Johnson Controls GLAS Installation Instructions Manual page 14

Connect optional C-wire adapter
Note: If you have a C-wire at your thermostat, skip
to Step 16. If you do not have a C-wire to power
your thermostat, use the included C-wire adapter to
provide power.
12. Remove the cover of your furnace or air handling
unit to access the control board and take a picture
of the current wiring for reference.
13. In your HVAC equipment, disconnect the
Y, W, R, or G thermostat wires that are currently
connected to the control board. Do not
disconnect any of the other wires.
GLAS smart thermostat installation instructions - 2018 Johnson Controls
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