T4 Pro TH4110U2005

Honeywell Home T4 Pro TH4110U2005

The Honeywell Home T4 Pro is a programmable digital thermostat designed to control compatible heating and cooling systems. It provides automatic temperature scheduling, manual temperature adjustments, heating and cooling modes, fan settings, and a digital display showing indoor temperature and system operating information.

The T4 Pro thermostat supports four programmable periods per day: Wake, Away, Home, and Sleep. Different temperature schedules can be configured for weekdays and weekends, allowing heating and cooling settings to change automatically according to the selected schedule.

The thermostat includes temporary and permanent temperature holds, keypad locking, adjustable display backlight brightness, Adaptive Intelligent Recovery, and built-in compressor protection.

Two models are covered:

• TH4110U2005: Provides heating and cooling control according to the connected system and installer configuration.
• TH4210U2002: Includes additional support for auxiliary and emergency heating functions on compatible systems.

The T4 Pro can operate using two AA batteries or compatible AC power supplied through the thermostat wiring. When a C-wire provides power, batteries are optional for backup. When AC power is not connected, batteries are required.

The thermostat also provides maintenance alerts, including low-battery warnings and air filter replacement reminders.

Product Overview and Features

Supported Models and Differences

TH4110U2005

The TH4110U2005 provides programmable heating and cooling control, fan operation, scheduling, temporary and permanent holds, and supported thermostat settings.

TH4210U2002

The TH4210U2002 includes the same general thermostat controls, with additional functions for compatible heating systems.

These include:

• Emergency Heat mode
• Auxiliary heating control
• Emergency heating terminal
• Additional heating-stage terminal

Available operating modes depend on the connected equipment and installer settings.

What’s Included in the Box

The Honeywell Home T4 Pro package includes the following components.

The UWP mounting system holds the thermostat on the wall.

The decorative cover plate and mounting hardware are supplied for the installation arrangement.

Technical Specifications

General Specifications

Electrical Ratings

The T4 Pro electrical ratings are specified for the thermostat terminals.

The W2 and E terminals apply specifically to the TH4210U model.

Thermostat Parts and Controls

The T4 Pro includes a digital display and five control buttons positioned beneath the screen.

Main Components

Five-Button Control Layout

The thermostat uses five physical buttons.

From left to right:

1. Minus (–)
2. Mode
3. Menu
4. Fan
5. Plus (+)

The functions displayed above these buttons can change when a settings menu is open.

Mode Button

The Mode button cycles through available heating and cooling operating modes.

Menu Button

The Menu button opens thermostat settings.

It provides access to time, date, program schedules, keypad locking, display brightness, and alerts.

Fan Button

The Fan button changes the fan operating setting.

Plus and Minus Buttons

The + and – buttons adjust the selected temperature.

They are also used to move through menu options and change values.

Thermostat Display Guide

The digital screen displays the information required for thermostat operation.

Display Indicators and Messages

Actual Indoor Temperature

The large temperature reading shows the measured indoor temperature during normal operation.

Temperature Setpoint

The setpoint represents the desired heating or cooling temperature.

Press + or – to change the selected setpoint.

System Status

The thermostat displays heating, cooling, emergency heat, or compressor protection information when the corresponding function is active.

Schedule Information

When the thermostat is operating according to the programmed schedule, the display indicates that it is following the time-based schedule.

Display Backlight Operation

The T4 Pro display wakes when any of its five buttons is pressed.

The illumination duration depends on how the thermostat is powered.

Display Backlight Duration

How to Wake the Display

Press any thermostat button.

The display illuminates and shows the current operating information.

Important Safety Instructions

Electrical Hazard Warning

CAUTION: ELECTRICAL HAZARD

Electrical connections can cause shock or damage to heating and cooling equipment.

Disconnect electrical power before beginning installation.

Compressor Damage Warning

CAUTION: EQUIPMENT DAMAGE HAZARD

Compressor protection is bypassed during testing.

Avoid repeatedly starting and stopping the compressor in quick succession during equipment testing.

