Pacific Energy’s Extended Burn Technology

Extended burn technology allows you to enjoy the longest cleanest burns without turning a single knob. Remember how your grandpa would wake up in the middle of the night worried about the charcoals. The mother of a baby would be obsessed every hour about going to the wood fire to place another log on top.

We all love a blazing hot fire. But what happens when we go to bed? We leave the house to work in the morning? We come back from work and need to make dinner? Or just enjoy the family? Or lay back on the couch? Pacific Energy solved all these items with the (EBT) extended burn technology.

But I had an old airtight stove that did just this

My old stove had a HUGE firebox, with spin-draft control, primary control and secondary air control. I would close them all down with a big load and I had no problem holding the fire overnight. Two years ago I listened to the complaints of my neighbours about my smokey chimney and purchased a new stove. I was hoping to have a long overnight burn and just the opposite happened. The new stove gives out more heat. Is slightly smaller but won’t hold the coals as long even at minimum settings. I rang my dealer and his answer was blame the new emissions certifications.

A recap of an ideal burn cycle in fires

An Ideal burn cycle should heat the load of fuelwood to gasification temperature (Stage 1), burn the volatile gases to extract their heat value and clean up the exhaust (Stage 2), then maximize the duration of the fire as the wood fiber burns down to its final, charcoaling phase (Stage 3).

 

The most oxygen-hungry of the three phases of a wood fire is (Stage 2). The temperature of the load approaches 280° and the wood resins begin to gasify. With a big load in a large firebox, the “bloom” of volatile gases that floods the firebox during (Stage 2) is considerable requiring a sizeable quantity of oxygen to burn and extract the heat value.

Your old wood stove

Closing down to airtight on your old stove starved the fire for air. This smoulders the burn and prolongs the duration. Your old stove could go so long between refuellings because those low, smouldering fires did not have enough oxygen in the firebox to consume the (Stage-2) bloom of volatile gases. The gases escaped up the flue, taking as much as half the heat value of that load of wood with them. Lost heat is not the bad news.  Smoldering causes excessive creosote formation in the flue, and complaints from smoked-out neighbours.

Clean air complaints

In 1988 complaints from smoked-out neighbours meant different regulators got involved to clean up the air. New emission regulations around the world required that new wood stoves consumed the gasified wood resins. Mainly accomplished through a process called secondary combustion. A second fire inside the firebox re-burns the exhaust from the primary fire. Secondary combustion in small fire boxes is easier than secondary combustion in big fireboxes. When a BIG load reaches (Stage 2), the “minimum” airflow required for secondary combustion can be substantial. Providing enough airflow to meet emissions standards during (Stage 2) burn presents a major engineering challenge and designers of large wood stoves.

Popular solution

The most popular solution is the incorporation of a “stop” in the design of the draft control. The draft can not be closed down below a certain point. While this method might get a stove through testing, there’s a big downside. With no “low” draft setting available, an abundance of combustion air is delivered to the fire even when it is not needed, causing faster than necessary fuel consumption during the other stages of the fire. This results in frustrated owners of large size stoves who can’t “hold” a fire as long as they might want to between refuellings.

Pacific Energy´s Extended Burn Technology patented solution

Pacific Energy’s Extended Burn Technology (EBT) is a patented solution developed while designing the large size Neo 2.5, Alderlea T6 and FP30 insert model. The engineers at Pacific Energy incorporated several of the same techniques used in their smaller models to extend the duration of each burn.

• Continuous-bead welded fireboxes
• Tight fitting loading doors to minimize unwanted air infiltration into the fire.
• A resistant heat deflector for high-temperature burns
• Amazingly complex designed and tested secondary burn baffle made of 304 stainless steel

Mindful of consumer complaints concerning the lack of low-end control built into many of today’s larger stoves, they introduced the patented Extended Burn Technology (EBT) device. The EBT delivers a burst of extra air to the fire only as needed to maintain secondary combustion during (Stage 2) of the fire.

1998: PE’s Patented “Series A” EBT Mechanism 2013: PE’s Patented “Series B” EBT Mechanism The original Extended Burn Technology device incorporates a pivot plate, mounted so its base covers a “boost air” intake opening. The plate is pivoted by an actuator arm attached to a bimetallic coil, which turns the arm in response to rising firebox temperatures when the volatile gases ignite at the beginning of Stage 2 of the burn. As the coil heats up, the plate hinges open to uncover the intake opening and provide extra air to the fire. When the gases have been consumed and the firebox temperature returns to normal, the coil contracts, lowering the base plate back down to seal the opening and stop the extra airflow.   The Series B device is driven by a predictable increase in chimney updraft at the beginning of Stage 2 due to the rise in exhaust temperature when the gasified resins ignite. The increased updraft draws a balanced pivot plate open, uncovering an intake opening to provide the “boost air” needed to ensure complete combustion of the volatile gases. Unlike the original EBT device, which delivers the boost air to the primary fire, the new device feeds the extra air to the secondary flames only. The operator retains control of the burn rate of the primary fire, and longer burn times are easier to achieve.

