CA3B Series 2.5, 3.0, 3.5, 4.0, 5.0 and 6.0 High efficiency, gas-fired condensing boiler with pre-mix modulating cylinder burners for natural gas (NG) or liquid propane gas (LPG), with Inox-Lamellar heat exchanger made of high-grade SA 240-316 Ti stainless steel. For operation without low limit on boiler return water temperature. For closed loop hot water heating systems with maximum supply water temperatures of 210°F (99°C) for a maximum operating pressure of 160 psig. Heating input: 2500 to 6000 MBH (733 to 1758 kW)