If your Honeywell thermostat is acting up, a reset may help—but you do not always need to restore it to factory settings.

A thermostat that has lost its Wi-Fi connection needs a different fix from one that keeps changing the temperature. Before resetting anything, check the model number and decide what you want to clear.

Which Reset Should You Use?

Honeywell thermostats do not all use the same reset procedure. The steps below cover several common Honeywell Home models. If your model is not listed, use the official instructions linked at the end of this guide.

How to Factory Reset a Honeywell Thermostat

A factory reset returns the thermostat to its default settings. Depending on the model, this can remove programmed schedules, Wi-Fi settings, preferences, and other configuration information.

Before proceeding: If you do not know how your heating and cooling system was configured, avoid a factory reset until you have checked the installation instructions. Some systems require specific installer settings to operate correctly.

Honeywell Home T9

These steps apply to the T9 models RCHT9510WF and RCHT9610WF.

1. Press the Menu icon on the thermostat.
2. Scroll to Advanced Setup and select it.
3. Select Reset.
4. Choose Factory Reset.
5. Follow any remaining prompts on the screen.

Once the reset is complete, you may need to configure the thermostat again.

Honeywell Home T5, T5+ and T6

Honeywell lists specific T5, T5+ and T6 models under its reset instructions, including RCHT8610WF, RCHT8612WF, TH6320WF2 and TH6220WF2.

1. Press and hold Menu.
2. Press > until you see Reset, and then select it.
3. Press > until you see Factory Reset, and then select it.
4. Congratulations! You’ve reset your device! You can now configure your device for its new settings, either using the Resideo App, or on the thermostat screen itself.

Check the model number before following these steps. Similar product names do not guarantee identical controls or menus.

Honeywell Smart Wi-Fi 9000

For the listed RTH9580WF, RTH9585WF and TH9320WF models, Honeywell’s instructions give this path:

1. Press Menu.
2. Press Restore Factory Defaults.
3. Select Yes to confirm.
4. Congratulations! You’ve reset your device!

Do not use this menu path for another thermostat simply because its screen looks similar.

How to Reset Honeywell Thermostat Wi-Fi

If your thermostat still controls the temperature but cannot connect to your home network, try the Wi-Fi settings before performing a factory reset.

The exact procedure depends on the model.

T9: Change the Wi-Fi Network

For the Honeywell Home T9 models RCHT9510WF and RCHT9610WF:

1. Press Menu.
2. Select Wi-Fi.
3. Choose Change Network.
4. Select your network and enter the password.

This procedure is useful if you have changed your router or Wi-Fi password. If the network does not appear, check that the router is working and that the network meets the thermostat’s requirements.

Other Honeywell models may have a separate Wi-Fi reset or setup option. Follow the instructions for your specific model rather than assuming the T9 procedure applies.

How to Reset the Temperature Schedule

If the thermostat keeps changing the temperature when you do not expect it to, check the schedule first. A programmed period may be overriding the temperature you selected manually.

You may not need a factory reset.

For the Honeywell Home T9 models RCHT9510WF and RCHT9610WF, Honeywell provides this schedule-reset procedure:

1. Press Menu.
2. Open Advanced Setup.
3. Select Reset.
4. Choose Schedule Reset.

A schedule reset is different from a factory reset. It targets the programmed schedule rather than restoring every thermostat setting.

Before clearing the schedule, check whether the thermostat is following a programmed period or whether a Hold setting is active. If you only want a different temperature for a short time, changing the current setting may be enough.

What If the Thermostat Still Does Not Work?

Resetting will not solve every thermostat problem. If the issue remains, check the symptom before trying another reset.

The display is blank. If your model uses batteries, check whether they need replacing. For a hardwired thermostat, a blank display may indicate a power problem involving the HVAC system or thermostat wiring. Do not handle wiring unless you know how to work safely with the equipment.

The thermostat will not connect to Wi-Fi. Confirm that your router is online and that you are entering the correct network password. If you recently changed network equipment, use the thermostat’s documented network setup procedure.

The temperature is wrong or keeps changing. Check the schedule, Hold settings and selected operating mode. A reset may not be necessary if a programmed setting is responsible.

The heating or cooling system will not run. Check the selected mode and setpoint. If the thermostat has power but the HVAC equipment does not respond, the cause may be outside the thermostat. A reset cannot repair a failed component or incorrect wiring.

If the thermostat still behaves incorrectly after the appropriate reset, consult the model-specific troubleshooting section in its manual or contact a qualified HVAC technician.

Where to Find the Correct Reset Instructions

​For the correct reset instructions, it’s best to download the user manual for your specific model.”

