The Wire Adder Module (WAM2/4) re-uses the existing 2-wire cable instead of needing a new 4-wire cable for Heating/Cooling home retrofits. It mounts in the furnace control box, gets its power from the existing 24VAC transformer and puts out heat, cool, and fan relay contact closures simultaneously with the heating/cooling thermostat operation.
The new Heating/Cooling thermostat should be the battery powered electronic type. The conventional switch action thermostat has heating and cooling anticipators which will have their action bypassed, which could cause wide temperature swings.
Dimensions: W: 1.20” x H: .85" x D: 3.20"