How To Wire An Advent Air AC System To A Two-Wire Furnace

Question:

I recently bought the Advent Air RV Air Conditioner System - Single Zone - 13,500 Btu - White to replace my 10 year old Dometic penguin AC. The Dometic had 3 wires going to the thermostat and 2 wires going to the furnace. The Advent needs 4 wires going to the thermostat and one wire going to the furnace. My Suburban furnace has two blue low voltage wires that connected to the two wires from the Dometic AC. I am not sure how to wire these low voltage wires. I thought it would be compatible. I should be able to run an additional wire between the furnace and the thermostat to make it 4 wires to the thermostat, but then I am not sure how to hook up the AC to the thermostat using 1 wire. Any help would be appreciated.

asked by: Michael S

Expert Reply:

Typically if there are two wires running from the furnace to the AC system then it means that the furnace has power already connected to it and it sends that through one of the wires up to the AC until the system calls for heat, at which point the relay will close and send power back to the furnace through the other wire. You'll want to connect the brown and white furnace wire from the controller # ACRG15 to the other wire send power back to the furnace.

To determine which wire is which you can use a multimeter # PT89ZR and place one lead to a good ground and the positive lead to either wire. One wire should read 12v DC and would be the power running from the furnace to the AC. You'll connect the AC wire to the other furnace wire so it can send power to furnace to activate it as needed. The power wire can just be capped off with some electrical tape.

expert reply by: Kevin C