1 in Isotherm Radiant Control Module c/w Circulator, Injection Mixing Valve, Hi-Limit Control and Temperature Gauge. A compact, pre-piped and pre-wired pump and mixing valve control designed to connect directly to a WATTS® 1 in Stainless Steel manifold. The Isotherm is designed to speed up radiant installations by providing a complete compact piping and mixing system ready to go. The Isotherm can handle up to 50,000 Btu/hr in a standard radiant heating system.