Power of Steam:

Steam is formed when water expands 1600 times. Steam consists of large amounts of heat, which makes water a cost-effective and ideal raw material for creating heat and power. High pressure boilers create steam by heating water at over 15 psi and have water pressure over 160 psig.

Combustion Efficiency:

Combustion efficiency differs from stack loss, which is the heat loss by flue gases and moisture. It is the measure of how well the fuel is being burnt in combustion. High pressure boilers are extremely efficient with all of the fuel being converted to thermal energy.

Thermal Efficiency:

High pressure boilers are up to 95% thermally efficient. Thermal efficiency is the ability of a heat exchanger to transfer heat from the heating process to water or steam.

Fuel-to-Steam Efficiency:

ASME Power Test Code is used to measure fuel-to-steam efficiency. It is the ratio of BTU output and the BTU input. The input is the amount of feedstock used in combustion, while the output is the steam produced. In most cases, high pressure boilers have an 85% fuel to steam efficiency.

Stack Temperature and Losses:

Temperature loss due to the combustion of gas in a boiler is called Stack temperature. An efficient boiler uses the maximum heat generated from combustion. To avoid stack loss, the amount of air is controlled in high pressure boilers to avoid excess air. The amount of air needed is dependent on the type of fuel.

Excess Air:

15 – 20 % excess air is normally required in burners to burn efficiently. However, the amount of excess air is kept to a minimum in high-pressure boilers. Existence of excess air can be proved by the rise of flue gas temperature.

Radiation and Convection Losses:

Radiation and convection losses are dependent on the type, size, and pressure of the boiler. These losses occur due to the difference in temperature of the boiler and its surroundings. Though it is impossible to totally eliminate radiation and convection losses, insulation of pipe and boiler body help in controlling their effect.

Heating Surface:

Efficiency of a boiler depends on the heating surface a boiler has per horsepower. Generally, a boiler produces 5 to 7.5 lbm/hr of steam per square foot of heating surface.

Flue Gas Passes:

The number of passes flue gas makes before leaving the boiler is an effective way of examining efficiency. As the gas moves around the boiler, it cools down changing its volume. The more passes it makes, the efficiency of the boiler increases, thus increasing the gas velocity.

Burner:

The performance of a boiler depends greatly on the burner, controller, and boiler working as a cumulative system. Furthermore, the efficiency of the burner is important to evaluate the cost of the boiler. Burners have precise air levels that ensure complete combustion.

Written by John Hamlin

These wood fired ovens with boilers are not required to meet EPA regulations. The North Hydro & Concept 2 Max Hydro both fit into the EPA’s definition of a wood cookstove, which is currently exempt from EPA regulations. These stoves meet Washington state wood cookstove standards.

The Concept 2 Max Hydro Central Heating Wood Range, and the Tim Sistem North Hydro Boiler with Oven, are designed with modern heating and cooking in mind. Both wood boiler cookstoves have glass doors on the firebox and oven for easy viewing. The glass door on the firebox has an excellent air-wash design for clean glass and a clear view of the crackling fire. The best part is that these stoves are definitely aesthetically appealing to those wanting an efficient heating source, and a stylish centerpiece for their home.

These European-made central heating cooking ranges provide the ability to connect into hydro heating. Yes, you can now efficiently heat your home with hot water, and have the ability to use the cooktop or wood-fired oven.  The sophistication of this superb wood burning hydronic cook stove is sure to please all consumers – from the novice to the advanced wood burner. These wood boiler stoves are available in a wide variety of colors to match all styles of decor: The North comes in stainless steel or black, while The Concept 2 Max Hydro comes in red, inox (stainless), gray, beige, and white.

These wood-burning central heating stoves are diverse in their radiant heating abilities. The Concept 2 Max Hydro also provides coal-burning capabilities, meaning it burns hotter, thus producing more BTUs. Personally, I love a wood burning stove that offers the ability to burn coal. I believe this is an excellent feature, as coal stoves pull in air from underneath the firebox for proper combustion air – this essentially works as a super charger when burning wood, allowing for easy ignition of the initial fire. In addition, if the stove can handle the high temperatures of coal, it is definitely built to last. Please keep in mind, however, that the North Hydro Wood Boiler Cook Range is rated to burn wood only.

You will not be disappointed with the ease and functionality of use of these wood fired ovens with boilers. It is critical that all boiler systems are set up properly and it is recommended that you consult a certified plumbing contractor when installing these systems. Once the system is properly installed, you will be pleased with the simplicity of the maintenance of the stove. The cooktop is removable, providing easy access for top and oven clean out. Ash clean out is located directly below the firebox, meaning all cleaning access is available from the front of the stove, perfect for tight clearance installations.

Heating with Hydronics

The Concept 2 Max Hydro & Tim Sistem North Hydro can be plumbed into a wide variety central heating systems, including both open and closed loop systems. Wood hydronic heating can be used for different applications too, including residential or commercial heating, radiant floor heating, domestic hot water, heated spa or swimming pool, greenhouses, farming, and snow melting. Every building or heating system is considered to be its own heating zone and should be installed with its own independent circuit controller, thermostat, and aquastat. Each heat zone will call for the correct water temperature depending on its heat distribution and room temperature required.