What is an overnight burn with extended burn technology

An overnight burn is not a burning fire. An overnight burn means having a clean glass door in the morning. A nice bed of coals. A warm stove ready to be lit up with very little effort. The best way to experience a real overnight burn is with Pacific Energy.

Shopping for a wood stove – Know your facts

Shopping for a wood stove requires that you differentiate thoughts and opinions from facts. As any scientist or mathematician will tell you, the more variables in any equation, the harder it is to draw accurate conclusions. This certainly holds true when it comes to wood heating stoves and fireplaces, where buying decisions are often made from anecdotal data provided by others, without considering all the facts behind the story. Here are a few true-life scenarios:

Thought 1:

“Non-catalytic wood stoves are cheap.”
Reasoning: “I recently replaced my non-catalytic certified approved wood stove with a catalytic model. Thanks to the catalytic converter, the new stove gives me more heat and longer burn times.”

Fact not mentioned:
The new stove has a larger firebox than the old stove.

Informed Shopping Conclusion:
Stoves with larger fireboxes can hold more fuel, so they can put out more heat for longer periods of time. The catalytic converter has nothing to do with it.

Thought 2:

“Cast iron wood stoves are crap.”

Reasoning: “We finally burned out our Invicta Auris woodstove which was made of plate steel, and replaced it with a Dovre Vintag which is cast iron. Now, the living room is unbearably hot, and the rest of the house is cold!”

Facts not mentioned:
1) The Invicta was a convection heater, designed to heat and circulate air.
2) The Dovre Vintag is a radiant heater, designed to heat objects.
3) While heated air is relatively easy to move throughout the house, radiant energy is not.

Informed Shopping Conclusion: 
Choose the right type of stove to heat your house. Radiant heaters work best when they’re centrally located in a big, open spaces.

Thought 3:

“Plate steel wood stoves are crap.”

Reasoning: “We loved our old cast iron Vermont Castings Resolute. It put out a nice, gentle heat and we could sit right next to it. The new Neo 2.5 plate steel stove blasts us right out of the room! Plate steel stoves are like blast furnaces.”

Facts not mentioned:
1) There is virtually no difference in the heat transfer efficiency of cast iron and plate steel.
2) The Vermont Castings Resolute was rated to heat 110mt2. The Neo 2.5 is rated to heat 215mt2.

Informed Shopping Conclusion:
Choosing a stove that is too large can be just as uncomfortable as choosing one that’s too small.

Thought 4:

“Soapstone wood stoves are useless.”
Reasoning: “We bought a new Lotus soapstone wood stove to heat our mountain vacation cabin. Every time we go up there, we freeze our buns off for two or three hours trying to bring the cabin up to temperature. In the meantime, the dumb thing smokes us out of the place!”

Facts not mentioned:
1) It takes a little skill and patience to get a cold soapstone stove (and its chimney) up to operating temperature.
2) Raising the temperature of a cold mountain cabin up to a comfortable level quickly is not something a soapstone stove is designed to do.

Informed Shopping Conclusion:
The happiest soapstone stove owners are folks who start a fire in the Fall and feed it until Spring, never letting the stones get cold. For a sporadically-visited cabin, soapstone should be the last choice.

Thought 5:

“New wood stoves are crap.”
Reasoning: “Last year, our neighbours gave us five tons of wood, which we figured would get us through this winter, so we took our fuel budget savings and used it to replace our 20-year-old woodstove with a brand new model. We’re only halfway through the burning season, and this monster has gobbled up almost all our wood already! We wish we had our old stove back.”

Facts not mentioned:
1) The 5 tons of wood the neighbours let go so graciously was soft wood.
2) 5 tons of soft wood has the fuel value of about 2-1/2 tons of Oak.

Informed Shopping Conclusion:
The fuelwood, not the newer design, is the problem here.

Thought 6:

“Certified approved wood stoves are crap.”
Reasoning: “Our old stove had a HUGE firebox and a draft control we could shut all the way down to just a crack, so one load of wood lasted around 16 hours or so. We just got a new certified approved stove, and we can’t turn it down the way we’re used to! The fire keeps burning no matter what we do, and we have to reload every 8 hours! We wish we had our old stove back.”