Rapid cycling can damage the compressor.

Mercury Disposal Warning

If the T4 Pro replaces an older thermostat containing mercury inside a sealed tube, do not place the old thermostat in household trash.

Contact the local waste management authority for instructions on proper recycling and disposal.

Electronic Waste Disposal

The T4 Pro must not be discarded with ordinary household waste at the end of its service life.

Take the product to an authorized electronic waste collection or recycling facility.

Before First Use

After the T4 Pro has been installed and connected to the heating or cooling system, the initial operating settings should be configured.

Initial Setup

1. Confirm that the thermostat is receiving power.
2. Check that the digital display operates.
3. Select the required system mode.
4. Choose the fan operating mode.
5. Set the current time.
6. Set the date.
7. Review the programmed temperature schedule.
8. Adjust the schedule if needed.
9. Save the settings.

The available system modes depend on the thermostat model and installer configuration.

Setting the Heating or Cooling Mode

The Mode button selects the system operating mode.

How to Change the System Mode

1. Press Mode.
2. The thermostat displays the next available mode.
3. Continue pressing Mode to cycle through the available settings.
4. Stop when the required mode appears.
5. Leave the displayed mode to activate it.

Available System Modes

How to Turn On Heating

1. Press Mode until Heat appears.
2. Use + or – to select the desired temperature.
3. Set the temperature above the current room temperature when heating is needed.
4. The display shows Heat On when heating operates.

How to Turn On Cooling

1. Press Mode until Cool appears.
2. Use + or – to select the desired temperature.
3. Set the temperature below the current indoor temperature when cooling is needed.
4. The display shows Cool On when cooling operates.

How to Turn Off Heating and Cooling

Press Mode until Off appears.

The thermostat stops normal heating and cooling operation.

Emergency Heat Mode – TH4210U2002

The TH4210U2002 supports Em Heat mode when connected to a compatible system.

To select it:

1. Press Mode.
2. Continue until Em Heat appears.
3. Leave the setting displayed to activate it.

Emergency heating operation is indicated by Em Heat On when active.

Selecting the Fan Mode

The Fan button controls the fan operating setting.

How to Change the Fan Setting

1. Press Fan.
2. The next available fan mode appears.
3. Continue pressing Fan until the required setting is displayed.
4. Leave the setting displayed to activate it.

Fan Modes

Auto Fan Mode

Select Auto when the fan should operate only during heating or cooling.

Continuous Fan Mode

Select On when continuous fan operation is required.

Available fan modes may vary depending on the connected equipment.

Setting the Time

The thermostat uses its clock to control scheduled temperature changes.

How to Set the Clock

1. Press Menu.
2. Use + or – to find TIME.
3. Press Select.
4. Choose a 12-hour or 24-hour clock format using + or –.
5. Press Select.
6. Adjust the hour using + or –.
7. Press Select.
8. Adjust the minutes using + or –.
9. Press Select to save and exit the Time menu.

Choosing 12-Hour or 24-Hour Time

Setting the Date

The thermostat allows the year, month, and date to be configured.

How to Set the Date

1. Press Menu if the Home screen is displayed.
2. Use + or – to find DATE.
3. Press Select.
4. Adjust the year using + or –.
5. Press Select.
6. Adjust the month.
7. Press Select.
8. Adjust the date.
9. Press Select to save and exit.

Understanding the Program Schedule

The T4 Pro supports four programmable temperature periods per day.

Different schedules can be configured for weekdays and weekends.

Daily Schedule Periods

Wake Period

Wake determines the temperature used during the morning after occupants wake up.

Away Period

Away sets the temperature for periods when the home is unoccupied.

This period can use energy-saving temperatures.

Home Period

Home controls the temperature during the evening when occupants return.

Sleep Period

Sleep controls the overnight temperature.

Factory-Programmed Heating and Cooling Schedule

The T4 Pro includes preset temperature settings.

Default Schedule

These settings can be changed according to household routines.

