HydroTherm now offers a six-page, full-color brochure featuring the complete line of KN-Series boilers. The publication provides detailed design and performance information for the popular KN-6, KN-10 and KN-20 commercial gas-fired, direct-vent cast iron boilers. The KN-Series features an efficiency rating of up to 99%, combined with a small footprint, clean-burning Tru-Flow technology, advanced controls with self-diagnostics, a proven spark igniter system with air-cooled, self-contained UV sensing and heating capacities ranging from 600 to 1999 mbh and 4:1 to 5:1 turndown. HydroTherm. Circle 24.