Wood Boilers

Quick Answers

• What parts of the Wood Gun Wood Boiler are made with carbon steel, and what parts are made from stainless steel?

• How easy is it to switch the Wood Gun from burning solid wood to pellets and vice-versa?

• How does wood gasification work?

• What wood moisture content level can this boiler handle?

• Why is heat storage not required with the Wood Gun™?

• The Wood Gun™ versus Competitors

• What is the difference between the BTU/Hr max rating and the Recommended Sizing BTU/Hr?

• What happens to the wood gases in the boiler during the shutdown phase?

• Can the Wood Gun be used as an outdoor wood furnace?

• Can this boiler be used on radiant heating systems?

• Can an Alternate Heating Systems boiler be operated in tandem with another boiler?

• How much does it cost to ship a boiler to my location?

The Wood Gun™ wood gasification boiler by Alternate Heating Systems, Inc. utilizes the most advanced technology available in wood and biomass burning devices.  The Wood Gun™ has been in existence for 26 years, and we believe that we have more experience with wood gasification boilers than most of our competitors.  We believe, and *independent testing laboratory results indicate, that this is the most efficient wood-burning device built today.  The Wood Gun™ is ideal for residential, commercial, and industrial applications where wood and wood by-products are available as a primary fuel source.  The Wood Gun™ wood boiler comes in sizes ranging from 100,000 to 1,000,000 BTU's.

The Wood Gun™ employs a downdraft wood gasification design which burns wood with wider moisture content.  These wood boilers work by drawing the wood gases off using an induction fan and then burning the gases underneath the wood so that much more complete combustion occurs. The wood is continually heated by the burning gases beneath it so that the gases continue to emanate from the wood.  Since the wood gases are much more fully combusted than in a standard wood burning device, the AHS wood boiler can burn wood with a wider range of moisture content than can a non-gasification wood boiler (see our wood gasification page for additional detailed information on moisture content of wood).  An additional feature is automatic switchover to oil heat, gas heat or electric heat backup.  An optional lockout feature maintains the secondary fuel mode in the event the wood charge is expended.

Particle Fuel Delivery for Industrial/Commercial Applications

When burning chunk wood in an AHS wood boiler, if the system is properly sized and quality hardwood is the fuel, the fire box typically only needs to be loaded two or three times a day (unless extreme cold conditions prevail).  Our automatic particle fuel delivery option is ideal for industrial/commercial customers with access to uniformly sized wood pieces, chips, pellets, etc.

If you want to burn both chunk wood and wood particles in your AHS wood boiler, it only takes about fifteen minutes (after shutting the system down and allowing it to cool) to change the system from one wood type to the other.

We feel that you can not find a more versatile wood boiler in the world that offers the capability to burn both chunk wood and automatically fed wood particles.

How Superior is the Efficiency of the Wood Gun™ wood boiler?

The Wood Gun™ wood boiler is a combustion system capable of burning wood and wood-based waste at a very high combustion efficiency, resulting in very low stack emissions.  Stack sampling on operating units has yielded particulate levels 50% less than the best results obtained by conventional up-draft boilers.  This level of performance is due to a number of unique design features not found on other wood waste combustion equipment.  In fact, the Wood Gun™ is so different that conventional wood boilers cannot be modified to incorporate these features without a complete redesign.

Stack Temperature

The stack temperature is an indicator of how completely the transfer efficiency is maintained.  The Alternate Heating Systems Inc. Wood Gun™ Boiler operates with one of the coolest stack temperatures of any wood boiler on the market (if not the coolest).  The stack temperature of a Wood Gun™ runs at less than 300 degrees Fahrenheit (typically 260 - 280 degrees).  The low stack temperatures of our boilers are almost unheard of on the market.  This low stack temperature can cause an interesting phenomenon as seen in the photo below.

Because the exhaust temperature is relatively low as it leaves the chimney, it is close to the dew point and steam will sometimes appear just above the chimney.  This should not be mistaken for smoke.  The steam is an indicator of the low stack temperature and the very efficient combustion of the Wood Gun™.  The exhaust from other boilers with higher stack temperatures (lower efficiency) will also form steam, but this only happens after the exhaust has moved higher into the atmosphere and so had time to cool to the point where condensation (steam) can occur.  The colder the outside air temperature, the more likely you are to to see steam from a Wood Gun™ wood boiler.

Carbon vs. Stainless Steel in our Wood Boilers

The internal surfaces of a Wood Gun™ Wood Boiler include any surface touched by the flame, smoke, wood or exhaust.  The internal surfaces may be manufactured with carbon steel or stainless steel - it's your choice.  We recommend stainless steel because carbon steel will show deterioration within 10 years though the unit may continue to function for as much as 20 years.  We have had stainless steel boilers in service for 20 years, and they show no sign of deterioration.  We use 1/4" thick 304 stainless steel (as opposed to 409) for unsurpassed quality.

Features

• Automatic cycling on and off in response to heating or hot water demand.

