Automated Wood Stoves Entering the Marketplace

Updated: Nov. 2020: There are at least a half dozen stoves on the market that are fully automated or have some automated features that are gaining traction.  Many of these features help the stove burn cleaner and are aiming at a demographic looking for easier operation.

We define a fully automated wood stove as one where the consumer can "load and leave" and not have to worry about adjusting the air flow to get an optimum burn.  On all traditional wood stoves, the consumer must adjust one or sometimes two levers that control the air.  Often consumers don't do this well, resulting in poor combustion that fails to maximize efficiency or minimize smoke.  Thus, even a brand new wood stove that performed very well in the test lab can perform very poorly in the hands of an inexperienced or inattentive operator.

There is only one fully automated stoves on the US market and several more that will be released in 2021.   MF Fire, a Baltimore-based company makes the fully automated Catalyst.  It uses electronic sensors to monitor combustion and adjust air flow as needed.  SBI has an automated stove in the final R&D stage and Buck stove is participating in an automated stove project, both of which are funded by the bioenergy office of the Department of Energy.

MF Fire, a small Maryland
company is trying to disrupt
traditional stove technology.

The automation in the Catalyst is a great option for consumers who want to minimize smoke from their stoves and enjoy the ease of automation.  You can more easily leave for the day or go to sleep at night knowing that your stove won't be smoldering away, which is one of the leading causes of excessive pollution from both old and new wood stoves.

The real promise of automation is not to get a hot stove to hit an ultra-low particulate matter number in a test lab, but to improve real-world results by seamlessly optimizing performance throughout the burn cycle, reducing start-up emissions, and even reducing emissions from unseasoned wood.  EPA certification testing does not test for real-world performance, and incentive programs do not yet recognize the positive attributes of automated or semi-automated stoves, so stove companies have not had much incentive to invest a lot of time, effort, and money in developing them.

In Europe, fully automated stoves have been on the market for some time and are beginning to gain wider recognition from consumers and air agencies.  Two companies have advanced automatic stoves that unfortunately are not available on the US market: The Danish company Hwam, who developed the Autopilot IHS, and Austria's Rika, who developed the Rikatronic.  In the United Kingdom, solid burning heating devices are classified by whether they are automatic or manual. To achieve a rating to be used in more polluted areas, manually operated stoves must submit lab tests showing 5 burns for each output level because “manually controlled appliances show much higher variation between tests.”  Automatic appliances only have to be tested 3 times at each output level.  The chart below shows a wide variety of technology that exists in both stoves and boilers in Europe, but only exists in boilers in the U.S. 

In 2013, 2014 and 2018, the Alliance for Green Heat partnered with Brookhaven National Lab to assess and test automated stoves and prototypes at stove design competitions.  Their designers aspire to be part of a real trend towards cleaner, more automated residential wood heating.  But can they do it at an affordable price point?  And, are consumers ready for them?  Here, we look at stoves with partially automated features that are already on the market.

Partial automation solutions

A bi-metal coil acts as a heat-
sensitive thermostat which can partially
control the opening and closing of the damper.

1. The bi-metal coil. One of the oldest forms of automation of steel wood stoves is the bi-metal coil which has been used on scores of stove models and is now mostly just used by a few catalytic stove makers, principally Blaze King and Vermont Castings.  A bi-metal coil is simply a thermostat run by a metal coil that can close a damper down when it's really hot, and open it up when it's cooler. The stove’s air inlet can still be operated manually, but the bimetal coil will adjust the air inlet further. They tend to not work nearly as well on non-cat stoves, because the temperatures in a non-cat firebox can be more unpredictable, and if the coil shuts down the air, or opens it too much, the stove would operate poorly, which adds far too much uncertainty in passing the EPA emissions certification test. A new, more sophisticated version of this technology is the VcV valve developed by a Australian company and Ben Myren.

The rotating trigger mechanism in the
Smartstove Collection by Englander
reduces air flow once the stove is hot.

