Natural GAS 84% AFUE Natural Gas/Liquid Propane Atmospheric Vent Water Boiler, 200 MBH, Series 3

Williamson GWA-200-N-T-S3-W – 200 MBH Natural Draft Gas Water Boiler

The Williamson GWA-200-N-T-S3-W is a cast iron, atmospheric-vented gas water boiler built for hydronic heating systems in residential and light commercial applications. With a 200,000 BTU/hr input and an 84% AFUE rating, this model is engineered for efficient and consistent performance while maintaining service-friendly features critical for field installation and maintenance.

Core Performance and Design Features

• Cast Iron Heat Exchanger: Sectional construction for longevity and uniform heat transfer; factory-assembled block ensures dimensional consistency and durability.
• Input/Output Capacity: 200,000 BTU/hr input; 170,000 BTU/hr DOE heating capacity; 147,000 BTU/hr Net I=B=R rating.
• Atmospheric Gas Burner: Stainless steel burners with intermittent pilot ignition and automatic vent damper to reduce off-cycle losses.
• Vent System: Natural draft with vertical draft hood; top-vent only configuration using standard B-vent through a chimney.
• Controls and Safeties: Includes factory-installed circulator (Taco 007), low water cutoff, pressure/temperature gauge, high limit control, and 30 PSI relief valve.
• Circulator Ready: Ships with pre-wired circulator, simplifying field wiring and reducing installation time.
• Field Convertible: Natural gas model with optional LP conversion kit available from the manufacturer.

Installation Considerations

This boiler is designed to be floor-mounted and requires a chimney connection for proper venting. Adequate combustion air must be available per code. Clearance for servicing should be maintained on all sides. The unit's front access panel simplifies servicing of the burner tray, pilot assembly, and gas valve.

Specifications at a Glance

• Model: GWA-200-N-T-S3-W
• Fuel: Natural gas (LP conversion kit available)
• Input: 200 MBH
• AFUE: 84%
• Net I=B=R Output: 147 MBH
• Maximum Working Pressure: 30 PSI
• Ignition: Intermittent electronic
• Venting: Natural draft, top-vent chimney

Professional Applications

Contractor Notes: The GWA-200 is well-suited for mid- to large-sized residential systems and retrofit installations where cast iron reliability and natural venting are desired. The compact footprint and factory-assembled jacket allow for quick placement. All components are serviceable from the front, with no need for side access in tight mechanical rooms.

Installation: Requires 120V electrical supply for controls and circulator. Must be installed in accordance with ANSI Z21.13 and local code requirements. For optimal system efficiency, pair with properly sized zone controls and circulators.