Solid Fuel - Coal - Multi-Fuel Boilers

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Alternate Heating Systems Coal Multi-Fuel Boiler

The Multi-Fuel boiler is a conventional upward draft boiler that offers excellent performance and rugged dependability complementing its hand fired coal capability. Its multiple fuel designation is due to the availability of optional fuel oil, gas or propane backup. Traditionally, Multi-Fuel boilers have been sold as wood/coal combinations. Due to EPA regulations, and no EPA Phase 2 approval for the the Multi-Fuel updraft units, they are sold for use with coal. When starting a new fire in the Multi-Fuel boilers, wood is the fuel of choice. Wood can be burned safely in the Multi-Fuel for the coal fire startup phase.

Legacy Stoves Cast Iron Grate System

WC/WOC40 and WC55/WOC55 models manufactured since April 2016 now include cast iron grates in place of the rotary grate. This grate system is inherited from our Legacy Stoves lineup, and offers better control of underfed combustion air. This grate system is robust and well-proven, having been used in Harman1 stoves and boilers for many years. 

Cast iron Grated as Seen in the WC/WOC40-55 Models

Triangular Rotary Grate

The air-cooled Rolla-Grate triangular rotary grate system is the heart of WC/WOC70 and WC/WOC100 Multi-Fuel models. This remarkable system adjusts to maximize burning efficiency for each fuel and provides a convenient method of removing expended ash from the boiler's firebox. The triangular grate design is made with a hollow core allowing airflow via convection in order to keep the grate cool. This cooling effect prevents warping of the grate components. Depending upon the model purchased there is a minimum of three grates. The boiler is designed so that each grate can be shaken or rotated individually so that ash can be removed only from areas where expended fuel has built up. Refractory-lined baffling diverts the exhaust through the boiler in order to reclaim as much heat as possible before the exhaust passes out the chimney. Water tubes located in the top of the unit serve to capture this additional heat.

Multi-Fuel Coal Boiler Triangular Rotary Grate System

Standard Equipment On All AHS Multi-Fuel Boilers:

  • Rolla-Grate™ Rotary Grate System (WC/WOC 70 & WC/WOC100)
  • Legacy Stoves Cast Iron Grate System (WC/WOC40 & WC/WOC55)
  • Opening can be increased from nearly closed to large opening for burning coal
  • Large Loading Door
  • Full gasket for maximum efficiency
  • Smoke Flap
  • Water Cooled Baffles
  • Forced Draft Fan
  • Large Removable Ash Pan
  • Dual Draft System
  • Through-the-door draft system for burning wood (startup and emergency use). Below-grate draft system for burning coal.
  • Automatic Draft Control
  • Firebrick Lined Firebox
  • Hydro Tested to 60lbs PSI
  • Constructed of 1/4" Steel Plate Throughout vessel
  • Honeywell Circulator Control Aquastat
  • Temperature/Pressure Gauge
  • ASME Tested Pressure Relief Valve

Our Multi-Fuel Boilers are not to be confused with "converted" or "re-designed" single fuel equipment. Every Alternate Heating Systems, Inc. Boiler boasts design and engineering to operate efficiently on Coal and Fuel Oil or Natural Gas/Propane.

EPA Regulations and the Multi-Fuel Boilers

Multi-Fuel boilers are safe and effective for heating with wood, but they are not EPA Phase II approved. For EPA approved wood heat, see our Wood Gun model E155.

Optional Equipment on AHS Multi-Fuel Boilers:

  • Riello Oil Burner. The Riello oil burner option is an excellent choice for burning oil in combination with burning other fuels - it is designed to let almost no air into the combustion chamber when not burning oil.
  • Domestic coil - factory installed (5 Gal. per min. max. output.)
  • Auto switch over
  • Soft Coal Linkage Kit (for burning bituminous coal)

Multi-Fuel Coal Boiler Specifications

Model: WC40 WC55 WC70 WC100
BTU/Hour Coal 150,000 225,000 265,000 400,000
Water Capacity, Gallons 40 55 70 95
Firebox Capacity, Cubic Feet 7.5 10 14 22
Coal Capacity 125 lbs 200 lbs 250 lbs 400 lbs
Max Log Length, Inches 24 24 36 38
Standard Door Opening 14" x 14" 14" x 14" 14" x 14" 16" x 16"
Height 44" 54" 59" 64"
Width 28" 28" 28" 34"
Depth 36" 36" 40" 50"
Height to Flue Opening (Center) 35" 45" 45" 50"
Flue Size 8" 8" 8" 8"
Weight, lbs 1,050 1,220 1,450 1,950
Typical Heating Capacity, Square Feet** 3,000 4,000 5,000 9,000
Specifications subject to change without notice

Multi-Fuel Coal (With Backup Fuel) Boiler Specifications

Model: WOC40 WOC55 WOC70 WOC100
BTU/Hour Coal 150,000 225,000 265,000 400,000
BTU/Hour Oil or Gas 225,000 225,000 250,000 400,000
Water Capacity, Gallons 44 59 75 100
Firebox Capacity, Cubic Feet 7.5 10 14 22
Coal Capacity 125 lbs 200 lbs 250 lbs 400 lbs
Max Log Length, Inches 24 24 36 38
Standard Door Opening 14" x 14" 14" x 14" 14" x 14" 16" x 16"
Height 44" 54" 59" 64"
Width 28" 28" 28" 34"
Depth 36" 36" 40" 50"
Height to Flue Opening (Center) 35" 45" 45" 50"
Flue Size 8" 8" 8" 8"
Weight, lbs 1,230 1,400 1,630 2,130
Typical Heating Capacity, Square Feet** 3,000 4,000 5,000 9,000

**Subject to building design and construction
Specifications subject to change without notice

Multi-Fuel Family Photos

Multi-Fuel Options

Multi-Fuel Brochure

EPA News Release

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