2. Better start-up: Several companies have features that help start-up: the Quadrafire "Automatic Combustion Control" and the Travis "Green Start."  They all use different automated approaches to starting the fire quicker and with fewer emissions.  After the start-up period, the stove operates like any other.

Quadrafire's Explorer 2 Start-Up air
control helps give the stove more
air in the first 25 minutes.

Another recent arrival on the market is Quadrafire’s Explorer II, which provides a similar automated start-up.  The website says “Automatic Combustion Control-provides the fire with air when it is most needed-leading to longer burns.”  A marketing video says the operation is so easy that all you have to do is “load the wood, light the fire and walk away.” According to the installation manual, ACC is basically a timer which the operator must manually initiate with a control mechanism.  Essentially, it opens the front air channel which allows air to enter for 25 minutes before closing.  Once the front air channel is closed, manual controls are used to deliver preheated air to the top of the firebox to burn the rest of the unburned gases in the remaining three combustion zones.

The slider on the Cape Cod
adjusts the rate of burns.

Travis industries Hybrid-Fire technology™ developed an automated “Greenstart” which shoots 1,400 degree air into the firebox for 15 minutes to start your fire, or when you reload.  The Greenstart can significantly reduce start-up emissions, and emissions during reloading on a low temperature bed of coals, by jumpstarting the start-up process and heating the wood up faster than it would with newspaper.  After the first 15 minutes, the stove has no automated features, but some of the Travis stoves that use catalysts are among the cleanest in the industry.  The Travis Cape Cod stove won second prize in the Wood Stove Decathlon.

3. Remote operation. A remote control device does not necessarily provide any automation to the air flow.  It can just allow you to do it manually from the couch.  However, some like the Nestor Martin’s Efel has a partial “automatic mode” that can keep the room at a desired temperature.  In timer mode, it can adjust the room temperature at a pre-set time. The stoves uses a simple ambient air thermostat in a remote control device that you can operate from the couch or anywhere nearby.  If you don’t use it in automatic mode, the remote control allows the user to adjust the intensity of the fire just as you would with a manual air control. One of the key things that distinguishes this Efel from truly automated stoves is that there are no sensors in the stove that can prevent the stove from smoldering or override an adjustment by the operator that would make the fire smolder.

HWAM's Autopilot technology uses
sensors, along with a bi-metal spring to
regulate combustion temperatures.

Fully automated stove on the European market

1. The final two stoves are more fully automated stoves and are on the market in Europe, but not in the US.  Danish company HWAM has integrated a new patented system: Autopilot.  Along with the Austrian Rikatronic, described below, the Hwam is one of the most advanced and fully automated stoves in Europe. HWAM 3630 IHS features a control system that electronically measures combustion conditions through the use of a lambda oxygen sensor and a thermocouple.  An onboard computer then allocates combustion air through three separate valves to help the consumer achieve the same results at home that are obtained in test labs under ideal conditions.  According to the Danish Technological institute, HWAM stoves with this system are 17% more efficient and produce 40% more heat.

Rikatronic has a microprocessor-controlled
motor and a flame temperature sensor
which drives the RLS air distribution system.
The light tells you the optimal time to reload.
By pressing the button, the stove knows
 it has fresh wood to handle. 

2. There are numerous versions of the Rikatronic wood heater system. The Fox II stove features manual and automatic control settings.  In manual mode the air distribution can be controlled in each combustion phase-even in the event of a power outage.  Automation in Rikatronic technology works with a microprocessor-controlled motor and flame temperature sensor which operates the RLS air distribution system.  Airflow in each of the 5 combustion zones is effectively adjusted for efficient burn.  A red light indicates the optimal time to reload the stove.  You can set the room temperature you want and once the required room temperature is reached, you can activate the eco mode by pressing the Rikatronic³ button.  This causes the air supply to be optimally controlled to maintain the fire for as long as possible, without smoldering, and to leave behind as little ash as possible.  Power consumption is 2 – 4 watts.

