How To Install And Configure A Smart Thermostat

After you buy the new smart thermostat, the next question you have probably is how to install and setup your new smart thermostat.

Depending on which smart thermostat you get, you might be greeted with a complex installation process. At least, this is what it might look like at first. The good news is that in many cases the configuration process is nowhere near as involved as the manufacturer’s instructions make it out to seem.

Manufacturers have a tendency to hire technical writers that make comparatively simple tasks into major projects. As long as you have a standard HVAC system in your home, you should be able to configure your smart thermostat with just a couple of regular tools.

Choosing A Location For Your New Thermostat

Replacing Existing Thermostat

When you’re replacing an existing thermostat, you probably won’t have much choice of where to put the new one. You probably have wires in your wall already, which means you can simply disconnect the old one and put on a new one.

If you’ve ever put in a new conventional thermostat after an older one failed, then the process is almost identical notwithstanding potential issues involving drawing power from a C-Wire. Some, like low voltage Nest Learning Thermostats, can serve as an easy replacement for your old thermostat irrespective of what wires you might have lying around inside your wall.

Installing A New Thermostat

If you’re selecting an entirely fresh location, then you have a greater amount of leeway when it comes to where you want to install it. You might want to put your new thermostat wherever it happens to be easiest to run wires to it, but this might not be the best idea.

Putting it anywhere near a wall heater or a register is going to make your thermostat confused about the actual internal temperature. Most homeowners should put their thermostat at least two studs away from where the heater is.

Finding Good Place In Home Layout

Putting the thermostat in sunlight or near the kitchen will also make it think that your home is much hotter than it is, even in the summer, which could end up unnecessarily cycling your air conditioning.

Vent registers and even television sets can tamper with the delicate circuitry that measures the temperature, so it may be best to find a sort of island of wall space not near anything so you can be sure there aren’t any issues. Homeowners should also keep in mind that their interior configuration could change in the future.

If you have a house for a long time, then your chances of reconfiguring your furniture and appliances go up. Think of how many times you moved the furniture around in your current home. You might also eventually buy a new appliance that doesn’t fit where your old ones did. Putting your thermostat in a place that this won’t be an issue is crucial.

Tools Needed For Thermostat Installation

Before you rush out to the hardware store or order a bunch of exotic tools online, take a deep breath and remember that you probably won’t even need anything that isn’t already sitting in your toolbox.

Most likely you’ll want the following tools:

  • Small Phillips and flathead screwdrivers
  • Needle-nose pliers
  • Wire stripper
  • Plastic wall anchors (if your thermostat doesn’t come with them)
  • Small level (some thermostats have that built-in)
  • Pencil
  • Masking tape
  • A bit of paint if you have to make a new hole or thermostat is smaller than the old one
  • Drill for the wall anchors, which may not be necessary if you’re replacing an existing thermostat

If you’re just swapping out your old thermostat for a new one, then you won’t even need this much. Two screwdrivers, your home WiFi password and the little ID card that came with your smart thermostat will be enough. Think of it like setting up any other digital device for the first time.

Safety First

One other piece of equipment you’ll want to have on hand is a vital bit of safety knowledge. While know-how might not seem like a tool, this one is critical if you’re replacing an existing thermostat. Old rotary-type thermostats often used a fluid link made out of liquid mercury suspended in a glass to control electrical current.

While the mercury is theoretically safe as long as the glass envelope doesn’t shatter, you don’t want to take any chances. Make sure that you’re extremely careful when you get rid of the old thermostat to avoid breaking this glass. Take it to a facility that can handle this kind of waste. Some hardware stores might be able to take it off your hands safely.

What Wires Will I Need?

Variety Of Thermostat Wires

When you first open up the back of your thermostat, you’ll find that there are some different wires back there that don’t look a thing like the standard electrical plugs found on AC equipment. Keep in mind that there aren’t any standards for wire colors. Any of the wires could be used for everything, and previous homeowners may have gotten a bit creative with them. The most standard wiring plan is as follows:

  • Red: R-Wire 24VAC from the furnace transformer
  • Green: G-Wire for fan control
  • White: W-Wire for heat control
  • Yellow: Y-Wire for AC control
  • Blue or Black: C-Wire (Common) for additional power

You may notice that you have more than one red wire. Heat and cooling calls might demand extra power, which is why these tend to show up in larger homes. Some homeowners might have fairly exotic HVAC systems that look and act normally while eating up an additional amount of power while starting or powering down.

