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If you’re looking to change the installer settings on your Honeywell thermostat, but don’t know how to enter the menu or which codes to adjust, you’ve come to the right place.

In this detailed guide, I’ve listed all the ISU setup codes and how to access the menu for each model. 

So without further ado, let’s get into the guide.

Before we begin …

Caution is strongly advised, as uninformed changes to these codes can lead to severe consequences such as inefficient energy use, potential damage to HVAC equipment, and even safety hazards. Users are strongly encouraged to seek professional HVAC technician assistance if in doubt about modifying these codes. While this guide can enhance understanding, it is not intended for DIY adjustments without in-depth knowledge of HVAC systems and thermostats. Always prioritize safety and efficiency when dealing with your HVAC system.

What are Setup Codes?

Setup codes, also known as ISU codes or function codes in older models, are essential in configuring your Honeywell thermostat.

These codes and functions allow you to adjust more advanced settings reserved only for professional installers and contractors. 

In certain instances, you can even compare it to the “Developer Mode / Developer Settings” found in smart devices.

These setup codes allow you to:

  • Initialize the thermostat
  • Program the HVAC system's specifications 
  • Configure temperature limits 
  • Manage time setting
  • Manage Wi-Fi settings
  • Set up screen locks
  • Create alerts and reminders for filters
  • And a host of other advanced options you can’t access in the conventional home screen menu.

The installer setup and the setup codes ensure your Honeywell thermostat is properly fine-tuned, optimizing its performance and providing you with complete control over your home's temperature and environment.

Model-Specific Setup Codes and How to Access the Installer Menu

So, in this section, I’ll cover all the setup codes native to each model and show you how to enter the advanced installer menu.

T10 Pro and T9 Models

Smart thermostat with a color touchscreen

T9 3

To make the most out of your Honeywell T9 and T10 Pro thermostats, it’s always a good idea to know how to access the installer setup and which codes/messages refer to which setting.

Below, you can find detailed instructions on accessing the installer menu and the list of installer settings native to the T10-style modern thermostats. 

Access the Installer Setup

To revise the installer settings in your Honeywell T10-Pro-style thermostat:

  1. Touch the menu icon (three horizontal lines) at the bottom of the display.
  2. Then, scroll down and select “Thermostat Information.”
  3. Write down the date code 
  4. Then, touch the left arrow at the top of the display to return to the previous screen.
  5. After that, scroll down and touch “Installer Options” 
  6. Enter the date code when prompted.
  7. Choose “Installer Setup.”
  8. Then for each setting, make the appropriate selection and touch “Next” at the bottom of the display to proceed to the next setting.
  9. Finally, to complete your setup and save your new settings, touch “Done” in the upper left of the display.
T10 Installer Options 1
How to enter the installer options in a Honeywell T10

Setup Codes List

There are too many codes to list here so instead, jump to page 17 in the PDF below. This is for the T10 Pro in particular. For more installation manuals with ISU codes, check out my list here.

T6 Pro Smart, T6 Pro Z-Wave, T5+, T6 Pro, and T4 Pro

Smart thermostats

T4 T5 T6 and 6000 series 1 2

Open the Installer Setup/Advanced Menu

  1. First, press and hold the Menu button for 5 seconds 
  2. The screen will change, opening up the advanced menu, then use the left or right arrows to navigate through the options numbers on the left
  3. Then, make the necessary changes and tap on “Done” to save and exit
T6 Pro Smart Advanced Menu
Enter the advanced menu on a T6 Pro-Style thermostat

From the installer setup in a T6 Pro-style thermostat, you can:

  • Screen Lock: Choose between fully or partially locking the thermostat's touch screen.
  • Rater View: A designated read-only area where you can view all the ventilation settings.
  • System Test: Run diagnostics to test the performance of your heating and cooling system.
  • Set the Range Stop Temperature: Customize the minimum, maximum, cool, and heat temperature set points according to your preferences.
  • Configure Resets: Explore and access all reset options such as schedule, Wi-Fi, and factory reset.

Heading into the Installer Setup (ISU) in a T6 Pro-Style Thermostat

For these models:

  1. Press and hold the CENTER and “+” buttons for about 3 seconds until the screen changes.
  2. Then, press the Select button to cycle through the available setup codes (smaller number shown on the top). 
  3. You can adjust values or options using the + or – buttons as needed. The values on the bottom indicate the current that is configured for each ISU setup code.
  4. After you’ve made the necessary changes for each setup code, press the Select button to save, or the Back button to discard changes and continue editing.
  5. To save all changes and return to the home screen, press Home

T6-T4 Smart Setup Codes List

There are too many codes to list here so instead, jump to page 11 in the PDF below. (Note: Click the rotate button, as the ISU codes page is rotated 90 degrees). This is for the TH6220WF2006 & TH6320WF2003 in particular. For more installation manuals with ISU codes, check out my list here.

9000 Series

Smart thermostat with a color touchscreen

9000 series 1

For the 9000 Series, you don’t get ISU codes. Instead, the thermostat splits up the installer options into two separate menus with the setting name instead of a short code. 