New Paper Undermines Stove Industry Variability Study

A new paper written by Woodstock Soapstone, a New Hampshire wood stove manufacturer, calls a key stove industry study misleading and flawed.  The industry study says the inherent variability in wood stove testing suggests that the EPA cannot lower emissions standards below 4.5 grams an hour. 

The EPA posted the 7-page Woodstock Soapstone paper today as part of the official record that the EPA can use to determine the final rule due in February 2015.  It was written by the company’s CEO, Tom Morrissey, and says the industry variability study is “based on a data sample that is small, old and deeply flawed.” 

The late Paul Tiegs from OMNI
 test labs was a  prominent
critic of variability being caused
mainly by fuel.

Morrissey’s paper argues that variability has much more to do with whether a manufacturer is paying for emission certification than inherent variability in the combustion process. “When a manufacturer pays for certification testing, why are the results so much better than at any other time the same stove is tested?” Morrissey asks.  The Alliance for Green Heat believes, as the Morrissey paper also suggests, that test labs have a range of operating procedures allowed by the EPA that can result in variable emission results.  The late test lab icon Paul Tiegs, a founder of Omni test labs, became a champion of tightening testing protocols to achieve consistency in testing, and rejected the notion that variability was mainly caused by solid fuel, as the industry study argues.

If the EPA, states, and air agencies take the Woodstock Soapstone paper seriously, it could unhinge a major industry legal strategy in the fight against stricter air pollution limits.  Many officials in the EPA and state air agencies were already critical or at least skeptical of the industry variability study.  However, there has not been such a detailed critique from inside (or outside) the stove industry before this.

The variability study was produced and written by Rick Curkeet, a hearth products engineer at the Intertek testing lab and Robert Ferguson, a consultant who is now working for HPBA on the proposed EPA regulations.  It was released in October 2010 in anticipation of the proposed EPA regulations and is called the “EPA Wood Heater Test Method Variability Study: Analysis of Uncertainty, Repeatability and Reproducibility.” 

[Update: Rick Curkeet submitted a rebuttal to the Morrissey paper on Sept. 10 and it should be posted in the EPA docket soon. His 7-page rebuttal defends his original study and he concludes that he stands by his "analysis and conclusions."]  

The study showed that there is a very wide range of variability between proficiency testing and certification testing of wood stoves.  HPBA contends that “it is arbitrary for EPA to define ... a value that is lower than the precision range” of the test method.  HPBA says the minimum justifiable emission limit is 4.5 grams an hour, which Washington State adopted in 1995 and has since become a de facto national standard.  The variability study does not say who paid for it but HPBA confirmed that they provided partial funding and extensively vetted early drafts in late summer and early fall of 2010.

While Morrissey’s paper is by far the most direct critique of the variability study, most experts agree that the understanding of variability in wood stove testing can be assessed in many more ways than the data set used by this industry study.  For example, compliance test data could be used.  The EPA requires that all stoves be retested after they produce between 2,500 and 10,000 units.  This data, if it could be obtained from the EPA, would provide possibly a more important data set than the one the industry study chose to use.  Another data set will be from the “K list” changes.  Most stove manufacturers are re-certifying their stoves in advance of the new EPA rules so they will have 5 years before they have to test again.  HPBA has been encouraging its members to recertify stoves with “K list” changes as they are allowed to do by the EPA so that they won’t have to face higher testing costs that include cord wood testing and the uncertainty of a new test method that may be harder to pass.  HPBA had urged the EPA to grandfather all stoves under 4.5 grams an hour until 2020.  In any case, these retests will provide a new and better data set to assess variability.

Even if high variability could be established and confirmed using various approaches and data sets by independent experts, the poor relations between industry and state air agencies and other key players has undermined the ability of the two sides to agree on much.  At a November 2012 meeting in Minneapolis convened by NESCAUM, Greg Green of the EPA left the room and urged the two sides to talk more amongst themselves.  That strategy did not work and very little productive communication occurred for more than a year, a result that is likely not beneficial to the interests of HPBA industry members. 

Greg Green, Alison Simcox and Gil 
Wood of the EPA listening to testimony 
at the Boston hearing on the NSPS.