While these sorts of devices are energy efficient insofar as they use comparatively little power when running, their calls could be a bit more complex and therefore necessitate these wires.

You may also have duplicates of the W-Wire, which is due to a second-stage heat system. Some homes with second-stage cooling systems will also have a second Y-Wire.

If you’re wiring a larger facility or place of work, then you might have yet another W-Wire to control a third-stage heat system. These might be marked if previous electricians did a good job. If not, then you’ll want to add your safe labels to prevent any mistakes once you’ve traced each one to the terminals on the existing thermostat.

Thermostat C-Wire

The presence of a C-Wire is more or less necessary for modern thermostats, since they gobble up additional power to remain connected to your Wi-Fi network. Smart thermostats have some other power needs too.

While you might not be used to thinking of every digital device as a computer, smart thermostats contain sophisticated general purpose PC clones burned into a single integrated circuit.

They boot a fully-featured Unix system. Imagine trying to run a PC without a proper power supply for a pretty graphic representation of why the C-Wire has become such a necessity.

Alternatives To Thermostat C-Wire

There are ways around this issue, however. For instance, ecobee4 smart thermostats come with something called a Power Extender Kit or PEK that provides energy to the thermostat without calling for a C-Wire. Some users additionally have adapters for wall power.

Venstar also makes a device that permits you to split some of the wires that come out of the back of your furnace, thus giving you an extra one to use as a control wire.

This can then free up another wire, which may be used as a C-Wire as each of the wires provide an equal amount of voltage in most cases. You can’t use the split line as a C-Wire, but that shouldn’t matter when you end up with another free one anyway.

Safety Precautions

When you finally do wire the terminals in the back of the thermostat, each of them should expose no excess copper at all if it can be avoided. Before you even think about beginning the process, you should turn the power off to the air conditioner and furnace at the circuit breaker.

You’ll also want to throw the cutoff switch if your HVAC comes with one. This should cut the electricity going to the thermostat, which is important since touching two wires together during the process by accident could blow out your transformer on top of the obvious safety consideration. Make sure you always kill power to the unit before doing any work.

Installing Smart Thermostat Step-by-Step Guide

As you might imagine, each thermostat tends to be a different beast. Some of the instructions are generic enough that they apply to nearly anything. Take a look at general advice before you try to configure your thermostat. The specifics of each can come later and here are the general steps:

Step 1 – Disconnecting The Power

Make sure that power to the system is cut out, which is best done by the electrical panel where the circuit breakers are. Split systems may have two circuit breakers, which both have to be powered down.

Step 2 – Removing Old Thermostat

If you have an existing thermostat, then you’ll want to remove the screws that hold it to the base. Some models might simply pop it right off with a little force. Don’t use too much to take it away, though, because you don’t want to make a mess out of your wall.

Step 3 – Identifying Wires

Your thermostat should still have wires attached at this point. Take a piece of paper and write down where each thermostat wire goes on the terminal board in the back. Some homeowners like to take a photograph of this assembly, so they know exactly where everything goes.

While you’ll want to pay close attention to the color of the insulation on each wire, make a note of anything that doesn’t necessarily match up with the accepted standards since you might have some creative wiring back there.

Step 4 – Disconnecting Wires

After making sure you have notes or photographs of where everything goes and are absolutely certain that the power is off, you can disconnect the wires from the old thermostat.

Once you’ve done so, it should come completely out of the wall. Be careful to make sure that nothing falls into the wall because it can be extremely difficult to fish wires back out of that hole.

Step 5 – Installing New Thermostat

Mount the new sub-base by using the same holes from before and then tighten it down. Attach the thermostat wires to the designated terminals by following your notes from before. They should be as cleanly attached as they were before.

Some thermostat models use screw terminals while others use various types of snap-in adapters. Regardless of the type, make sure no wires are touching and ensure that all of the various pieces of copper are completely hidden from view. Attach the thermostat to the sub-base before you tighten everything up and restore the juice.

