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Precision Boilers – FTH Flexible Watertube Hot Water Boiler

Capacities: 860 MBH to 17,220 MBH (25 BHP to 500 BHP) up to 86% efficiency

ASME Section IV “H” Stamp
(160 PSI & 250°F)

UL subject 795/726/2096
ASME Safety Code CSD-1



Precision FTH Series are “Flex-Tube” forced draft hot water boilers noted for their small footprint and high fuel-to-output efficiency, exceeding 82-85% for gas and 86% for oil.

Precision FTH Series Boilers utilize 1-1/2″ OD tubes in a serpentine tube configuration designed to absorb thermal shock. The pressure vessel is warranted against thermal shock damage for a period of 25 years. This design accommodates up to 150°F temperature differences from the supply and return, offers virtually instantaneous hot water.

Precision FTH-1 thru 3 Series Boilers utilize a unique 5-pass tube design with upper and lower headers located on the left or dight side. The serpentine bends insure an even flow of gases through the heat. transfer area of the boiler as well as equal water flow. The serpentine bends also create tangent water walls on all but one side of the combustion chamber. An upper plenum plate diverts the flue gases to the burner end to facilitate flue gas recirculation.

Precision FTH Series hot water boilers are designed with the return in the lower header and the supply in the upper header. This allows the water to circulate equally through the tubes with positive circulation.


Standard Features:

  • Flex-Tube design with mechanical or welded tube attachments
  • Electronic Combustion Control with Off-On, Low-High off, Low-High-Low, or Modulating Firing
  • Inspection Opening in lower drum for easy access and cleaning
  • Power Flame forced draft burners (AS Standard)
  • Totally encased rear downcomer


FTH Standard Boiler Trim:
Hot water Boilers
(Standard Design Pressure 150 psig)

  • Operating Temperature Control
  • High Temperature Safeties
  • Pressure & Temperature Gauges
  • Probe-Type Low Water Cutoff
  • ASME Safety Relief Valve
  • Drain & Vent Valves


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