Commercial Wood Boilers


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The E140 model is available in both carbon steel and stainless steel. It puts out 140,000btu/hr and will heat up to 4,000 square feet. The E140 is rated at over 80% efficient.

The E140 can be used with any heating application (water-based, steam, forced-air). The Wood Gun has been tried and true for over 35 years! It was built to reduce the labor involved in a typical wood stove…

The Wood Gun™ wood gasification boiler by Alternate Heating Systems is perhaps today’s most efficient wood-burning device. This uncompromising multifuel system is ideal for any application using conventional log wood as fuel. The AHS Wood Gun™ E140 is well suited for up to 4,000 square feet, subject to building design and construction.

The firebox of each Wood Gun™ can accommodate wood sizes ranging from unsplit logs to complete rounds up to 10”. The large firebox must 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 and included ash scoop and rake make cleaning fast and convenient.

A high-velocity 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.

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 to construct 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 deterioration, even after over 35 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 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, which is 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 into our uniquely designed swirl chamber. This is where the bulk of heat exchange takes place. Above the heat exchanger, the super-heated refractory gasifies 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 like an oil or gas-fired boiler. Fuel is not consumed during the off-cycle because oxygen is not present in the combustion chamber. With the large super-heated refractory mass, re-ignition of the fuel occurs automatically when a drop in water temperature signals the need for heat. Depending on boiler size, automatic re-ignition is capable up to 4 hours after the last firing cycle.

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 goes up the chimney in many other boilers.

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

Call For Pricing (717) 987-0099

Assembled Specifications



Typical Heating Capacity (square ft)


Standard Door Opening (in)


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

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.

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.

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 running which would blow the remaining heat out through the flue.

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 E140 is capable of producing 130,000 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.

Variable Speed Induction Fan

This enables the BTU output to be easily changed. This is accomplished by upgrading the 1-phase motor to a 3-phase motor and controlling the motor with a Variable Frequency Drive.

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.

Low Pressure Steam

With this option, the Honeywell Aquastats are switched out for Honeywell PressureTrolls and two Low Water Cutoffs are included. An automatic water fill valve and Steam Relief-Valve are also included. In some models, the vessel is changed slightly to allow for a larger steam shelf. The Wood Gun can produce steam up to 15 psi. To know what size steam boiler you need, first, figure the amount of BTU/hr needed for your home, then add 20% to the total. This extra 20% is only needed to create the initial head of steam.

Canister Pool Heater

Heat your pool with wood! Available in either Carbon Steel or Stainless Steel. This is a separate canister from the vessel.

Automatic Feed

The Wood Gun™ series can be ordered with the ability to automatically feed itself wood particle fuels, such as sawdust, wood chips, shaving, pellets, etc. The Wood Gun™ auto-feed system loads the fuel into the firebox from the top. Only slight reconfiguration is required to still burn logwood in the firebox! This option comes with a photo-eye sensor, which controls when more fuel is needed, and an upgraded control center, which allows the user to easily control the entire system in one location. Touchscreen controls are available as well.

Additional Required Pieces:

  • Rotary Airlock – Rubber blades or machined stainless steel.
  • Fuel-Valve – acts as a second airlock, available in stainless steel.
  • Transition Tubes – available in stainless steel – connects the boiler to Airlock, Fuel-Valve, and Auger
  • Auger – available in nearly any diameter (4″, 6″, 8″, 10″) and any length
  • Diverter Bricks
  • Secondary Air Brick with cover

Custom Engineering

At Alternate Heating Systems we have expert fabricators and engineers ready to tackle any design change! Whether it is 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.