FLX Watertube Boiler

Packaged Watertube Boilers

  • Steam or Hot Water
  • 1,500-25,000 MBH Input
  • Natural Gas, #2 Light Oil, Propane, Digester Gas
  • 15-250 psig Design Pressure
  • Available to <9 ppm NOx
  • Field Erectable


The FLX is a UL listed packaged boiler that is versatile and can handle both commercial and Industrial applications. The compact 5-pass bent water-tube design provides efficiency ratings up to 81% (Steam) and 85% (Hot water).


The FLX's burner can burn non-standard and 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 10:1 turndown (Uncontrolled emissions) and 5:1 (Controlled emissions)
  • Small footprint
  • Thermal shock resistance, 25-year limited pressure vessel warranty
  • Hinge-mounted burner and removable panels allow easy access for service and maintenance


The FLX has distinct design features that include non-welded ferrule tubes for ease of tube replacement. The package includes a burner for a completely integrated and engineered solution from a single source. Removable sectioned side panel design permits full access to all tubes. 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 FLX 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.

The FLX field erectable option allows you to replace boilers in tough to access spaces. The pressure vessel is assembled at the factory and hydro tested before shipment. During the disassembly, the tubes are matched marked for easy installation on site.


Steam Applications, Terminology and How to Achieve Best Results →

Learn how the industry defines steam from utility, saturated and superheated to filtered and clean. Applications for the various steam types will be covered along with operation best practices.

Boiler Room Installation Considerations for Safety, Reliability, and Efficiency →

There are several factors that are important to consider when installing either a steam or hydronic boiler system in order to maximize safety, reliability and efficiency. Learn about the several aspects that help to ensure proper boiler installation.

FLX Packaged Boiler Video →

  • Process Steam
  • Industrial Process
  • Building Heat
  • Sterilization
  • Healthcare