Emerson Sensi ST55 Smart Thermostat-FEATURED

Emerson Sensi ST55 Smart Thermostat User Manual

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Emerson Sensi ST55 Smart Thermostat

Emerson Sensi ST55 Smart Thermostat


You Will Need

Gather this information before you begin the installation for a smoother walk-through.

  • Sensi Password
    • Found on the back of the Welcome Guide, or back of the thermostat face plate labeled “Sensi Security Code”)
  • Wi-Fi Network Name/SSID
    • Make sure this is a 2.4GHz network.
  • Wi-Fi Network Password
  • Screwdriver
  • Hardware in Sensi Smart thermostat packaging

Download the Sensi app

The Sensi Smart Thermostat is a Wi-Fi-enabled device. To install and configure your thermostat correctly, you must use the Sensi app. To start the installation process, download the Sensi app to your smartphone or tablet. It is a free download. The Sensi app requires the following Operating System (OS) software to download:

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Android (Google Play) version 5.0 or later

iOS (Apple) version 10.0 or later
*Note that in the iOS store, the Sensi App will ONLY appear on an “iPhone only” Search. On an iPad, change the search criteria in the App Store.

Create an account

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When you download the Sensi app, you will be prompted to create an account. This is required to access your thermostat remotely and use all the features Sensi offers. Use a valid email address and a password of your choosing to create an account. Remember this email address and password. Your Sensi thermostat will be linked to this email address once it is registered.



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Once you have downloaded the Sensi app, and have created an account, you are ready to install the thermostat to your wall and connect it to Wi-Fi. If no thermostats are registered yet, tap the “+” sign to add a thermostat.
Then, choose which thermostat you purchased.

  • 1F87U-42WF series
  • ST55 series
    Note: You can check your model number on the back of the thermostat faceplate.

Install Path

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After creating an account, signing in, and choosing your model, the app will ask you whether or not the thermostat is already on the wall. You will either choose “No, it needs to be installed,” or “Yes, it is on the wall.”
The first option will walk through the entire installation process. If you did not have this thermostat professionally installed, choose this option.
The second option is for connecting your thermostat to Wi-Fi only. If you have had a professional install your thermostat, and you just need to connect the Sensi thermostat to your home Wi-Fi network, choose this option.
No, it needs to be installed.

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This option will walk you through the entire installation process, including identifying and connecting your wiring, as well as connecting to Wi-Fi. The Sensi app will walk through a step-by-step process for installation.

Gather Tools and Package Contents

Gather all the necessary tools for installation.

  • Turn Off Power
    Turn off the power to your heating and air conditioning system before handling your thermostat wires.Emerson Sensi ST55 Smart Thermostat-6
  • Remove Old Thermostat Cover
    Remove the cover using a screwdriver or by pushing the pressure latch. Some covers pull off while others need to be released using a screwdriver.
  • Photograph Your Wiring
    THIS IS IMPORTANT. The Sensi app will prompt you to take a picture of your existing thermostat and old wiring in case you need it later.
    This can be helpful for troubleshooting with our technical support team if necessary. The picture you take will be saved to your camera roll or photo gallery.Emerson Sensi ST55 Smart Thermostat-7
  • Throw Away Any Jumper Wires
    Sensi has a jumper wire built into it, and you will not need any jumper wires from your old unit.
  • Choose Wire Terminals
    Choose the terminal labels that have wires attached to them on your old thermostat here. The app will tell you if you have a valid configuration.
    If you are getting an invalid configuration message you can learn more about compatibility at sensi.emerson.com/en-ua/compatibility. A c-wire, or “common wire”, is required for heat only, cool only & heat pump applications. You can learn more about installing a c-wire at sensi.emerson.com/en-us/c-wire.Emerson Sensi ST55 Smart Thermostat-8
  • System Type
    Select what type of system you have.
  • Label Your Wires
    Using the provided wire label stickers, label your wires by removing one wire at a time.Emerson Sensi ST55 Smart Thermostat-9
  • Disconnect Wires and Remove Base
    After all of your wires are labeled, remove the old thermostat base from the wall.
  • Install Sensi Base
    Use the provided mounting screws and secure the Sensi base to the wall.Emerson Sensi ST55 Smart Thermostat-10
  • Connect the Wires
    Once the Sensi base is mounted and secured on the wall, insert the wires into the terminals. Simply push the wires into the terminal slots. Use a screwdriver to secure each wire in place
  • Attach Cover
    Push the front display onto the thermostat base.Emerson Sensi ST55 Smart Thermostat-11
  • Turn On Power
    Turn the power to your system back on.

