Tuesday, July 23, 2024

Portage & Main ML30 Coal Outdoor Water Furnace

Portage & Main ML30 Coal Outdoor Water Furnace

Coal Boilers are EPA Exempt.

The Portage and Main coal / biomass stoker can efficiently distribute heat throughout the home / building by using any forced air heat source already installed or add a plate exchanger to connect to an existing indoor boiler.  The boiler can also be used to produce unlimited domestic hot water.  The ML30 outdoor water furnace by Portage and Main is designed to automatically meter fuel into the fire, functionally “stoking” the fire.  Merely load the hopper with pellets, sunflower seed hulls, biomass or coal and go.  Burning wood is an option with the ML30 model by removing the stoker and installing grates and fan.

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Heating with coal is economical and the available indoor hopper eliminates coal freezing troubles.  Using coal also minimizes the need for expensive fuels such as natural gas, oil and propane.  The ML30 boiler is super efficient and can be used for heating new building(s) or be integrated into existing heating systems.  Moreover, the water furnace does not require daily feeding as other outdoor furnaces.   The stoker model has user determined metering controls for fuel.  The user decides and sets how much fuel goes into the stove according to the heat desired / required.

The ML30 outdoor water furnace has many features, listed below, that are signature to Portage and Main furnaces.


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.

Rounded firepot and water jacket is stronger, longer lasting as well as cleaner and more efficient

Three 3” diameter heat transfer water tubes

Rotating heavy duty self-cleaning high out put 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 to come on for 30 seconds every 30 minutes


Last pass through before exiting chimney


Digital Johnson control is programmable to one degree.

High limit safety aquastat, a manual aquastat, can control the furnace if the Johnson control fails

Variable Frequency Drive (VFD) speed control feed rate -   allows for burning of any grade fuel

Adjustable drive overloads for fan and stoker

Burn back protection by parallel wiring to insuring stoker and fan will stop if overload/jam occurs as well as timer device


Heavy-duty Bonfiglioli Gear Box Drive and heavy-duty ¼ HP AC 220 Volt 3-Phase Leeson drive motor (inverter rated)


Automatic 5’ ash remover auger


Fuel feed hopper designed to fit under hopper bottom bin – auger made with 3/8” flighting


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 which is rated for 2200 degrees F and the heat exchanger door is lined with refractory brick

Solid rope gaskets on fire door heat exchanger and cleaning access doors keep the unit air tight

Powder coated finish on the one piece roof, paint on the rest of the furnace


Firepot and inside water jacket are made of 1/4” W44 cold rolled steel.

The outside water jacket is made of 3/16” W44 cold rolled steel.

All Parts are laser cut and are boiler style welded – welding inside and outside helps prevent weld corrosion.

Optional Features: 

Highly efficient multi-pass heat exchanger with 180 degree turns


Stoker can be easily removed and grates and fan installed to burn wood.



Specifications Stoker Model ML30
HEIGHT (inches) 72
WIDTH (inches) 48
LENGTH (inches) 57
WEIGHT (pounds) 2,000
STOKER WEIGHT (pounds) 400
FIRE BOX SIZE (diameter x length) 30” x 44”
HEATING AREA (square feet) up to 10,000
WATER CAPACITY (U.S. gallons) 120
EST. BTU OUTPUT up to 400,000

* Available with trough style exchanger. Can burn wood by taking out stoker and adding fan.





Portage & Main ML30 Coal Outdoor Water Furnace

Portage & Main ML30 Coal Outdoor Water Furnace

Portage & Main ML30 Coal Outdoor Water Furnace

Portage & Main ML30 Coal Outdoor Water Furnace

*Shipping is not included.

Please call or email for a shipping quote.  


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