The wire adder module (WAM2/4) re-uses the existing 2-wire cable instead of needing a new 4-wire cable for heating/cooling retrofits. It mounts in the furnace control box, gets it's power from the existing 24 VAC 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.

ae Wire Adder Module, 24 VAC (+/-15%), 50/60 Hz, 0 - 50 deg C, 1.2 in W x 0.85 in H x 3.2 in D

• Easily mounts in furnace control box
• Output LED indication for fan, heating and cooling
• Input signal: DC voltage from 4-wire combining network

• Specification Sheet https://assets.unilogcorp.com/267/ITEM/DOC/ae_A0093_Specification_Sheet.pdf