Over 92.5% Efficient

Wood-Fired Energy Independence

Heat your commercial application for far less money than fuel oil, propane, natural gas and even off-peak electric rates with WoodMaster’s Flex Fuel Series. Choose the least expensive fuel — cordwood and wood pellets — and burn less of it, guaranteed. Calculate your savings.


Why Flex Fuel

  • The Industry Leader
  • Money-back guarantee and 13 years proven reliability.
  • Engineered using world leading technology with WoodMaster quality built right in.
  • Over 92.5% efficient based on EN 303-5 test standard

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Flex Fuel 30 kW

  • Fire box: 22.5″ L x 14″ W x 25″ H
  • Fuel door size: 13.5″ W x 9.5″ H
    reversible with built-in smoke bypass
  • Heavy duty mild steel construction
  • Draft: Fan-induced down draft
  • Overall size*: 24″ W x 48″ L x 54″ H
  • Capacity: 24 gallons
  • Btu: 100,000
  • Warranty: 10 years
  • Shipping weight: 1400 lbs.
  • Cordwood, wood pellets

Flex Fuel 60 kW

  • Fire box: 26.5″ L x 22″ W x 28″ H
  • Fuel door size: 21.5″ W x 10″ H
    reversible with built-in smoke bypass
  • Heavy duty mild steel construction
  • Draft: Fan-induced down draft
  • Overall size*: 32.5″ W x 60″ L x 60″ H
  • Capacity: 50 gallons
  • Btu: 200,000
  • Warranty: 10 years
  • Shipping weight: 1800 lbs.
  • Cordwood, wood pellets


  1. Fuel Options—cordwood and wood pellets —help you control savings and provides ease of operation.
  2. Lambda sensor analyzes levels in the stack and sends it to the eco manager, saving you more with higher efficiency and fewer emissions.
  3. Variable speed fan adjusts the air intake to reach the optimal burn for efficiency, emissions and prolonged product life.
  4. Eco manager pulls the system together—from the lambda sensor to the draft inducer—enabling user-friendly maintenance.
  5. Optional self-ignition is programmable by time or water temperature.
  6. Self-cleaning heat exchangers assist in maintaining money-saving efficiency levels—with less maintenance.
  7. Wood gasification technology provides excellent combustion at high temperatures for better efficiency and fewer emissions.
  8. Large ash chamber makes ash cleanup quick and easy.
  9. Smoke extraction directs remaining smoke to the flue when you open the loading doors.
  10. Easily converts from one fuel to another once installed. This gives you more options with less time.
  11. Solar capable which is another option to save even more money and use less fuel.


The plumbing between the furnace and tank must be to the manufacturer’s specifications.


Cleaning the Furnace

  • Disconnect the power source prior to cleaning. Never clean your furnace during operation.
  • Wait for the furnace to cool before cleaning the furnace.
  • Correctly dispose of the ashes in a sealed metal container away from flammable materials.
  • Cleaning intervals will vary depending on the quality of the fuel being used.

Cleaning Intervals

  • Air Feed: As required following visual inspections
  • Ash Chamber: Every 2 weeks
  • Heat Exchanger: Automatic

Cleaning the Air Passages

Before firing the furnace, check that all the air openings above the grate are free of ash. It may be necessary to use the ash scraper to open them. Regularly check that the air openings are not clogged with tar. Manually clean the turbulators every 4000 hours. If necessary scrape the primary air feed openings inside the firebox with the ash scraper to maintain air flow.

Cleaning the Ash Chamber

  • Check that the furnace is not operational and is cool
  • Open the outer enclosure door
  • Open the ash chamber door
  • Push the ash tray onto the bottom door frame
  • Use the ash scraper to carefully pull the ash onto the ash tray. Leave approximately .5 in of ash in the entire bottom of ash chamber to extend the life of the refractory
  • Carefully remove the filled ash try and empty it into a metal container for final disposal
  • Clean the area around the door seal to ensure the door closes properly
  • Close the ash door, making sure the door is closed tight

Owner’s Resources


  • All installation and operations must follow STATE and LOCAL CODES for wiring, plumbing, and firing of this unit. These CODES may differ from the owner’s manual. Installation must be performed by a Qualified Installer.
  • Read and follow the directions carefully. Retain the owner’s manual for as long as you own your WoodMaster furnace.
  • Your Flex fuel must be installed by a professional and should follow all local, state and federal laws and regulations. All installations must be pre approved by WoodMaster. Any use of an unapproved installation may result in a voided warranty.

