FLX Premix Watertube Boiler

Packaged Watertube Boilers

  • Boiler Horsepower: 75 - 250
  • Input Capacity (MBH): 3,150 - 10,500
  • Steam or Hot Water: Both
  • Vessel Design: Watertube
  • Number of Passes: 5
  • Design Temperature (deg F): 235, 340, 355
  • Fuel: Natural Gas, Propane
  • Emissions (ppm NOx): <20, <9
  • Steam or Hot Water
  • 75-250 HP (3,150-10,500 MBH Input)
  • Natural Gas, Propane 
  • 15-250 psig Design Pressure
  • Premix Burner Technology
  • Standard sub-20 ppm NOx, Optional sub-9 ppm NOx
  • Field Erectable


The FLX Premix (FLXPM) boiler achieves best-in-class combustion performance with low emissions. Premix burner technology enables the boiler to attain <20 ppm NOx without FGR and <10 CO as standard on natural gas. The modulating burner control automatically adjusts the air/gas mixture for maximum efficiency and optimum turndown.


The Flextube can burn renewable fuels and features a fully modulating burner to ensure optimum efficiency throughout the firing range. It can also help meet emissions reduction goals, down to <9 ppm NOx with low CO.

  • Product Overview
  • Related Resources
  • Applications
  • Up to 5:1 turndown
  • Small footprint
  • Thermal shock resistance
  • Hinge-mounted burner and removable panels allow easy access for service and maintenance
  • 25-year limited pressure vessel warranty


The FLXPM integrates a servo-driven, fuel-input control valve with air-input control via a variable-frequency-driven fan for precise fuel/air ratio control. The field erectable option allows you to replace boilers in tough to access spaces. The pressure vessel is assembled at the factory and hydro tested. During the disassembling the tubes are matched marked for easy installation on site. The boiler is a 5-pass cross flow water tube design. This allows for maximum heat transfer thru every pass. The gas flow design of the FLXPM does not require baffles which lowers maintenance costs throughout the boilers life. A fully water-cooled furnace reduces heat loss from the furnace section. The design eliminates the need for costly maintenance on side or rear insulation, which reduces the total cost of ownership.


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FLX Packaged Boiler Video →

  • Process Steam
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