So instead of relying on a long list of codes, this thermostat streamlines the configuration process into the actual names or labels for these configurations. 

The Advanced Preferences enable users to adjust mostly software-related aspects such as display settings, temperature swing control, and air filter reminders.

System Setup, on the other hand, focuses more on configuring the HVAC components and fine-tuning the system. These include setting up the type of heating and cooling equipment, fan controls, heat pump balance points, heating/cooling stages, cycles per hour, etc.

Setting Advanced Preferences

To access the advanced preferences menu:

  1. Tap “MENU” on the thermostat.
  2. Then choose “Preferences” 
  3. After that, tap on “Advanced Preferences”
  4. This will bring up the list of advanced preferences settings. 
  5. Adjust settings on each screen as desired, pressing “Next” to navigate through the available options.
  6. Once all adjustments are made, hit “Done” to save and exit the Advanced Preferences menu.
9000 series advanced prefs
Accessing the advanced preferences tab in a 9000 series

List of Advanced Preferences

Option NameSettings and Available Options
Scheduling OptionsSelect between “Non-programmable” or “Programmable.” 
Programmable uses the default or customized programming schedule to automatically adjust temperature settings for different times of the day.
Temperature Indication ScaleSelect between Fahrenheit or Celsius. 
Heating and Cooling System ChangeoverDecide on the Minimum Cooling setpoints and Maximum Heating temperature setpoints. 
Number of Schedule PeriodsSelect between 2 Periods Per Day or 4 scheduled periods Per Day.
Temperature LimitsDecide on the Minimum Cooling setpoints  and Maximum Heating temperature setpoints. 
Keypad LockoutLock the screen. Select between Unlocked/Partially Locked/Locked options 
Clock FormatSelect Between 12 Hour or 24 Hour. 
Daylight Saving TimeSelect between On and Off. The thermostat will automatically change the time and date according to daylight savings
Indoor Display OffsetsSet the display offset for indoor temperatures and humidity percentages
Table showing the advanced preferences options on a 9000-series thermostat

Entering the System Setup Menu

  1. Start by tapping “MENU” on your thermostat.
  2. Then, choose “System Setup” to view the available settings for customization.
  3. Adjust the displayed options as necessary and tap “Next” to proceed through each screen/option.
  4. After making all necessary changes, press “Done” to save your settings and exit the setup process.
  5. If needed, consult your contractor or specification sheets of the thermostat or HVAC equipment for more detailed information on configuring the thermostat.

List of System Setup Options

Option NameSettings and Available Options
LanguagePick your preferred language between English, Français, Español.
Thermostat installed inSet Thermostat location setting. Options between Home and Business. 
Defaults to “home”/residential
Your thermostat locationEnter a name for this thermostat. Tap on “Thermostat” and type in a new name. 
This is useful when you have several thermostats in different rooms
Your thermostat controlsPick the HVAC system type: Heating, Cooling, or Both. 
Defaults to “Both.”
Your system typePick between Forced Air, Heat Pump, Hot Water, or Steam. 
Depending on your system type, the following prompts may vary.
Defaults to “Forced Air”
Your forced air heating system typePick the type of Forced Air heating system. Options between Gas/Oil or Electric.
Defaults to Gas/Oil. 
Only available if you choose “Force Air” in the previous setting
Efficiency of your heating systemSelect the efficiency type for your Forced Air System. Options between Standard or High.
Defaults to “Standard Efficiency Forced Air”
Your heating system typePick the specific heating system.
Only shows up if you selected “Hot Water” or “Steam” from the previous settings
Number of cooling stagesSelect between the stages available for your cooling system. 
Options between “1 Stage” or “2 Stages.” Defaults to the former. 
You can tell the stages by checking for the Y and Y2 wires. 
Number of heating stagesSelect stages for your heating system. 
Check the W and W2 wires to confirm
Your fan controlSelect which system controls the fan. 
Options between “thermostat” or “heating system.” 
Defaults to “thermostat”
Type of changeover valvePick the option for the changeover valve. 
Options between “Cooling changeover valve” or “heating changeover valve.”
Check wires to confirm the setting. 
This option only shows up if you selected “Heat Pump” as the system type.
Number of heat pump compressor stagesSelect the number of stages available for your heat pump. 
Check Y and Y2 wires to confirm this.
Your backup heatSelect if you have a backup heat system. Pick between “Yes” or “No.” 
Table for the installer settings in a 9000-Series thermostat

VisionPRO 8000

The VisionPRO 8000 offers users the option to customize advanced settings through two separate menus: the Preferences menu and the Installer options.

