Compatibility Check

[cfwchoi]

Hello, 

Current setup has only 4 wires connected, but I found 4 additional wires back of the panel.

Should I install all 8 wires,  or

just current 4 wires + C wire?    

I also need to identify which color wire is C-wire(blue or black)

Current SETUP

Yello -> Y

White -> O

Green -> G

Red -> R

, Found 4 More Wires.    Black, Blue, Brown, Orange

Thanks.

[sporfrog]

The compatibility checker might be helpful in your situation.

https://store.google.com/us/widget/compatibility/thermostat

In general, and best practice is NOT to connect wires that are not needed or used for the thermostat and HVAC system.  Just tuck them in the wall or out of the way in case they are needed in the future.

It is possible Blue, Black or maybe one of the other 2 tucked wires is "Common".  Often it is blue.  However if it is not connected at the HVAC equipment it won't be much use to the thermostat.  You can check:

1. Using a multimeter
2. Examine the HVAC system to see if one of the wires is connected to a C terminal.

NOTE:  I am not an HVAC specialist.  Use caution when testing wires.  If you decide to check the HVAC equipment make sure power is OFF first!!!  Consult an expert if needed.