HONEYWELL R845A1030. Switching relay with internal transformer, Dpst line voltage relays. Switching Relay provides DPST switching for hydronic zone controlled heating systems or SPST control of two seperate loads. One load must be line voltage; the other may be either line or low voltage. The R845A may be directly controlled by any 2-wire series 80 thermostat, such as the T86A Round Thermostat or T852A Electric Clock Thermostat.