Touch 2 Smart Thermostat ST76

Sensi Touch 2 Smart Thermostat 1F96U 

The Sensi Touch 2 Smart Thermostat is a Wi-Fi-enabled thermostat installed and configured through the Sensi app. This installation guide applies to the 1F96U-42WF series and ST76 series and covers the complete process for replacing an existing thermostat, identifying HVAC wiring, mounting the Sensi base, connecting the thermostat, setting up Wi-Fi and checking system configuration.      

A key installation requirement is a C-wire. Unlike some thermostats that can operate without one, the Sensi Touch 2 requires a C-wire to provide continuous power. The guide states that a missing or incorrectly connected C-wire can cause the touchscreen to remain blank or repeatedly flash.      

The thermostat connects through a 2.4GHz Wi-Fi network and uses Bluetooth during the initial app-assisted connection process.      

Installation Requirements

Before installation, the official guide recommends having the following ready:

Download the Sensi App

The Sensi app is required to install and configure the thermostat correctly.

To begin:

1. Download the Sensi app to a compatible smartphone or tablet.
2. Open the app.
3. Create an account using a valid email address.
4. Choose and save a password.
5. Use that account during thermostat registration.

Once registered, the thermostat is associated with the email address used for the Sensi account. The account is also required for remote thermostat access and Sensi features.   

Add the Sensi Touch 2 to the App

After signing in:

1. Tap the plus (+) sign if no thermostats are registered.
2. Select the thermostat being installed.
3. Choose Sensi Touch 2 Smart Thermostat.

The Touch 2 option covers:

• 1F96U-42WF series
• ST76 series

The model number can be found on the back of the thermostat cover.   

Choose the Correct Installation Path

The Sensi app asks whether the thermostat is already mounted.

Not Mounted

The Not Mounted option is intended for a full DIY installation. It walks the installer through:

• Identifying the wires on the old thermostat
• Labeling the wires
• Connecting them to the Sensi Touch 2
• Checking HVAC configuration
• Connecting the thermostat to Wi-Fi

The official guide recommends choosing Not Mounted for DIY installations.   

Is Currently Mounted

Choose Is Currently Mounted when a professional has already installed the thermostat on the wall.

This path verifies the existing wiring, confirms the HVAC system type and then continues with Wi-Fi configuration.   

Important C-Wire Requirement

The Sensi Touch 2 requires a C-wire.   

The C-wire provides continuous power to the thermostat. If the C-wire is missing, loose or not connected correctly at the HVAC control board, the touchscreen may:

• Stay blank
• Flash instead of remaining on
• Fail to start after installation

The troubleshooting section states that the thermostat will not operate normally without adequate power from the C-wire.   

Turn Off HVAC Power Before Installation

Before handling thermostat wiring, turn off power to the heating and air-conditioning system.   

This should be done before removing the existing thermostat cover or disconnecting any wires.

Remove the Old Thermostat

Remove the Existing Cover

Depending on the previous thermostat, the cover may:

• Pull straight off
• Release using a pressure latch
• Require a screwdriver

The cover should be removed carefully without disturbing the wiring.   

Photograph the Existing Wiring

Before disconnecting anything, take a clear photo of the existing thermostat wiring.

The Sensi app prompts the installer to do this, and the photo is saved to the phone’s camera roll or gallery. The image can be useful later during troubleshooting or when speaking with technical support.   

Remove Old Jumper Wires

The Sensi thermostat has a built-in jumper, so jumper wires from the previous thermostat are not required.

Remove old jumper wires rather than transferring them to the Sensi Touch 2.   

Identify the Existing Wire Terminals

In the Sensi app, select the terminal labels that currently have wires attached to them.

The app checks the configuration and indicates whether the identified wiring is valid.   

If the app reports an invalid configuration, the official guide directs users to Sensi’s system compatibility information.

Select the Furnace Type

The app also asks for the type of heating system being connected.