Frequently Asked Questions

Does resetting a Honeywell thermostat erase the schedule?

It depends on the reset type. A schedule reset is intended to clear the programmed schedule. A factory reset may remove additional settings, depending on the model.

How do I reset a Honeywell thermostat without a reset button?

Many Honeywell thermostats use on-screen menus or button combinations instead of a dedicated reset button. The correct method depends on the model, so check its instructions before trying a button sequence.

Will a factory reset fix a Honeywell thermostat that is not connecting to Wi-Fi?

Not necessarily. If the problem is a changed network name or password, reconnecting through the Wi-Fi settings may be sufficient. Try the model’s documented network procedure before erasing all settings.

What should I do if none of the reset methods work?

Confirm the model number and check the troubleshooting instructions in its manual. If the thermostat has a blank display, the HVAC system does not respond, or the controls still fail, the issue may require further electrical or equipment diagnosis rather than another reset.

Need the instructions for your exact thermostat? Find the model number first, then use the matching Honeywell manual. The correct procedure can vary even between thermostats in the same product family.

This guide covers the Venstar VOYAGER T4900 Owner’s Manual (P/N 88-1012, Rev. 5), the 60-page document for Venstar’s multi-stage Voyager thermostat. The T4900 is not a simple heat-and-cool dial: it stages heating and cooling, adds humidity control, and can take an optional wireless module. The steps below follow the manual and name its own controls and menus, and the PDF is linked here. Confirm anything that looks unfamiliar against the printed guide before you energize the system.

Table of Contents

• What the T4900 Is
• Before You Start
• Buttons and Display
• Choosing a Mode
• Setting the Clock and Day
• Programming the Time Periods
• Fan, Override and Emergency Heat
• Wireless Modules and Holiday
• Installation and Wiring
• Installer Setup Highlights
• Troubleshooting (From the Manual)
• FAQ

What the T4900 Is

The Voyager T4900 is a 24 VAC digital thermostat built around four buttons plus a scrolling backlit LCD. What makes it the high-end model in the line:

• Multi-stage heating and cooling. The backplate carries staged terminals: W1/O/B, W2 and W3 for heating stages and Y1 and Y2 for cooling, so it can run a multi-stage system rather than a single on/off call.
• Humidity control. Dedicated HUM and DEHUM terminals drive a humidifier and a dehumidifier.
• Optional wireless module. The thermostat accepts a Wi-Fi, Z-Wave, ZigBee or Venstar RF module, and Venstar’s Wi-Fi path ties into a Skyport account.
• Fully time-based program. You choose a 7-day, 5-1-1-day, 1-day or non-program schedule, each day with up to four periods.

Before You Start

The manual’s cautions are straightforward. Turn off power to the heating and cooling system before removing any wires. The T4900 is a 24 VAC low-voltage thermostat; it is not for line-voltage or millivolt equipment. If the thermostat you are removing contains mercury, recycle it rather than bin it. The guide also notes the unit can receive firmware updates from the manufacturer over its wireless module, which is worth knowing before you assume a screen is “wrong.”

Buttons and Display

The front of the T4900 has backlit buttons; the scrolling display walks you through the setup screens. The controls the manual identifies:

• MODE moves between operating modes and advances through setup steps.
• WARMER and COOLER raise or lower the setpoint, and change values in setup.
• SETUP opens the user, installer and technician menus.
• PROGRAM enters the time-period schedule.
• FAN toggles constant fan; OVERRIDE forces occupancy; EMERGENCY runs emergency heat; SET CLOCK sets time and day.

The display shows icons for the current stage, the program period (Occupied 1, 2, 3 or Unoccupied), a heat or cool demand indicator (red for heat, green for cool), and, with a module installed, a wireless-connection icon.

Choosing a Mode

Press MODE to cycle the operating mode. The manual’s modes are Heat Only, Cool Only, Auto (Auto-Changeover) and Off. In Auto, the thermostat decides whether to heat or cool based on room demand, and pressing WARMER or COOLER shifts both the heat and cool setpoints together. To set them separately, switch to Heat or Cool, adjust, then return to Auto.

Setting the Clock and Day

Press SET CLOCK, then use WARMER or COOLER to set the time; press MODE to jump to the day, adjust, and press SET CLOCK again to confirm. A tip in the guide: hold the FAN button while pressing WARMER or COOLER to change the time in hours. If a Wi-Fi module is fitted, the clock is managed through the account and the local SET CLOCK step is not used.

