Product Description
The Weil-McLain 381-359-366 is the CGI-8 Series 5 cast iron gas-fired hot water boiler built for residential and light commercial hydronic heating systems. It delivers 164,000 BTU of verified IBR-rated output from a 222,000 BTU input, achieving a steady 84% thermal efficiency. That balance of input and output makes it a reliable workhorse for forced hot water heating in larger homes, multi-family buildings, and light commercial spaces where consistent heat delivery is essential. The boiler runs on natural gas and uses spark ignition, eliminating the need for a standing pilot light and reducing ongoing gas consumption during standby periods. The 120-volt electrical connection integrates cleanly into standard residential and commercial electrical systems. Cast iron section construction is the defining feature of this boiler. Cast iron holds heat longer than steel, resists corrosion over decades of service, and handles the thermal cycling demands of hydronic heating without warping or degrading. The insulated steel jacket surrounding the sections reduces standby heat loss, keeping the boiler operating efficiently even in unconditioned mechanical rooms. This unit ships as a complete assembly with a Taco 007 circulator pump already included, saving installation time and ensuring component compatibility right out of the box. The Taco 007 is a proven wet-rotor circulator widely used in residential hydronic systems. Power vent configuration allows for flexible flue routing with a 3-inch vent connection, giving installers more placement options compared to natural draft designs. The water connection measures 1-1/2 inches, the gas connection measures 3/4 inches, and the pressure relief valve is factory-set at 30 psi. Physical dimensions are 25 inches wide, 23-1/4 inches deep, and 28-3/8 inches tall. The DOE heating capacity rating is 189,000 BTU. Weil-McLain backs the heat exchanger with a 20-year warranty and covers parts for 2 years. Installation must be performed by a licensed heating professional in accordance with all applicable codes and manufacturer guidelines.
- 164,000 BTU IBR-rated output with 84% efficiency on natural gas for reliable hydronic heating
- Cast iron section construction with insulated steel jacket for long service life and reduced standby heat loss
- Includes Taco 007 circulator pump and features spark ignition with power vent configuration
Product Highlights
The Weil-McLain CGI-8 Series 5 is a proven cast iron hot water boiler suited for demanding residential and light commercial hydronic heating applications. It combines high BTU output, durable construction, and a complete circulator package for efficient and straightforward installation.
Product Information
Standard Information
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Brand: WEIL-MCLAIN
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Manufacturer Part Number: 381-359-366
Technical Specifications
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Product Type: Boiler
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Boiler Type: Standard
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System Type: Hydronic (Water)
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Application: Heating
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Fuel Type: Natural Gas
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Ignition Type: Spark Ignition
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Vent Type: Power Vent
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BTU Output: 164,000 BTU
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BTU Input: 222,000 BTU
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IBR Rating: 164,000 BTU
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DOE Rating: 189,000 BTU
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Efficiency: 84%
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Voltage: 120V
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Vent Size: 3 inches
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Gas Connection: 3/4 inches
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Water Connection: 1-1/2 inches
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Pressure Relief: 30 psi
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Width: 25 inches
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Depth: 23-1/4 inches
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Height: 28-3/8 inches
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Warranty: 20 Years (Heat Exchanger) / 2 Years (Parts)