Facts not mentioned:
1) The old smoulder pot blanketed the entire neighbourhood with thick black smoke all the time.
2) With the old stove, the chimney needed cleaning several times per season, and there were still several chimney fires.
3) Today’s approved stoves are designed to be smolder-proof (the fire still burns clean, even at the lowest draft setting).

Informed Shopping Conclusion:
The neighbours are happier, and so will they be when they find out they’re burning about half the wood to heat the house and only need to clean the chimney about once per year while enjoying the flame through a clean glass.

Build a wood stove from a scrap barrel

I want to build a wood stove with a pretty 50  gallon metal drum. Make a baffle box out of steel with a 10 cm gap to increase the heat output. I might use an old catalytic converter from a truck as an option. No policeman is going to look for you if there is some smoke and this would be a great heat source.

Review of the rocket stove

Your barrel stove idea to build a wood stove is nothing new: similar designs have been around since….. well, since barrels. I’ve seen several variations of your double-baffle idea over the years, and while incorporating baffles in the design might improve the burn of barrel stoves a bit, I hope you realize that you’re never going to build a stove that even approaches the efficiency of an approved design (I’m going to assume that your idea of incorporating a catalytic converter out of a truck is not something you’ve actually tried, because there’s no way that would ever work).

The point is, certified approved designs are better than homemade stoves in several respects:

1. They heat the same area while burning about half the fuel (saves half the cutting, splitting, hauling, not to mention usage of the wood resource).
2. Their stay-clear viewing windows allow you to ensure your fire is burning properly from across the room (prevents smouldering, assures utmost burning efficiency).
3. They cut the formation of creosote in the chimney by about 90% (less frequent need for sweeping, less chance of having a chimney fire).
4. If you ever do have a fire, your certified stove and installation ensures that your insurance company will pay your claim. (Seen many sad clients who build a wood stove house fires).
5. They are MUCH kinder to the environment, as they exhaust the only 1/20th of the particulate emissions into the airshed as not approved stoves. Since our generation has finally come to the realization that protecting the environment is everybody’s business, deliberately burning a homemade smoke dragon like you describe could be looked at like tossing your empty drink cans out of your car window.

My own self-welded stove

I don’t like any of the wood stoves you sell or any of the wood stoves I’ve seen anywhere else. They are all too small, they all have such dinky little viewing windows. I’m pretty handy with as a welder and want to build my own wood stove to heat my 120mt2  home (which is very well insulated). The stove I have in mind would need to meet the minimum certificate emissions standards without a catalytic converter and I have an old firebox like the wood stove my Dad used to have, which is big enough to hold 76cm pieces of wood, or even bigger (I cut my own wood, and don’t want to have to whack up small pieces). I also want to have a larger glass door than the ones I see on manufactured wood stoves. I’ve been all over the web and you seem to know your stuff. I feel like if I just understood the theories I could weld something up and make modifications to it until I get it to work right. Can you tell me the basics to build a wood stove as I need to know to design this thing? Also, if you have the time or any tips you care to share that might be helpful. It’s getting cold outside!

Problems with your own build a wood stove concept

Let’s start with a basic overview of how non-catalytic wood stoves clean up the smoke emissions. The concept is pretty simple: in order to meet standards, you’ll need to create a second fire inside the wood stove’s firebox to reburn the exhaust from the primary fire. The secondary burn area in an approved stove is usually located at the top of the firebox. Designed in such a way that the exhaust from the fire must pass through it on the way out the chimney. In operation, the wood exhaust ignites inside the chamber, creating a 600+ degree flame (much hotter than the wood fire below) which burns up approximately 90% of the smoke particles as they pass through it.

In order to fire off your secondary burn, three things must be present at the same time and in the right amounts: fuel, heat and oxygen. The fuel part is easy: it is the smoke from the primary fire. Likewise the heat: ceramic blanket insulation used above the chamber to trap the heat from the fire below and ensure light-off temperatures. The oxygen part gets a little tricky: since the primary fire has consumed most of the oxygen available in the firebox, preheated air must be introduced into the reburn area so secondary combustion can occur. Your design challenge will be to figure out a way to preheat the secondary combustion air to the right temperature and cause it to be drawn into your secondary burn area in measured quantities that automatically adjust with the draft control that supplies air to the primary fire, keeping in mind that the secondary flame must keep burning and cleaning up the exhaust even when the primary draft control is at its lowest setting.

Tip: Over 1000 wood stove manufacturers worldwide have gone out of business in recent years as a result of being unable to engineer a stove that would burn clean enough to meet emissions standards. The sad fact is, unless you are an exceptionally talented thermal design engineer with a background in wood combustion and lots of time and materials for prototype testing, your BIY secondary burn design probably isn’t going to work.

