The Switching Relay 302P connects up to two thermostats and operates circulators to provide heating to a zoned hydronic heating system. Zone 1 has optional priority over zone 2 and can be used to provide heat to an indirect domestic hot water tank. The 302P includes optional exercising to prevent circulator seizure when not in use, and optional post purge operation of the last operating zone to maximize energy savings. The 302P provides a RoomResponseTM signal to modulating-condensing boilers to optimize comfort while improving boiler efficiency.