The Sensi Smart Thermostat is a Wi-Fi-enabled thermostat designed to help users control their heating and cooling system through the Sensi mobile app. This installation guide applies to Sensi Smart Thermostat models 1F87U-42WF and ST55.
The thermostat setup is handled through the Sensi app, which guides users through installation, wiring, HVAC system selection, Wi-Fi setup, thermostat registration, and account access. The guide is useful for both DIY users and homeowners whose thermostat was already installed by a professional.
Supported Models
| Product | Model |
| Sensi Smart Thermostat | 1F87U-42WF |
| Sensi Smart Thermostat | ST55 |
The model number can be found on the back of the thermostat cover.
What You Need Before Installation
Before starting the installation, prepare the following:
| Requirement | Purpose |
| 2.4GHz Wi-Fi network name/SSID | Required for Wi-Fi connection |
| Wi-Fi password | Needed during app setup |
| Screwdriver | Used to remove the old thermostat and secure wiring |
| Included Sensi hardware | Used to mount and install the thermostat |
| Sensi app | Required for guided setup and configuration |
The thermostat must be connected to a 2.4GHz Wi-Fi network. The app-based installation may not work properly if the home network is hidden, incompatible, or using the wrong band.
Downloading the Sensi App
The Sensi Smart Thermostat must be installed and configured using the Sensi app. The app is free and available for smartphones and tablets through the App Store and Google Play.
To begin:
- Download the Sensi app.
- Open the app.
- Create a Sensi account.
- Use a valid email address and password.
- Keep the login details safe, because the thermostat will be linked to this account after registration.
The manual notes that the “Install a device” option is only for HomeKit installation. Users may lose available features if they do not create a Sensi account.
Creating a Sensi Account
A Sensi account is required to access the thermostat remotely and use Sensi features. After downloading the app, users are prompted to create an account with an email address and password.
If the password is forgotten later, tap Forgot Password on the Sensi app login screen. A temporary password will be sent to the email address used for the account.
Parts and Key Components
The manual focuses on installation and wiring rather than a full product parts diagram. However, the setup process references these important components:
| Component | Function |
| Thermostat cover/front display | Main thermostat control and display area |
| Thermostat base/sub-base | Mounts to the wall and holds wiring terminals |
| Wire terminals | Connect HVAC system wires |
| Built-in jumper | Replaces old jumper wires from the previous thermostat |
| RC/RH internal jumper | Used for transformer wiring; may need clipping on two-transformer systems |
| Mounting screws | Secure the thermostat base to the wall |
| Menu button | Used during Wi-Fi setup |
| Mode button | Used to start Wi-Fi setup |
| L terminal | Heat pump L terminal connection |
| Y2/W2 terminals | Used for second-stage cooling/heating or accessories depending on setup |
The wiring diagram on page 10 shows the terminal layout for conventional and heat pump systems.
How to Install the Sensi Smart Thermostat
Step 1: Add the Thermostat to the Sensi App
Once the Sensi app is downloaded and the account is created:
- Open the Sensi app.
- Tap the plus (+) sign.
- Choose the Sensi Smart Thermostat option.
- Select the correct model series.
The app will then begin the guided installation process.
Step 2: Choose Installation Type
The app asks whether the thermostat is already mounted on the wall.
Not Mounted
Choose Not Mounted for a DIY installation. This path walks through the complete setup process, including wire identification, wire labeling, wiring, HVAC configuration, and Wi-Fi connection.
The manual recommends this option for DIY users because it helps make sure the thermostat is wired and configured correctly.
Is Currently Mounted
Choose Is Currently Mounted if a professional technician already installed the thermostat. This option asks users to identify the wires already connected to the Sensi base, confirm system settings, and continue to Wi-Fi setup.
Step 3: Remove the Old Thermostat
Before handling thermostat wires, turn off power to the heating and air conditioning system.
Then follow these steps:
- Gather the required tools and package contents.
- Turn off HVAC power.
- Remove the old thermostat cover.
- Take a clear photo of the old wiring.
- Throw away old jumper wires.
- Select the wire terminals that had wires attached on the old thermostat.