Select the applicable furnace or heating source so the thermostat can be configured correctly for the HVAC equipment.   

Label the Existing Thermostat Wires

Before disconnecting each wire:

1. Use the provided wire labels.
2. Label one wire at a time according to its existing thermostat terminal.
3. Verify the label before disconnecting the wire.
4. Continue until every connected wire has been identified.

After all wires have been labeled, remove the old thermostat base from the wall.   

Install the Sensi Touch 2 Base

Use the provided mounting screws to secure the new thermostat base to the wall.   

The base should be mounted before connecting the thermostat wires.

Connect the Wires

For a new installation:

1. Match each labeled wire to the corresponding Sensi terminal.
2. Push the wire into the correct terminal slot.
3. Make sure it is seated securely.
4. Repeat for every required wire.   

Unlike the screw-terminal installation described for some other Sensi models, the Touch 2 uses terminal slots into which the wires are pushed.

Attach the Thermostat Cover

Once all wires are connected, push the Sensi Touch 2 thermostat cover onto the mounted base.   

Restore power to the HVAC system after the cover is attached.

Checking an Already-Mounted Sensi Touch 2

When the thermostat has already been professionally mounted, use the Is Currently Mounted setup path.

The official procedure is:

1. Turn off HVAC power.
2. Hold the thermostat with both hands.
3. Pull it straight forward to detach the touchscreen cover from the base.
4. Identify which terminals have wires connected.
5. Confirm that a C-wire is installed.
6. Select the furnace type in the app.
7. Push the thermostat cover back onto the base.
8. Restore HVAC power.   

Wiring Terminal Guide

The conventional and heat-pump diagrams on page 12 show the main Sensi Touch 2 thermostat terminals:

The diagrams on page 12 show separate conventional and heat-pump configurations and also identify different functions for some terminals based on system type.      

Conventional HVAC System Wiring

For conventional systems without a heat pump, the page 12 diagram covers both single-stage and multi-stage equipment.   

Single-Stage Configuration

The diagram lists the following single-stage configuration options:

• AC1
• GA1
• EL1

In this setup, the thermostat can use separate RC and RH power connections, C common, first-stage cooling, fan and first-stage heating.   

Multi-Stage Configuration

The conventional multi-stage configuration includes:

• AC2
• GA2
• EL2

The wiring diagram provides terminals for second-stage cooling and second-stage heating.   

RC and RH Jumper for Two-Transformer Systems

The diagram includes an internal jumper between RC and RH on the back of the thermostat.

For systems using separate RC and RH wires from two transformers, the manual instructs the installer to clip the internal RC/RH jumper.   

Heat Pump Wiring

The heat-pump diagram on page 12 covers both:

• HP1 — single-stage heat pump
• HP2 — multi-stage heat pump   

The diagram identifies:

• Y for first-stage compressor
• Y2/* for second-stage compressor on applicable systems
• O/B for the reversing valve
• G for the indoor fan
• W/E and W2/* for auxiliary/emergency heat functions
• C for common power

The exact use of W/E and W2/* changes according to whether the system is HP1 or HP2.   

HVAC Configuration Menu

The thermostat configuration reference on page 10 provides settings for outdoor equipment, indoor equipment, reversing-valve behavior and wired accessories.   

Outdoor Equipment Settings

The Outdoor Equipment setting identifies both the equipment type and number of stages.

According to the guide:

• AC1 — single-stage air-conditioning system
• AC2 — two-stage air-conditioning system
• HP1 — single-stage heat pump
• HP2 — multi-stage heat pump
• None — no applicable outdoor equipment selection   

Indoor Equipment Settings

The guide provides the following indoor-equipment options:

• GA1 — single-stage gas
• GA2 — multi-stage gas
• EL1 — single-stage electric
• EL2 — multi-stage electric
• Fan — fan-only equipment   

Reversing Valve Settings

The configuration menu includes:

• O
• B
• 6
• None

When configured as O, the reversing valve is energized during cooling, which the guide says covers most applications.