Next, let’s look at wood stove viewing window basics. Early attempts at adding viewing windows to wood stoves were miserable failures, as the windows turned black almost immediately from contact with the wood smoke. Since it is kind of silly to go to the expense of incorporating a viewing window if you can’t see through it, wood stove manufacturers soon learned to incorporate an “airwash” in the design of the stove, taking a portion of the incoming combustion air, preheating it, and directing it across the inside surface of the window to keep the smoke away. Airwash designs are a little tricky, as they require building the necessary preheating chambers into the design of the stove and then providing a means to direct the airflow across the inside window surface without adversely affecting burning efficiency. When you build a wood stove yourself most people end up eliminating the viewing window totally because as it is extremely difficult to have a clean glass viewing fire.

Tip: Manufacturers know that a big view of the fire will appeal to wood stove buyers, and make every effort to provide the largest viewing window that can be kept clean by the airwash system. Pacific Energy where leaders in the industry. As you build a wood stove, modify and retest your stove with various airwash delivery systems and various sizes of windows, you’ll find that there’s a limit to how big the window can be and still be kept clean by the airwash. You could save yourself a lot of futile effort by resigning yourself to a viewing window that is about the same size as the ones you see on manufactured stoves.

Finally, let’s tackle firebox sizing. Wood stove manufacturers know that people who buck up their own fuelwood want fireboxes that can hold larger pieces of wood, because cutting wood is hard work, and larger pieces mean fewer cuts. So why, in recent years, have these manufacturers been making their fireboxes SMALLER, instead of larger? In a word, heat. Too much heat. Remember that 600+ degree burn in the secondary burn chamber? Your Dad’s stove didn’t have one of those. If it had and was as big as you describe, he wouldn’t have been able to stand the heat long enough to go into the house, let alone get close enough to the stove to add one of his 70cm chunks of wood to the fire.

Tip: Our highest output wood stove, the Pacific Energy FP30, has a firebox measuring just 50cm x45cmx 33cm (76 litres), yet generates up to 29 Kw per hour (enough to heat a  275mt2 house). If you do manage to design and build a reburn chamber that works and wants to heat your 120mt2 house without blasting your family out into the yard, you’ll want to plan a firebox that will accommodate your 70cm logs after they’ve been cut in half. This won’t cause you any extra labour at cutting time because if your reburn design works, you’re only going to burn about half the wood your Dad did to heat the same area.

Here’s something you didn’t ask about, but need to know: Country and district laws prohibit installation of any wood burning heater that isn’t listed and certified. Obtaining this approval is not practical for a single stove: even if you were able to build a stove that would be safe enough and clean-burning enough to pass, you’d be out about twenty grand for the safety and emissions testing. If you were to go ahead and install your home-built wood stove without listing labels from the test labs, you most likely wouldn’t be able to get a permit from your Authority to install it. In the event of a fire claim, the insurance adjuster might notice the lack of listing labels or ask to see your installation permit, at which point your coverage would probably hit the fan.

To sum up, the most likely product of your efforts to build a wood stove will be an illegal, wood-gobbling, creosote manufacturing smoke dragon with a viewing window you can’t see through. And no insurance coverage in the event that this monster burns your house down.

BIY Thanks

I just read your page concerning the gentleman that wanted tips on how to build a wood stove. I have to say I appreciate the complete, well thought out and intelligent response. You could have just said it’s too hard you cannot do it and it would be illegal, In my mind a worthless, frustrating answer that would indicate we are all too stupid to understand a thorough explanation.

Thank you for taking the time to give a very good answer to a relevant question !!

Thanks for the kind words! They used to say, “Asking a question is not stupid. Having the answer and not sharing it is stupid.”

Question: Vermont Castings catalytic compared to non-catalytic

I was wondering if you could share your opinion about the Vermont Castings “Defiant Catalytic” woodstove compared to non-catalytic. We had to replace the catalytic converter two years after installation, and now must replace several burned-out internal parts not covered by the warranty. We’ve also had trouble since day one controlling the fire. We were told this stove is cutting edge technology. I really like how the cast iron looks with the porcelain finish, but frankly, we don’t like the catalytic converter. We notice that all the woodstoves on your web pages are all noncatalytic. Are these not required to reduce emissions?

Answer: How catalytic stoves were developed

Regulations across many countries limit the amount of particulate matter, measured in grams per hour, that may be emitted by a woodstove. They don’t tell the manufacturers which method to use to achieve this level. Certificates such as EPA, EN13240, 15aB-VG, DIN+, I.BlmschV Stufe 1/2, Nordic Swan, Flamme Verte all indicate different parameters of efficiency and emission. Incorporating a catalytic converter is only one way to clean up woodstove exhaust, and it is far from the most popular.

