How To Install a Programmable Thermostat

32mmx how to install a programmable thermostat

Installing a programmable thermostat in your home or office can save you up to 15% of the energy that you are now using for your HVAC system.

This is one of the most cost-effective energy decisions that you can make for your home, and the cost of doing so is relatively inexpensive. We have found in the past that many people have considered having one installed but never got around to it either because they thought it would be an expensive undertaking, or else they wanted to do it themselves but weren’t really sure how.

A programmable thermostat will automatically set back the temperature in your home at desired times, and will turn down the heat or the cooling to whatever temperature you program in. It’s basically something that you can set and forget, and then your energy savings will add up by themselves.

This is something that most homeowners can do themselves with some simple instruction. The job itself should take no more than an hour. Let’s go over the procedure of the actual installation, but first, I’d like to mention that City Duct does supply and install programmable thermostats, and we can also install your’s for you if you’ve already bought one yourself.

If you would like more information on this service then please contact our office. It is also more cost-effective to have this service done in conjunction with your annual furnace cleaning and inspection, or when we are already in your home doing your air duct cleaning.

For this demonstration, we will be replacing a typical White Rodgers heat/cool thermostat with a Honeywell Pro4000 model. You can use whichever model you choose though, and the installation will still be pretty much the same.

heat-cool-thermostat honeywell-pro4000-programmable-thermostat

The first thing you should do is to test the operation of the entire HVAC system by first turning the furnace fan on by the switch on the thermostat. Just turn it to ON, and as soon as you know that the fan comes on, then turn it off. Next, check the cooling. Set the temperature to its lowest setting and then select “cool”. You should hear your outdoor unit and your furnace fan come on immediately.

Once you know it can work then change the system switch to the off position and wait for everything to stop. Next, turn the heat all the way up and then using the system switch again, turn it to heat. Once you know that the heat works, then you’ve just tested everything that your current thermostat can do, and you now know that everthing works for sure. You next step is to go downstairs and turn off the furnace power switch.

Most people tend to skip the initial testing procedure because its their home, and they are already confident that everything will work. But when I go into someone’s home to do this job I always like to test it all first. It only takes a few minutes.

Now we will begin by first removing the cover of the old thermostat. That’s the part that has the temperature dial on it. Just pull it off, and inside you will see a secondary plate which should look similar to the picture below. You will need to unscrew the plate to access the thermostat wires and the thermostat mounting screws.

heat-cool-thermostat-cover-removed dusty-thermostat

Did you ever realize how much dust can accumulate inside your thermostat?

Now we can see the thermostat wires and see where they are all connected. In most cases there are four wires… a red (supplies power – terminal R and RC), a green (controls the fan – terminal G), a white (controls the heating – terminal W), and a black or yellow wire (controls the cooling – terminal Y). Carefully make note of which colour wire goes where. If you have two black and two white wires then you will have to mark the actual wires somehow (duct tape and a pen) as you remove them. The thermostat in the picture above was wired up with Bell Canada phone wire instead of the proper 18 gauge thermostat control wiring, that’s why you see an additional wire on each of these connections. The thick red wire in the picture is a jumper wire, which gives power to both the R and RC terminals. Programmable thermostats come with a built-in metal jumper between those two terminals, so we will no longer need that small piece of wire there.

The next step is to remove all those wires from the old thermostat mounting plate. When you take the last wire off, BE CAREFUL… if you lose the thermostat wire inside the wall you will have to try to fish it out, and this is not always easy to do.

I like to leave the last wire attached, and then take the screws out of the mounting plate. Let the whole thing hang there for now with one wire still connected while you get your new thermostat ready. You’ll also be able to tell how much “play” you have with your thermostat wire. If you have lots then you’re lucky.

Once you’ve got the mounting plate from the new one ready, you’ll have to remove that last wire. As soon as you do that, feed it through the hole in the back of the new mounting plate and connect one wire to where it will go. The important thing here is not to lose that wire in the wall!

Level the mounting plate, get that secured to the wall and continue to connect the remaining wires. If you have a sufficient amount of wire to work with, cut off the bare ends of the wires that were previously exposed and strip off a new 1/2″ of the wire. This will give you a better and cleaner connection on the new terminals. The rest of the job is going to be much easier.

Check if there are any switches on the inside of the new thermostat and refer to the installation instructions before you snap the new cover in place. On some models there is a switch inside that enables you to select how your thermostat will display… either Celsius or Fahrenheit.

Once you’ve got that done, install the new batteries and snap the cover in place. All that’s left now is to program the new thermostat and check its operation.

Here is the new digital thermostat completely installed. This one is perfectly level and you can see a small piece of cardboard sticking up on the top left. That contains some pull-out instructions that tell you how to change the time on your display. That’s a good idea because you’ll probably otherwise forget how to adjust the time settings every time the clocks go ahead or back an hour.


Every thermostat is a little bit different from the other, so you’ll have to refer to the installation booklet for the programming procedure. Setting up the program is usually pretty simple, and you will have to set up one program including times and temperatures for the heating mode and again for cooling. Some units come pre-programmed from the factory, but you can always change anything any time you wish, to suit your own personal comfort levels.

Most programmable thermostats have a 5-2 program. This means that all the weekdays will share one program, and the weekends will share another. The weekday schedule will normally have four settings… wake, leave, return and sleep. Set the desired temperature for the time you normally get up. The thermostat will teach itself how long it takes to heat up your house, and will make the furnace come on a few minutes before your wake time arrives.

The “leave” setting is for when you normally leave the house for the day. If no one is usually home during this time, then it makes sense to have your thermostat turn down the heat automatically for you. You are also able to easily override any set program at any time.

You will set the “return” setting to the time and temperature you want for when you normally get home from work, and when that time comes, your home will be exactly at the temperature you have pre-selected.

Your “sleep” setting will also be one of your lowest settings, and this will save you from having to remember to turn down your heat before you go to bed… it’s all automatic now.

Weekend programs don’t have four time selections. There are “wake” and  “sleep” settings only.

The final step in the installation procedure is to test the operation of the thermostat. Turn the furnace power switch back on and test the operation of the thermostat again just like we did at the beginning. If everything seems to be working fine then you are good to go.

You will start saving money on your heating and cooling bills right away, and that digital display looks pretty cool too, doesn’t it? 🙂

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Also Read : Daylight Saving Time

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