Accessing the Preferences Menu

Tap on “MENU” on the thermostat screen and select “Preferences”.After that, choose from the following options:

  • Set up reminders for filter changes
  • Choose between Fahrenheit or Celsius for temperature display
  • Select 12-hour or 24-hour clock display
  • Adjust screen backlighting levels
  • Configure alert light settings
  • Determine scheduling options 
  • Toggle the adaptive recovery feature
  • Set up a default schedule for daily adjustments
  • Choose to enable or disable daylight saving time adjustments

After making the necessary changes, you can save your settings by touching “Done”, or cancel any changes by selecting “Cancel”.

8000 series preferences
Entering the Preferences menu on a Honeywell 8000

Installer Options

To access Installer Options on your Honeywell thermostat, you'll need to locate the password or date code, typically found in the user manual or on the thermostat itself.

Find the Password and Access the installer setup

You can find the date code or password on the back of the thermostat or by going to the Menu, selecting “Dealer Information,” and scrolling to the bottom to see the Date Code. After which, you can access the installer setup. Here’s how

  1. Find the date code/password at the back of the thermostat
  2. Alternatively, you can tap on “Menu” > “Dealer Information”
  3. Make sure to note down the date code
  4. After that, return to the Menu and pick “Installer Options” 
  5. Then, input your password/date code
  6. Pick “Installer Setup”
  7. After that, follow the prompts to select pick the available options and customize as desired.
8000 series find password and installer setup
Finding the password and accessing the installer setup in a Honeywell 8000 series thermostat

6000-1000 Series

Access the Advanced Functions on the 6000/6500 Series

  1. First, press and hold the Fan and up arrow buttons simultaneously for about 3 seconds.
  2. After that, the screen will change and display two numbers, and the button labels will change to Done, Back, blank, and Next.
  3. Using the Next button, adjust the function number (the larger number on the left) to the one you want to change.
  4. Adjust the settings for that function by pressing the up or down arrows until the desired option (the smaller number on the right) appears.
  5. Continue this process for each function you want to modify.
  6. Once you've made all your changes, press Done to save and exit the setup menu.

Enter the Advanced Menu on the 5000-1000 Series

  1. To start the setup process, press and hold both the up and down arrow buttons simultaneously until the display changes.
  2. Then, you can press both arrow keys for one second to switch to the next function.
  3. You can alter the settings assigned to each function using the up or down arrow buttons.
  4. Once you have successfully configured your thermostat, press run or hold both the up and down arrows together to save the settings and exit the configuration menu.

List of Functions and Options for 6000-1000 Series Thermostats

There are too many codes to list here so instead, jump to page 9 in the PDF below. This is for the TH4110B in particular. For more installation manuals with ISU codes, check out my list here.

FAQs

How Do I Verify the Cooling/Heating Stages and Backup Systems in My HVAC System?

To confirm the cooling and heating stages as well as backup systems in your Honeywell thermostat, you'll need to examine your HVAC system's specifications or consult a professional.

You can also inspect the thermostat wiring to identify the stages or systems available.

Can I Access the Setup Menu After I've Initialized the Settings? 

Yes, in most models, you can re-enter the setup mode. Refer to the manual that’s specific to your model or check the guides above.

Can I Change Schedules Using the Installer Settings Menu? 

You can't edit schedules via the installer settings. However, in certain models, you can change the type of schedule in the installer menu.

Do all Thermostats Share the Same ISU Codes?

Different manufacturers may use different ISU (Installer Setup) codes when it comes to setting up thermostats.

However, with Honeywell thermostats, these codes are typically consistent across models.

When Should I Revisit the Installer Setup Menu on My Thermostat? 

You should reconfigure the installer setup or preferences whenever you switch over to a different HVAC system, set up new components, repairs, or just want to change the advanced settings.

What's the Difference Between Aux and E Wires? 

The Aux stands for auxiliary heating and E wire is used for emergency heating. These two are distince as the aux can switch on automatically by the thermostat whereas the Emergency heat neds to be switched on manually.

What's the Deadband in Thermostats?

The deadband in a thermostat refers to a temperature range where neither the heating nor the cooling system is activated.

In Honeywell thermostats, the deadband is separate from the differential temperature.

Why are there Compressor or Backup Heat Lockout Settings?

Compressor or backup heat lockout settings are in place to prevent these components from operating inefficiently or unnecessarily, providing a safety feature to avoid unnecessary wear and tear.

What's the ASHRAE Ventilation Control Method?

Regarding ventilation, ANSI/ASHRAE Standards 62.1 and 62.2 are the accepted benchmarks for ventilation system design and indoor air quality.

What's the Reversing Valve?

A reversing valve is a type of valve and is a component in a heat pump, that changes the direction of refrigerant flow.

What are ERV/HRV ventilators?

Energy recovery ventilators (ERVs) and heat recovery ventilators (HRVs) are devices that exchange heat and moisture, offering more control over humidity levels in the home, especially in warm and humid climates.

Conclusion

Although the average consumer doesn’t need to worry about the installer settings or ISU setup codes, it doesn’t hurt to know how to access this menu on your Honeywell thermostat and change the settings if necessary. 

However, always make sure you fully understand the different options you’re configuring, and don't make any changes if you're not 100% sure what you are doing.

Sources

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