The Sensi Lite Smart Thermostat is a Wi-Fi-enabled thermostat designed to help homeowners control heating and cooling through the Sensi mobile app. This installation guide applies to the Sensi Lite Smart Thermostat 1F76U-22WFB series and ST25 series.
The thermostat must be installed and configured through the Sensi app, which guides users through wiring, HVAC system setup, Wi-Fi connection, registration, and account access. The app-based installation flow is especially useful for DIY users because it helps confirm wire labels and system compatibility before the thermostat is fully connected.
Compatible Models
This guide covers the following Sensi Lite Smart Thermostat models:
| Product | Model Series |
| Sensi Lite Smart Thermostat | ST25 series |
| Sensi Lite Smart Thermostat | 1F76U-22WFB series |
The model number can be checked on the back of the thermostat cover.
What You Need Before Installation
Before starting the installation, gather the required items so the setup process goes smoothly.
You will need:
| Item | Purpose |
| 2.4GHz Wi-Fi network name/SSID | Required for thermostat connection |
| Wi-Fi password | Needed during app setup |
| Screwdriver | Used to remove the old thermostat and mount the new base |
| Included thermostat hardware | Screws, labels, batteries, and mounting parts supplied in the package |
| Sensi app | Required for installation, Wi-Fi setup, and configuration |
The thermostat is compatible with 2.4GHz Wi-Fi networks only. If the home network does not appear in the app, it may be hidden or incompatible.
Downloading the Sensi App
The Sensi Lite thermostat must be installed using the Sensi app. The app is available as a free download for smartphones and tablets.
To begin:
- Download the Sensi app from the App Store or Google Play.
- Open the app.
- Create a Sensi account using a valid email address.
- Save the email and password, because the thermostat will be linked to this account after registration.
A Sensi account is required for remote access and app-based thermostat control.
Creating a Sensi Account
After downloading the app, users are prompted to create an account. The account connects the thermostat to the user’s email address and allows access to Sensi features, remote control, and device management.
Use a valid email address and a secure password. If the password is forgotten later, the app login screen includes a Forgot Password option. A temporary password will be sent to the email address linked to the account.
Sensi Lite Thermostat Parts and Key Components
The manual focuses mainly on installation rather than a full parts diagram, but the setup process references these key components:
| Part or Component | Function |
| Thermostat cover | Front display/control section that attaches to the base |
| Thermostat base | Mounts to the wall and holds wire terminals |
| Wire terminals | Connect HVAC system wires |
| QR code/PIN | Used to connect the thermostat to the app and Wi-Fi |
| Mode button | Used during Wi-Fi setup |
| AAA batteries | Power the thermostat display and operation |
| Mounting screws | Secure the thermostat base to the wall |
The QR code is located on the back of the thermostat or in the Welcome/Get Started insert included in the box.
How to Install the Sensi Lite Smart Thermostat
Step 1: Add the Thermostat in the Sensi App
Open the Sensi app and tap the plus (+) sign to add a thermostat. Select the Sensi Lite model option for the ST25 series or 1F76U-22WFB series.
Step 2: Choose the Installation Type
The app asks whether the thermostat is already mounted.
Choose Not Mounted if installing the thermostat yourself. This option walks through the full installation, including wire identification, labeling, wiring, and Wi-Fi setup.
Choose Is Currently Mounted if a professional technician has already installed the thermostat. This option checks the existing wiring and continues to Wi-Fi setup.
For DIY installation, the manual recommends choosing Not Mounted to make sure the thermostat is wired and configured correctly.
Step 3: Remove the Old Thermostat
Before touching any wiring, turn off power to the heating and cooling system.
Then:
- Remove the old thermostat cover.
- Take a clear photo of the existing wiring.
- Remove and discard any old jumper wires.
- Select the old thermostat wire terminals in the app.
- Confirm the wiring configuration in the app.
- Label each wire using the included stickers.
- Disconnect the wires.
- Remove the old thermostat base from the wall.
The wiring photo is important because it can help during troubleshooting or when contacting technical support.
Wiring and Mounting Instructions
Install the Sensi Base
Use the included mounting screws to secure the Sensi thermostat base to the wall. Make sure the base sits flat and the wires can reach the correct terminals.
Connect the Wires
Insert each labeled wire into the matching terminal on the Sensi base. Tighten the terminal screws after inserting the wires.
The manual notes that Sensi has a built-in jumper, so old jumper wires from the previous thermostat are not needed.
QR Code Setup and Thermostat Cover Installation
After the base is installed and wired:
- Scan the QR code on the thermostat or the Welcome/Get Started insert.
- Allow Bluetooth access when prompted.
- If scanning fails, tap Use PIN and manually enter the code under the QR code.
- Install the two provided AAA batteries.
- Push the thermostat cover onto the base.
- Turn the HVAC system power back on.
Bluetooth access is required during the connection process.
Connecting the Sensi Lite Thermostat to Wi-Fi
To connect the thermostat to Wi-Fi:
- Press and hold the Mode button on the thermostat for four seconds.