Heating Schedule

The factory heating temperatures are:

• Wake: 70°F
• Away: 62°F
• Home: 70°F
• Sleep: 62°F

Cooling Schedule

The factory cooling temperatures are:

• Wake: 78°F
• Away: 85°F
• Home: 78°F
• Sleep: 82°F

How to Program the Honeywell T4 Pro Thermostat

The T4 Pro allows scheduled start times and heating and cooling temperatures to be configured for selected days.

Step 1: Open the Programming Menu

1. Press Menu.
2. The display shows PROG.
3. Press Select.
4. The display shows ON.
5. Press Select to continue.

Step 2: Select the Day or Group of Days

1. Use + or – to select the day or group of days to edit.
2. Press Select.

The thermostat supports separate weekday and weekend settings.

Step 3: Select a Schedule Period

1. Use + or – to select a period.
2. Choose Wake, Away, Home, or Sleep.
3. Press Select.

Step 4: Enable or Disable the Period

The display shows ON.

Press Select to keep the selected period enabled.

To disable it:

1. Use + or – to change ON to OFF.
2. Press Select.

Step 5: Set the Start Time

1. The schedule start time begins flashing.
2. Press + or – to adjust the time.
3. Press Select.

Step 6: Set the Heating Temperature

1. The heating setpoint begins flashing.
2. Press + or – to select the desired Heat temperature.
3. Press Select.

Step 7: Set the Cooling Temperature

1. The cooling setpoint begins flashing.
2. Press + or – to adjust the Cool temperature.
3. Press Select.

Step 8: Program the Remaining Periods

Repeat the procedure for the remaining schedule periods.

Step 9: Save the Schedule

Press Home when programming is complete.

The thermostat saves the schedule and returns to the Home screen.

Turning the Program Schedule On or Off

The programmed schedule can be enabled or disabled.

How to Turn Off Scheduling

1. Press Menu.
2. Select PROG.
3. Press Select.
4. When ON appears, use + or – to select OFF.
5. Press Select.

How to Turn Scheduling Back On

1. Open Menu.
2. Select PROG.
3. Change the schedule setting to ON.
4. Press Select.
5. Return to the Home screen.

Temporarily Changing the Temperature

A temporary hold changes the temperature without permanently changing the programmed schedule.

How to Activate Temporary Hold

1. Press + or –.
2. Adjust the desired temperature.
3. Stop when the required setpoint appears.

No additional action is necessary.

The thermostat maintains the selected temperature until the next programmed period begins.

How Long Does Temporary Hold Last?

Temporary Hold remains active until the next scheduled period.

When that period begins, the thermostat resumes the programmed temperature.

How to Cancel Temporary Hold

1. Press + or –.
2. Select Cancel.

The thermostat returns to the programmed schedule.

Permanently Holding a Temperature

Permanent Hold allows the thermostat to maintain a manually selected temperature until the override is cancelled.

How to Activate Permanent Hold

1. Press + or – to change the temperature.
2. The display shows TEMPORARY HOLD.
3. The temperature setpoint begins flashing.
4. While the setpoint is flashing, press Hold, using the Mode button.
5. The thermostat changes to Permanent Hold.

How to Cancel Permanent Hold

1. Press + or –.
2. Select Cancel.

The thermostat resumes its programmed schedule.

Temporary Hold vs. Permanent Hold

Keypad Lock Settings

The T4 Pro includes a keypad lock function to restrict thermostat changes.

Available Lock Settings

How to Lock the Thermostat

1. Press Menu.
2. Use + or – to find LOCK.
3. Press Select.
4. Choose OFF, PART, or ON.
5. Press Select to save.

On some models, keypad lock settings are accessible only through the installer menu.

How to Unlock the Honeywell T4 Pro Thermostat

The T4 Pro uses the unlock password 1234.

Unlock Instructions

1. Press the center button.
2. The password entry screen appears.
3. Use + or – to set the first digit to 1.
4. Press Select.
5. Set the second digit to 2.
6. Press Select.
7. Set the third digit to 3.
8. Press Select.
9. Set the fourth digit to 4.
10. Press Select again.