The story of the catalytic woodstove

The story of the catalytic woodstove begins over two decades ago when only a handful of places had as yet passed a woodstove emissions regulations. At that time, manufacturers who wanted to sell woodstoves in regulated regions found that by simply incorporating a catalytic after burner into existing models was a relatively inexpensive way to clean up the exhaust. (Your “Defiant Catalytic”, for example, is basically the same stove as VC’s old Defiant model, but with a catalytic converter added). This “band-aid” approach produced several models which, while clean-burning enough to sell in regulated places, didn’t turn out to perform as reliably in the field as the high-emissions models the woodstove manufacturers such as Pacific Energy continued to sell in the much larger, unregulated marketplaces.

Back in the ’80s, we dealt with a few catalytic woodstoves, but dropped them almost immediately because of negative customer feedback (the need to “babysit” the stove until it came up to catalytic ignition temperature before activating the converter, lack of control of the fire, the frequent need to service or replace the expensive converter element, etc.). By and large, these complaints remained unresolved by the manufacturers, presumably because:

1. Solutions didn’t readily present themselves
2. The numbers of catalytic stoves sold at that time were relatively small.

Emission testing certificates

When the certificates stepped up the level and announced their intention to outlaw high-emissions models, many manufacturers (Vermont Castings among them) were left with only their “band-aid” catalytic models to sell; suddenly, catalytic-equipped woodstoves were being sold in large numbers all over the country, and consumer complaints multiplied proportionately whereas Pacific Energy continued to innovate and design its Alderlea woodstove.

One by one, manufacturers grew tired of the customer dissatisfaction, expensive warranty repairs and poor performance associated with their catalytic models, and began to reject the trouble-prone catalytic technology in favor of an alternative, non-catalytic, clean burning technology that had been developed in other countries, where woodstove emissions had already been a hot topic for over fifteen years in countries like Canada, Denmark, Austria, NewZealand, Australia. With some design improvements, technology was developed to comply with the stricter standards, and was easily applied to woodstoves of plate steel construction, where only a few changes on the assembly line were needed to convert from catalytic technology to the non-catalytic secondary burn designs.

Cast Iron Stoves

Not so with cast iron stoves like your Defiant,  or other cast iron stoves like Jotul or Dovre. Manufacturers of plate steel woodstoves could weld up a prototype in a few hours, then test, modify, reweld, and retest it as needed until standards are met, cast iron stove manufacturers would be faced with a tedious and expensive process involving design engineering and foundry work, as all preliminary parts would have to be cast in custom-made molds, one at a time, prior to assembly and testing. Thus, manufacturers of cast iron stoves tended to lag behind the rest of the industry in adapting their models to the new non-catalytic technology. Meanwhile, the basic non-catalytic design underwent further refinements, and other secondary burn designs were developed until non-catalytic technology became the standard in the marketplace.

Vermont Castings has for some years now been actively engaged in the process of adding non-catalytic models to their product lineup one by one, starting with their smaller models (the non-catalytic design is easier to implement in smaller stoves).

In the meantime, catalytic technology has also continued to improve. Repositioning of the converter relative to the flame path addresses the flame impingement problem, which had previously shortened the lifespans of the converters in earlier designs. Changes in both the substrate and the catalyst itself have resulted in longer lifespans and more consistent performance. Re-designed access openings and holding brackets have made cleaning and replacement the element less of a chore. Consumer education has perhaps been the biggest factor: today’s catalytic stove owners seem better informed about what not to burn, and are generally more knowledgeable about care and maintenance of the converter itself (like keeping it clean, and replacing it when needed).

Pacific Energy Alderlea non-catalytic woodstove

You asked for our opinion, so here you go: if the problems you describe have become more than a nuisance, the best solution we can come up with would be to trade your Defiant in for a non-catalytic stove. All new woodstoves sold should hold some kind of certificate unlike manufactured self-welded stoves, so any stove you buy will be a low-emissions design, whether it has a catalytic converter or not. Pacific Energy, Lotus and TermaTech have sold non-catalytic woodstoves for over 20 years now. Pacific Energy approaching 40 years and in our experience, non-catalytic technology has proven itself effective, reliable, and easy to operate. Since you mention above that you really like the looks of your Defiant, you might consider an Alderlea T5 in porcelain finish or an Alderlea T6 from Pacific Energy with extended burn technology which combines modern interior design and a very similar traditional cast iron exterior, which is, as you might have guessed, is non-catalytic.