FibberservCL FSSEG-X3 User Manual page 56

If your old thermostat is labelled 120V or 240V or has thick wires with wire nuts, your system is high
voltage.
If you are not sure, please contact support.
Step 4: label wires with Tags
!
Step 5: Install the wiring module (Optional)
Note: Check your wires, see if there's C-wire. If you have the C-wire, skip this step 5 and go to step
6, if you don't have the C-wire, continue with step 5.
The C-wire provides power to the smart thermostat.
If you don't have a C-wire in your old system, you need to install the wiring module to use the exiting
wires to power your thermostat.
1. Find the control board of your HVAC system.
Use the tags provided to label the wires from the control board to the thermostat.