The hard line approach to critics is what prompted Morrissey to write his rebuttal of the variability study which begins as a defense of test reports of his own stoves that had been called into serious question by HPBA, Rick Curkeet and Roger Purinton at Jotul stoves in formal comments to the EPA.  Ironically, proof that catalytic or non-catallytic wood stoves can be consistently clean has become the biggest threat to the mainstream stove industry that HPBA represents.  This conflict between cleaner catalytic stoves and not-as-clean non-catalytic stoves became very heated and public in an EPA hearing in Boston on February 26, 2014.  But it was preceded by the release of study in 2013 by non-catalytic makers that dismissed the effectiveness of catalytic stoves to reduce wood smoke in real world settings.  If this public rift within HPBA had not happened, the stove industry would likely have made it through the EPA rule making with a much more unified voice. 

According to interviews with non-catalytic stove manufacturers, they felt it was vital for the EPA to understand that very low emission numbers from catalytic stoves in testing labs did not accurately reflect emissions in peoples’ homes as catalysts often clog, are not replaced, and are not properly engaged and used by consumers.  This issue has proved to be key because the EPA proposed emission limits of 1.3 grams an hour in 2020, a number that only a few catalytic stoves can appear to meet.  The company that has produced tests showing it can meet it is Woodstock Soapstone.

The Woodstock Soapstone defense of its test results and critique of the variability study comes at an important time when the EPA is finalizing its new wood heater standards, known as the New Source Performance Standards (NSPS).  It is believed that as of September or October, the EPA staff will have made most of their key decisions to send to Washington for review and approval by senior EPA officials and EPA lawyers.  Attempts between HPBA and air agencies to reach any agreements behind the scenes could still be fruitful, but time is running out.  And even if any agreements could be reached, the EPA may not adopt them.

The regulation and emission limits for outdoor wood boilers are also hotly contested but the testing variability for boilers is not a big issue, nor is it an issue with pellet stoves.  One solution, supported in part by the Alliance for Green Heat, would be to set separate emissions standards for pellet stoves, catalytic stoves and non-catalytic stoves, based on how clean each technology has become.  The argument for separating pellet stoves from cat and non-cat wood stoves may be even stronger because they use a different and very uniform fuel and are burned in a much more controlled combustion setting.  The Catalytic Hearth Caucus, of which Woodstock Soapstone is a member, strongly opposed separate emission limits for cat and non-cat stoves as well.  Ultimately, HPBA did not recommend setting separate emission limits that Jotul and other non-catalytic manufacturers initially appeared to support.  At this point in the process, the EPA may have already decided to set a single emission standard for these very different technologies, as they had proposed.

If senior leadership at EPA sees reliable data that at least one stove can consistently be tested under 1.3 grams an hour, they now have a better legal foundation to stick to their proposed 1.3 gram an hour standard.  And this is the nightmare scenario that HPBA and non-catalytic stove manufacturers fear.

Stove experts like Tom Morrissey, Robert Ferguson and Rick Curkeet are not only savvy about how stoves are tested, they are also skilled number crunchers.  Interpreting stove test data is like any other data set: it can yield very different conclusions based on what data is used, how it is interpreted and what statistical methods are applied.  The EPA in turn has to assess the reliability of each study and they can reasonably expect that their assessments will be challenged in court.

Tom Morrissey, top, 2nd from right and
the team that designed and built the
Ideal Steel for a 2013 competition

The stove that Tom Morrissey says is reliably and consistently less than 1.3 grams an hour was specifically built to win the 2013 Wood Stove Design Challenge, and it did. The Wood Stove Decathlon judged stove on 5 categories: emissions, efficiency, affordability, consumer appeal and innovation.  The Ideal Steel Hybrid is certified by the EPA at 1.0 grams an hour and gets 82% efficiency.  A second place winner, the Cape Cod, was a similar hybrid stove by Travis Industries that is certified at even lower  0.5 grams an hour.  Travis however does not say that they can reliably or consistently test at such low emission numbers, particularly with cord wood.  Woodstock Soapstone says testing shows that their Ideal Steel Hybrid is as clean with cord wood as it is with crib wood.