- Wait for the setup and Wi-Fi icons to appear.
- In the Sensi app, select the home Wi-Fi network.
- Enter the Wi-Fi password.
- Name the thermostat.
- Register the thermostat using the Locate Me option or by manually entering the address, city, state, ZIP code, country, and time zone.
- Add contractor information if available.
- Tap Start Using Sensi to open the app’s main screen.
The thermostat only works with 2.4GHz Wi-Fi. Users should check router settings if the network does not appear.
HVAC Configuration Menu
The manual includes a configuration reference for checking HVAC setup. This is useful if the system does not operate correctly after installation.
| Menu Item | Description | Options |
| Outdoor Equipment | Select AC or heat pump equipment | AC, HP, — |
| Indoor Equipment | Select gas furnace, electric furnace, or fan-only setup | GA, FN, EL |
| Reversing Valve or Multistage Position | Configure O/B, second-stage heating/cooling, or 3-wire zone hydronic setup | O, B, 2H, 2C, 6, — |
| Multistage Equipment | Select second-stage heating/cooling or zone setup | 2H, 2C, 6, — |
For heat pump systems, the reversing valve must be configured as O or B depending on the system. Some manufacturers, such as Rheem or Ruud, may use the B terminal.
Supported System Types
The wiring diagrams in the manual cover two main categories:
Conventional Single-Stage or Multi-Stage Systems
These systems may include:
| Connection Type | Function |
| First-stage heat | Heating control |
| First-stage cool | Cooling control |
| Indoor blower/fan | Fan operation |
| Common wire | 24V common connection |
| 24VAC power | HVAC system power |
| Second-stage heat/cool | Multi-stage system support |
The manual notes that the system can support multi-stage heating or multi-stage cooling, but not both at the same time.
Heat Pump Systems
Heat pump configurations may include:
| Connection Type | Function |
| Reversing valve | Heat pump changeover |
| Compressor | First-stage heat and cool |
| Auxiliary/emergency heat | Backup heating |
| Indoor blower | Fan control |
| Common wire | 24V common connection |
| 24VAC power | HVAC system power |
A common wire is required on heat-only, cool-only, or heat pump systems.
Installing Multiple Sensi Thermostats
To install more than one thermostat, follow the same process in the Sensi app.
After installing the first thermostat:
- Open the Sensi app.
- Go to the main screen.
- Tap the plus (+) sign.
- Add the next thermostat to the same account.
There is no stated limit on how many devices can access the thermostat when logged into the same Sensi account.
Accessing the Thermostat from Other Devices
Any device logged into the same Sensi account can control thermostats registered to that account.
This means users should be careful when sharing their Sensi email and password. Anyone with access to the account can control all thermostats connected to it. Account email and password settings can be changed inside the app.
Troubleshooting Guide
Heating or Cooling Is Not Turning On
If heating or cooling does not start, check the following:
| Problem Area | What to Check |
| HVAC power | Make sure the system has power |
| Control board | Check for error codes |
| Breakers | Reset breakers if needed |
| Furnace/air handler doors | Make sure panels are closed and secured |
| Wire connections | Confirm wires are seated tightly |
| Thermostat wiring | Follow the Sensi app wiring instructions |
| HVAC equipment | Reinstall the original thermostat to test whether the issue is with the system |
If the original thermostat also does not turn on heating or cooling, the HVAC system may need professional service.
Thermostat Screen Is Not Turning On
If the screen does not turn on after installation, the batteries may not be installed correctly. Remove and reinstall the two AAA batteries, making sure the polarity is correct.
Wi-Fi Connection Problems
If the thermostat does not connect to Wi-Fi:
- Make sure the Sensi app is updated.
- Restart the smartphone or tablet.
- Reboot the router by unplugging it for a few minutes.
- Make sure Bluetooth is enabled on the phone.
- Allow Bluetooth access for the Sensi app.
- Turn on Location access in phone settings.
- Allow Location access for the Sensi app.
- Try another phone or tablet.
- Confirm the network is 2.4GHz.
Reconnecting After Router or Password Changes
If the router is replaced or the Wi-Fi password changes, the thermostat must be reconnected to Wi-Fi. The process may vary depending on the smart device being used. The manual points users to Sensi’s support article for reconnecting the thermostat.
Maintenance and Account Tips
The installation guide does not include routine cleaning instructions, but it does provide important account and access guidance.
| Task | How to Manage It |
| Change email preferences | Use the Account area in the app |
| Change account email | Use app account settings |
| Reset forgotten password | Tap Forgot Password on login screen |
| Add another thermostat | Tap + on the app main screen |
| Allow another device access | Log in using the same Sensi account |
For iOS, account settings are accessed by tapping the person icon in the upper-right corner. For Android, tap the three dots in the upper-right corner.
Technical Support and Customer Help
For installation problems, setup questions, Wi-Fi issues, or thermostat troubleshooting, users can visit the Sensi support site.
Support Website: https://sensi.copeland.com/en-us/support
Phone Support: (888) 605-7131