The SB615’s proprietary Buderus Kondens® heating surface generates up to 10% greater condensation versus smooth surfaces. Its intelligent water channeling facilitates the condensation process and created even greater energy efficiency (up to 98%). The SB615 utilizes standard US burners and conventional controls and is a perfect match with thermostream boilers in multiple boiler systems. This series uses conventional forced draft gas burners and can be used with either natural gas or propane. The SB615 is constructed with stainless steel fire tubes and a full three-pass flue design extracts latent heating and maximizes overall efficiency. Its simplified system design eliminates the need for dedicated boiler pumps, bypass and or shunt pumps.