Best Burn Practices:

  1. Read and follow all operating instructions supplied by the manufacturer.
  2. FUEL USED: Only those listed fuels recommended by the manufacturer of your unit. Never use the following: trash, plastics, gasoline, rubber, naphtha, household garbage, material treated with petroleum products (particle board, railroad ties and pressure treated wood), leaves, paper products, and cardboard.
  3. LOADING FUEL: For a more efficient burn, pay careful attention to loading times and amounts. Follow the manufacturer’s written instructions for recommended loading times and amounts.
  4. STARTERS: Do not use lighter fluids, gasoline, or chemicals.
  5. LOCATION: It is recommended that the unit be located with due consideration to the prevailing wind direction.
    • Furnace should be located no less than 100 feet from any residence not served by the furnace.
    • If located within 100 feet to 300 feet to any residence not served by the furnace, it is recommended that the stack be at least 2 feet higher than the peak of that residence.

Flex Fuel Owners Manual

Le Manuel de Propriétaire français


WoodMaster FLEX FUEL Warranty

600 Polk Ave. SW – Red Lake Falls, MN 56750
Toll free (800) 932-3629 or (218) 253-4328

Ten-Year Warranty on Firebox and Water Jacket

Northwest Manufacturing, Inc. of Red Lake Falls, MN 56750 warrants material and labor on any defects in workmanship on the firebox and water jacket for a period of ten (10) years from the purchase date to the original owner only. If there is a leak in your properly delivered and installed WoodMaster Flex Fuel furnace in the first year, WoodMaster will replace the furnace at no cost to the original owner. (A leak means; a leak in the firebox or water jacket.) Northwest Manufacturing, Inc. will not be responsible for environmental conditions we cannot control. Therefore, Northwest Manufacturing, Inc. will only pay these percentages of costs of warranty work per year, years two (2) through five (5) – 100% of warranty work, the sixth (6) year – 70% of warranty work, the seventh (7) year – 60% of warranty work, the eight (8) year – 40% of warranty work, the ninth (9) year – 20% of warranty work, the tenth (10) year – 10% of warranty work. After the tenth year Northwest Manufacturing, Inc. provides no other warranty. A blow down of the furnace and tank must be performed yearly after each heating season and every six months if the furnace is used year round. After the furnace has had a blow down performed, an annual water test must be taken and immediately treat and refill the furnace. Failure to send in a water sample annually will void the warranty. This warranty is limited to defective parts – repair and/or replacement only, and excludes any incidental and consequential damages connected therewith. Northwest Manufacturing, Inc. is not responsible for replacement of water, water treatment, antifreeze, costs of transportation, or shipping charges. WoodMaster will not cover any construction or modification costs due to the furnace being in a non-accessible area. Any construction or modification costs are the customer’s responsibility. (Example: We will not pay to remove the furnace out of a basement or crawl space.) WARNING: Northwest Manufacturing, Inc. will not warranty the inside of firebox due to ash corrosion. Ashes must be taken care of as displayed on the maintenance list located in your owner’s manual. The firebox must be completely cleaned of all ashes and creosote a minimum of two (2) times per year, preferably half way through the heating season and immediately after the heating season. If the furnace is being used year round, more maintenance is required thus the firebox must be completely cleaned of all ashes and creosote a minimum of four (4) times per year. Installation of an approved Class “A” insulated chimney and chimney cap must be used. Two Year Warranty on Additional Components – Parts and Labor Northwest Manufacturing, Inc. warrants to the original owner only, any additional components, including, but not limited to the outer shell, paint, insulation, doors and latches during normal usage for a period of two (2) years from the date of purchase. One-Year Warranty on Electrical Components – Parts and Labor Northwest Manufacturing, Inc. warrants to the original owner only, any electrical components in the furnace that is defective during normal usage for a period of one (1) year from the date of purchase. Additional Components & Warranty Guidelines. Northwest Mfg. Inc. will warranty all thermal storage tanks on the WoodMaster Flex Fuel Furnace for a period of one (1) year. If there is a leak in your properly delivered and installed WoodMaster Flex Fuel Thermal Storage Tank within the first year, WoodMaster will repair the tank at no cost to the original owner. Northwest Manufacturing, Inc. will warranty for a period of one (1) year, any factory defects in materials or workmanship to the wood pellet or wood chip auger attachments and inserts for the WoodMaster Flex Fuel. High temperature refractory materials are not covered under these warranties. In use, small cracks can occur with these products and will not change the performance of the furnace. Parts will be replaced on an even exchange basis. These warranties apply only if the device is installed and operated as defined in the Owner’s Manual. WoodMaster Furnaces are not intended to be the only source of heat; therefore a backup system should be in place to prevent any damage caused by lack of heat. Your dealer may charge you for a service call to do warranty work. Damage caused by abuse, accidents, improper installation, overheating, corrosion, freezing, negligence, or excess creosote buildup will not be covered under warranty. Damage caused by burning flammable materials (such as petroleum products), or green wood will not be covered under warranty. Antifreeze – Only nontoxic antifreeze is acceptable. Antifreeze will break down over a period of time and therefore should be tested annually. Always dispose of antifreeze by state and local codes. Loss of antifreeze under any condition will not be covered. How to file a claim – ANY CLAIM UNDER THIS WARRANTY MUST BE MADE TO YOUR DEALER.