Some manufacturers, including Rheem or Ruud, may use B, which energizes the reversing valve during heating.   

The guide also discusses configuration for three-wire hydronic zone systems in this setting.   

Humidifier and Dehumidifier Configuration

The HVAC configuration menu supports wired accessory settings for a:

• Humidifier
• Dehumidifier

If one of these devices is wired to the thermostat, set its corresponding configuration option to Yes.   

Accessory Device Wiring

Page 13 includes diagrams for both two-wire and one-wire accessory devices.   

Two-Wire Accessory

For a two-wire accessory:

• The accessory has its own power source.
• The thermostat is used to switch the accessory on.
• The switch on the back of the thermostat should be set to Accessory.   

One-Wire Accessory

For a one-wire accessory:

• The accessory pulls power from the HVAC system.
• The switch on the back of the thermostat should be set to System.   

How to Connect the Sensi Touch 2 to Wi-Fi

After the thermostat has been installed and HVAC power restored, Wi-Fi setup can begin.

Open Wi-Fi Setup on the Thermostat

On the thermostat touchscreen:

1. Tap Menu in the upper-left corner.
2. Select Wi-Fi.
3. Tap Connect.   

Scan the QR Code

The Sensi Touch 2 displays a QR code during setup.

In the Sensi app:

1. Scan the QR code shown on the thermostat screen.
2. Allow Bluetooth access when prompted.
3. Continue through the connection process.   

If the QR Code Will Not Scan

Select Use Security PIN in the app and manually enter the code displayed on the thermostat touchscreen.   

Connect to the Home Wi-Fi Network

From the available network list:

1. Select the home Wi-Fi network.
2. Enter the Wi-Fi password.
3. Continue with the app prompts.   

The Sensi Touch 2 installation process requires a 2.4GHz network. If the network does not appear, the guide states that it may be hidden or incompatible with Sensi.   

Name the Thermostat

After connecting to Wi-Fi, select a suggested thermostat name or create a custom one.

Tap Next to continue.   

Register the Thermostat

The app then asks the user to register the Sensi Touch 2.

Registration can use:

• Locate Me, or
• Manual entry of street address, city, state, ZIP code, country and time zone.   

If a registered Sensi contractor installed the thermostat, contractor information can optionally be entered before completing setup.   

Tap Start Using Sensi when setup is complete.

Troubleshooting: Heating or Cooling Does Not Turn On

If the HVAC system does not start after installation, the official guide recommends checking the following:

1. Make sure the HVAC system has power.
2. Look for an error code on the HVAC control board.
3. Reset the breakers.
4. Make sure furnace or air-handler access panels are closed and secured.
5. Check each thermostat wire for a secure connection.
6. Make sure the wires are pushed fully into the Sensi terminal block.
7. Confirm that the thermostat was wired according to the Sensi app.   

A wire should not pull free when gently tugged. If a connection seems loose, press the terminal paddle, remove the wire and insert it again securely.   

If the HVAC control board shows an error or the system has no power, the guide recommends contacting an HVAC professional.   

Test With the Original Thermostat

As a troubleshooting step, the original thermostat can be reinstalled.

If heating or cooling still fails with the previous thermostat, the problem may be with the HVAC equipment rather than the Sensi Touch 2. Professional service may then be required.   

Troubleshooting a Blank or Flashing Display

A blank or repeatedly flashing touchscreen usually indicates that the thermostat is not receiving enough power.   

The Sensi Touch 2 requires a C-wire.

No Wire Connected to C

If there is no wire in the thermostat’s C terminal, the guide directs DIY installers to Sensi’s C-wire installation resources.

For some heat-only systems, an external transformer may be an option.   

C-Wire Is Installed but Screen Is Still Blank

If a C-wire is already connected:

1. Check that the wire connects to C at the thermostat.
2. Trace the same wire to the HVAC control board.
3. Confirm that it is securely connected to the C terminal at the system control board.
4. Gently tug the C-wire at the HVAC board to verify that it is secured.
5. Gently check all thermostat wires for secure connections.
6. Confirm that HVAC breakers are on.   

