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How To Add Another Thermostat In The House [Ultimate Guide]

If you have rooms in your home where you need either a cooler or warmer temperature than the general temperature your HVAC system provides in the rest of your house, the adding of an extra thermostat to create a separate zone in your home might solve the problem. Perhaps you are considering it but have some questions before you make your final decision. Like most homeowners, you probably wonder whether adding another thermostat and creating a zoned home will be possible in your specific circumstances and also whether you will be able to do it yourself. 

Generally speaking, it is always possible to add an extra thermostat to any HVAC home system to create a zoned system in your house. If the second thermostat is correctly installed, set, and used you will save on your electricity bill. If you are a DIY enthusiast you will be able to do the installation yourself. 

In this article, we’ll discuss the steps you’ll have to take to add a second thermostat to your HVAC system. We will discuss the generic aspects and have a look at some specific steps to take with certain brands. The FAQs at the end of the article will answer most of the questions you might still have relating to the adding of another thermostat. 

For this article, we’ll only discuss adding one extra thermostat. If you want to add multiple thermostats, the principles will be the same as for one additional thermostat. 

Second thermostat needed for zoned home

If your home has areas that are cooler or warmer than others, the use of two different thermostats can be a solution to get the air in your home more evenly conditioned. The problem can relatively easy be solved if you have a single air conditioning/heating unit. You can convert the ductwork, insert dampers and install an additional thermostat.  

When you wire two thermostats to your heating or cooling system with the accompanying zone control and with dampers installed in the ductwork, you’ll have two separate temperature zones in your home.

When installing a second thermostat to create a zoned home, most of the work is done on the duct system that is currently in your house. The duct is modified with a bypass and zone dampers, and a zone control board are also added to the system.  

After a zoned system has been set up, the zone board controls the dampers and the thermostats.  When one of the zones need more cooling or heat, the dampers are regulated to send what is needed to the zone that is calling for it. With this set-up, you can get cooling or heating, but not at the same time.

How to add another thermostat to your HVAC system

To add a second thermostat to create a zoned home, is not a matter of just connecting another thermostat and everything will be in place. You’ll have to plan exactly in which zone or room do you need a different temperature than the rest of your house. And then you’ll have to prepare your existing HVAC system to accept and utilize the thermostat.

1. Prepare the duct system and damper

To utilize the zone-effect an extra thermostat can provide, the air ducts in your house have to be altered and a damper inserted in the applicable place. Dampers are the “doors” in the ducts that open and close to allow or stop airflow. They are the tools used to control the temperature in zoned areas in your house. 

When your created zone needs airflow to maintain a selected temperature, the damper will open and allow cool or hot air to pass through. When the zone has reached the desired temperature, the damper closes again and the airflow into that zone stops. The damper servicing the room or zone is connected with wires to the added thermostat in that zone to determine when the “door” should open or close.

To prepare the ducts and insert the damper, the following steps should be followed:

Step 1 – plan with a diagram

The first step is to start with a simple diagram of your existing HVAC duct system. Mark the duct that is feeding the room or zone where you require a different temperature than the rest of the house. 

Step 2 – determine the place for the damper and measure duct

After you’ve identified the room and duct, find the location where the duct to this zone branches away from the main duct. This is the place where you will have to insert a damper. The damper will either let all the air pass through the main duct or will open up for some air to flow into the zone – keeping the temperature in the zone on the preselected temperature. 

Get to the duct, measure it and buy a zone damper to fit.

Step 3 – cut a hole in the duct and insert damper

After you’ve purchased the damper your next step is to get to the duct and cut a hole in the ductwork to fit in the zone damper. Ensure that it is properly sized for the ductwork. Before you cut the hole, also verify whether you have a drop-in or slide-in damper, and cut the hole accordingly. After you’ve secured the damper with screws, seal it with silicone caulking. 

Step 4 – wiring to control box/panel

You are now in the process of creating a zoning system consisting of a damper and a thermostat for this specific room or zone in your house. The thermostat and damper system will be wired into a central control panel or box to sequence the second thermostat’s call with the zone dampers in the ducts and the HVAC system.

To connect the damper to the control box, strip the ends of the wires from the damper and attach them to the zone control box or panel.  Tighten the screws to hold the wires securely. 

As there might be small wiring differences between different brands of dampers, you have to consult the information brochure or information on the damper’s box before you connect any wires.   

Step 5 – mount the second thermostat

The last step is to mount the zone control box either on the ductwork or a nearby wall. 

2. Wiring of the second thermostat

Now you are ready to connect and wire the extra thermostat.  Make the connections according to the manufacturer’s instructions in their manual. In principle, you have to follow the same wire-connection steps whether it is the only or a second thermostat. 

But because it is a second thermostat, you also have to ensure that you run a wire from the thermostat to the zone control box. Consult your thermostat’s manual for the wiring color codes.  

