An Equipment Interface Module (EIM) acts as the “bridge” between a thermostat and a dual-fuel HVAC system when you can’t pull additional control wires to the thermostat. Instead of running multiple new conductors, the thermostat communicates with the EIM using only the few wires already in the wall—or wirelessly if it’s a RedLINK setup. The EIM is installed at the equipment and provides a full set of terminals (R, C, W, Y, G, O/B, Aux, etc.), allowing it to control the heat pump, the furnace, an

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