Wood Boilers- indoor/outdoor, open/closed, gasification……what???

Will someone just level with me?

I have been in the Fire/Hearth/HVAC/Building industries for over 32 yrs.  The one thing I know for sure is that I don’t know everything……….the following is just my honest assessment based on my experience. 

One of the reasons I love what we do is because I’m always learning new things. Our goal as a company is very simple; help folks cut through the “hype” and figure out what they need to accomplish their goal. Our job in my opinion is to tell the truth and give honest advice based on our experience, what works and what may not meet the customer’s expectations. Obadiah's Woodstoves and Wildfire Fighters

Please visit our website for one of the largest selections of Boilers found anywhere. We have a large selection of residential, commercial, agricultural and industrial indoor and outdoor boilers. Commercial Waste Oil Boilers, Commercial Biomass Furnaces , Commercial Biomass Boilers, Commercial Pellet Boilers , Commercial Coal Furnaces , Commercial Coal Boilers , Commercial Wood Furnaces, Commercial Wood Boilers . We offer waste oil, trash burning boilers that burn cleanly from Glenwood Boilers. Waste Oil Boilers We also offer Coal, Pellet, Chip and Corn burning boilers from Traeger, Americas Heat, Pelco, WoodMaster, Glenwood, Portage and Main, as well as Biomass Boilers that will burn anything from sawdust to horse manure from Glenwood and others. Coal, Corn, Chip, Pellet and Biomass Boilers We specialize in North American built high efficiency gasification boilers from Econoburn, Woodmaster Flex Fuel, Pro Fab Elite and Portage and Main Economizer. North American Gasification Boilers We offer European import Gasification Boilers from Attack, Biomass, Effecta, and EKO. European Gasification Boilers We also offer simple non electric boilers like the AquaGem by DS Stoves. Non Electric Amish Wood Boilers and Furnaces Obadiah's has special liquidation sales occasional and occasionally you can find super deals like what we're offering on the Greenwood boilers now, from Pro Fab Industries. Greenwood Liquidation Boilers And Furnaces 

I have spoken with several folks who called me because they now have an outdoor boiler sitting in their back yards with CONDEMEDED DO NOT USE sticker on it. Worse yet, the unit is only a couple of years old.

What happened you ask? They qualified for financing and the largest outdoor boiler company in the world was there with an aggressive sales force and before they knew it that had a note for anywhere between $10-20k depending on their installation. Did anybody ever take the time to tell them that there was a potential EPA problem looming on the horizon……….or that their community was fixing to outlaw outdoor boilers…….no, the sale was more important than the truth.

The folks above were not our customers; however, we like to think that we could have prevented their predicament with some simple friendly advice.  Let’s see if we can clear the smoke out of the air here, so to speak, and get down to honesty and some basic laws of physics, thermodynamics and simple reality. My hope is to lay a foundation for you to make an informed choice.

Outdoor boilers, why the bad rap? Well very simply…….most don’t burn very clean and are simple smug pots that smolder all day long. Top that off with a customer who has never burned wood before, or worse, a trash burner who thinks he now has an incinerator…….and you have a recipe for unhappy neighbors.  Combine someone with asthma, or other respiratory problems and things can get really bad fast.

There are some very simple designs that will never work if you’re trying to achieve a clean burn.  In order to burn fire needs three things, fuel, air, and heat = COMBUSTION. To burn clean, wood needs to burn very hot, the hotter the better = the cleaner burn you get.

It is next to impossible to achieve those kinds of temperatures with a firebox wrapped in steel filled with water. The water will always act as a heat sink and absorb most of the heat needed for total combustion. Most outdoor non-gasification boilers operate this way. In my opinion, unless you live in NW Montana or some wide open area and lots of smoke is still carbon neutral…..stay away from this kind of boiler. They cannot burn clean if the firebox is surrounded in water.

 

Outdoor Boilers………..think about that for a few moments…………let it sink in. Outdoor boilers are almost an oxymoron when you really think about it. You are taking the very expensive boiler and pumps that you’re using to heat your home, or shop……..and sticking it outside in the coldest possible place. Does that really make that much sense? Yeah ok, get the wood and bugs out of the house, I’m all for that, no problem, but I ask you what about the wood you are going to put in your nice new shiny wood outdoor boiler? Are you planning on dumping it on the ground out in the middle of the yard and dig your wood out of the rain snow and mud and use that to feed your boiler. If so, you’ll be sadly disappointed. Wet, green wood does not burn well. Furthermore it stinks and more than half the BTUs are consumed drying out the wood so it can burn. Even with the “most efficient boiler”, your efficiency will still would drop by half and the chimney will plug up with creosote and become a fire hazard.

