Portage & Main

Ultimizer Wood Series


Smart Burning Made Easy!

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The Ultimizer wood series is the product of more than 50 years of research and development that has earned Portage & Main Outdoor Boilers the reputation as an industry leader. With four sizes available, heating from under 2,000 sq ft to 12,000 sq ft, producing up to 500,000 BTUs. The Ultimizer can be connected to virtually any existing forced air or hydronic radiant heating system. Heat your home, domestic hot water, other buildings, hot tub, swimming pool, and more. In case you are looking for an EPA approved Wood Gasification Boiler we suggest you have a look at www.polarfurnace.com

Portage & Main ULTIMIZER

Portage & Main – Fireglow Process


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We pride in serving with quality & innovation since 1973. Be rest assured that we will support you end to end


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Our R&D team designed a conventional/gasifier boiler for optimal combustion with refractory firepot lining 


Easy Financing & Support

We turn smoke into usable heat . This sectional boiler design is user friendly, low maintenance & highly efficient

Unique Features & Benefits

Portage & Main Ultimizer


1st : First pass
2nd : Second pass
3rd : Third pass
4th : Fourth pass
A. Refractory brick lining & dry base design
B. Air from above & below
C. Full length quad-pass heat exchanger and upper baffle
D. Water – cooled rear baffle
E. Sectional, easy to repair design

A. Refractory Brick Lining

The Portage & Main Ultimizer is a refractory lined, dry base boiler. In the industry it has become known as an “updraft gasifier” because of its efficient burn. The Ultimizer is simple to use, easy to maintain and not fussy about the fuel it burns. It is very important to understand the “fire triangle” in order to fully appreciate the advantages of the Ultimizer design, and how it will save you fuel, money and time. To achieve a clean, efficient burn with complete combustion, an optimal balance of OXYGEN, HEAT & FUEL is required. The Portage & Main Ultimizer has been specifically designed to achieve this optimal balance.

Dry base design, zero ash line corrosion & no bridging 
The heat stored in the refractory lining helps ensure that a more complete combustion process occurs. I.e. fuel is reduced to charcoal in a 3-stage process.

STAGE 1: The fuel is heated to evaporate and drive out moisture. This starts at 212 degrees F

STAGE 2: It starts to break down on a chemical level at 500 degrees F. Volatile matter is vaporized. These vapors contain 50% to 60% of the heat value of the fuel, making it imperative for them to be burnt properly at a temperature in the range 1100 degrees F for maximum combustion efficiency. When all the volatile gases have been released, the remaining material is charcoal

STAGE 3: Charcoal burns at temperatures in excess of 1100 degrees F. Latent heat also helps in the re-ignition of the fire at the start of the next burn cycle. It also helps to dissipate moisture that is a result of the combustion process. The dry base boiler design gives a very hot burn. The water jacket sits above the brick line so it isn’t up against the fire, taking away the heat prematurely. This eliminates ash line corrosion and the fuel is completely burnt, resulting in considerably less ash.

B. Air from above & below

Exhaust gases make their 1st and 2nd pass at the top of the firebox where they move under and around a water-cooled baffle and into the heat exchanger. Gases then travel to the front of the boiler in a 3rd pass, make a 180 degree turn and move in a 4th pass to the back of the heat exchanger. In this way, all available heat is taken from exhaust gases before they exit the chimney. It gives up to 50% more heat transfer compared to other non water-cooled, non brick lined designs.

C. Full length quad-pass heat exchanger and upper baffle

The Ultimizer heat exchanger runs the full length of the boiler. It is completely surrounded by water which gives maximum heat transfer.

D. Water-cooled rear baffle

The water-cooled baffle at the rear of the Ultimizer fire pot absorbs heat and traps combustion vapors. Turbulence is created when air is introduced from below and above the fire. This turbulence provides an optimal burning environment for the vapors, leading to a hotter and more efficient burn. Also, by trapping the vapors, they are thoroughly burnt before entering the high efficiency heat exchanger. This heat exchanger is totally surrounded by water for maximum heat transfer.

E. Sectional, easy to repair design

Not a throwaway design like other brands are. The Ultimizer weighs substantially more than other brand boilers. That’s due to the heavy weight, long lasting, quality materials that go into our design. It provides a long-term, sustainable solution to your heating needs. At the end of its long life, the water jacket can be replaced. Just remove the top half of the boiler and bolt on a new top section, no welding required and your trusty boiler is good to go again. This means a very sustainable warranty, resulting in savings for the customer of several thousand dollars by rebuilding rather than replacing the entire boiler.

Portage & Main Boilers 

Confidently Recommended By Family & Friends

Portage & Main Ultimizer Boiler Features



📝Portage & Main Ultimizer Features


🔥 1. Refractory Lined Firebox

The Portage & Main Ultimizer is a refractory lined, dry-based boiler. A 2-1/2″ thick refractory lining surrounds the fire pot. This absorbs heat, facilitating a hot, efficient burn. The refractory also serves to evaporate moisture and eliminate caustic ash line corrosion. The Ultimizer has become known in the industry as the “updraft gasifier” due to the efficiency of its burn. The Ultimizer is simple to use, easy to maintain, and not fussy about the fuel it burns.

🔥 2. High-Efficiency Quad Pass Heat Exchanger

The heat exchanger runs the full length of the furnace and is completely surrounded by water. This means that combustion gases are kept in the boiler for longer and that the heat is fully extracted. Exhaust gases make their 1st and 2nd pass at the top of the fire pot where they move under and around a water-cooled baffle and into the heat exchanger. Gases then travel to the front of the boiler in a 3rd pass, make a 180-degree turn, and in the 4th pass move towards the rear of the heat exchanger. In this way, all available heat is taken from the gases before they exit the chimney. This design gives up to 50% more heat transfer compared to other non-water-cooled brick-lined designs.

