The RA 15/6T and TB is a special conversion valve that allows a single connection point-at the side of the radiator- to serve as both the supply & return for a hot water based system. An example of its application is the transformation of a 1-pipe steam system into a hot water based system. There are two versions to this valve: RA15/6T Internal bypass allowing for series piping to the radiators/baseboards. This series piping provides continuous flow but the supply water temperature will decrease. RA15/6TB A conventional two-pipe system where each radiator/baseboard is supplied. A traditional supply and return manifold can be utilized. With the installation of the RA 15/6T and TB valves any RA2000 thermostatic operator or TWA electronic actuator can be mounted, providing individual temperature regulation and controlled comfort for the room.