E500 Wood Boiler

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The E500 is a commercial wood gasification boiler. It is available in carbon steel or stainless steel and can heat up to 20,000 square feet. It has been manufactured in Pennsylvania since 1981. This model is commonly used with our automatic self-loading equipment. Self-loading wood boilers are the best way to utilize the cost-effectiveness of wood in larger applications!

The Wood Gun series of boilers is one of the most fuel-effective choices available. While standard boilers waste two-thirds of a fuel’s energy potential, the E500 Wood Gun catches and utilizes 66% more burning matter, converting it all into clean, consistent heat.

The Wood Gun was designed to lessen the work involved in general maintenance…

The E500 can take on whole logs of up to 10 inches in diameter. This wood boiler relieves you of a good amount of log-cutting job; the ability to use logs of up to a maximum of 40% moisture saves on wood drying time; and, due to our trademark Swirl Chamber with Exhaust Scrubbing innovation, the Wood Gun’s heat exchanger is able to clean itself—so the only weekly cleaning you’ll have to do is dump the ash.

The Wood Gun series can be utilized with any heating system (water-based, steam, forced-air).

The E500 can be ordered with the equipment to make it a self-loading wood boiler, which enables you to heat an assortment of wood particle fuels, varying from sawdust and wood chips to shavings, pellets, and other wood wastes¹. Additionally, with an AHS automatic feed system, if you want to use logwood in the unit, you can change the firebox slightly to accept logwood; it takes about 15 minutes.

How it functions

Top Feed WG Big


The E500, as a self-loading wood boiler, can use an assortment of fuels. For example, we can burn soft or hardwoods with moisture ranging from 5% to 40%. We can accommodate sawdust, chips, or mulch. In a typical setting, particle fuel is transported by a blower or other ways to a large storage bin. From there, the fuel is transported on request through an auger and a bin agitator, which discharges material uniformly. A photoelectric sensor (3) supervises the height of the fuel in the fuel chamber (4) and turns on the feed system when more fuel is needed in the firebox.

Two main safety features of the AHS self-loading wood boilers are the rotary air-lock (1) and the fuel valve (2). It is essential to regulate the airflow through the gasification boiler system to control burning and permit off cycle. It is vital that no air penetrates into the boiler from the top feed opening. This is achieved using a rotary valve, a device that utilizes the same concept as a department store’s spinning door. The fuel valve is a device that separates the fuel that is being burned in the fuel chamber and the fuel that is in the loading system, preventing the ignition of the fuel in the loading system.

The Wood Gun combustion chamber (5) is situated below the fuel chamber and is comprised of cast refractory sections, which are placed end to end to make up the three tunnels. This material has properties and texture similar to firebrick and helps to create the environment needed to achieve the high temperatures required for clean combustion. Slots in the refractory bricks provide passageways from the fuel chamber to the combustion chamber. Smaller fuel particles are prevented from falling through the slots by a fuel diversion structure (6). A variety of shapes and sizes of fuel diverter blocks are available based on the size and kind of fuel.

Once the gas is released during the gasification process, it will be drawn toward the fuel diverter and through the slots in the combustion chamber, where temperatures in excess of 2000° F are attained. The powerful heat generated here spreads through the refractory lining (7) in the lower portion of the fuel chamber, evaporating water from the fuel and allowing it to gasify (pyrolysis).

In order to draw the gases into the combustion chamber, a draft-inducing fan (8) is used. The fuel can effectively burn upside down due to the negative pressure. This is important because it allows fuel to be loaded continuously without extinguishing the fire. Once the gases are drawn into the combustion chamber, they pass through the firetubes (9), where most of the heat exchange takes place. On small-scale Wood Guns like the one shown, only one firetube is present. Multiple firetubes are used to increase the surface area available for heat exchange in the larger models. After the firetubes, the gases are given a swirling action as they pass through the swirl chamber (10) and into the cyclone ash separator (11). Here, ash is removed from the exhaust air and deposited for easy disposal. Due to the unique design of the swirl chamber, the swirling motion scrubs the inner chambers, preventing much of the ash buildup that could decrease efficiency. Exhaust air then exits through the top of the cyclone ash collector into the flue, which has cooled to about 350 F.

The E500 has seals on all doors and on the automatic intake damper (air valve). During off-cycle, the air valve (s) close and completely eliminate air from entering the firebox. The fire soon goes out due to a lack of air. Thanks to our huge superheated refractory mass, the fire reignites immediately after off-cycle when oxygen is reintroduced to the system. By operating in this fashion, we do not waste any fuel when it is not needed.

¹An assortment of fuels can be heated, such as maize, nutshells, cherry seeds, and paper pellets. Fuel sources are restricted only by natural concerns, like the amount of soot produced, and fuel economy concerns, like accessibility and BTUs per pound.

  • Gasification
  • Range of Biofuels
  • Fuel Efficient
  • Minimal Maintenance
  • Lifetime Durability
  • Versatile Applications
  • Automatic Feed Available
  • Standard ASME Certification
  • Made in USA
Call For Pricing(717) 987-0099
Assembled Specifications



Typical Heating Capacity (square ft)


Weight (lbs)


Flue Size (in)


Fuel Type

Soft, Hard Logwood*, Biomass*

Optional Backup Fuel


Standard Door Opening (in)


Firebox Capacity (cubic ft)


Firebox Length (in)


Approximate Water Capacity (gal)


Width (cyclone removed) (in)


Height (in)


Depth (in)


Electric Requirements

220V, 60Hz, 20Amp

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

Alternate Heating

Smoke Exhaust Hood

The Smoke Exhaust Hood mounts over the load 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.

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.

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

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.

Low-Pressure Steam

With this option, the Honeywell Aquastasts 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 required for your home, then add 20% to the total. This extra 20% is only needed to create the initial head of steam.

Note: only available on Carbon Steel boilers.

Canister Pool Heater

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

Custom Engineering

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