🔥 3. Water Cooled Baffle

The water-cooled fire pot baffle absorbs heat and traps combustion gases. Turbulence is created when air is introduced from below and above the fire. This turbulence provides an optimal burning environment for the gases and leads to a hotter, more efficient burn. The trapped gasses are thoroughly burnt before entering the high-efficiency fully water-cooled heat exchanger.

🔥 4. Water Jacket Above The Brick Line

The Ultimizer water jacket sits above the brick line – not against the fire. This eliminates ash line corrosion and means that fuel is completely burnt. There is considerably less ash. Other brands of water jackets sit against the fire and this takes away valuable heat prematurely, and bridging of fuel becomes a problem.

🔥 5. Shaker Grates

Make cleaning out ash easy. Just rock the grates with the handle. The shaker plates are manufactured from North American 3/4” plate steel – not poorer quality imported cast iron which doesn’t last.

🔥 6. Forced Air

Self-modulated air is introduced both under and over the fire, resulting in a fully efficient burn. No extra controls are required, controlled with a weighted flapper.

🔥 7. Fire Pot Loading Door

Multi-layer insulated fire door with a heavy-duty adjustable handle and superior, high-density silicone-enhanced gaskets

🔥 8. Ash Pan Or Scoop

Makes removing ash easy. Also gives an entry point for the under-fire air

🔥 9. Heat Exchanger Cleanout Door

Allows easy access to the fully water-cooled quad-pass heat exchanger.
Only minimal cleaning is necessary due to the refractory lining and high-temperature burn. Most of the smoke has already been burnt, so creosote build-up is greatly reduced

🔥10. The Front Door

Acts like a storm door on a house. Helps reduce moisture buildup and corrosion. This additional outer door combines with a multi-layer insulated inner fire door. Truly reduces heat loss

🔥 11. Back Door

Housing for the boiler hookups, aquastats, and other components. Dry, fully lockable, and secure. All insulation is covered with galvanized steel for a safer, cleaner finish

🔥 12. Aquastat

Made by Johnson Controls. Time-tested, off-the-shelf, reliable. Easy to source, easy to set, and simple to operate.

🔥 13. Water Indicator Float

The water level indicator gauge is well-placed for easy viewing and is designed to reduce evaporation.

🔥 14. Sectional Design

The Last Boiler You Need to Buy. Not a throw-away design as so many products are these days.
The heavy-duty refractory brick, which gives the Ultimizer the ability to burn hot and clean, also safeguards against ash line corrosion. This in turn means that just the top half of the boiler can be easily replaced at a fraction of the cost of a complete boiler. If you ever need to rebuild, the entire fire pot and water jacket can be removed by simply unbolting the top section from the bottom section just above the bricks. The new top section then bolts into place. In less than half a day, with no welding required, you can have a fully rebuilt boiler.


Most Trusted Outdoor Wood Boiler

since 1973


Clean, green wood heat from an outdoor furnace

Green, sustainable, inexpensive space heating and domestic hot water is what I wanted for my house and workshop.


It was early 2010 when I began researching outdoor wood furnaces as an option for making this happen. A week before this past Christmas, I lit the first oak and maple fire in the unit I installed, and my hints at this project in my columns over the last few months have got people asking me for more specifics.

Outdoor wood furnaces have been around for decades, but it’s only in the last few years that new combustion technology means these systems now burn clean enough to be considered truly green.

All outdoor wood furnaces look pretty much the same from a distance. Imagine a small, metal building, like a half-size garden shed. There’s a door at one end that opens into a firebox. Energy from burning wood heats water to about 82C (180F) in an insulated tank within the building, where this water is available to be circulated to and from structures to be heated via underground pipes. The hot water can be used in radiators, in-floor heating pipes, or to warm air used in forced air heating systems.

Outdoor furnaces move the fire, ash and danger of heating with wood outside. They also have large fireboxes that handle big wood that’s easier to cut and split than smaller stuff. These are the two main advantages that got me thinking about outdoor wood furnaces in the first place. But as I soon discovered, there are two technical issues when it comes to assessing the quality of any particular unit. First, what percentage of heat energy from the wood actually makes it to the water in the storage tank? And second, how cleanly does the unit burn?

When the guy who works at the little country hardware store where I buy my stuff heard I was installing an outdoor furnace, he wondered why. “Don’t those outdoor furnaces burn a rainforest worth of wood each year?” Well yes, they do. Or at least some models do. The difference between efficient and inefficient outdoor furnaces means burning either 15 cords of wood a year or 30, and as I discovered, something called a fire-tube boiler is key to frugal operation.

The outdoor furnace I bought is made by a Canadian company called Portage and Main, and their fire-tube boiler design is one reason I chose them. Multiple hollow steel tubes run through the boiler tank itself, surrounded by water. Exhaust gases are directed through these tubes where they transfer huge amounts of heat to the water before heading up the chimney.

This fire-tube design originated in 1804, and was an enduring feature of marine and locomotive boilers in their time. Fire tubes are even used in modern industrial boilers today.


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About Portage & Main

Our head office is located in Prince Albert, Saskatchewan, Canada. Our dealer network spans North America and we would be glad to put you in touch with one of our knowledgeable agents. Our staff oversees the development of new products, monitors production, designs heating systems, and offers tech support for installers. All our wood furnaces are designed for installation outdoors and deliver wood heat indoors.







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