Triangle Tube’s Challenger Solo boiler is a high-efficiency modulating, condensing boiler, perfect for small- to mid-sized residences. The lightweight Challenger comes in four models from 84,000 Btu/ 145,000 Btu/hr. Vent with either twin vent and air piping (PVC, CPVC, PP or SS) or with concentric venting. With an AFUE up to 95 percent, the Challenger will accept either natural gas or propane, and has a turndown ratio of nearly 4 to