Placement

Since most people following this article are going to be replacing their thermostats rather than doing a complete first installation, placement is probably a non-issue. However, it is important to note there are places your new thermostat should and shouldn’t go. The best placement is on an interior wall, about five feet above the floor, and in the main living area.

Never place the thermostat near a fireplace, on an uninsulated outside wall, near the kitchen, near an appliance that produces waste heat, or in direct sunlight they may be coming through a window at some point during the day.

Tools Needed

The following are tools and supplies needed to remove the old thermostat and install the new one:

• Phillips screwdriver
• Drill
• Drill bit (3/16” for drywall, 7/32” for plaster)
• Hammer
• Pencil
• Electrical tape
• Small level (optional)
• Fresh alkaline batteries

Removing Old Thermostat

• Shut off power to the furnace. This is found as a fuse or switch at the circuit-breaker panel.
• Remove cover and old thermostat, but leave wallplate with WIRES ATTACHED. I use a wire-tester to make sure the exposed wires are not “hot” and are in fact off at the circuit breaker panel.
• Count the number of wires coming out of the wall and attached to terminals in your old thermostat. Do not count any wires attached to terminals marked “C” or “C1” in your total. Most systems have 5 wires or less.
• If any wires are loose and not attached to a terminal, do not connect them to your new thermostat. Wires that are loose or marked “C” or “C1” should be wrapped with electrical tape to cover exposed ends.
• Use a screwdriver to disconnect wires one by one. As you disconnect each wire, wrap it with a label matching the letter on your old thermostat. Most new thermostats come with adhesive labels in the package. If it doesn’t, use tape and label. In most situations, the old wall plate still attached to the wall will have letter designations such as Y, W, G, R, Rc, O, or B. Ignore wire colors and use ONLY letter designations to identify wire types. Now, after saying this, on VERY old thermostats there may be only two wires available…a white wire and a red wire. If you have such a system, simply label the red “R” and the white “W”.
• Remove the old wallplate only after all wires are labeled.
• Do NOT let wires fall into the wall opening!
• Mercury doesn't belong in a landfill! Check your local county hazardous waste disposal guidelines to find out where you can take the old thermostat. Click here for Hamilton County, Ohio Guidelines.