Solid, Reliable, Time Tested Cast Iron Boiler with "Out-of-the-Box" Simplicity For years, the Series 2 has been the industry benchmark for cast iron gas-fired boilers. Its time proven design blends a long lasting cast iron heat exchanger with a heavy-duty steel base and high quality boiler controls to provide exceptional value for the homeowner. Heating professionals across the country have relied on the Series 2 to provide their customers years of comfortable, low maintenance operation making it an exceptional value in your home.