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Portage & Main ML42 Outdoor Water Furnace - Obadiah's Wood Boilers

Portage & Main ML42 Outdoor Water Furnace.

Founded by Andy Naggy in 1973, Portage and Main has humble beginnings in one man’s personal workshop. Today, the company is one of the best in the business- a universally recognized name in outdoor water furnaces that continues to take inspiration from Naggy’s idea of making durable appliances with simple, reliable manufacturing concepts.

Portage And Main operates out of Piney, a small community along the border of Manitoba, Minnesota, and Ontario. Their manufacturing plant is a modern, state-of-the-art facility that makes use of computer assisted design, laser cutting, and robot welding. Don’t let that fool you, though: Portage And Main understands the value of keeping jobs local, with the Piney facility being reliable backbone for most of the residents. They also use strictly North American materials in constructing their furnaces, so you can take comfort in knowing that when you purchase from Portage and Main, you’re supporting local economies.

While many outdoor furnace manufacturers use single-pass welding to get the job done as cheaply as possible, Portage and Main goes the extra mile by employing double-pass welds, making for maximum strength and corrosion resistance. You won’t find weak construction in a Portage and Main furnace- not only is the double-pass policy one you can count on, but each furnace is rigorously tested to ensure you get the best furnace while Portage & Main keeps their reputation.

Portage and Main values what most of us in this part of the world hold dear: Independence. They understand that many of us want to take care of ourselves and be self-sufficient. While you can count on Portage and Main to be there for you if something goes wrong with your system, you can also rest easy knowing that your outdoor water furnace was built by like-minded individuals who crave energy independence as much as you do.

Features of the ML Outdoor Water Furnace

Portage & Main Double Weld - Obadiah's Wood Boilers Portage & Main ML42 Outdoor Water Furnace - Obadiah's Wood Boilers
  • Double pass with reversing flow tube heat exchange is standard
  • Water-filled baffle provides first and second pass of heat exchanger and catches fly ash.
  • Four 3” diameter heat transfer water tubes
  • Rotating, self-cleaning high output cast-iron stoker head available in 18” or 20”
  • Combustion blower induces air through the specially designed slots in the stoker head
  • Stoker in “Fire Keep Mode” controlled by adjustable time override, 30 seconds every 30 minutes
  • Digital Johnson control is programmable to one degree
  • Variable Frequency Drive (VFD) speed control feed rate and allows for burning of any grade fuel
  • Adjustable drive overloads for fan and stoker
  • stoker and fan auto-stop if overload/jam occurs
  • Automatic 5’ ash remover auger
  • Fuel feed hopper designed to fit under hopper bottom bin
  • Indoor hopper available in custom sizes
  • Float is easy to read, low water shut-down safety switch on stokers
  • Fire door insulated with Roxul insulation, rated for 2200 degrees F
  • heat exchanger door is lined with refractory brick
  • Firepot and inside water jacket are made of 1/4” W44 cold rolled steel
  • All Parts are laser cut and are boiler-style welded


Interested in a Portage & Main furnace? Check out the following for more information!

Portage & Main Boilers at Obadiah’s Woodstoves
Portage & Main Brochure – An informative brochure from Portage & Main (to download, right click and select “Save As…”)
Portage & Main Manual – Models ML30, ML36, ML42 – The owner’s manual for ML series of Portage & Main Outdoor Water Furnaces. (to download, right click and select “Save As…”)