- Let the app confirm whether the wiring configuration is valid.
- Select the furnace type.
- Label each wire using the provided wire stickers.
- Disconnect the wires.
- Remove the old thermostat base from the wall.
The wiring photo is important because it can help if troubleshooting or support is needed later.
Step 4: Secure the Sensi Base to the Wall
After removing the old thermostat base, install the new Sensi base.
Use the provided mounting screws to secure the base to the wall. Make sure the base is positioned correctly, the wires are accessible, and the wire labels are still visible before connecting them.
Step 5a: Connect Wiring for a New Installation
For a Not Mounted installation:
- Insert each labeled wire into the correct terminal.
- Push the wire into the terminal slot.
- Use a screwdriver to secure each wire.
- Push the front display onto the thermostat base.
- Turn system power back on.
The manual explains that Sensi has a built-in jumper, so old jumper wires from the previous thermostat are not needed.
Step 5b: Setup for an Already Mounted Thermostat
For an Is Currently Mounted setup:
- Turn off power to the heating and cooling system.
- Pull the thermostat cover straight toward you with both hands.
- Identify which terminal labels have wires attached.
- Select the furnace type.
- Push the thermostat cover back onto the base.
- Turn system power back on.
This setup path helps confirm that the thermostat is configured correctly for the HVAC system type.
Step 6: Connect the Sensi Smart Thermostat to Wi-Fi
After wiring and installation, connect the thermostat to Wi-Fi.
On the thermostat:
- Press Menu.
- Press Mode.
- Wait for the Wi-Fi icon in the upper-left corner to flash.
- Look for the display code in the middle of the thermostat.
The thermostat may show 00, 11, or 22. This code identifies the Sensi version and helps the app guide the correct connection process.
Then follow the Sensi app instructions to connect the thermostat to the home Wi-Fi network. The Wi-Fi setup process may vary based on the phone operating system, Sensi app version, and thermostat version.
For iPhone users, the manual notes that HomeKit-related errors may require checking Sensi app permissions and allowing access to Home Data.
Naming and Registering the Thermostat
After the thermostat connects to Wi-Fi, the app prompts users to name and register it.
Registration may include:
| Information | Purpose |
| Thermostat name | Helps identify the device in the app |
| Street address | Used for thermostat location |
| City, state, ZIP code | Helps complete registration |
| Country | Location setting |
| Time zone | Used for correct scheduling and time display |
| Contractor information | Optional, if a Sensi partner installed the thermostat |
Users can choose Locate Me or manually enter the address information. After setup, tap Start Using Sensi to open the app’s main screen.
HVAC Configuration Menu
The Sensi Smart Thermostat includes a physical thermostat configuration menu for checking or adjusting HVAC settings.
| Display Code / Menu Item | Default | Options |
| Wireless Setup | — | Connect |
| Fahrenheit or Celsius | F | F, C |
| Outdoor Equipment Configuration | AC2 | AC1, AC2, HP1, HP2, AC0 |
| Indoor Equipment Configuration | EL2 | EL1, EL2, GA1, GA2, Fan |
| Reversing Valve Position | O | O, B |
| Circulating Fan | OFF | Off, 10%–100% in 5% increments |
| Humidification Add Accessory | OFF | Off, On |
| Humidification Set Point | OFF | Off, 5%–50% in 5% increments |
| Dehumidification Add Accessory | Od | Od, Oc |
| Dehumidification Set Point | OFF | Off, 40%–95% in 5% increments |
| Wireless Radio | ON | Off, On |
For heat pumps, the reversing valve can be set to O or B. The O setting is commonly used when the reversing valve energizes in cooling, while B is used by some systems that energize in heating.
Supported HVAC System Types
Conventional Single-Stage and Multi-Stage Systems
The wiring diagram on page 10 covers conventional systems without a heat pump.
| Terminal | Function |
| RC | Power for cooling, 24V |
| RH | Power for heating, 24V |
| C | Common wire, 24V |
| Y | First-stage cooling |
| Y2 | Second-stage cooling or humidifier if configured |
| W/E | First-stage heat |
| W2 | Second-stage heat or dehumidifier if configured |
| G | Indoor blower fan |
| O/B | Heat pump changeover, zone panel, or 3-wire hot water zone valve connection |
| L | Heat pump L terminal connection |
For two-transformer systems with separate RC and RH wires, the internal RC/RH jumper on the back of the thermostat should be clipped.
