How to Change a Thermostat

First before you attempt to change your own thermostat you need to make sure you have the right thermostat and correct amount of wires to hook to your themostat.

Lets discuss the proper thermostat first. Many times I have been called to install a thermostat that a customer has purchased themself. Sometimes they will get a heat pump thermostat when they really need a thermostat for gas, oil or electric units. So make sure you know what type of system you have.

Now the wiring for your new thermostat. If you have a heatpump system the number of wires you need should be already there. Most heatpump wires require 6-7 wires , some may need more if you have a two speed heat pump.

Now if you have an air conditioner with either gas, fuel or electric heater in most cases you will need 4-5 wires. Some digital thermostats require a common wire so that the display shows and so the thermostat will work.

To change your thermostat first turn your breakers off that control your air conditioner and heater. Take your cover off the thermostat and access the wires that are connected to the thermostat. DO NOT DISCONNECT YOUR WIRES UNTIL YOU WRITTEN DOWN WHAT COLOR OF WIRE GOES TO WHICH TERMINAL. I would also compare the new thermostat terminals to the old one. If you are unable to figure out how to wireup the new thermostat then call a service company. You will be better off paying somebody to install it for you versus burning something up that cost you more money.

If you feel like you can proceed make sure you look at the diagrams that come with the new thermostat. they will have good information that you will need to properly wire the new thermostat.

Most thermostats have a similar terminal lables such as R, Y, W, E, C, G, and O/B. The O/B is for heat pump units. The O/B is for the reversing valve of the heat pump unit.

So make sure you have the proper thermostat and the correct number of wires needed and follow the instructions. I am going to put down the terminal lables that are most common and describe their purpose. These descriptions are the most common, but you still need to read the instructions and study your wire diagrams with the new thermostat.

HEAT PUMP TERMINALS

R - Power
Y & W - Cooling/ 1st Stage Heat
W2- Electric Heat 2nd Stage
E- Emergency Heat
C- Common
G- Fan
O/B - Reversing Valve

Y/W will sometimes have a jumper to each other or will just have a termial 'Y'.

O/B is for the reversing valve which ever therminal is used on your old thermostat use the same on the new t'stat.

G - is the blower/fan circuit

W2- is the second stage heat/strip heater

E- emergency heat/ strip heaters

C- common

R- Power

AIR CONDITIONER/ GAS, FUEL. ELECTRIC

R- Power

Y- Cooling

W- Heat

G- Fan

C- Common