper set point, the fan is turned off and/or the combustion air damper closes. During off cycles the fire smolders and much of the smoke condenses as creosote on the cold steel internal surfaces.
Three major improvements significantly reduced the smoke produced!
(includes pictures)
http://www.woodheat.org/technology/outbobpen2.htmBarney
I use mine for a house with no real smoke problem. I never try to bu ild a big fire but fill it three times a day getting a good charcoal bed that is always hot. I do not have a fan to force the draft but a very sensitive control that opens the draft at a small drop in house temperature. The heat in the house is constant
– better than oil.There are water pipes right through the firebox and I have never had flaming chunks coming out the unit. Even if it did I question if it would ignite the snow etc.
Response to Barney from John (WoodHeat.org) You are also careful about building a good fire. If all outdoor boiler owners did this, we wouldn't have as big a problem with them. In our experience, though, it is rare for users to build careful fires. More often they tend to fill up their boiler with unsplit, unseasoned logs so it will run as long as possible between loadings and this leads to a huge smoke plume when it fires after an off cycle. We wish more users were as conscientious as you are.
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http://www.woodboilerheat.com/revstats-GreenwoodFurnace-1.htmThe neighbors have complained bitterly about the smoke and the town has issued us a cease and desist order.
http://www.greenwoodfurnace-warning.infoWe wanted to avoid the stigma that is commonly associated with "Outdoor Wood-Burning Boilers" (OWBs) Many communities have been negatively impacted by OWBs with poor combustion technology that makes them smoke like "locomotives," and the resulting bad press has given any "outdoor furnace" product a bad name in the minds of local officials.
Can the Greenwood Model 100 operate under full load with no visible smoke? Yes, it can and does...sometimes. But not when starting, not when refueling and not after the creosote builds up. With creosote it smokes most of the time.
Many states allow NO VISIBLE EMISSIONS, others allow no more than 3 minutes in any 30 period (non-cumulative) and some allow no more than 6 minutes in any 60 minute period (non-cumulative). With the Greenwood products, you could be in real trouble here (as we were…and still are).
On top of state restrictions, many communities have local smoke or nuisance ordinances that can further restrict any smoke emissions.
You could end up with a Cease and Desist Order like the one that we received.
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One of my neighbors has a water jacketed boiler, my other neighbor lives a quarter mile away and has asthma and definitely notices my neighbor that uses the water jacketed boiler. He is particularly sensitive to the issue of smoke and has no awareness of my Greenwood at all. The smoke is not a problem for me or my neighbor, which I am quite pleased about.
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Burning unseasoned wood and/or low firebox temperatures are the most common causes of creosote.
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Some of the other negative reviews obviously did not have their boilers correctly installed and fine tuned. Or they are using wood that is not at all seasoned. Or they are operating their boiler when there is little demand placed on the boiler to supply heat.
The only thing I can complain about is that you do get smoke out the door when you want to load it with wood. But this can be easily minimized if you wait until the fire has burned down and the boiler temperature is 160 or below.
At the moment we are having a warm spell so I let the fire die out today as it is hardly worth it to burn wood with such little demand for heat.
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Wood Boiler - Hot Water from Wood
http://warmair.net/html/wood_boiler.htmlA wood boiler burns wood in a sealed firebox surrounded by a water jacket. A circulator is used to deliver the hot water to the house. It was determined years ago that when water was heated by a wood fire, a drastic temperature drop occured and often created an exhaust problem.
In other words, the fire cools down and creosote is produced. A build up of creosote inside the chimney can ignite and become a fire hazard.
One of the remedies was to locate the wood boiler outside the building.
The outdoor wood boiler is enclosed in a shed with its own chimney, and located a safe distance from the house. Water lines, connecting the house to the shed, are buried below the frost line. The hot water can be used for domestic tap water via an indirect water heater, or for space heating. Space heating is accomplished via baseboard heat, radiant floor heat, or hydro-air heat, depending on the desired application.
The exchange of heat, from wood to water, is less efficient than the simpler exchange from wood to air, and the wood boiler tends to make a considerable amount of smoke. An amount that many people, who usually live nearby, have decided is unbearable. A number of states and municipalities have drawn strict enforcement codes regarding the use of outdoor wood boilers, so check with local authorities before you decide to make a purchase.
http://smartpei.typepad.com/robert_patersons_weblog/2004/11/home_heating_oihtml