To install a seven-wire thermostat, mount the wall plate, and connect the thermostat wires to the thermostat in the same fashion as they are connected to the HVAC unit. Make sure the power is shut off on the HVAC unit before beginning the thermostat installation.
Begin by turning off the power to the HVAC unit at the circuit breaker. Confirm that the power is off by checking the unit with a volt meter. Remove the HVAC unit access panel, and examine how the wires are connected. The wires connect to the thermostat unit in the exact same fashion.
Next, install the thermostat wall plate to the wall using drywall anchors and screws. Connect the red wire to the R terminal, white wire to the W terminal, green to G, yellow to Y, black to C, light blue to Y2 and brown to the W2 terminal. It may be necessary to strip the wires about one-quarter inch so the ends are exposed.
Once the wires are all connected, snap the thermostat into the wall unit. Be sure not to pinch the wire behind the thermostat when snapping it into place. There should be a small indent the wires fit into. Turn on the power to the HVAC unit, and set the thermostat to the desired temperature.