If you stick your new shiny outdoor boiler outback so the bugs need to form an expedition to get to the house, there are some drawbacks. The further away you go, the longer the trench is that someone needs to dig to bury the lines that run hot water back to the house. Now think about that line that you’re going to bury in the ground. It is usually two PEX pipes wrapped in some kind of insulation in between, stuffed in a long black corrugated pipe. This stuff runs between $5-10 per ft. They make a better product with close cell foam injected which has a higher R-value for $10-20 per ft.

Underground Insulated Pipe- The Good, The Bad, The Ugly Truth…..

95% of all underground pipes leave no gaps between the feed and return PEX lines.  When you consider the BTU bleed off factor you get when you bury this low R value pipe in the ground, not to mention the very low R-Values, I wonder how the contractor could sleep at night. So many BTUs are cancelled out in the pipe before they reach the place where the BTUs are needed.  In a water to air heat exchanger, this can be a problem on really long runs. My advice is, if you’re going with an outdoor boiler, run two corrugated lines with two hot feeds in one pipe and two cold returns in the other. Don’t skimp here; otherwise you’ll be heating the ground next to your home and not your home or shop. Here is a good place to see what has happened to others. http://www.hearth.com/talk/threads/insulated-underground-pex.48808/

I have heard that some of the underground PEX pipe companies claim less than 1 degree heat loss in 100’……..please…        Let’s take a simple look at this idea and see how much sense it all makes to you.

In some cases when you are heating several separate buildings, moving heat between them underground, is necessary. If you must bury your feed and return in the ground, do it right the first time, since digging it back up again is very expensive. So let’s take a look at what kind of underground PEX pipe is available. Consider this; even if you live in Georgia, the soil temps in the winter are within about 20-30 degrees of Montana temps below our frost line. The key is how deep you bury your pipes.  In northern climates most folks dig below the frost line for their area.  Where I live that is 7’.  At 7’ depth the ground pretty much stays in the 50 degree range. See my point?  The water lines that feed our outdoor water hydrants are buried that deep so they don’t freeze.

                                                                                                  

When you look closely at underground PEX pipe you’ll find lots of variations. In my opinion, you want the highest R value possible for as long as possible. The ground is a cold damp place and most insulation will become waterlogged and lose their R-values.  In most high efficiency wood boiler installs we are looking for as many BTUs per pound of wood as possible. To do this requires that most of the BTUs stay inside the PEX until they arrive where they are most needed. Therefore we use two separate lines, one for the feed, and one for the return. I run them separately instead of all inside one pipe, because it is very hard to insulate the cold return from the hot feed inside one pipe. Of course most outdoor wood boilers are so inefficient, line loss does not matter either.

You can save a lot of chopping and wood handling by reducing the amount of BTU loss in your installation. Here are some pictures of various underground PEX systems and what to watch out for.  The type of pipe shown has very low R-Value and will lose lots of BTUs. Notice the air space and no insulation between the Feed and Return. This is very bad.

Next if you look at this pipe it has more wraps and is better insulated, but still has just one wrap of insulation between the Hot Feed and Cold Return. Still not good as they work to cancel each other out in the end. Your hot feed temps will be much lower as they have been cooled by the cooler return line temps. Bury your Feed and Return lines separately using underground pipe like ThermoPEX  shown on the right.

I like to lay my pipe in a trench that has a layer of at least 2” thick rdgid foam that is about 14” wide and is laid in the bottom before I lay the pipe. I then lay the Feed and Return pipe’s on top of the foam. We then call in an insulation contractor who sprays the entire trench with at least 24” of foam. We then cover it with heavy gauge plastic to shed moisture and bury it. We lose very little BTUs to the soil.

I have also done the same thing above ground on short runs that we can enclose with both rigid and spray polyuerathane 2 part expansive foam. This foam can absorb water and it will loose its R value if it gets damp. So it is very important to protect all foam from moisture. It is easiest to keep moisture out above ground. Below ground is always going to be damp and eventually your R Values will drop over time. A simple roof to shed water above the pipe when it is installed above ground works well.

I have seen folks build a trough from foam panels and ply wood, lay in their ThermoPEX and fill with Foam beads and closed off. They build a roof over it all and have easy access if they have a problem later on down the road.