3. Add the second thermostat to the HVAC system

Brands and models have different ways to add thermostats to the HVAC system. We’ll briefly discuss some of the well-known brands, but you’ll find full details in the specific thermostat’s manual.  

Honeywell thermostat

On the thermostat

  • Touch the Plus (+) icon on the home screen, and select “Add.”
  • Touch the down arrow to “Add device manually.”
  • Select “Thermostat” and touch “Honeywell Total Connect Comfort.”
  • Tap “You are connected” and sign in to your Honeywell Total Connect Comfort account.

If the thermostat doesn’t start working, take it off the wall/duct and turn off your router. Wait for about 60 seconds and then turn on the router again and put the thermostat back on the wall/duct. If the thermostat is still not working, try the following steps to connect to the Wi-Fi: 

  • Set the thermostat switch to “Off.”
  • Open the battery door by inserting a coin into the slot on the door and pushing it open.
  • Remove the batteries.
  • Insert the batteries backwards – the negative pole with the positive terminal.
  • Remove the batteries after about 15 seconds and put them back in the correct way, and close the battery door. 

If it is still not working, the best will be to contact a nearby electrician.

On the app

  • In the SmartThings Classic mobile app, tap “Marketplace.”
  • Under “Things,” tap “Thermostats.”
  • Select the added Honeywell Wi-Fi thermostat.
  • Tap “Connect Now.”
  • Tap the field that says ”Click to enter Honeywell Credentials.”
  • Sign in to your Honeywell Total Connect Comfort account.

Nest Thermostat

If you’ve added a Nest thermostat to your HVAC system as the second thermostat, you have to register it via the app.  

  • Open the Nest app.
  • Sign in to your account.
  • From the home screen, tap on “Settings.”
  • Tap “Add product.”
  • Tap “Continue without scanning” and then select the type of Nest thermostat you want to add.
  • Follow the Nest app’s instructions and prompts.

Ecobee Thermostat

If you’ve added an Ecobee thermostat as the second thermostat you have to register it on your account. To start the registration process, log in to your Ecobee account from the web portal or the mobile app. 

Registering an additional Ecobee thermostat via the online web portal

  • After you’ve logged in, click the icon in the top right corner of the screen.
  • Click “Add Thermostat.”
  • Type in the 4-digit registration code from your thermostat and then click “Next.”
  • Proceed by filling in the required fields when prompted.
  • Once you’re finished, return to your thermostat and tap “OK” at the bottom right corner to complete the registration.

Registering an additional Ecobee thermostat via the app

  • Tap the Plus (+) icon in the top right corner.
  • Select “Register a device.”
  • Select the “Ecobee thermostat” option. 
  • Enter the 4-digit registration code from your thermostat and then tap “Next.”
  • Your Ecobee is now registered as a second thermostat and can be accessed remotely through the app or the web portal. 

Is it necessary to have more than two thermostats – as in one in every room?

 With all this said about 2 thermostats and the benefits of a zoned home, the question arises whether it wouldn’t be a good idea to have a thermostat in every room. Then every room can be at a different temperature when required. And you would have more control over your home’s temperature.

There are a few reasons why this is not necessary. While two thermostats are very effective and almost always work without technical issues and fulfil most homeowners’ requirements, too many thermostats can easily lead to technical glitches. A thermostat in every room will be quite expensive and the temperature required in most of the rooms of a house is normally the same.  

Nowadays smart thermostats are great options because with a smart thermostat you don’t need one for every room. 

FAQ

Q: Can I have 2 or more thermostats in my house?

A: Yes, you can have 2 or more thermostats in your house. You can cool your house equally by installing a single central air-conditioning unit with two or more thermostats. 

Q: How does a house with 2 thermostats work?

AThe house is divided into two zones — in many instances an upstairs and a downstairs zone.  There is a thermostat in each zone to control the temperature in that zone. Each zone of the house can be turned down or closed off to save energy. 

Q: Can two thermostats control one zone?

A: Yes, you can use two thermostats to control one HVAC zone. If correctly installed, set, and used you will save on your electricity bill. 

Q: Can I connect more than one thermostat to a single HVAC unit?

A: You can also connect more than one thermostat to a single HVAC unit.

Q: How much does it cost to have a second thermostat installed?

A: Most electricians can install a second thermostat in a house or apartment in less than two hours. They normally charge $65-$85 per hour. Thus the total labor cost will range from $65 to $170. You can, however, also add a second thermostat yourself if you want to and save on the labor cost. 

Conclusion

In many homes, especially older houses, simple HVAC systems with only one thermostat, are often not very efficient in maintaining the right temperature throughout the home. There are several options to upgrade HVAC systems, and the adding of a second thermostat to make the home a zoned house is one option often chosen.

We hope that this article has helped to indicate all the aspects that have to be attended to during the upgrading and given you some useful steps and tips.