The CREST condensing boiler upgrade provides up to 96% thermal efficiency in six models ranging from 2.5 MBtu/h to 6 MBtu/h. The models feature an  upgraded combustion system and an updated 316L stainless steel heat exchanger. Features also include an enhanced modulating burner that delivers a turndown ratio up to 20:1 and flexible flow rates up to 600 gpm to meet the needs of the largest commercial applications. The boiler offers commercial installers six venting options and permits direct-vent air intake and exhaust runs of up to 100’ using AL29-4C stainless steel vent pipe on all models as well as CPVC, PVC and Polypropylene on the 2501-3501 models. Lochinvar.