TheHRC-43S staging relay is intended for use with the slave output on the HTC analogue range of controllers. This module allows for three extra heating and cooling stages designed for the control of triple compressor HEAT PUMP units. The third relay stage is set to energise 3 oC above setpoint and 3 oC below setpoint. The HRC-43S controller is ideally suited for DIN rail mounting in a switchboard, or directly inside the A/C unit if required.