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Maximizing Burn Efficiency in an Outdoor Boiler : The Portage & Main Refractory Brick

What is an Efficient Burn

Portage and Main’s Ultimizer design and robust, quality manufacturing ensure that their furnaces achieve the best, hottest and most efficient burn. An efficient burn requires a balance of three elements: Fuel, Oxygen and Heat

Fire Triangle

What is refractory brick?

Historically, bricks have been used to contain fire and absorb heat. Whether it be in a simple outside firepit, kilns, fireboxes or in the lining of an industrial chimney. Because it won’t burn, brick creates a great barrier between the flames, other combustibles, and people who are using the fire. A refractory brick’s composition withstands extremely high temperatures, resists melting, and has low thermal conductivity (even lower than concrete) which aids in energy efficiency.

Portage & Main Refractory Brick

Ultimizer Refractory Bricks

  • Refractory bricks contain around 25 to 30% alumina and 60 to 70% of silica and magnesium oxides.*Refractory bricks find application in the construction of kilns, incinerators, furnaces, etc.
  • Refractory bricks are found in all high efficiency indoor stoves and fireplace
  • They can achieve temperatures up to 2100⁰ Celsius
  • They have the incredible thermal capacity that helps different structures to remain stable at extreme temperatures.

Portage and Main refractory bricks are made from specially formulated ceramic designed to withstand high heat and impacts during high heat events. Their composition is made from heat-resistant compounds of silica, aluminum, magnesium oxide, and silicon carbide. They are very rugged and withstand the popping and minor explosions associated with burning wood in an enclosed area. Over time refractory brick may crack like all types of bricks, but this won’t change their purpose or degrade them in any way. The bricks stay in place and continue to retain and reflect heat despite the cracks.

Portage & Main Refractory Brick lined firebox

At Portage and Main we take refractory brick one step further. We encapsulate a layer of stainless-steel mesh inside the refractory components to keep them together even in the most demanding environments. The interlocking mesh helps strengthen the brick to protect from cracking, damage and degradation.

Stainless Steel Mesh

Our refractory brick is manufactured by RecTec; a company that specializes in all types of high end, high temperature refractory. This is an industrial forging kiln type of brick that is used in order to forge metal – so it is extremely durable and superior in holding heat energy.

Stainless Steel Mesh

Why is using this brick a superior method?

  • Protection from Heat, Moisture & Ash

These specialized refractory bricks are 2 inches thick. They serve to maintain interior temperatures and eliminate ash line corrosion at the base of the firebox from excess heat. Both functions serve to increase the longevity of the stove.

Even after your fire shuts down, any residual moisture will continue to evaporate as the bricks remain hot. There is no need to worry about moisture trapped in the ash as it will evaporate from the heat of the bricks. These bricks are also corrosion proof – not affected by ash build up that can be caustic. Some other brands encourage leaving a layer of ash to achieve a higher burn temperature which can lead to ash line corrosion.

All wood, even seasoned “dry” wood, contains up to 20% moisture. Sometimes unseasoned wood is used for fuel with even more moisture content. The refractory lined firebox will burn hot enough to burn hydrogen – it is this extreme heat that is needed in order to handle wood with extra moisture.

  • Heat Retention and Return

These bricks create a thermal mass which stores heat and returns it to the fire for a more balanced, efficient burn. Retaining heat also makes restarting the fire easier. Refractory bricks are used in wood stoves and fireplaces; why should it be any different for a wood boiler. It makes good sense.

  • Less Mess

Because these bricks create a hotter, balanced burn, more smoke is burned in the firebox so less smoke travels through the heat exchanger. This reduces build up and therefore less time cleaning residue from the heat exchanger chamber. Less build up also results in better heat transfer to the surrounding water.

How does Refractory Brick impact efficiency?

  • Thermal Retention Technology

This refractory brick makes the stove burn hotter. High temperatures require lower amounts of fuel and oxygen. Hotter burns mean for more complete and balanced combustion and more complete combustion means less wood to generate the same amount of heat. The fire triangle will equalize and therefore result in a balanced, efficient and cleaner burn.
Refractory Brick = Hotter burn = balanced burn = superior efficiency

The bricks also have the ability to retain heat which creates a thermal mass. A thermal mass is simply an object that holds heat. Whenever your boiler is idle, moisture will drip down the interior wall of the boiler. When that moisture drips into the brick base, it evaporates because of the bricks’ thermal retention.

Portage & Main_Inside_Boiler

Hotter Burn = Balanced Burn = Superior Efficiency

  • Combustion Balanced Design

P&M refractory bricks on the lower portion of the firebox do not come into contact with the water jacket. There is no water behind the refractor. This allows the firebox to burn very hot without losing heat to the surrounding water. Other brands’ fireboxes are surrounded by the water jacket which pulls heat away from the fire preventing a hot burn and therefore, the combustion is not balanced. Portage and Main firebox burns extremely hot reducing fuel consumption.

Combustion is balanced when the fire burns hot and doesn’t depend on more wood to keep the temperature up.
Portage and Main understands that burning the hottest fire is essential to saving time and money! This refractory brick designed firebox lining results in superior efficiency and balanced combustion.

How are competitors fireboxes designed & built?

Our refractory brick lined firebox design is unique to Portage and Main. Other brands’ fireboxes are encased in the water jacket which absorbs heat preventing the fire getting to its hottest, most efficient burn. This design just doesn’t make sense if you want an efficient burn. Building and designing with refractory bricks costs more but makes sense. The bricks are the key to the hottest, best, most efficient burn possible.

Other brands fireboxes bases are completely cooled by water, it never completely dries; leaving moisture at the bottom which can cause corrosion and the necessity of raking ash more often.

Our competitors have not duplicated our design as it is costlier to manufacture a more effective product. The other brands will price their product competitively to Portage and Main, but is a lesser efficient product; Portage and Main is, by far, the best quality and most efficient.





Portage and Main_Logo_2024

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.







(306) 922-1722


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