These wood fired ovens with boilers will produce heat in two efficient distribution forms. First, the boiler will provide radiant convection heat within the room where the stove is located, heating an area of approximately 1,000 square feet.  Second, you can plumb the boiler system which produces approximately 26,000 BTUs on the North Hydro or 75,000 BTUs on the Concept 2 Max Hydo. This allows you to use these appliances as hot water central-heating with the added bonus of a wood-fired oven that can be used as your primary residential heat source*. The boiler will heat the water that the pump transfers through the pipes, providing hot water to the room-heating units that are using radiant heat and convection to heat the room air. These units are usually called baseboard heaters, panels, radiators, or convectors.

*Note: Depending on size of home, insulation, and external temperatures.

We’ve had a chance to get our hands on both the Concept 2 Max Hydro and the North Hydro, so please check out our videos to learn more about these great hybrid boilers.

You can now find these products on Obadiah’s website too! Check out the links below:

North Hydro Wood Cookstove with Boiler

Concept 2 Max Hydro Wood Boiler with Oven

– Article by Sarah Chain

“Kitchen Boiler Connections” is a large collection, totaling over 140 pages, but its robust index can help you seek out just about any specific aspect of boiler installation you’re looking for more information on.

Download the eBook “Kitchen Boiler Connections” in PDF form, here (right click, “Save As..”).

“Hot Water Supply and Kitchen Boiler Connections: A Selection of Practical Letters & Articles Relating to Water Backs & Range Boilers, Compiled from the Metal Worker” by William Hutton, despite its age, outlines the basic principles involved in domestic hot water heating and range boilers. There’s a multitude of diagrams, drawings, and explanations covering just about every detail you can imagine. It’s a dense read, and if you’re after a specific topic, we recommend flipping to its extensive index beginning on page 203 (211 in the PDF).

Download the eBook “Hot Water Supply and Kitchen Boiler Connections: A Selection of Practical Letters & Articles Relating to Water Backs & Range Boilers, Compiled from the Metal Worker” in PDF form, here (right click, “Save As..”).

We’ve talked about batch burners before, but here’s a refresher: All EPA gasification boilers require thermal batteries to store their BTUs. Basically, the BTUs are stored in a water tank and pulled out whenever your home calls for heat. This inevitably becomes a juggling act: If you don’t have enough BTUs stored when you fire the boiler, the water will boil and the pressure relief valve will open, dumping the BTUs so the tank doesn’t explode (which is good for your safety, but no so much for your warmth). If you’ve connected forced air or a radiator to your boiler, then the temperature needed to make heat has to be above 160 degrees. Since water boils at 212 degrees, most boiler users keep the water storage set to 200 degrees just to avoid triggering the pressure relief valve.

This is wasteful. Think of the situation like this: You have deposited $200 in a bank account, but you’re only allowed to withdraw $40 from it. Period. The account always has to have $160 in it, but because you can’t touch that $160, it is essentially worthless to you. That’s the reality of European batch burners; because they do not idle and modulate like modern gas, oil, or electric boilers do, you are forced to maintain heat that you can’t even use. It’s a trade-off that you accept as a wood-fired boiler user, but… What if you didn’t have to?

That’s where the WoodMaster CleanFire Boiler comes in. Obadiah’s has worked with WoodMaster in the past and we have always been impressed with their ability to stay on the cutting edge of technology, but the CleanFire really takes things to a new level.

First, the issue of BTUs. While a batch boiler is constantly expending energy on heating, even if you’re not using it, the WoodMaster CleanFire wastes nothing. By modulating heat according to demand, the CleanFire can shut down when the load is not there and ramp up BTUs when they are needed, eliminating the requirement for thermal batteries altogether. This is the only wood-burning boiler in its class that has been able to make modulation work effectively, and it’s one of the many reasons we’re very excited about the CleanFire.

So, let’s dive into the gritty details:

Like other WoodMaster products, the CleanFire’s combustion process uses a lambda sensor, which monitors the oxygen levels and adjusts the boiler to maintain an optimal burn. During the burn, gases leaving the combustion chamber are mixed with oxygen in an injection tube, ensuring complete combustion through the catalyst. WoodMaster has been designing boilers for years and, in our experience, they had the burn process down to an exact science before they even began working on the CleanFire. However, with this unit they have once again demonstrated their ability to make consistently outstanding units.

The combustion process itself is made possible by WoodMaster’s unique control board. With over 300 settings used to maintain furnace modulation, you can easily burn at the optimum rate every single time without resorting to inefficient techniques like batch burning or quick cycling. Sensors built into the unit allow the control to read internal and external water temperatures, adjusting the boiler automatically to satisfy the heat load. You also never have to worry about overheating, as the board displays water and catalyst temperatures, 02 level, boiler pressure, and gives you a history of alarm details. Plus, the WoodMaster CleanFire is WiFi-ready, meaning you can monitor the system in home and even link it to your smartphone. That’s right: You no longer have to worry about leaving home and coming back to a surprise disaster, because with WoodMaster’s control board, you can stay updated no matter where you are. It’s a relatively small touch, but features like this really demonstrate the kind of forward-thinking that the wood boiler industry desperately needs more of.