The keypad unlocks when the correct password is entered.

If the Unlock Code Is Incorrect

The display flashes –.

Press Back to return to the previous digit.

Enter the correct number and press Select.

Adjusting the Display Backlight Brightness

The T4 Pro allows the idle display brightness to be adjusted when the thermostat is powered through the C-wire.

Backlight Brightness Levels

The available brightness settings range from 1 to 5.

How to Change the Backlight Brightness

1. Press Menu.
2. Use + or – to find LITE.
3. Press Select.
4. The current brightness setting appears.
5. Press + or – to select the desired level.
6. Press Select to save and exit.

The idle backlight function is available only when the C-wire is connected.

Adaptive Intelligent Recovery

Adaptive Intelligent Recovery allows the thermostat to begin heating or cooling before the scheduled start time.

The thermostat learns how long the connected system normally takes to reach the desired temperature.

How Adaptive Intelligent Recovery Works

Over time, the thermostat adjusts when heating or cooling begins.

For example, if the Wake period is scheduled to begin at 6:00 AM, the thermostat may start heating earlier so the selected temperature is reached by 6:00 AM.

Recovery Indicator

The display can show Recovery when the thermostat is operating according to this function.

Built-In Compressor Protection

The T4 Pro includes compressor protection to prevent damage caused by restarting a compressor too soon after shutdown.

How Compressor Protection Works

1. The compressor stops operating.
2. A new heating or cooling request occurs.
3. The thermostat delays compressor restarting.
4. Cool On or Heat On flashes.
5. The compressor remains off during the protection period.
6. The message stops flashing when restarting is permitted.

Why Is Cool On Flashing?

Flashing Cool On indicates that compressor protection is active.

The thermostat prevents the compressor from restarting immediately.

Wait approximately five minutes for the system to restart safely.

Why Is Heat On Flashing?

On compatible heat pump systems, Heat On may flash when compressor protection is active.

The compressor will resume operation after the safe restart period.

Battery Operation and Replacement

The T4 Pro uses two AA batteries.

Batteries are optional for backup power when the thermostat is connected to AC power.

If the thermostat does not have an AC power connection, batteries are required.

Battery Specifications

When to Replace the Batteries

Replace both batteries:

• When the low-battery icon appears.
• When BATT appears on the screen.
• Once per year.
• Before leaving the home unoccupied for more than one month.

How to Replace the AA Batteries

1. Hold the thermostat securely.
2. Press gently to loosen it from the wall mount.
3. Carefully pull the thermostat away from the wall.
4. Locate the battery compartment.
5. Remove the existing batteries.
6. Insert two fresh AA alkaline batteries according to the polarity markings.
7. Reinstall the thermostat on the wall mount.

Does Battery Replacement Reset the Thermostat?

If fresh batteries are installed within two minutes, the time and day do not need to be reset.

Other thermostat settings are stored permanently in memory and do not require battery power to remain saved.

Low-Battery Warnings

The thermostat provides warning messages as the batteries approach depletion.

BATT Warning

When the batteries need replacement, the Home screen displays:

• BATT
• Alert icon
• Battery icon

Very Low Battery

When battery power becomes very low, the thermostat disables its backlight to conserve power.

Critically Low Battery

When the battery charge becomes critically low, the display shows only:

• BATT
• Alert icon
• Battery icon

Fresh batteries should be installed immediately.

Thermostat Alerts and Reminders

The T4 Pro displays an alert icon when a maintenance reminder or system alert is present.

The alerts menu allows supported reminders to be viewed, snoozed, or cleared.

Opening the Alerts Menu

1. Press Menu.
2. Use + or – to find ALRT.
3. Press Select.
4. Review the displayed alert.

Air Filter Replacement Reminder

The thermostat can display a reminder when the heating or cooling system’s air filter requires replacement.