Heat Pump Systems
The heat pump wiring diagram on page 10 covers single-stage and multi-stage heat pump systems.
| Terminal | Function |
| RC | Power for cooling, 24V |
| RH | Power for heating, 24V |
| C | Common wire, 24V |
| Y | First-stage heat and cool compressor |
| Y2 | Second-stage heat and cool compressor |
| W/E | First-stage auxiliary/emergency heat |
| W2 | Additional auxiliary/emergency heat or dehumidifier depending on setup |
| G | Indoor blower fan |
| O/B | Heat pump reversing valve |
| L | Heat pump L terminal connection |
The thermostat includes an internal jumper between RC and RH on the back of the unit.
Wi-Fi Troubleshooting
If the thermostat does not connect to Wi-Fi, try the following:
| Issue | Recommended Fix |
| Sensi app is outdated | Update the app from the app store |
| Phone issue | Reboot the smartphone |
| Router issue | Unplug the router for a few minutes, then plug it back in |
| iPhone permission issue | Turn on Keychain and allow Home Data |
| Location issue | Turn on Location services |
| App permissions issue | Allow Location and Nearby Devices |
| Android network switching | Turn off “Switch to mobile data,” “Smart Network Switch,” or “Avoid poor connections” |
| Setup instability | Turn off mobile data during setup |
| Device-specific issue | Try another smartphone or tablet |
The thermostat setup may fail if the phone disconnects from Wi-Fi during installation, especially on Android devices that automatically switch to mobile data.
Reconnecting to Wi-Fi
If the router is replaced or the Wi-Fi password changes, the thermostat must be reconnected to Wi-Fi.
The reconnection process depends on the smart device being used. The manual directs users to Sensi’s reconnection support article for detailed steps.
Heating or Cooling Troubleshooting
If the system does not heat or cool correctly, check the HVAC configuration menu on the thermostat.
Common causes include:
| Possible Cause | What to Check |
| Incorrect outdoor equipment setting | Confirm AC or heat pump configuration |
| Incorrect indoor equipment setting | Confirm gas, electric, or fan setup |
| Wrong reversing valve setting | Check O/B heat pump setting |
| Loose wiring | Confirm all wires are secure |
| Wrong terminal selection | Compare wiring with the app and old wiring photo |
| Accessory misconfiguration | Check humidifier/dehumidifier settings |
| Power issue | Confirm HVAC power and breakers |
The app and physical thermostat configuration menu should match the actual HVAC system.
Accessing the Thermostat from Other Devices
Any device logged into the same Sensi account can control all thermostats registered to that account.
The manual warns users to be careful when sharing the Sensi account email and password. Anyone with those login details can access and control registered thermostats. There is no stated limit to the number of devices that can access the thermostat.
Installing Multiple Sensi Smart Thermostats
To install more than one thermostat:
- Install the first thermostat using the Sensi app.
- Open the app main screen.
- Tap the plus (+) sign.
- Add the next thermostat.
- Repeat the installation process.
Each thermostat should be added and registered separately.
Account Settings and Password Help
Users can access account settings inside the Sensi app to update email preferences, account details, and the email address connected to the thermostat.
| Device | How to Access Account Area |
| iOS | Tap the person icon in the upper-right corner |
| Android | Tap the three dots in the upper-right corner |
For a forgotten password, tap Forgot Password on the login screen. A temporary password will be sent to the registered email address.
Technical Support
For installation problems, setup issues, Wi-Fi connection problems, and thermostat feature help, users can contact Sensi support.
| Support Option | Details |
| Support website | sensihelp.com |
| Phone support | (888) 605-7131 |
| Compatibility help | sensi.copeland.com/en-us/compatibility |
| Wi-Fi reconnection support | sensi.copeland.com/en-us/support/reconnecting-sensi-thermostat-to-wifi |