To connect a Honeywell RTH600D thermostat, first disconnect the electricity to the air handler. Remove a small portion of the insulation from each of the color-coded thermostat wire using wire strippers. Unfasten the screws over the connections with a flathead screwdriver, and insert the applicable wire and re-tighten the bolts.
The air handler relays a 24-volt power source to the thermostat through the wire having a red insulation. Push the end of the red insulation wire into the space under the thermostat's R-terminal.
The yellow insulation wire operates the cooling cycle of the heat pump and connects to the Y-terminal of the thermostat. The white insulation wire runs the primary heating cycle of the heat pump and connects to the W-terminal. Similarly, the pink insulation wire runs the secondary heat source of the heat pump and links to the W2-terminal.
The orange insulation wire, if used, connects to the O- and B-terminals and sends power to the heat pump’s reversing valve. The Rheem heat pump uses the B-terminal.
The tan insulation wire, if used, powers up emergency heating and joins to the E-terminal. The green insulation wire connected to the G-terminal operates the heat pump’s fan relay. The brown insulation wire, if used, connects to the heat-only or cool-only transformer common terminal. It gets linked to the C-terminal.
Finally, push the end of the wire with black insulation under the X-terminal. It supplies the thermostat with a common connection.