WoodMaster has also ensured the CleanFire is user-friendly to everyone, not just those with years of experience in using wood boilers. The CleanFire has no water storage or wet firebox; instead, it uses a dry fire chamber which is not in contact with water. This leads to several advantages including no creosote build-up, and no ash corrosion. Imagine, a heating unit where you don’t have to worry about expensive, decaying parts (without air, corrosion cannot take place) and one where you no longer have to put in a back-breaking effort every spring to get rid of the mess that builds up throughout the cold season. In fact, with the dry fire chamber, the CleanFire takes only a few minutes to clean. You can expect to clean the heat exchanger tubes twice a year and remove the ash from the bottom chamber as needed, but that’s it. Simple.

If you take care of the WoodMaster CleanFire, it will take care of you. The pressure chamber is ASME-certified (it will be available commercially even in Massachusetts and New York!) meaning the materials and workmanship are of the highest quality, so you can expect a lifespan that is easily 40 to 50 years with proper maintenance. Since the boiler meets or exceeds EPA Step 2 requirements for certifications, you will be able to make full use of the boiler without worrying about federal restrictions down the road. The CleanFire’s final retail price has yet to be announced, but make no mistake: It is built to be the last outdoor furnace you will ever need to buy.

There are a number of other details about the CleanFire that make it stand out, including an autofill function so you never have to worry about low water, separate blow down valves for each vessel, programmable LED lighting, and important safety features such as a low water cutoff and high limit control. It’s also UL and ULC certified, which is a comforting official stamp on just how reliable the boiler really is.

Obadiah’s and WoodMaster are both family-operated businesses, we care about our customers and work very hard to bring only the best heating products to the public. It’s been a slow process getting the CleanFire ready for the market, but once it is, Obadiah’s will initially be the exclusive online dealer. Our experience in engineering and hydronics allows us to do what other WoodMaster dealers currently cannot, and we could not be more excited about the opportunity.

As a result, the EPA has updated many of their regulations in hopes of creating cleaner air across the United States. But what does that mean to you? We recently wrote an article about the new regulations, but many people still had specific questions: What kind of boiler are you allowed to own as a resident? What about as a business? If you live outside of the United States, what boilers are you allowed to purchase?

We heard your questions, and dug through miles of government documents to bring you the answers without all the legalese.

Frequently Asked Questions

• What is “40 CFR Part 60?”
• What is “40 CFR Part 63?”
• What exactly is a “hydronic heater”?
• I live in the United States. What regulations apply to me for residential wood boilers?
• What regulations apply if I want to buy a commercial wood boiler?
• I own a wood boiler and it doesn’t meet the EPA’s new standards. What should I do?
• I live in the United States. Can I legally operate a wood boiler that is not EPA-Certified?
• I live in Canada. Can I purchase a residential wood boiler that is not EPA-Certified?
• What regulations apply to commercial wood boilers in Canada?
• Resources

What is “40 CFR Part 60?”

“40 CFR Part 60” is the name of the EPA’s set of regulations for residential wood stoves and wood boilers. Its full title is “The Source Performance Standards for New Residential Wood Heaters, New Residential Hydronic Heaters and Forced-Air Furnaces,” or “The NSPS” for short. These regulations were updated in 2015, and most states have adopted them as part of their local laws.

What is “40 CFR Part 63?”

“40 CFR Part 63” is the set of regulations for commercial, industrial, and institutional wood boilers. These types of boilers are also called “area sources,” which means they emit less than 10 tons annually of a single hazardous air pollutant or less than 25 tons annually of a combination of hazardous air pollutants. They’re typically found in places like schools, manufacturing buildings, event centers, and other similarly large buildings.

What exactly is a “hydronic heater”?

A “Hydronic Heater” is what the EPA calls a wood boiler. According to the EPA: “Hydronic heaters (also called outdoor wood heaters or outdoor wood boilers) are typically located outside the buildings they heat in small sheds with short smokestacks. Typically, they burn wood to heat liquid (water or water-antifreeze) that is piped to provide heat and hot water to occupied buildings such as homes, barns and greenhouses. However, hydronic heaters may also be located indoors and they may use other biomass as fuel (such as corn or wood pellets).”

I live in the United States. What regulations apply to me for residential wood boilers?

To meet EPA certification, a residential wood boiler must meet the following emission standards for particulate matter: 0.32 lb/mmBtu heat output (weighted average) and a cap of 18 g/hr for each individual test run. You can find a full list of wood boilers certified by the EPA as of February 2016, here.The EPA’s Emission Limits for Residential Wood Boilers (40 CFR Part 60):

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What regulations apply if I want to buy a commercial-size wood boiler?

Commercial boiler regulations are found in 40 CFR Part 63, the “National Emission Standards for Hazardous Air Pollutants for Area Sources: Industrial, Commercial, and Institutional Boilers.” These types of boilers typically provide heat for buildings like manufacturing plants, greenhouses, trade goods housing, real estate, educational services, religious organizations, public administration, and other similarly-sized buildings. Boilers for these types of buildings have to put out some serious heat, but they must not exceed the limits in this table from the EPA:The EPA’s Emission Limits for Commercial Wood Boilers (40 CFR Part 63):

This chart by the EPA has more information on the exceptions to these rules (for example, if you shut down your boiler for seven months out of the year, you might qualify as a seasonal boiler). We also suggest that anyone operating a large building with a boiler installation read 40 CFR Part 63, which can be found in the resources at the bottom of this post.

