Alternate Heating Systems

WoodGun Wood Gasification Boilers

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How Wood Gasification Works

Wood gas is produced by applying high heat to wood in a process called pyrolysis. The wood gas is drawn through the bottom of the firebox and into our uniquely designed refractory by an induction fan. The gases are combined with oxygen and combusted in the refractory. The super heated gases pass through the interconnected refractory tunnels and into our uniquely designed swirl chamber. This is where the bulk of heat exchange takes place. Above the heat exchanger, the superheated refractory continues to gasify the wood remaining in the firebox. After combustion the residual ash is combined with high velocity air flow to scrub the heat exchanger preventing any build up. This process leads to unparalleled consistency in heat exchange. Most ash exits the unit and is collected in the cyclone ash separator for fast and easy removal.

The Wood Gun™ cycles on and off much like an oil or gas fired boiler. During the off cycle, fuel is not consumed because oxygen is not present in the combustion chamber. With the large superheated refractory mass, re-ignition of the fuel occurs automatically when a drop in water temperature signals the need for heat. Automatic re-ignition can take place as long as 4 hours or more after the last firing cycle depending on boiler size.

During the off cycle, wood gas inside the firebox condenses on the inner walls forming a solid that will eventually fall off. This combines with the remaining fuel, adding energy that in many other boilers goes up the chimney.

AHS Wood Gun™ E155

The AHS Wood Gun™ E155 is well suited for homes up to 4000 square feet, subject to building design and construction. The Wood Gun E155 is the only EPA qualified indoor wood boiler that does not require thermal storage!

The Wood Gun 155 features added insulation on the front and rear as compared to the original Wood Gun. The optional smoke exhaust hood, shown at left, removes smoke and water vapor that may be released when the load door is opened.

Wood Size, Moisture and ... No Smoke

The firebox of each Wood Gun™ can accommodate wood sizes ranging from unsplit logs to full rounds. Typically, the large firebox need only be loaded 2-3 times daily. The Wood Gun™ will handle wood of relatively high moisture content, as high as 35% moisture, freeing you from curing a 12-18 month supply of wood (30% moisture or less is preferred). Unlike European style gasifiers, the Wood Gun excels on full rounds.

Wood Gun boilers use ¼” thick Type 304 stainless steel in the construction of the firebox, heat exchanger and door frames. We use Type 304 stainless steel for its unsurpassed quality and longevity. Our stainless steel boilers show no signs of deterioration, even after well over 20 years of service.

Weekly cleaning allows for optimal performance. The easy access front and rear inspection doors along with included ash scoop and rake make cleaning fast and convenient.

Exhaust stack temperature is one indicator of transfer efficiency. During combustion, temperatures of around 2000° Fahrenheit can be obtained. Amazingly, our exhaust stack temperature ranges from about 260-300° Fahrenheit. This stack temperature is unheard of in the industry. The Alternate Heating Systems Wood Gun™ is truly the pinnacle of wood fueled heating devices.

A high velocity, variable speed draft fan moves air through the wood allowing for easy cold start up. After the gasification process begins this air movement produces intense flames and very high temperatures in the gasification tunnel. In turn The air flows through the heat exchanger, cleaning it as it passes through.

Exhaust emitted from the Wood Gun™ gasification boiler is not smoke, but the moisture condensing due to cold temperature. Even the vapor trail dissipates within a short distance. When installed, maintained and operated properly, it produces no visible smoke, and prevents creosote formation in the chimney.

Optional Wood Gun™ Accessories

  • Domestic hot water coil
  • Draft cycle timer - extends reignition period for times of low demand
  • Low water cutoff - safety shutdown if water level drops
  • Low temperature shutdown - fan shutdown if fire goes out
  • Smoke exhaust hood - 485 CFM
  • Fuel oil backup package available with either manual or automatic switchover
  • Canister pool heater - carbon steel or stainless steel
  • ASME and UL Certified on request

Limited Warranty

Alternate Heating Systems boilers and furnaces are warranted against defects in materials and workmanship for the following

  • Boiler Vessel - 20 years
  • All other components - 1 year.

A copy of the complete warranty text, detailing coverage,
limitations, warranty claim procedure and state law rights is
available from Alternate Heating Systems.


Sold, installed and serviced by America Radiant, the Wood Gun™ wood gasification boiler by Alternate Heating Systems is perhaps the most efficient wood burning device on the market today. This uncompromising multifuel system is ideal for any residential application where conventional log wood is used as fuel.