Even though smart thermostats are internally very different from more traditional units, most of the magic happens in software. This means that the method you use to connect it should be identical to the way any existing units are installed. You won’t have to add any computerized control wires or anything like that, since the thermostat sends the same voltage codes a traditional one would.

Installing The ecobee4 Smart Thermostat

If you’re installing an ecobee4 unit, then you naturally have an installation process that’s almost identical to what you’ve seen above. However, there are two extra steps you may have to follow through with.

After you’ve made sure to cut the juice, you can wire the PEK to your furnace transformer board to make up for the lack of a C-Wire. You need to locate the terminals on the furnace control board that feed wires to the thermostat and wire the included cables right to the screw terminals.

You won’t need anything more than a regular screwdriver to accomplish this. Once you’ve done so, the PEK will simply stick to your furnace’s metal housing because it features a metallic back. This step should take all of three minutes.

Each ecobee4 comes with a remote room sensor that you need to find a place for in your home. After you link your phone to the system, you’ll be able to locate and sync up the sensor with a linear menu in the app.

This lets the ecobee4 know what the temperature is like in other parts of the house even if they aren’t anywhere near the thermostat itself. Pulling a tab on the back of the remote sensor is enough to activate the battery.

If you’d rather use the touchscreen on the ecobee, then you simply need to turn on the sensor to get it to realize that you’ve switched it on. By the way, if you’re installing an older ecobee3, then you should find that the PEK wires to your furnace the same way. Even the sensors are the same.

Installing The Nest 3rd Generation Learning Thermostat

Once again, the Nest 3rd Generation Learning Thermostat has an installation process that follows along pretty well with most smart thermostats. One big issue that you might run into involves stranded thermostat wires.

Look very closely at the end of your wires and make sure that they aren’t stranded like a piece of stereo speaker wire. Nest equipment doesn’t support this kind of design. They do contract with certified Nest Pro installers to replace this system, which might be an option if you’ve run into this problem.

The only other major extra step you’ll have when working with your new Nest thermostat involves jumper wires. Short leads sometimes jump two connectors.

Nest Learning devices don’t use these, but the company encourages you to hold onto any jumpers while making a note of exactly where they go. This way you can reinstall your current thermostat if you ever moved and wanted to take your Nest unit to your new location.

Setting Up Your New Thermostat

Once you have your new thermostat in place, you’re going to need to configure it. As with everything else, different engineering teams from various manufacturers decided to try some very configuration methods.

Engineers from Nest went with a method that seems fairly self-explanatory to most users. You’ll first want to select your language. The thermostat will then pick a time setting based on which language you put in.

American users will notice that they default to 12 hour time while users in the UK get 24 hour time. Unfortunately, it doesn’t seem possible to change the time setting independent of the language options.

While you don’t need to connect your thermostat to the Internet for it to control your HVAC system, you can enter your WiFi password next and then configure your location. The rest of the setup process follows quite naturally.

You’ll answer a few simple yes or no questions about the equipment that you’re working with as well as undergo a quick systems test. Once you’re done with this, you’ll be able to set the temperature and configure the Nest app.

This process should be the same for pretty much any version of the Nest Learning thermostats. They did streamline it quite a bit when they came out with the new Nest 3rd generation devices, but this refers more to speed than anything else. You’ll find that setting up an ecobee4 isn’t too much different.

If you’re the proud owner of a new ecobee device, then it doesn’t matter whether you’re using the PEK or a C-Wire as your configuration process will be more or less identical. When you first turn on your new unit, you’ll be told what wires are attached to the device, and you’ll get asked to confirm that.

It will then ask you several questions about whether or not you have any extra accessories connected to your HVAC system. You’ll be able to select which scale you’d prefer to use. Unlike Nest devices, you can select Fahrenheit or Celsius freely. You’ll then need to set an ideal temperature and even a name for your thermostat.

In either case, you can then download the mobile app and sync it to your thermostat. This requires almost no effort at all if you’re used to configuring apps. One problem you might run into is if you’re configuring a Honeywell RTH9580WF.