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I own a wood boiler and it doesn’t meet the EPA’s new standards. What should I do?

Great news for you: The EPA’s updated wood boiler regulations do not apply to any boilers that were sold before December 31, 2015. If you bought your boiler before that date and it was in compliance with the regulations set at the time of installation, you don’t have to do a thing!

Note for Washington State residents: NO outdoor wood boilers are allow in your state as of 2016. Visit the Washington Department of Ecology for more information.

I live in the United States. Can I legally operate a wood boiler that is not EPA-Certified?

In most states, the answer is no. Under federal law (42 U.S.C. §7416), a state’s regulations for wood heaters such as wood boilers are required to be equal to or greater than the EPA’s regulations. If you buy a wood boiler that is not EPA-certified, it probably does not comply with your local laws.

We checked the laws for each state to see how they regulate wood boilers and have created a summary of where wood boilers have to be EPA-certified and where they do not (see the table below). The vast majority of states require wood boilers to be EPA-certified. Most states have done this by referencing or incorporating 40 CFR Part 60 directly into their list of state laws but some, like Washington state, have stronger restrictions than the EPA. However, several states such as Missouri, Hawaii, and Michigan have chosen to ignore the EPA’s regulations altogether, and many others states simply have no information available online. If you live in a state we’ve listed as “no data” please check with your local Department of Environmental Quality to see what regulations apply to you, and if you have any information yourself please share it with us in the comments.

Wood Boiler Regulations By State

Some states make exceptions to EPA certification if you don’t have access to other heating options. These exceptions are too numerous to list here, but please contact your state’s environmental department for more information.

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I live in Canada. Can I purchase a residential wood boiler that is not EPA-Certified?

Yes. In Canada, residential indoor boilers and furnaces are only subject to “The Code of Practice for Residential Wood Burning Appliances,” which says that a boiler must have a particulate emission limit of 0.4 g/MJ. This is roughly equal to 0.93 lb/mmBtu, much higher than the EPA’s requirement of 0.32 lb/mmBtu for residential wood heaters. Many boilers that do not meet the EPA’s emission standards do meet the standards in Canada.

Canada Residents: Keep in mind that “The Code” exists in Canada to provide municipalities with advice on best practices for reducing emissions. Local governments have the final say in what laws apply to you, so please check your area’s guidelines before purchasing a boiler. You can read “The Code” online, here (see page 18 for emission limit details).

Manufacturers and distributors should also know that, according to the EPA, wood boilers manufactured in the United States for export are exempt from the EPA’s emission limits (NSPS Page 45, § 60.5472). U.S. manufacturers and retailers are allowed to sell non-EPA-certified wood boilers and furnaces to anyone outside of the United States.

What regulations apply to commercial wood boilers in Canada?

Commercial boilers in Canada are required to be manufactured to standards set by local or provincial Boiler and Pressure Vessel Act, all of which ultimately refer to the Canadian Boiler and Pressure Vessel Code (CSA B51). CSA B51 relies on ASME standards. Basically: If a boiler is ASME-certified, it meets Canadian standards of manufacturing. However, you may be required to obtain a wood burning permit from your local government.

Have more questions? Submit them in the comments below and we will do our best to answer them!

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Resources

The List of EPA-Certified Hydronic Heaters (updated Feb. 2016)
40 CFR Part 60 – The New Source Performance Standards for Residential Wood Heaters and Hydronic Heaters
40 CFR Part 63 – National Emission Standards for Hazardous Air Pollutants for Industrial, Commercial, and Institutional Boilers Area Sources – Subpart JJJJJJ
Summary of the EPA’s requirements for Residential Wood Boilers
EPA’s Burnwise Program – Click your state to find links to local regulation information
Cookstove Community – EPA Woodstove Regulations: What You Need To Know

Wood boilers are growing in popularity every year with people looking for effective ways to use wood heat, and if you’ve had any experience using a boiler, you know how wonderful they can be. However, like wood stoves, wood boilers produce smoke. And also like wood stoves, the amount of smoke produced by a wood boiler, called particulate matter, is regulated by The Environmental Protection Agency (EPA). You can find a detailed explanation of particulate matter and how it can be dangerous to wood heat users here, as well as an explanation of how the EPA’s regulations affect users of wood stoves.

In a nutshell, burning wood releases a certain type of particle that is dangerous when inhaled in large quantities. To help keep emissions low, in 1988 the EPA implemented the New Source Performance Standard (NSPS) for residential wood heaters as part of the Clear Air Act. In recent years, the EPA has been reviewing the NSPS in order to make it more relevant to current heating technology, and that review concluded in the spring of 2015 when the EPA released the revised edition of the NSPS.

Do I Have To Follow These Regulations?

It’s important that you understand the legality of these standards. While the NSPS is federal regulation, it does not in itself impose any requirements on state and local governments. However, the contents of the NSPS are part of the Clean Air Act, and that act requires each state to have a plan to maintain the National Ambient Air Quality Standard (NAAQS). Because states are not allowed to have emission limits weaker than those set in the NAAQS, the limits found in your state’s laws will be at least equal to what the EPA sets in their regulations. Some states such as Washington, Vermont, and New York, have regulations that are even stricter than those set by the EPA.