The Alliance for Green Heat promotes cleaner and more efficient residential wood heating to reduce our reliance on fossil fuels and help families affordably heat their homes.  Founded in 2009, the Alliance is based in Takoma Park, Maryland and is registered as a non-profit, 501c3 educational organization.

Woodstock Soapstone, Travis and Wittus Win the Wood Stove Decathlon

FOR IMMEDIATE RELEASE: November 20, 2013

Woodstock Soapstone, Travis and Wittus    Win the Wood Stove Decathlon

Catalytic, Masonry and Electronically Controlled Stoves Show High Results in Testing

Washington D.C. – In an international competition to significantly reduce pollution from wood stoves on the National Mall, one finalist, Woodstock Soapstone of New Hampshire, won first prize of $25,000. Two other teams, Travis of Washington State and Wittus of New York, were awarded $5,000 each. The teams were recognized for all around performance in efficiency and emissions, affordability, consumer appeal and innovation. Members of Congress Dan Benishek (R-MI), Chris Van Hollen (D-MD), Jared Huffman (D-CA), Paul Tonko (D-NY) took part in the awards ceremony.

The Woodstock Soapstone Team

In accepting the first prize of $25,000, Woodstock Soapstone owner Tom Morrissey announced that he was giving part of the prize money to two other teams - Walker Stove and Intensi-Fire - who had come to the Decathlon on a shoestring and needed funds for their work. Travis donated their $5,000 to the Alliance for Green Heat to help pay for the expenses of the Decathlon.

“These award-winning technologies are part of the solution for millions of Americans to reduce their reliance on fossil heating fuels,” said John Ackerly Founder and President of the Alliance for Green Heat, which organized the Wood Stove Decathlon. "We'd like to thank all the teams for participating and contributing to an ongoing educational effort to help the US government appreciate the potential of cleaner and more efficient wood heating," Ackerly added.

Competitors represented a wide range of wood stove technologies. Two of the top three winners were catalytic hybrid stoves. While the three masonry stoves did not take home prizes, they had some of the highest scores in efficiency and cleanliness.  

The Wittus Twin Fire, that was tied for second prize overall, scored highest in the efficiency category. Travis’s Cape Cod Hybrid, which also tied for second overall, scored highest in consumer appeal and for low carbon monoxide. The Hwam 3630 IHS scored highest in innovation, with its oxygen sensor and control device that alerted the consumer when and how much wood to reload. The Woodstock Soapstone, which won the Grand Prize, also won in the affordability category. And the University of Maryland’s stove, the Mulciber, won in the lowest particulate matter category. 

The overall ranking of stoves was:

WOODSTOCK SOAPSTONE		1
TRAVIS		2
WITTUS		2
INTER-CONTINENTAL		3
TILE STOVE		3
HWAM		3
TULIKIVI		4
INTENSI-FIRE		5
MULCIBER		5
WALKER STOVES		6
SMART STOVE		7
KIMBERLY		8

The competition differed from EPA tests of wood stoves in several key respects to more closely resemble how consumers use stoves. First, the stoves in the competition were tested using cordwood instead of 2x4s and 4x4s. Second, technicians loaded stoves with 12 pounds of wood per cubic foot of firebox space for the first round of testing, whereas EPA only uses 7 pounds of wood per cubic foot.

Two of the stoves made small amounts of electricity and four had electronic control systems. More detailed analysis will be forthcoming. The primary funders of the Wood Stove Decathlon are NYSERDA, the Osprey Foundation, the District of Columbia Urban Forestry Administration, the US Forest Service, the West Penn Power Sustainable Energy Fund and the Arbolito Foundation. 

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The Alliance for Green Heat is an independent non-profit that promotes high-efficiency wood heating as a low-carbon, sustainable and affordable heating solution. The Alliance seeks to make wood heat a cleaner and more efficient renewable energy option, particularly for those who cannot afford fossil fuel heat.