Air Filter Reminder Message

The display shows:

REPL – Replace Air Filter

How to Check the Air Filter Reminder

1. Press Menu.
2. Use + or – to locate ALRT.
3. Press Select.
4. The display shows REPL when the air filter reminder is active.

Resideo recommends replacing the air filter before clearing the reminder.

How to Snooze the Air Filter Reminder

1. Open Menu.
2. Select ALRT.
3. Press Select to view the alert.
4. Press Select to access the snooze option.
5. SNZE appears.
6. Press Select again.

The reminder is postponed for seven days.

How to Clear the Air Filter Reminder

1. Open the ALRT menu.
2. Select the active reminder.
3. Press Select.
4. Use the navigation buttons to locate CLER.
5. Press Select.

The reminder is cleared.

Snoozing and Clearing Other Alerts

Supported reminders can be managed through the ALRT menu.

Snoozing an Alert

1. Press Menu.
2. Find ALRT using + or –.
3. Press Select.
4. Select the active reminder.
5. Choose SNZE.
6. Press Select.

The reminder is postponed for seven days.

Clearing an Alert

1. Open ALRT.
2. Select the active reminder.
3. Navigate to CLER.
4. Press Select.

Some alerts cannot be snoozed or cleared.

If an alert cannot be removed, contact a local heating and cooling professional because the system may require service.

Troubleshooting Guide

The following troubleshooting procedures address the operating problems identified for the T4 Pro.

Common Problems and Solutions

Thermostat Display Is Blank

If the display is blank:

1. Check the circuit breaker.
2. Reset the breaker if necessary.
3. Make sure the heating and cooling system power switch is on.
4. Confirm that the furnace door is securely closed.
5. Check that fresh AA alkaline batteries are correctly installed.

Heating System Does Not Respond

If the heating system does not operate:

1. Press Mode until Heat appears.
2. Set the desired temperature above the current room temperature.
3. Check the circuit breaker.
4. Confirm that the heating system power switch is on.
5. Make sure the furnace door is closed.
6. Wait five minutes for the system to respond.

Cooling System Does Not Respond

If cooling does not operate:

1. Press Mode until Cool appears.
2. Set the desired temperature below the current indoor temperature.
3. Check the circuit breaker.
4. Confirm that the cooling system power switch is on.
5. Make sure the furnace door is securely closed.
6. Wait five minutes.

Temperature Settings Do Not Change

If the thermostat does not allow the temperature to be adjusted:

1. Check whether the display shows Unlock.
2. Unlock the thermostat if required.
3. Confirm that the correct operating mode is selected.
4. Check the available temperature range.

Temperature Setting Limits

If the selected temperature cannot be adjusted within these ranges, the installer may have configured temperature range stops.

Contact the installer to check the configured limits.

Cool On Keeps Flashing

Flashing Cool On indicates compressor protection.

Wait approximately five minutes for the system to restart.

Heat On Keeps Flashing

On a heat pump system, flashing Heat On indicates compressor protection.

Allow the safe restart period to finish.

Thermostat Is Locked

If the thermostat displays an unlock prompt:

1. Press the center button.
2. Enter 1234.
3. Use Select to confirm each digit.
4. Press Select again to complete the unlock process.

BATT Warning Appears

Replace both AA batteries with fresh alkaline batteries.

The low-battery warning appears approximately two months before the batteries are depleted.

Air Filter Reminder Does Not Clear

Some alerts cannot be snoozed or cleared.

Contact a heating and cooling professional if the reminder cannot be removed through the ALRT menu.

Display Messages and Indicator Guide

Maintenance Instructions

Routine thermostat maintenance includes battery replacement, reviewing alerts, and checking the heating and cooling system’s maintenance reminders.

Battery Maintenance

• Replace both AA batteries once per year.
• Replace batteries immediately when the low-battery warning appears.
• Use fresh alkaline batteries.
• Replace batteries before leaving home for more than one month.
• Reinstall batteries within two minutes to retain the time and day.