In discussing the Clean Air Act’s overall function, EPA spokesperson Lisa Conner says that “the emission guidelines found in the NSPS generally constitute the goal that states have to meet when developing standards for existing sources.” But while many states use the regulations in the NSPS as a guideline for determining air quality laws, you may find that the best boiler for you has a legal, acceptable amount of PM emissions without being EPA-certified.

So before installing a wood heating system of any kind, you absolutely must check to see what local laws and regulations are applicable to you; following them is in the best interest of you and your community. You can get in touch with your local Department of Environmental Quality for more information, or visit the EPA’s Burnwise Program to learn how your state is dealing with wood smoke.

The New Source Performance Standard and Wood Boilers

So what do these updates mean to you, as a user of an indoor or outdoor wood boiler?

The EPA defines “wood-burning hydronic heaters” (wood boilers/wood furnaces) as “a fuel-burning device designed to burn wood or wood pellet fuel for the purpose of heating building space and/or water through the distribution, typically through pipes, of a fluid heated in the device, typically water or a water and antifreeze mixture.”

Until this year, usage of wood boilers was not covered by the NSPS, meaning that you could burn whatever you wanted in your boiler, in any way you saw fit. But an increase in use of wood boilers over the last eight years has led to a decrease in air quality in some areas of the country, and as a result, the EPA has established emission limits. The new limits are broken into two phases in order to ease the wood heating industry’s transition into them, and do not apply to wood boilers in use prior to the effective date.

Emission Limits For Wood Boilers

The emission limits for wood boilers set in the 2015 revision of the NSPS are:

The revision to the NSPS also requires the operator of a wood boiler to operate it “in a manner that is consistent with the owner’s manual” and that “manufacturers discuss the best operating practices in the owner’s manual.” In their updated Small Entity Compliance Guide (May 2015), the EPA establishes prohibited fuel types that include the following for wood boilers:

• Residential or commercial garbage
• Lawn clippings or yard waste
• Materials containing rubber, including tires
• Materials containing plastic
• Waste petroleum products, paints or paint thinners, or asphalt products
• Materials containing asbestos
• Construction or demolition debris
• Paper products, cardboard, plywood, or particleboard
• Railroad ties, pressure treated wood or pallets
• Manure or animal remains
• Salt water driftwood or other previously salt water saturated materials
• Unseasoned wood (defined as wood with an average moisture content of 20% or more)
• Any materials that are not included in the warranty and owner’s manual for the subject wood heater
• Any materials that were not included in the certification tests for the subject wood heater

Eliminating the use of these materials as fuel will greatly reduce poor combustion that causes hazardous environmental conditions.

On May 15, 2015, Step 1 of the NSPS revisions for wood boilers went into effect. Any EPA-certified wood boiler manufactured on or after that date is required to adhere to the 0.32 lb/mmBtu heat output. To ease the transition process to cleaner boilers, retailers are allowed to sell any inventory that does not meet Step 1’s requirements as long as it was made before 5/15/15. This transition period ends on 12/31/15. After that date, all wood boilers sold at retail must meet the Step 1 emissions limit.

Note that it is still legal to sell or own a wood boiler that is not EPA-certified, and that it is only illegal to operate a boiler that does not comply with state or city air quality laws. Chances are your local state laws already reflect the EPA’s update to the NSPS, but please check with your Department of Environmental Quality to find out what regulations apply to you before purchasing a wood boiler.

What about Manufacturing Wood Boilers?

All wood-burning hydronic heaters manufactured after 5/15/15 or sold in the United States after 12/31/2015 will be required to have a permanent label affixed to it that includes the month and year of manufacture, model name/number, certification test emission value with test method and standard met, and serial number. These labels must be easily visible before and after the unit is installed. More details about the information required to be on labels can be found on page 170 of the NSPS (Subpart AAA, § 60.536).

As seen in the table above, there is a cord wood alternative compliance option for wood boilers. The EPA is allowing this option for manufacturers who choose to certify using cord wood (rather than crib wood) to meet the Step 2 limits for wood boilers. Cord wood testing is a better measure of how hydronic heaters actually perform in home use, but the EPA was concerned that many manufacturers would not be able to design their units to perform well with cord wood testing. Allowing a slightly higher emissions limit encourages small businesses to follow the example of industry leaders, with less economic impact for those that are unable to meet the Step 2 requirements by 2020.

Manufacturers of wood boilers should note that the emission limits under Step 1 are the same as those currently needed to qualify for the EPA’s voluntary Hydronic Heater Program. If a manufacturer participated in and was “phase 2” qualified under that program, in most cases they will be automatically EPA-certified under the revised NSPS. Other manufacturers that have been certified by the New York State Department of Environmental Conservation (NYSDEC) to show they comply with Step 1 emission limits will also be automatically EPA-certified, as will any manufacturer with RHNY-qualified pellet hydronic heaters.

Specifics about certification testing and the third-party certification process can be found in section 4.1 of the 2015 Small Entity Compliance Guide.

Summary

Wood boilers have been manufactured and used for years without any form of regulation, and while many manufacturers and owners have taken great care to mind their environmental impact, the actions of less mindful individuals have resulted in a need for emission standards. By setting limits on emissions, the EPA hopes to greatly reduce the amount of dangerous PM2.5 in the air over the course of the next decade.