Connecting to Wi-Fi

This portion of the installation guide covers how to connect your thermostat to Wi-Fi. If you chose “No, it needs to be installed,” the app will provide instructions for installing and wiring your thermostat before you connect to Wi-Fi. If you had your Sensi thermostat installed by a professional or if you have already installed and wired your Sensi thermostat yourself, but have not yet connected to Wi-Fi, choose “Yes, it is on the wall.” The app will jump right into connecting your thermostat to Wi-Fi.Emerson Sensi ST55 Smart Thermostat-12

On the thermostat, press Menu, and then Mode. The Wi-Fi icon in the upper left-hand corner will flash, and 00, 11, or 22 will be displayed in the middle of the thermostat. This determines what Sensi version you have.

Follow the step-by-step instructions in the Sensi app. The Wi-Fi connection process will be slightly different based on your device’s operating system (iOS/Android), Sensi app version, and the version of the Sensi thermostat that you have. If you are connecting with an iPhone/iPad, and you see 11 or 22 displayed on your screen, you’ll have the option to connect your thermostat with Apple HomeKit. After connecting to the Sensi network, you’ll enter the Sensi password, printed on the Welcome Guide (or found on the back of the thermostat face plate as “Sensi Security Code”). Then you’ll connect to your Wi-Fi network.Emerson Sensi ST55 Smart Thermostat-13

Name Thermostat
You can select a name or choose a custom name for your thermostat. Press “Next” to continue.Emerson Sensi ST55 Smart Thermostat-14
Register thermostat
After successfully connecting Sensi, the app will prompt you to register the thermostat. You can either choose the “Locate Me” option or fill in your street address, city, state, zip code, country and time zone manually. Press “Next” to continue.

Contractor Information

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If a contractor professionally installed your thermostat and registered as a Sensi partner, they have the option to input their phone number here. If there is not a registered number available, simply hit “Next” to continue.
Start Using Sensi
Congratulations on successfully installing Sensi. Press “Start Using Sensi” to open the main screen of the app.


Connecting to Wi-Fi Troubleshooting

If you’re having trouble connecting to Wi-Fi, here are some tips to try:

  • Make sure the Sensi app is up-to-date and running the latest version available in your app store.
  • Reboot your smartphone.
  • Reboot your router by unplugging it from the wall for a few minutes and then plugging it back in.
  • After your router reboots, and your Wi-Fi network has internet access again, make sure that your phone is connected to your 2.4GHz Wi-Fi network.
  • If you’re on an iPhone, make sure Keychain is On, and Home Data is allowed for the Sensi app.
  • If you’re on an Android, go into your phone’s Advanced Wi-Fi Settings and turn off the “Switch to mobile data” feature. (Depending on your Android, it may be called “Smart Network Switch” or “Avoid poor connections.”)
  • It may be easier to just turn “Mobile Data” off completely for setup. You can find this in your Connection settings.
  • Try another smartphone or tablet. Simply download the Sensi app and sign into the app using the email address and password you used when you created your account.

Reconnecting to Wi-Fi

If you replaced your router or changed your Wi-Fi network password, you will need to reconnect your thermostat to Wi-Fi. This is different depending on what smart device you are using. Please see our support article for more information on how to reconnect.sensi.emerson.com/en-us/support/reconnecting-Sensi-thermostat-to-wifi

HVAC configuration menu
If you chose the option “No, it needs to be installed”and walked through the installation process on the Sensi app, the app should have correctly configured your thermostat for your system type. However, if you are experiencing an issue or you want to check your system configurations, you can manually configure your thermostat as well. Learn more about how to properly configure your thermostat by searching “configure” on our support site at sensi.emerson.com/en-us/support.

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Accessing your Sensi thermostat from other devices
When you log into your Sensi account with your email address and password, the app will be able to control all the thermostats registered to your Sensi account. If you give someone else your email address and password to your Sensi account, they will be able to log in and control any thermostats registered to that account. You can change your email address and password from inside the app. Be aware of this when giving out your information. There is no limit to the number of devices that can access the thermostat.
Forgot password
If you forgot the password to your Sensi account, click on “Forgot Password” on the login screen of the Sensi app. A temporary password will be sent to the email address that you use to login.

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Installing multiple thermostats

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If you are installing more than one thermostat, follow the same installation process in the Sensi app. Once you have one thermostat installed, open the Sensi app on your phone. At the main screen, tap the + sign to add another thermostat to your account.
Accessing account information
You can use the Account area to access your email preferences and change your account information and email address associated with your Sensi.
For iOS: Tap the person icon in the upper right-hand corner.
For Android: Tap the three dots in
the upper right-hand corner.

Technical support

For problems connecting your Sensi thermostat, call or email the Sensi Technical Support team, and they will be happy to help you or your contractor walk through any steps needed to troubleshoot the Sensi thermostat. sensi.emerson.com/en-us/support (888) 605.7131 [email protected]



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Download Manual: Emerson Sensi ST55 Smart Thermostat Installation Guide


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Emerson Sensi ST55 Smart Thermostat User Manual





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