Dave's DIY Home Projects: How to Install Electric Thermostat

With older house, a lot of time the thermostat in it would be the older version. They works ok, but not as efficient and accurate. Replacing it to a programmable electric thermostat would be recommended.

There are many choices available in the market place. Depending on your budget, you could choose a more fundamental unit that gives you the basic functionalities. With higher budget, there are more options such as the WiFi/Smart one like Nest, Ecobee or Honeywell WiFi Smart thermostats. Also, check with manufacturer to make sure these new Smart thermostats is compatible with your existing systems. For example, check this link for the Nest Incompatibility Guide.

In this project, we installed the Honeywell RTH6350 5-2 Programmable Thermostat. This particular one is simple and easy to use, within the budget we are working with.

Step 1. Turn off circuit breaker for the Air Conditioner. Turn off the ones for the AC and the Air Handler. The AC circuit breaker is for the outside Air conditioning unit, and the Air Handler is for the furnace and broiler inside.

Turn off AC circuit breaker and Air Handler circuit breaker

Step 2. Remove the old Thermostat. First, take off the cover, then, remove unit from the wall.

Caution with older thermostat. There could be glass bulbs on it that has mercury in it. Be careful when removing the unit from the wall.

Be careful with glass bulbs in old thermostat

Step 4. Then, you should be able to see all the wires for the unit. First, we need to label them, with labels provided from the new unit. Label each of the wires with the corresponding letter code..