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The infinity wires are not "thermostat wires" in a sense. They are communicating wires as it is installed. You would have to retire both at the furnace and thermostat and possibly the outdoor unit to the traditional terminals. W, R, G, Y, Y2 etc. this will dumb down your system a little. Not sure I would suggest it, but I know you like the nest. Agiain you would need to rewire where the control wires connect to the air handler/furnace and possibly where they land at the outdoor unit. Make sure power is completely off and start at the furnace/air handler, then the outdoor and nest. Don't attempt to power it up before its all verified. You could damage the controls by feeding low voltage into communication terminals which may burn the microprocessor up.