Weil-mclain 381-800-875 Gas Steam Boiler 125 Mbh

Product Description

The WEIL-MCLAIN 381-800-875 is a cast iron residential gas steam boiler rated at 125 MBH AGA input, 78 MBH net IBR output, and 82% AFUE. It operates on natural gas with electronic intermittent ignition and is designed for floor-mount installation in residential heating systems. The heat exchanger is cast iron, built to handle both steam and hot water applications. A stainless steel, non-linting pilot burner and automatic vent configuration make this unit well-suited for straightforward service and replacement work. Licensed HVAC and plumbing professionals handle installation and commissioning on this class of boiler.

The 381-800-875 is configured as a residential package steam boiler for natural gas supply. It fits hydronic heating systems requiring reliable steam output with a floor-mounted cast iron boiler. The unit ships configured for natural gas with electronic intermittent ignition only. Optional left end section openings allow for future integration of a tankless heater with the appropriate heater cover plate and control. This boiler is manufactured in the USA and meets CSA, ASME H, AHRI, and DOE applicable standards.

Key Features

• Cast iron heat exchanger with 10-year limited warranty coverage
• 82% AFUE natural gas fired with 125 MBH AGA input rating
• Electronic intermittent ignition with stainless steel non-linting pilot burner
• Automatic vent system using 6-inch vent connection
• ASME 15 PSI relief valve included; pressure rated to 50 PSI
• Optional tankless heater section available via left end section openings

Compatibility

Designed as an OEM residential floor-mount cast iron steam boiler replacement or new installation for natural gas hydronic heating systems meeting CSA, ASME H, AHRI, and DOE standards.

Installation Notes

Installation must be performed by a licensed HVAC technician or plumber in accordance with local codes and the applicable IFGC and ASME requirements. Shut off the gas supply and disconnect electrical power before any service or replacement work. The 6-inch vent connection requires proper venting to outdoor combustion exhaust per local mechanical code. Do not modify the factory gas train or ignition wiring configuration without consulting the manufacturer installation documentation.

Technical Specifications

• Boiler Type: Steam
• Fuel Type: Natural Gas
• AGA Input Rating: 125 MBH
• DOE Heating Capacity: 104 MBH
• Net IBR Rating: 78 MBH
• AFUE Rating: 82%
• Ignition Type: Electronic Intermittent
• Burner Type: Stainless Steel Non-Linting Pilot
• Heat Exchanger Material: Cast Iron
• Pressure Rating: 50 psi
• Relief Valve: 15 psi ASME Relief Valve Supplied
• Venting Type: Automatic Vent
• Vent Size: 6 inches
• Supply Connection: 3 inches Threaded
• Return Connection: 2.5 inches Threaded
• Gas Connection: 0.5 inches
• Water Content: 9.8 gallons
• Boiler Dimensions: 21.25 inches L x 27.625 inches W x 33.75 inches H
• Mounting Type: Floor Mount
• Applicable Standards: CSA, ASME H, AHRI, DOE
• Warranty: 10 Year Limited (Heat Exchanger), 2 Year Limited (Other Parts)
• Country of Origin: USA

Standard Information

• Brand: WEIL-MCLAIN
• Manufacturer Part Number: 381-800-875