Heat Handlers and Water to Air Heat Exchangers-The Truth

Few folks will tell you the truth about forced air systems. Air is a great insulater -  just look at your new high effeciency thermal windows. How do they work?  There is an air space under vacuum and in some cases injected with Argon gas to further increase thermal effeciency.  Very simply, air is a fantastic insulator.

So that means that heating air is inherently not very efficient to begin with……the higher the humidity in the air, the better it transfers heat, the drier the air, the better it transfers the cold. On the other hand, water has excellent thermal conductivity properties. It also can store and transfer heat very effectively. Therefore hot water heat is the most efficient way to heat anything. Water is also a very effective way to cool things, hence the way a nuclear reactor is cooled.  Remove the water flow and we all have witnessed what happens….

Heat handlers are an easy way to make heat; they also allow folks with forced air furnaces to utilize hot water heat  and realize some cost savings compared to burning fossil fuels.  If you live in an area where you need air conditioning most of the year, then forced air makes sense and I would not worry much about effeciency loss either.

If you are starting fresh with no heating system, the radiant In-floor heat is something you’ll never want to live without, once you have experienced it. There is very little temp diffrence between the floor and ceiling, which cuts down on heat loss through your roof. Your floors are warm as are your feet;  toasty warm as we call it.

If you already have forced air and want a wood boiler to cut your fuel bills, it is not that difficult to add a water and air heat exchanger into your exsisting plenum, to make hot air. You do not need to run radiant flooring or baseboards to make it work.

The picture on the left shows a typical hot water/hot air system. If you have to have air conditioning in the summer through your central air system, this would be how it would be set up utilizing the exsisting plenum. There is  also a way to heat your domestic hot water with this set up.

The Pro Fab Heat Handler is a complete self contained plug and play system that works great with the HPBA Vesta  Award Winning Elite 100 and 200 Gasification boilers.

The key to burning wood cleanly and efficiently

Man has been burning wood as a renewable, carbon neutral fuel for thosands of years.  It is only recently that we have given much thought to what is coming out of the chimney.

We Americans do seem to be behind the curve in this realm. There are some wonderful new North American products out there, but in reality, the Europeans have been at this game a long time. They have it down pretty good if you are comparing a high tech gasification boiler to a firebox submerged in water.

The EPA has been clamping down on woodstoves in the USA for many years. The new EPA rated stoves burn cleaner, longer, produce more heat, and with less wood. American and Canadian manufacturers have stepped up to the plate and re-engineered their product line.  More and more communities are concerned about airborn particulate. They are passing regulations requiring all new  and replacement stoves be EPA certifed and display the test results so the world can see. It is a behind the scene competition among manufacturers to produce the cleanest stoves. It is now a sense of pride to build the cleanest stoves. 

Some manufacturers added catalytic combustors and a new replaceable product for their dealers that needs servicing every year and replacement every few years. The better manufacturers played around with secondary combustion.  By injecting air into the top of the firebox they found they could reburn the gasses and get more heat and less smoke. Today the best woodstoves do not rely on catalytic combustors.

The EPA is now taking a long hard look at wood fired boilers. The only boilers that will meet the new regulations, are the newer style gasification boilers that have been used in Europe for over 30 yrs! http://www.health.ny.gov/environmental/outdoors/air/owb/purchase.htm

Did you realize that in Switzerland it would be illegal to sell or install a typical North American outdoor wood boiler which has been sold and installed by the tens of thousands across North America? The same holds true for most of Europe. They are amazed that we would burn such an outragous product and even more stunned at how popular they are here. But that is changing rapdily as folks begin to do their homework online and can see how the rest of the world does it.

3 Steps to Complete Combustion.

To burn solid fuels such as wood efficiently, you need complete combustion. For complete combustion you need 3 things - fuel, air and ingnition. How you control that process determins how well combustion occurs. By moving the combustion below the firebox where the wood sits, you super heat the fuel which vaporizes as a gas, the gas is drawn through a funnel which is re-combustion occurs at aprox 2000 degrees. There is very little particulate that escapes the chimney. Instead of smoke there is water vapor.

Here are some various pictures of gasfiaction boilers where the combustion chamber is below and combustion is controlled through variable speed blowers and oxygen controls. As you can see by the way the fire burns and how hot it gets, the thick refractory reflects all that intense infrared energy back raising the combustion temps like that of a steel blast furnace, far higher than if it were surounded with water and steel. The Pro Fab Elite is a good example shown on the right below.

