I replaced an existing Honeywell programmable thermostat with a new Z-wave enabled CT101-L thermostat yesterday. All went well, and the C, W, Y, R and G wires found their proper target connectors. The thermostat's working fine, and I'm able to control it remotely. (Haven't tested air-conditioning on account of the deep freeze here in Minnesota, but I'm assuming that's OK).
My question is about an unused brown-colored wire tucked back into the wall. This loops back on itself, and wasn't connected to anything on the old thermostat. I'm not sure where / how to trace this back to the furnace.
What is this wire? Is it an outside temperature / humidity sensor (which would be more than awesome), or just something that's a standard part of the cable (which probably is also good, so I can probably add said sensor). Or does using it somewhere unlock some more thermostat goodness?