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Which is the Best Heat Exchanger for an Outdoor Boiler in 2024

The Portage and Main Ultimizer Quad Pass Heat Exchanger

Portage and Main Ultimizer Outdoor wood furnace’s design and robust, quality manufacturing ensure that their furnaces achieve hotter, slower and more balanced burn which means higher efficiency. An efficient burn requires a balance of three elements:
Fuel, Oxygen and Heat

Fire Triangle

What is a heat exchanger?

Simply defined, a heat exchanger transfers heat. In a Portage & Main outdoor wood furnace, this heat exchanger transfers heat from the firebox to water surrounding the chamber. How is the heat exchanger designed and constructed?

Portage & Main have a unique Quad Pass designed heat exchanger. The design includes a water-cooled baffle at the top of the firebox. The heat then moves to the heat exchanger which is surrounded and separated by water-cooled walls and dividers.
This design makes the transfer of heat extremely efficient.

Double welded boiler style joints are exclusive to Portage & Maine outdoor water furnaces. All parts are laser-cut for precision fitting which allows the bevel to be double welded for total penetration welds. The fire chamber and heat exchanger are made a quarter-inch w44 cold roll mild steel which eliminates the problems associated with other metals.

How does a Portage & Main heat exchanger work?

First: After the fuel, heat and oxygen mix to create a balanced burn, some heat energy is transferred first to the water jacket surrounding the top of the firebox.

Second: Air is introduced above the fire which help burn the smoke and gasses. There is a baffle near the back of the fire chamber which serves a dual purpose. The baffle is water-cooled so absorbs heat but also traps the hot gasses and smoke. This trapping of gasses, oxygen and fire creates combustion storms which causes the fire to burn hotter.

Hotter burn = complete combustion = best efficiency

Three and Four: After combustion, this exhaust heat then travels horizontally through the heat exchanger at the top of the furnace. This is an industry-leading, 180⁰ reverse turn, water-cooled chamber that runs the full length of the furnace. This results in the largest heat transfer area of any updraft boiler design.

The Portage and Main chimney exit out the back of the furnace versus cutting it short out the top like other furnaces. This added length means more heat absorbed to the surrounding water and less heat escaping. Its dual chamber design, fully surrounded by water, and added length results in maximum heat transfer resulting in low temperature chimney escape.

Portage & Main Quad Pass Heat Exchanger

Frequently Asked Questions


Q. How does the Portage & Main heat exchanger compare to competitors?

Portage and Main heat exchanger first transfers heat in the firebox to the water-cooled baffle. Other furnaces baffles are sheet metal not water-cooled. Also, our baffle is situated vertically to trap burn for maximum turbulence while others baffles are horizontal allowing low circulation of combustion without turbulence.
Portage and Main heat exchanger design and construction is second to none. Constructed with double welded steel, and dual chamber designed with a water-cooled divider wall. Our competitors don’t use double welded steel and the heat exchanger is separated with a steel plate which deflects heat instead of absorbing heat.
The Portage and Main furnace chimney exits out the back of the furnace versus cutting it short out the top like alternate furnace designs. The competitors shorter heat exchanger results in up to 40% less heat transfer. Portage and Main heat exchanger running the full length means more heat absorbed to the surrounding water and less heat escaping up the chimney.
Furthermore, our heat exchanger is completely surrounded by water and has a larger volume capacity. Water-cooled and larger volume allows for maximum surface area heat transfer. Other heat exchangers have smaller volume and surface area resulting in 10% less heat transfer and higher heat loss.

Q. How can you clean the heat exchanger ?

Some competitors’ units have elbows and chambers that make accessibility to cleaning out their heat exchangers very difficult. Cleaning out the Portage & Main heat exchanger is fast, clean and easy. Simply pull the tool with the soot towards the front, then push it to the left side and back into the firebox where it can be burned up. This simple and fast way keeps all the mess inside the unit! As shown above, the Portage & Main heat exchanger the most efficient and effective heat exchanger on the market – second to none!



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


Monday-Friday : 8am to 5pm CST

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