The pictures demonstrate how a wood gasification boiler works. Combustion takes place at extreme tempertures below the firebox, essentially cooking the cordwood in the firebox above. As the wood cooks it releases gasses which are then burned cleanly.

Other high effeciency wood boiler designs

The Seton and the Greenwood boilers will also achive simular particulate exhaust results by an extrodinarily long flame length during burn and the massive cast refractory construction. The infrared is bounced around inside the firebox and the flames are pulled up through the heat exchanger and down through the exhaust, mounted on the rear of the boiler near the floor. The smoke temps here generally are only about 300 degrees. Pretty remarkable when you consider that over 1200 degrees went into the hot water heat exchanger!

The Seton/Greenwood boiler is a very simple yet efficient design. It works well as long as it is properly installed.  As with all solid fuel boilers, it is imperative that the heat exchanger inside the boiler return side, never fall below 140 degrees or it will condensate and corrosion will begin to the boiler itself.

All wood fired boilers should have a Dan Foss type mixing/tempering valve that makes sure the water inside the boiler always stays in the safe zone (above 140 degrees) and the extra BTUs are bled off to be used in heating applications.

A few benefits to the Seton/Greenwood  is that it converts the wood to coke when it is not calling for heat, so it can be used without water storage. When the temp calls for heat the draft opens and reignition occurs instantly if the unit has built up thermal energy inside the boiler from several weeks use. This boiler can burn large full rounds without a problem. It is much more forgiving to operate and burn, even if your wood is not perfectly seasoned. It is also mechanical so it is very reliable and not prone to power surge damage.

Water Storage or no water storage- what is the best way to go with installing a wood boiler?

This is the million dollar question, in my my humble opinion water storage is the best way to go, if you can make it happen. Let me explain it the way the Europeans view effcient hot water solid fuel boilers.

Picture this, you have a gallon of fuel and you have a generator. You need to produce eletricity to power your home. Running a large generator at an idle all day long does not make a gallon of fuel go very far, but run the generator at a more efficient speed and use that power to charge your battery bank. You can then draw a little power as needed later and the generator does not need to run except to charge the battery bank again. Depending on how frugal you are with your stored energy, will determin how long you can go on a charge.

Now picture that same generator as your new high tech gasifiaction boiler hooked to a set of storage tanks that are designed to store the BTU’s produced when the boiler is fired up as needed. What are the benefits you ask? Lots! Once again once you’ve experienced it, you wonder why you would ever do it any other way……..now you only need to run the boiler when needed, if the weather is mild, you pull less BTUs from your storage tanks and they stay hotter longer. So in mild weather you may only fire the boiler once a week when the tank temps drop below a certain temp, which triggers a flashing light somewhere that lets someone know its time to fire the boiler. In extreme cold you may have to fire the boiler every other day. The boiler runs at an optimal computer controlled combustion, the best and most effeceint of these employ Labada Technolgy which also montiers the CO output. This all basicly translates into per pound of wood fed to the boiler, you are getting over 90% back in usable BTUs. That means less wood hauled, split, stacked seasoned……..and feed to the boiler. If you are buying your wood, that really adds up fast.

Letting any solid fuel boiler idle for days is a very inefficient use of the wood, even a high efficiency gasification boiler does not retain that efficiency at idle. All boilers burn best at optimal temperatures. It is a good idea to have water storage for any boiler installation, because the same principle exsist in all solid fuel appliances -  you can not shut the fire down once started as you can with gas or oil by turning on and off a valve to control the flow of fuel. Once the wood is lit it takes a while to achieve good combustion temps. It is not good to stop, or interupt the process once it has begun. It is best to burn hot and store the energy in as large of tanks as your installation BTU demands dictate. It is best to do an energy audit and figure out the BTU load in the worst of weather. Then you can figure how many BTUs you should be able to store to last you between fires. We had a customer that was an over the road trucker who was home every other week.  He loved it that he could go 9 days in the coldest of weather before having to fire his boiler, so his wife did not have to bother with it at all. 

Installing your tank inside the home in the basement puts all those BTUs that do bleed off, inside the structure that you are heating, so there is little heat loss.