If you’re ever in the settings menu, then you might find that you can disconnect from the network easily here. Should this happen during the configuration process, just touch the SSID tag of your home router and enter the password.

A lot of users think there’s something wrong with their thermostat, but this is a useful feature Honeywell’s engineers added to help those who connected to a public WiFi network by mistake.

How To Set The Thermostat To Save Energy

Smart thermostats can save you on energy bills, but you need to set them up right. A few simple tips can go a long way. Don’t go crazy with the energy settings first off. Keep them somewhat close to what you had with your last thermostat if those were reasonable.

Most smart thermostats need to get notified, either with sensors or a gesture, when you’re not in the house. This lets them dial down the heat or AC when you’re not home. You’ll also want to set the thermostat to a more conservative setting when you’re going to be away for a long period.

Consider some of the other following tips too:

  • Don’t crank the heat or AC, since your furnace will heat or cool at the same rate regardless of the setting.
  • Never keep the factory settings since these are probably not best for you.
  • If you’re in a house with others, try slowly moving the temperature to cooler settings in the winter and warmer ones in the summer. This will help avoid so-called thermostat wars while helping others adjust to saving energy.
  • Your home loses temperature rapidly, but don’t be afraid to turn off the furnace. As the temperature falls the rate of heat loss falls with it.
  • While it might look like you’re going to save more energy doing so, don’t allow your thermostat to drop below 55°F in the winter. Your pipes might burst otherwise.
  • Remember that you can also always manually turn your thermostat off too. Turning it off and opening windows in the summer to cool down the rooms with the breeze could be the ultimate way to save on power.

The Ideal Thermostat Settings

Optimal comfort differs among different consumers. Many people feel that in the winter 68-72° Fahrenheit is a good range. Some people prefer to drop this down to 58° in the evening, though 62° might be better for most. In the summer, you might want to set your thermostat to 78° when you’re home.

Feel free to raise it into the 80s when you’re not there. You could save up to 8 percent on your electrical bill per degree you raise your thermostat. If you’re having trouble figuring out comfortable settings, then feel free to experiment a bit.

Smart thermostats offer suggestions, and those using the Nest Learning Thermostat even earn leaf icons when they select decent settings. There’s also an online tool that could be of some help. If your settings don’t feel ideal even if they mathematically seem to be, then you might want to change the way you dress.

There’s no reason you can’t dress warmer in the winter while dropping the temperature down. Likewise, wear shorts in your home in the summer while hiking the temperature up.

You may have gotten so used to the way you had the old thermostat set that you subconsciously dressed to match the temperature you had it set at. Don’t forget about blankets in the winter either.

Resources & Further Reading

Thermostat Location

Where to Install Your Nest Learning Thermostat

Thermostat Placement

Is Your Thermostat Placement All Wrong?

Strategies For Improving Thermal Comfort (PDF)


How To Wire A Thermostat

What Tools or Materials are Necessary for the Installation of My New Thermostat?

How to Install a Programmable Thermostat

Thermostat Wiring Guides

Wire Connections (Infographic)

Installing Your ecobee4

Add-a-Wire Accessory Installation Instructions (PDF)

How to Wire a Thermostat

Thermostat Installation

How to Hook Up a Home Thermostat

How to Install a Thermostat

Smart Thermostat Install and Setup

How to Install an ecobee3 Smart Thermostat

Installing the Nest Learning Thermostat (VIDEO)

How to Tell if Your Heating and Cooling System Will Work with the Nest Thermostat

How to Install Your Nest Learning Thermostat

Thermostat Configuration

A Step-by-Step Guide to Setup on the Nest Learning Thermostat

How to Install a New Low-Voltage Thermostat

How to Install and Set Up the Ecobee Smart Thermostat

Honeywell RTH9580WF Setup (PDF)

Energy Conservation

Install a Smart Thermostat

How to Improve Energy Savings

Programmable Thermostats

Recommended Thermostat Settings

Science Behind Modulating Heat

Saving With Thermostats

Ideal Thermostat Settings

Ideal Thermostat Temperature

Recommended Thermostat Settings

Is There A Perfect Temperature To Set Your Thermostat?

Recommended Thermostat Settings for Winter

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