Whether you’re manufacturing wood boilers, selling them, or just enjoying the benefits of their heat, understanding the EPA’s regulations and how your state interprets them will go a long way towards helping you get the most out of wood heat.

Resources

The New Source Performance Standards for Residential Wood Heaters
2015 Small Entity Compliance Guide
Summary of Requirements for Wood-fired Hydronic Heaters

When one thinks “Canada”, however, the word “cold” comes to mind pretty quickly. How could such a large, unconventional structure stand up to the notoriously chilly weather of Alberta? Physics, and some clever design work.

First, a note about the creators: The Solar Dragon has some powerful minds behind it in the form of Alberta’s Living Design Systems. Owner Paul Belanger has over thirty years of experience with solar and energy efficient designs, and since 1998 has designed or built 34 solar and straw bale buildings. Living Design System’s has won multiple environmental awards for their designs, have built more straw bale buildings than any other company in Western Canada, and have a long history of customer satisfaction throughout Canada that continues today. For this project, Belanger teamed up with electronics engineer Kurt Klingbiel, who installed the solar electrical system in the house, and whose experience with pressure systems and copper plumbing made the crafty mechanics of the home possible.

Living Design’s expertise is inherent in the Solar Dragon design. By using a combination of straw bale walls, cellulose ceiling insulation, and a type 2 EPS foundation insulation, the heat load of this design is only 25% of a conventionally built house of the same size in Canada. This particular house has a large area of south-facing glazing in the central living area, making for a very significant passive solar component. Taking advantage of this passive component is a giant thermal mass designed right into the house, in the form of a concrete slab-on-grad floor.

As mentioned earlier, the Solar Dragon draws heavily from Asian aesthetics and home design. The owners of this space frequently travel to India, and Living Design Systems incorporated this preference into the basics of the home by applying sacred geometry, including a beautiful central pine support post reminiscent of the “Tree Of Life”, symbolic in many eastern religions and Christianity.

All the elegant design in the world won’t stand up to the harsh winters of the north, however, so the Solar Dragon makes use of four heat sources: Passive solar gain, biomass heaters (wood stoves), a biomass water boiler with thermal tank, and active solar thermal panels on a solar chimney. Any one of these heat sources would provide enough heat for the entire home on its own, but this set up allows for redundancy, ensuring that the home will have heat no matter what (there is also an additional backup electric hot water tank).

The Solar Dragon’s primary source of heat is passive solar gain, provided by the large south facing windows on the house. These windows are not covered with drapes or blinds at any time, allowing them to effectively collect heat from the sun (insolation). Even on a cold winter day, clear sunlight hitting these windows provides far more energy than all three of the biomass burners combined. Making use of the greenhouse effect, this setup traps heat in the floor of the central part of the house.

In the long daylight hours of the spring and summer, the integrated design of a solar chimney provides the vast majority of all domestic hot water needs (in rare occasions, you may need the boiler during the summer). This chimney serves several roles: Solar hot air panels are mounted to the south side, it houses the large thermal hot water tank, and is also the chase for the boiler chimney (which adds some heat to the space around the hot water tank).

But passive solar gain and a solar chimney are not always enough in a northern climate with short sunlight hours in the winter. That’s where the other three heat sources come in handy, and one of the biomass heaters takes the form of a woodstove located in the east alcove. This alcove makes exceptional use of wood heat by taking convection into account, allowing natural warm air to flow to all nearby bedrooms, whose temperature can be control simply by opening or closing a door. By designing the alcove like this and placing it in the lowest level of the house, away from any warm air sources other than the stove, the room becomes the coolest in the summer and the warmest in the winter.

Belanger also added an Esse Ironheart wood cookstove to the kitchen, one of Obadiah’s favorite cookstoves. The Esse is powerful enough to heat the central area on its own, but also provides a reliable way to cook just about anything. Its unique dogbone-style hotplate on the stove top can accommodate up to half a dozen pans at once, the oven is one of the most spacious of any cookstove available, and by using a system of indirect heat, the Ironheart ensures that your food is perfectly cooked and not dried out. It’s also one of the most efficient cookstoves out there, making it a perfect fit for an environmentally-conscious household like this one.

Now, the boiler. The wood boiler installed in the Solar Dragon is a Greenwood 100 (which are no longer in production; for a similar boiler, Living Design Systems and Obadiah’s recommend Glenwood). It acts as the main source of domestic hot water and home heating energy, and sends most of that energy in the form of hot water to the 400 gallon thermal water storage tank in the solar chimney, which is thoroughly insulated to prevent the loss of high water temperatures. The boiler puts out 100,000 BTUs and after a four to five hour burn, the tank’s temperature in the solar chimney rises from 100 F to 165 F. The thermal tank is not pressurized, and as a result, a hot water pressure pump takes water from the tank to a secondary tank for domestic hot water (which is also well insulated).

Not only does the boiler provide domestic hot water, but during the winter, it is one of two primary sources of heat for the in-floor heating system located in the mudroom/foyer and bathrooms. A classy bonus to be sure, and not one you expect in most self-sustained buildings.

