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Cleaver-Brooks Flexible Watertube Boilers

Cleaver-Brooks Flexible Watertube Boilers

The FLX is a UL listed package 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 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.

Size Range

FLX: 1,500-25,000 MBH Input FLX PM: 75-250 HP (3,150-10,500 MBH Input)


For rapid response for low or high-temperature pressure heating, back up fuel oil and field erectable. Applications include heating for universities, medical facilities, office complexes and process applications such as manufacturing, food processing and pharmaceuticals.


Natural Gas, #2 Light Oil, Propane, Digester Gas (Natural Gas, Propane on FLX PM)


15-250 psig Design Pressure


<20 ppm standard, available to less than 9 ppm