Commercial Wood Boilers

E155 SS

The E155 SS model is made of stainless steel. Because of its robust construction, this model offers durability and longevity unsurpassed by competitors’ units, ensuring that your stove will last a lifetime.

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 commercial application where conventional log wood is used as fuel. The AHS Wood Gun™ E155 is well suited for buildings up to 4000 square feet, subject to building design and construction.

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 loading door is opened.

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.

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.

A high velocity, variable speed draft fan moves air through the wood allowing for an easy cold startup. 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.

Wood Gun™ boilers can be fitted with either fuel oil, natural gas, or LP gas backup (non-UL version only). The Riello fuel oil burner will allow you the option of automatic backup. This allows you to save money by burning a renewable fuel source and the convenience of burning oil. The oil backup system is rated over 84% efficient. With an efficiency rating that rivals top-of-the-line oil units, you cannot go wrong.

Stainless Steel Construction

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.


The Wood Gun™ wood gasification boiler, when installed, maintained, and operated properly, produces no visible smoke, and creosote formation in the chimney is prevented.

Stack Temperature

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.

How it works

Wood gas is produced by applying high heat to wood is 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 airflow 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.

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  • Made in Pennsylvania
  • Since 1981
  • 1/4″ Stainless Steel Construction
  • Fuel-Efficient
  • Minimal Maintenance
  • Versatile Applications
  • EPA Step 1 Certified

Call For Pricing (717) 987-0099

Assembled Specifications


150,000 MAX

Typical Heating Capacity (square ft)


Standard Door Opening


Firebox Capacity (cubic ft)


Firebox Length (in)


Approximate Water Capacity (gal)


Width (cyclone removed) (in)


Height (in)


Depth (in)


Flue Size (in)


Weight (without gas/oil backup) (lbs)


Alternate Heating

Domestic Coil

This Domestic Coil features a 100° F rise at 5 gallons per minute, 50° water inlet temperature and, 65 PSI water pressure. It is threaded into a 4 IN NPT threaded fitting provided on the boiler for this purpose.

Alternate Heating

Smoke Exhaust Hood

The Smoke Exhaust Hood mounts over the loading door, capturing any smoke that may escape during the fuel-loading process. This smoke is then vented directly to the outside through a separate vent. When tolerance for smoke is low, the smoke exhaust hood is essential.

Low Temperature Shutdown

If all the fuel has been consumed in your boiler, the Low Temperature Shutdown Feature prevents the boiler from attempting to fire. This keeps the draft fan from blowing the remaining heat out through the flue.

Variable Speed Induction Fan

The E155 comes standard with a variable speed induction fan. This allows the BTU output to be changed on-demand as needed. The boiler will adjust the fan speed automatically to match the current heat load. This is accomplished by switching out the 1-phase motor to a 3-phase motor and controlling the motor with a Variable Frequency Drive.

Cycle Timer

This feature adds a timer that triggers the boiler to run for 10 minutes every 2 hours, even if there is no call for heat. This maintains an internal temperature above the kindling point, reducing the need to manually relight the unit during periods of low demand.

Oil/Propane/Natural Gas Backup

The Wood Gun wood boiler can be fitted with a backup fuel option. This requires a dedicated firing tube that must be built in during manufacturing.

The E155 is capable of producing 80,000 BTU/hr when burning oil, propane, or natural gas.

Automatic/Manual Switching

For #2 fuel oil, the oil backup can function in an automatic switch-over scenario, with fuel oil taking over when the boiler has exhausted its wood fuel. For other fuels, such as natural gas or propane, switch-over is manual only.

Low Water Cutoff

A Low Water Cutoff senses the water level in the boiler’s vessel and will shut the unit down if the water level drops to an unsafe level. Available with automatic reset or manual reset.

ASME Certification

The ASME Certification guarantees the steel grade and weld quality of the boiler water jacket. Each ASME Certified water jacket has been pressure tested to 60 PSI and includes a 30 PSI release valve.

Custom Engineering

At Alternate Heating Systems we have expert fabricators and engineers ready to tackle any design change! Whether it’s a custom bin, moving the cyclone to the other side, an extra load door, water storage tank, or whatever you may need to fit your application.