The water tank in the solar chimney is not heated solely by the boiler, however. Installed on the south side of the of the solar chimney are solar hot air panels, which also provide heat to the water and reduce the number of boiler burns required per week. In central Alberta, where the Solar Dragon is located, these panels alone will still provide hot water two out of three days during the winter. In the spring or summer, the boiler will rarely (if ever) be needed- with the long hours of daylight, the solar panels will do all the heating work when it comes to domestic hot water.

What does all this mean for the residents of the Solar Dragon?

No heating bill. At all.

That’s certainly an enticing idea for those of us in northern climates, especially once winter rolls around. After a few months of paying for gas or electric heat, the idea of being cold starts to sound better than being broke. With the Solar Dragon, however, you’ll never have to make that trade-off; it simply requires that you provide enough firewood to feed the boiler and biomass heaters for the winter. A little bit of preparation before the snow hits means an entire winter of worry-free heating, and that sounds perfect to us.

The Solar Dragon is a shining example of self-sufficiency, an off-grid home that does not sacrifice comfort for independence. It’s also a model of alternative energy use, something that Obadiah’s has advocated for decades. Paul and his team at Living Design Systems have shown here that reliance on gas or electric is increasingly unnecessary, and that harnessing the power of solar and biomass heat is a rewarding, effective way to live naturally.

To learn more about the Solar Dragon and Living Design Systems, please check out their official website.

Construction Photos

Finished Design Photos

Man has been burning wood as a renewable, carbon-neutral fuel for thousands of years, but it’s only recently that we have given much thought to what is coming out of the chimney. As Americans, we seem to be more behind the curve in this realm more than most countries. 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.

Here in the USA, more and more communities are concerned about airborne particulate, and with the government clamping down on woodstoves over the years, new EPA-rated stoves are burning cleaner, longer, and produce more heat with less wood. States are passing regulations requiring all new and replacement stoves to be EPA-certified and to display test results where the world can see. As a result, North American manufacturers have stepped up to the plate and re-engineered their product line, leading to a behind-the-scenes competition amongst manufacturers to produce the cleanest stoves. It is now a sense of pride to build the cleanest stove.

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 re-burn the gasses and get more heat and less smoke. Today, the best woodstoves do not rely on catalytic combustors.

All of this leads to the fact that the EPA is now taking a long hard look at wood-fired boilers, and the only boilers that will meet their new regulations are the style of gasification boilers that have been used in Europe for over thirty years!

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

3 Steps to Complete Combustion

To efficiently burn solid fuels such as wood, you need complete combustion. For complete combustion you need 3 things: Fuel, air, and ignition. How you control that process determines 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, and that gas is drawn through a funnel where re-combustion occurs at 2000 degrees. There is very little particulate that escapes the chimney; instead of smoke, there is water vapor.

Below are various pictures of gasification boilers where the combustion chamber is below, with combustion 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 temperature. It’s like that of a steel blast furnace, and far higher than if it were surrounded with water and steel. The Pro Fab Elite (below) is a good example.

1. Is the system a closed system or an open system?

Advantages of a closed system

No oxygen can get into the water, thereby eliminating the possibility of corrosion through oxidation (rust). There’s no need to keep the outdoor boiler water separate from the indoor system, which eliminates the extra expense and inefficiency of a plate exchanger. A closed system also does not need as big of a circulator because of the pressure in the system, has a much longer life span without needing to treat the boiler’s water, and there’s no need to keep the system re-supplied with water.

Advantages of an open system

If boiling occurs in the boiler, the water just steams off and is less likely to rupture plastic underground piping. All closed systems, however, require a pressure relief valve that will explode if the boiler pressure gets too high. Water temperature also can’t get as high as with a closed system, which could be an advantage or a disadvantage depending on the application. Greenhouses, livestock buildings, and lumber kilns all require high water temperature for effective heating.

2. What is the efficiency rating?

Combustion efficiency should be nearly 100%

Combustion efficiency can be ascertained by ash content, creosote build-up, and smoke. If there is no smoke, very little ash, and little creosote deposits, the fire is burning at peak efficiency. In a solid fuel boiler, this is accomplished by proper amounts of combustion air injected into the firebox at the right spots. However, quality of wood will also affect the ash content and smoke level. Wood that is half rotten or has a lot of bark on it makes more ashes and smoke than good, quality firewood. A forced draft is usually necessary for proper fuel combustion, and a hot fire is also necessary for good combustion efficiency. When a solid burns, it goes through a chemical reaction that breaks it down into a liquid, a gas, and a solid. In wood, the liquid is the tar (creosote), the gas is wood gas, and the solid is charcoal. The creosote and gas leave the charcoal at the same time and produce the smoke. If the fire is a “cold” fire, the creosote will separate from the wood gas and condense as a tarry substance either in the chimney or in the boiler. This happens when there isn’t sufficient oxygen to burn the gases and produce a hot fire, which leads to smoldering, and will produce un-burnt smoke and creosote. Keep in mind that creosote is not a good thing to have to deal with, even if it is only in the stove and not in the chimney. Aside from the fact that it’s a fire hazard, creosote is acidic and will cause corrosion, as well as retard heat transfer.