Air Filter Maintenance

When the thermostat displays REPL:

1. Check the heating and cooling system’s air filter.
2. Replace the filter as recommended.
3. Open the ALRT menu.
4. Clear the reminder or snooze it for seven days if needed.

Checking Thermostat Operation

The thermostat display can be used to check:

• Actual indoor temperature
• Temperature setpoint
• Current time
• Active schedule
• Heating or cooling status
• Fan mode
• Battery condition
• Alerts and reminders

Warranty Information

The Honeywell Home T4 Pro thermostat includes a five-year limited warranty.

Warranty Details

Mexico Warranty Information

The document also includes a warranty policy for Mexico.

The Mexican warranty identifies Instromet Mexicana S. de R.L. de C.V. as the responsible importer and warranty provider.

The warranty covers qualifying manufacturing defects under normal use for five years from the consumer’s purchase date.

Depending on the circumstances, the product may be repaired or replaced under the warranty conditions.

Mexico Warranty Service

Mexico Warranty Exclusions

The Mexican warranty excludes certain conditions, including:

• Damage caused by use outside normal operating conditions.
• Failure to follow the operating or installation instructions.
• Unauthorized modifications or repairs.
• Normal wear or consumer-caused damage.
• Labor costs for reinstallation.

Proof of purchase and applicable warranty documentation may be required.

Customer Support Information

For assistance with the T4 Pro thermostat, use the Honeywell Home and Resideo support resources.

Environmental and Disposal Information

Mercury-Containing Thermostat Disposal

If the T4 Pro replaces an older thermostat that contains mercury in a sealed tube, the old device must not be disposed of with ordinary household waste.

Contact the local waste management authority for proper recycling and disposal instructions.

Electronic Waste Disposal

At the end of the thermostat’s service life, take it to an authorized electronic waste collection center or recycler.

Do not discard the thermostat with ordinary household waste.

Correct disposal helps reduce potential environmental and health risks.

Frequently Asked Questions

1. How do I program a Honeywell T4 Pro TH4110U2005 or TH4210U2002 thermostat?

Press Menu, select PROG, and press Select. Choose the day or group of days, then select Wake, Away, Home, or Sleep. Set the start time, heating temperature, and cooling temperature. Repeat for the remaining periods and press Home to save.

2. How do I set the time and date on the Honeywell T4 Pro?

Press Menu and navigate to TIME. Select the 12-hour or 24-hour format, then adjust the hour and minutes. To set the date, open DATE and configure the year, month, and day using the Plus and Minus buttons.

3. How do I unlock the Honeywell T4 Pro thermostat?

Press the center button and enter the password 1234. Use Plus or Minus to adjust each digit, pressing Select after every digit. Press Select again after entering the fourth digit to unlock the keypad.

4. What is the difference between Temporary Hold and Permanent Hold?

Temporary Hold maintains a manually selected temperature until the next scheduled period. Permanent Hold maintains the selected temperature until it is manually cancelled. Both can be cancelled by pressing Plus or Minus and selecting Cancel.

5. Why is Cool On flashing on my Honeywell T4 Pro?

Flashing Cool On indicates that the compressor protection function is active. The thermostat delays compressor restarting to prevent equipment damage. Wait approximately five minutes for the system to restart safely.

6. How do I replace the batteries in a Honeywell T4 Pro thermostat?

Gently remove the thermostat from its wall mount, replace the two AA batteries with fresh alkaline batteries, and reinstall the thermostat. If the batteries are replaced within two minutes, the time and day settings are retained.

7. What does REPL mean on the Honeywell T4 Pro thermostat?

REPL is an air filter replacement reminder. Check and replace the heating or cooling system’s air filter. Then open Menu → ALRT to clear the reminder or snooze it for seven days.

8. What is the difference between the Honeywell TH4110U2005 and TH4210U2002?

Both models belong to the T4 Pro programmable thermostat series and support heating and cooling schedules, temperature holds, and fan controls. The TH4210U2002 additionally supports auxiliary and emergency heating functions on compatible systems.