bsi138• BSI138 • BSI172 BSI241 BSI276 PROTECT YOUR INVESTMENT REGISTER YOUR WARRANTY AT . The following terms are used throughoutBermuda Gas Fired Cast Iron Steam Boiler BSI series, Sea Level. BtuH Input: 138,000; Gas Type: NG; Sections: 5; AFUE: 82.0%; Flue Diam.: 6; Width: 19-14; Heht