Things You'll Need
Wire strippers
Slotted screwdriver
Honeywell's model RTH230B programmable thermostat allows a user to predetermine the time an air-conditioning and heating systems turns on and off. Using this energy-saving feature can automatically turn the system off when not needed and turn the system back on before the user returns. The RTH230B contains filter replacement and battery replacement indicators. Its digital display shows the temperature in degrees Fahrenheit or Celsius. The RTH230B will not operate a heat-pump or multi-stage air-conditioning system.
Step 1
Turn off the circuit breaker to the heating and air-conditioning unit the RTH230B controls. The circuit breaker uses a "Furnace" or "Air Handler" label.
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Step 2
Remove 1/4 inch of the color-coded insulation from the wires that lead to the RTH230B thermostat with wire strippers. Heating and air-conditioning systems connect to this thermostat model with four wires; red, green, white and yellow colored wires. Heat-only and cool-only connect to this thermostat model with either two or three wires, depending on whether or not the furnace requires a thermostat-activated fan relay.
Step 3
Loosen the RTH230B's "Rc" or "Rh" terminal with a slotted screwdriver. Loosen the "Rh" terminal for heat-only systems and the "Rc" terminal for all others. Slip the red-colored wire into the loose terminal and tighten the terminal screw. Leave the jumper wire, the short section of wire, between "Rc" and "Rh" unless the thermostat connects to a heat-only or cool-only system.
Step 4
Loosen the RTH230B's "W" terminal, if used, with a slotted screwdriver. Slip the white-colored wire into the "W" terminal and tighten the screw with the screwdriver. The RTH230B uses the "W" terminal for both heat-only systems and the heating cycle in a central heating and air-conditioning system.
Step 5
Loosen the RTH230B's "Y" terminal, if used, with a slotted screwdriver. Slip the yellow-colored wire into the "Y" terminal and tighten the screw with the screwdriver. The RTH230B uses the "Y" terminal for both cool-only systems and the cooling cycle in a central heating and air-conditioning system.
Step 6
Loosen the RTH230B's "G" terminal, if used, with a slotted screwdriver. Slip the green-colored wire into the "G" terminal and tighten the screw with the correct screwdriver. The RTH230B uses the "G" terminal to operate the fan relay in all central heating and cooling systems, and when a heat-only or cool-only system requires a thermostat-activated fan relay. Heat-only and cool-only systems requiring a thermostat-activated fan relay connect to the thermostat with three wire strands, red, white or yellow, and green.
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