Next comes choosing a good gasification boiler. Today in North America you have far more choices than you did just 10 yrs ago. Pioneers like Craig Issod of www.hearth.com saw the handwriting on the wall and began importing the HS Tarm line of boilers way back when. These were cutting edge technology back then and there were few competitiors. Others soon followed and now you also have many options to pick from in European gasification boilers. Polish imports like EKO and BioMass offer a big bang for the buck. The new Effecta boiler is a Swedish built contender utilizing Lambda Technolgy. The Vigas has gained populairty particularly back east. If you want to stay North American made, the Pro Fab Empyre Elite series offers a great value for the price. The Woodmaster Flex Fuel Boiler is a state of the art US/German venture that is awesome and also utilizes Lambda Technolgy.

Whichever model boiler you go with, pick your dealer wisely. Great deals can be found online, but what happens when there are problems down the road. If your dealer won’t support you, you could be in a pickle. Also make sure you have a good installer who is familiar with installing boilers and has lots of happy customers. If you are capable of doing the installation yourself, review your local codes, so you understand all the requirements to do the installation properly. If your dealer does not know as much as you, maybe you better find a different dealer. Boilers are not something to play with if your not sure exactly what you are doing. Find a licenced professional to help you do the installation properly.

 

Where to install your wood boiler?

Your choice here should always be indoors in my opion. If you have a walk out basement, build a boiler room with a wood room and a shoot to feed the wood downstairs. Everything is nice and warm. If you don’t have a walk out basement, some boilers are extremely heavy and most stairways cannot support the weight.  Have a pro look at it first.

If you want the smoke and mess out of the house, I agree.  Add a shed on the back of the house, or build a freestanding boiler house to shelter your boiler and the wood you’ll be feeding it.

Here are some pictures of a perfect installation in my opionion.  Hopefully they will give you some ideas on how best to plan your new wood boiler installation.

This is a very professional clean installation belonging to our customer Charlie Woltz.  We can not take credit for this installation, but it is something everyone would be proud of.  

It is very well thought out and clean! It is obvious that the installer really took pride in their workmanship. There are many componets to a properly installed boiler system. If installed properly, a wood fired boiler system should give you 30 yrs of trouble free service.

Open or Closed System, what does that mean and what are the benefits?

The easiest way to explain this is to compare a boiler system to a vehicle cooling system. On a vehicle, the cooling system is closed.  There is a pressurized cap that will vent if the tempertures get to hot and the system begins to boil over. Rather than exploding, the cap releases the presure and the fluid escapes. There is also a thermosat in the system which opens and closes according the coolent temps. When the vehicle is cold in the morning, the thermosat is closed and recirculates the water through the engine block, allowing the engine to reach operating temps faster. Once the engine is warm, the thermosat opens and coolent flows through the system, regulating the tempertures to the engine so it runs at optimum temps. Now picture your wood boiler as the engine and the cooling system as your radiant heating system. They are very similar in design.

The main benefit of a closed system is that the water will not boil as quickly and it boils at a hotter temperture than 220 degrees which is where water boils at sea level.  That changes with elevation. So in a nut shell, you can run a boiler hotter under pressure than you can an open system.

So why would you want an open system? The main reason is saftey, an open system is not presurized and therefore can not explode if improperly installed. In many places it is a crime to mess with a pressurized boiler system if your not properly licensed to do so. Many people have died in boiler explosions over the years, so the authorities are pretty strict for obvious saftey reasons. Properly installed, pressurized boilers are as safe as any domestic hot water tank.  

Open system boiler systems are non pressurized and called “Open” because they vent naturally to the atsmosphere. If the boiler is overfired and boils, steam comes out a pipe and is vented. It cannot explode because it can not build pressure. There are many boilers in service that employ this method.  The main drawback of these types system is they must be mointered constantly and kept full of water. The water is constantly evaporated off the system and must be replaced or the boiler will eventualy fail from overheating. It will normally make a terrible racket causing you to think there is an 800 lb. gorilla inside that is not happy. If that happens you have a few minutes to save your boiler. There are automated fill systems that will keep your boiler full of water at all times. If you choose an open boiler system, make sure you invest in a good one. If the automated fill system fails it will normaly either flood the boiler room with tap water, or not add water as needed. Always check this system and make sure it is functioning properly.

There is such a thing as an combo open/closed boiler system. This is common when you find the boiler is an open system and the radiant system is closed. Most radiant systems and heat handlers are closed. The way this is accomplished is through a heat exchanger that can be a finplate, or a sidearm exchanger. The open boiler system is its own loop and it circulates that way. BTUs are transferred through a heat exchanger into the closed loop system.