Combi Wall Mount Natural Gas Boiler, 120,000 BTU

Williamson FreeStyle FS-120-C Condensing Wall-Mount Boiler – High-Efficiency Performance in a Compact Platform

The Williamson FS-120-C FreeStyle is a gas-fired condensing boiler engineered for residential and light commercial hydronic applications. It delivers a modulation range of 12,000 to 120,000 BTU/hr and features a stainless steel heat exchanger with a 10:1 turndown ratio, making it suitable for varied load conditions and zoning strategies. Designed for wall-mount installation, this unit provides high-efficiency performance in a compact footprint for space-constrained mechanical rooms.

Product Highlights

• Input Range: 12,000–120,000 BTU/hr
• DOE Heating Capacity: 109,000 BTU/hr
• AFUE Rating: 92.2%
• Net I=B=R Rating: 95,000 BTU/hr (water)
• Combustion Control: Full modulation with 10:1 turndown
• Ignition: Electronic spark ignition with flame rectification

Design & Material Advantages

• Primary Heat Exchanger: Single-tube, large-diameter 316L stainless steel for improved corrosion resistance and reduced fouling
• Fuel Flexibility: Convertible for use with either natural gas or propane (conversion kit required)
• Venting: Approved for 3" PVC, CPVC, polypropylene, or stainless steel venting systems
• Display and Controls: Digital Honeywell control interface with outdoor reset capability for optimized seasonal efficiency

Installation Parameters

• Mounting: Wall-mounted design with included bracket kit
• Venting Configuration: Direct vent (sealed combustion); horizontal or vertical terminations permitted
• Maximum Vent Length: Per venting material and termination type—refer to I&O manual for specifics
• Clearances: Minimum required service access must be observed per manufacturer documentation

Serviceability and Application Scope

The FS-120-C is service-friendly, with accessible internal components and field-replaceable sensors, valves, and boards. The modulating design and outdoor reset integration allow for smooth operation in multi-zone radiant, baseboard, or panel heating systems. Recommended for installations requiring space efficiency and control precision without compromising on BTU output.

Warranty Information

• Residential Heat Exchanger: 10-year limited warranty
• Commercial Heat Exchanger: 5-year limited warranty
• Parts: 2-year limited warranty

Typical Use Cases

• Residential hydronic heat with zoning control
• Light commercial buildings with moderate demand and compact boiler room access
• Applications requiring sealed combustion for indoor air quality or code compliance