Natural GAS 84% AFUE Natural Gas/Liquid Propane Atmospheric Vent Water Boiler Series 3

Williamson GWA-100-N-T-S3-W – 100,000 BTU Gas-Fired Atmospheric Boiler

The Williamson GWA-100-N-T-S3-W is a residential-grade, cast iron, gas-fired water boiler built for hot water systems operating at standard pressure. Rated at 100,000 BTU/hr input with an 83.3% AFUE, this unit delivers reliable heat using natural gas and a traditional atmospheric vent configuration. Its compact footprint and robust components make it well-suited for new construction or retrofit applications in single- and multi-family dwellings.

System Features and Design

• Heat Exchanger: Cast iron sectional design ensures long thermal life and consistent heat transfer performance.
• Combustion: Natural gas-fired with intermittent electronic ignition and stainless steel burners for clean, quiet operation.
• Controls: Factory-equipped with integrated control module and a built-in low water cut-off for system protection.
• Venting: Atmospheric draft with a 5-inch flue outlet – designed for B-vent or lined masonry chimney applications.
• Serviceability: Accessible top and front panels facilitate maintenance, with keyed wiring for simple electrical work.

Performance Ratings

• Input: 100,000 BTU/h
• DOE Heating Capacity: 84,000 BTU/h
• Net I=B=R Rating: 73,000 BTU/h
• Annual Fuel Utilization Efficiency (AFUE): 83.3%

Product Dimensions & Specifications

• Width: 20-1/4"
• Depth: 27-1/2"
• Height: 30-3/4"
• Shipping Weight: Approx. 245 lbs
• Vent Size: 5"
• Water Content: 4.3 gallons

Installation Guidance

This boiler is designed for closed-loop, low-pressure hydronic heating systems using fin-tube baseboard, cast iron radiators, or radiant panel distribution. Installation requires proper gas line sizing, venting verification, and compliance with local mechanical codes. A licensed HVAC or plumbing professional is required for commissioning, combustion testing, and full system integration.

Applications

The GWA-100-N-T-S3-W is suitable for light commercial or residential buildings requiring dependable, mid-range heat output. Its robust design and accessible control layout make it a practical choice for service contractors and installers seeking reliability and performance consistency.