• Domestic hot water coil provides abundant quantities of hot water.

• Exceptionally safe and clean burning. The use of dense refractory material cast into specific shapes causes complete combustion to occur at temperatures of up to 2000° F.

• When operated properly in the gasification mode, visible smoke is eliminated and creosote formation inside the chimney is prevented.

• The large cyclone separator removes most of the fly ash resulting in very low emission.

• Spontaneous re-ignition of the wood will occur after an off period of 2-8 hours. Factors such as the quality and quantity of the fuel charge as well as the size of the unit also determine how long a system can go without burning and then have spontaneous re-ignition occur.

• Automatic fuel delivery systems are available for wood waste products such as sawdust, shavings, woodchips and densified biomass. These are designed more for industrial/commercial applications rather than residential.

• Wood Gun™ readily adapts to new or existing hot air systems through the use of a heat convection coil.

• The design maintains all heated walls at the same temperature using a "water wall".  This constant temperature eliminates stress fractures caused by differences in temperature between components of the boiler thus increasing it's life.  In addition, this design produces greater efficiency because heat that is normally lost through a drywall is captured in the water wall.

Customer Commitment

• We use standard parts in our boiler designs.  The first wood gasification boiler was built 26 years ago and all parts are still available as replacement parts.

Diagram of Wood Gasification Boiler

The Swirl Chamber

HOW DOES THE UNIQUE DESIGN OF THE WOOD GUN SWIRL CHAMBER DIFFER FROM OTHER WOOD GASIFICATION BOILERS?

The SWIRL CHAMBER is where 90% of the heat exchange takes place in the Wood Gun. The Wood Gun refractory emits 2000 degree fahrenheit exhaust air temperature which is directed into the SWIRL CHAMBER and has an exiting exhaust air temp of only 275 degrees at high fire. This unheard of heat transfer efficiency is due to our unique design. The exhaust air spins through a large diameter drum assisted by a 3400 rpm draft inducer making a swirling action. Both the exhaust air and the ash from the wood, scrub the walls of the heat exchanger at a high rate of speed, in turn keeping it clean and efficient. This self-cleaning action prevents the troublesome routine cleaning of the heat exchanger that has plagued the Wood Boiler industry for years.

*The temperature varies from Boiler size, wood quality, moisture content and flue height. 

The CYCLONE ASH SEPARATOR is where the majority of the ash is collected. Since the design of the Swirl chamber is to use the ash as a cleaning agent, we can allow the ash to exit the boiler with the exhaust air.  The speed of the ash is increased using a high velocity orifice, discharging it into a cyclonic action device (the CYCLONE), spinning the heavy particles out of the exhaust stream and finally funneling them into the stainless steel ash pan allowing the exhaust to exit the cyclone top into the chimney pipe. 

Illustrated Features

Routine cleaning of combustion chamber is necessary to maintain optimum performance. Easy-open Inspection Doors Front and rear make cleaning a snap.

Improved Air Valve design permits easy replacement of gasket disc.

	The Air Valve closed.
			Removable Clean-out Plug provides direct access to combustion chamber

Draft inducing fan produces high velocity and intense flame in combustion chamber. Unlike conventional heating equipment, the flame production in the Wood Gun ™ follows a downward path with temperatures of up to 2000° Fahrenheit.
	Inside the wood chamber looking through the wood loading door.

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What is Biomass?

According to Forest Bioenergy, biomass is any organic matter including forest and mill residues, agricultural crops and wastes, wood and wood wastes, animal wastes, livestock operation residues, aquatic plants, and municipal and industrial wastes.  The Wood Gun™ wood boiler would therefore qualify as a biomass burner.  Biomass is a renewable energy resource.  Significant effort is being expended to develop biomass as an energy resource in the United States.  There are currently five Regional Biomass Energy Programs established and funded by the U.S. Department of Energy.  The Northeast Regional Biomass Program is one of these programs.  As an example of the potential of biomass in energy production, a report entitled "Securing a Place for Biomass in the Northeast United States:  A Review of Renewable Energy and Related Policies" states:
"Biomass currently provides about four percent (7,500 megawatts) of all the electricity produced in the U.S."  The report further states that "Accordingly, the U.S. Department of Energy (DOE) asserts that the potential exists for biomass power to grow to an industry with 30,000 megawatts (MW) of capacity".

We believe that purchasing a Wood Gun™ wood gasification boiler would make you a part of the growing and beneficial trend of burning renewable biomass.

Specifications

Alternate Heating Systems, Inc. standard sized Wood Gun™ Boilers are smaller than the intermediate sized boilers but include the same features and performance.

* Specifications and design subject to change without notice.
All specifications shown are approximate.

** Models E180 and above have a built-in oil firing chamber that is present whether or not the oil burner option is ordered (see Wood Gasification Boiler diagram above).  On models E100 and E140 the oil burning chamber is external to the unit and is only included when the oil burner option is ordered.