C-Wire Voltage Check

If a voltmeter is available, the guide instructs the installer to set it to AC and measure between:

RH or RC and C

The expected reading is:

20–30VAC

If voltage is below 20VAC, the thermostat will not turn on.   

Troubleshooting Wi-Fi Connection Problems

If the Sensi Touch 2 will not connect to Wi-Fi:

1. Make sure the Sensi app is updated.
2. Restart the smartphone.
3. Reboot the router by unplugging it for a few minutes and reconnecting it.
4. Make sure Bluetooth is enabled.
5. Allow Bluetooth access for the Sensi app.
6. Make sure Location access is enabled.
7. Allow Location access for the Sensi app.
8. Try another smartphone or tablet if necessary.
9. Sign in on the second device using the same Sensi account credentials.   

Also confirm that the network being selected is 2.4GHz.   

Reconnecting After a Router or Password Change

If the home router is replaced or the Wi-Fi password changes, the thermostat must be connected to Wi-Fi again.

The official guide notes that the exact reconnection procedure varies according to the smart device being used.   

Accessing Sensi Touch 2 From Multiple Devices

A thermostat registered to a Sensi account can be controlled from other phones or tablets by signing into the same account.

The guide states that there is no limit to the number of devices that can access thermostats registered to the account.   

Anyone who is given the account email address and password can access thermostats registered to that account, so account credentials should be shared carefully.   

Forgot Sensi Account Password

From the Sensi login screen:

1. Tap Forgot Password.
2. A temporary password is sent to the email address used for the account.   

Installing Multiple Sensi Thermostats

To add another thermostat after the first one has been installed:

1. Open the Sensi app.
2. Go to the main screen.
3. Tap the + sign.
4. Follow the normal installation process for the additional thermostat.   

Managing Account Information

The Account section of the Sensi app can be used to manage email preferences and update account information.

According to the guide:

• iOS: Tap the person icon in the upper-right corner.
• Android: Tap the three dots in the upper-right corner.   

Technical Support

For installation problems or help using Sensi features, the official installation guide provides:

Support Website: sensihelp.com
Technical Support Phone: (888) 605-7131   

Frequently Asked Questions

Does the Sensi Touch 2 require a C-wire?

Yes. The official guide states that the Sensi Touch 2 requires a C-wire. The C-wire powers the thermostat, and the touchscreen may stay blank or flash if the thermostat does not receive sufficient power.      

Does the Sensi Touch 2 work with 5GHz Wi-Fi?

The installation guide specifies a 2.4GHz Wi-Fi network. If the network does not appear during setup, the guide says it may be hidden or incompatible with Sensi.   

How do you put the Sensi Touch 2 into Wi-Fi setup mode?

On the touchscreen, tap Menu, select Wi-Fi, and then tap Connect. The app then scans the QR code displayed on the thermostat to continue setup.   

Why is the Sensi Touch 2 screen blank after installation?

A blank or flashing screen usually means the thermostat is not receiving enough power. Check the C-wire at both the thermostat and HVAC control board, verify the breakers are on and, if a voltmeter is available, check for 20–30VAC between RH/RC and C.   

Why is the heating or cooling not turning on after installing the Sensi Touch 2?

Check HVAC power, breakers, furnace or air-handler panels, thermostat wiring and the system configuration in the Sensi app. If the system also fails with the previous thermostat, the official guide recommends professional HVAC service.   

How do you connect another phone to the Sensi Touch 2?

Install the Sensi app on the additional device and sign in with the same account email address and password. All thermostats registered to that account become accessible, and the guide states that there is no limit to the number of devices that can access them.   

How do you add another Sensi thermostat to the same account?

Open the Sensi app’s main screen, tap the + sign, and follow the installation process for the next thermostat.