Replace Dial Thermostat With Programmable Thermostat

Replacing an old or defective thermostat is one of the easiest procedures that people have unfortunately been paying professionals for. Below is a step-by-step procedure on to replace thermostat by yourself and economically restoring your home’s heating system back to its former glory.


To Replace Thermostat : What Materials You Need ?

replace dial thermostat with programmable thermostat

Before we get down to work, here are the basic tools you need to have to hand:

1. A screwdriver

2. A masking tape

3. A pencil

4. A felt-tipped pen

5. A carpenter’s level

6. Batteries

7. An electrical tape

8. Wire strippers

9. Wire cutters

10. A hammer

11. Drywall anchors

12. A drill

Step 1

Switch off the power connection to the thermostat at your home’s circuit breaker box. This is logically to avoid a possible electrocution while performing the procedure.

replace dial thermostat with programmable thermostat

Step 2

The second step on to replace thermostat is to unhouse the old thermostat by removing the screws attaching it to the wall and pull it gently from the wall to expose the underneath wires.

Step 3

Examine and find out how and where the wires are attached to the thermostat by the terminal screws. There is the heater wire and you may also find a second, for the air conditioner. The terminal screws connecting different devices to the thermostat are marked with letters such as Y, G, W, R and RC. Before removing the wires, wrap each of them with a masking tape and mark them with the letters on their corresponding terminal screws using a felt-tipped pen.

What Are The Next Steps In The Process ?

Step 4

Loosen the terminal screws and gently remove the wires hooked on the screws. Remove the mounting-plate screws of the thermostat and pull it from the wall.

Step 5

Check if the new thermostat’s mounting plate can fit perfectly onto the old plate’s position or if you need to drill new holes for the screws. If you have to drill new holes, hold the mounting-plate in position and use the carpenter’s level to make it straight and even. Use a pencil to mark the screw hole points on the wall.

replace dial thermostat with programmable thermostat

Step 6

Drill into the wall at the marks. Use a hammer to drive the drywall anchors in to the wall until the outer ends are level with the wall. Hold the mounting-plate in position against the wall, spin the wires through the holes underneath and then fasten the mounting-plate to the wall using the provided screws.

What To Do With The Wires On The Thermostat ?

Step 7

Take a look at the ends of the wires of the thermostat by stripping approximately inch of the insulator off the wires using wire strippers. If the exposed metal underneath is corroded or frayed, cut off the wire ends using wire cutters.

Step 8

Loosen the screw terminals of the new thermostat. In a clockwise spin, wrap wires around screw terminals with corresponding letter marks. Use the screwdriver to tighten the screws. Your skill on to replace thermostat is somewhat measured by your keenness in this very crucial step. 

Sometimes the screw terminal designations could be different from what was on your old thermostat. When this is the case, you will most likely find on the packaging an instruction booklet to guide you through the wiring process and generally to replace thermostat. If you find wires marked C1 and C that were connected to the old thermostat on the terminal screws, do not use them on the new thermostat.

Separate them from the rest of the wires and use electrical tape to wrap their ends until the bare metal ends are no longer visible. Now, gently insert them back into the wall. Also, you may find other wires sticking out of the wall that were near the old thermostat but were not connected to it. Do not use them; wrap their ends completely with electrical tape and insert them back into the wall.

Step 9

Push protruding wires into the wall and make sure the mounting plate is well fastened to the drywall anchors. If it’s not, try fastening the screws a little more. Now pin the thermostat onto the wall plate; slide the wall plate tabs into their respective slots at the back of the thermostat and snap it into place. Then, turn on the power at the circuit breaker.


Do not forget to turn the power at the circuit breaker before you embark on replacing your thermostat. Also, do not attach wires on the wall to your new thermostat based on their color. Fires have been reported to start like this.

So, there you go. That’s how you replace thermostat with a new one without the hand of an expert. We know wires can be intimidating sometimes, but then they won’t kill you for doing the right thing.  

Honeywell RTH221B1021/A 1 Week Programmable Thermostatheater

replace dial thermostat with programmable thermostat

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