Heating efficiency should be above 85%

There must be sufficient heat exchange area to transfer all the heat from the fire into the water. In a hot fire, this is mostly accomplished through a multi-pass heat exchanger. This means that the heat from the fire is forced to pass through a set of tubes, fins, or a bank of water pipes. A rule of thumb is that the bigger the firebox is the more tubes, fins, or pipes are necessary. If the boiler has water around the firebox, this is considered the first heat exchange pass. If it does not, the heat must make several passes through tubes, fins, or pipe banks before exiting through the chimney.

A clean heat exchanger is also necessary for efficient transfer of heat, and it is important to discover what fuel was used to determine the efficiency rating of the boiler. If wood was used, the rating is only a best guess. The reason for this is that to get an efficiency rating, there must be a known input BTU to receive an output BTU. The difference between these numbers is the efficiency rating. Wood does not provide a reliable input BTU because of the great variation in wood (type, moisture content, forest or fence row tree, kiln dried or air cured, etc.). Charts are available, but they are inaccurate. Heating efficiency can only be accurately rated using a fuel like oil, propane, natural gas, or coal.

3. What kind of Firebox?

Size

The firebox should be big enough to last for ten to twelve hours, but not so big that it can last for a couple of days. Oversized fireboxes result in smoldering, inefficient, smoky fires. They use more wood because the heating value from the burning gases is not available. When burnt hot, the stack temperature on these boilers can reach dangerous levels.

Type

The best firebox is the one with water around it, as this provides the best heat exchange. Some fireboxes are lined with refractory, a design to make a hot fire with hot firebrick. This is a great idea for burning wood, but not for burning coal. And even though this works relatively well for wood, there are still some drawbacks: One is that the refractory is not very impact-resistant. Because of the high temperatures in the firebox, reloading often requires throwing the firewood in, hitting the refractory and causing it to fall apart over time. The refractory also protects the boiler shell, so when it begins to crack and come apart, the shell is in jeopardy of being exposed to temperatures it wasn’t made for. In this type of firebox, there is more residual heat that the water needs to absorb, thereby requiring more water capacity, which will increase the size and weight of the boiler.

4. How much water capacity?

There should be sufficient water capacity in the boiler to absorb the heat that is still being emitted from the fire after the draft has shut down. Too much water (high mass) is not good, because it has a cooling effect on the fire and creates a demand lag. In burning wood or coal, low mass (too little water) is not a good idea either; this will introduce thermal shock to the boiler and significantly shorten its life. There also usually isn’t sufficient water to absorb the residual heat in the firebox, which often leads to boiling and other associated problems.

Many of the “gasification” boilers today are actually “batch burners” that require water storage to work properly because they do not idle. They burn at a high temperature, non-stop, until they run out of fuel- storing the BTUs in the hot water which boils at 212 degrees. For more on batch burners, see this post: The Problems with European-Style Batch Burner Boilers.

5. What type of construction?

Steel

Boiler plate is the industry standard for all pressurized heating systems. Boiler plate steel is carbon steel of a grade and specification approved by the ASME Boiler and Pressure Vessel Code. If the boiler is a closed system, it must have been tested by the manufacturer to sixty PSI. If the boiler is an open system, there can be no pressure checks because the steel will not handle pressure. The boiler should be made out of .25″ thick material for the water jacket, and should not have places where there is steel that could get hotter than the temperature of the steel it is welded to. An exception would be a fin type secondary heat exchanger, but even in that case, there should be expansion joints in the fins and they should not be in the firebox. Failure to abide by these principles will result in cracking and premature failure of the heating unit.

Stainless Steel

Some companies are now touting the benefits of stainless steel in boiler construction, but this is misleading. The only benefit of stainless steel is anti-corrosion, which could also be corrected by changing to a closed system. Stainless steel cracks easily (resulting in water leaks) when exposed to high heat and the heat exchange rate is slower for stainless steel than for mild steel. This results in reduced efficiency. Grades of stainless to steer clear of are 304 and 316. If the boiler is made from 409 stainless, there is a possibility that it will work, but you must bear in mind that 409 is a poor grade and does corrode. The extra expense is often not worth it.

6. What type of gasification?

Gasification boilers are being touted as the route to take for high efficiency. However, keep in mind that there is high combustion efficiency and high heating efficiency. Make sure the heating efficiency is as high as the combustion efficiency. The best gasification boilers are the ones that burn the gases inside the firebox and not in a separate gasification chamber. “Upside down burn” gasification boilers have stringent requirements for quality and moisture of wood to the point that sometimes the wood has to be purchased just to pass. These boilers can also be hard to start and, during periods of low demand, the gasification chamber can cool down to the point that when the fire tries to restart there is not enough heat left to ignite the gases. As a result, in many cases the firebox gets very heavily tarred with creosote, which becomes corrosive and shortens the life of the boiler.

Firebox gas combustion boilers are usually more forgiving and offer more fuel options. This technology is also widely used today in all EPA-rated woodstoves, which produce very little particulate without relying on computers, sensors, or combustion blowers to burn very clean and efficiently. By simply using the draft from the chimney, which is essentially a vacuum, combustion air is drawn into various locations in the combustion chamber to achieve maximum combustion efficiency.

Below is a cross sectional view of Napoleon Woodstove’s design called the “Twin Vortex EPA Engine”, which will help you understand the principle used in the EPA combustion chambers.