Programming the Time Periods

Press PROGRAM to enter scheduling. First pick the program type: 7 Day lets every day differ, 5-1-1 groups weekdays and gives Saturday and Sunday their own schedule, 1 Day applies one pattern to all days, and Non-program runs a single fixed setpoint. Each programmed day uses up to four periods, named Occupied 1, Occupied 2, Unoccupied and Sleep in the display. Set a period’s start time with WARMER or COOLER and its heat and cool setpoints the same way, pressing MODE to advance. To save and exit, press PROGRAM; to copy one day to the next, press the up arrow then MODE, and press MODE again to push that day’s schedule to the following days.

Fan, Override and Emergency Heat

• Fan. Press FAN for “Fan On,” which runs the blower continuously; press again to return to auto, where the fan runs only during a heating or cooling call. Fan On is not offered in the Off mode.
• Override. During an unoccupied period, pressing OVERRIDE forces the thermostat into the Occupied 1 settings for 30 minutes; each extra press extends it.
• Emergency heat. Only when the unit is set up for a heat pump, pressing EMERGENCY bypasses the compressor and runs the backup heat.

Wireless Modules and Holiday

The T4900 can carry one of four modules: Wi-Fi, Z-Wave, ZigBee or Venstar RF. Wi-Fi setup and status live under the Accessory menu, and Venstar’s Wi-Fi service uses a Skyport account; when a Wi-Fi module is present, some local functions such as setting the clock or the Holiday program move to the account. The Holiday feature runs temporary energy-saving settings for a set number of days without changing your normal schedule.

Installation and Wiring

The guide matches each labeled wire from the old thermostat to the same-letter terminal on the new one. The T4900 backplate terminals, from the manual:

Behind the board are dip switches that tell the thermostat what it is driving: an equipment switch (Gas/Electric or Heat Pump), a fan/aux switch, and, for heat pumps, an O or B switch for the reversing valve. The manual’s sample wiring covers conventional systems (3- and 4-wire) and heat pumps (5- and 6-wire with the O/B valve). To test the install, the guide sends you into Technician Setup, where each output can be exercised.

Installer Setup Highlights

Most of the T4900’s depth lives in Installer Setup, reached from the SETUP menu. The manual’s installer section covers: setpoint limits (three lock levels so a setpoint cannot be pushed past a floor or ceiling), stage deadbands and the minutes between stages, fan purge and other timers, humidify and dehumidify control, the programmable AUX output (by temperature, humidity or time), dry-contact and remote-sensor options, and a reset that returns every setting to its defaults. A technician screen adds sensor calibration and equipment testing.

Troubleshooting (From the Manual)

These are the guide’s own symptom, cause and remedy entries. Nothing here is added beyond the printed list.

FAQ

How many heating and cooling stages does the T4900 run?

The backplate provides three heating stages (W1/O/B, W2, W3) and two cooling stages (Y1, Y2), and the installer setup includes stage deadbands up to a fourth heating stage. Stage control is configured during installer setup.

Can the T4900 work without the wireless module?

Yes. Every function runs from the buttons and display; the Wi-Fi, Z-Wave, ZigBee or Venstar RF module only adds remote control and account-based clock and holiday settings.

Why can’t I set the clock on the thermostat?

When a Wi-Fi module is installed, the clock is handled through the Venstar Skyport account, so the local SET CLOCK step is disabled.

What does pressing OVERRIDE do?

During an unoccupied period, OVERRIDE drops the thermostat into the Occupied 1 settings for 30 minutes, and each additional press extends that window.

How do I copy one day’s schedule to the rest of the week?

Program the first day, then press the up arrow and MODE to copy it to the next day, and press MODE again to repeat it across the following days.

Venstar support, the one-year limited warranty and full menus are covered at the back of the printed manual; for setup questions the guide points you to your installing dealer and Venstar.

This page is the Honeywell Lyric T5 Programmable Thermostat User Manual explained. The source is Honeywell’s official Lyric T5 Wi-Fi Programmable Thermostat User Guide, document number 33-3991, the booklet shown for model RCHT8610WF2006 (other Lyric T5 Wi-Fi models share it). The guide runs about 33 pages and covers the touchscreen, the Lyric app, scheduling, Wi-Fi, alerts, and troubleshooting.

Download Honeywell Lyric T5 Programmable Thermostat User Manual (PDF)

Contents

• What the Lyric T5 Can Do
• Touchscreen, System Modes, and Fan Modes
• Connecting to Wi-Fi and the Lyric App
• Scheduling and Overrides
• Main Menu Settings and Reset Options
• Alerts and Maintenance Reminders
• Compatibility Before You Install
• Troubleshooting
• Getting Help and Warranty

What the Lyric T5 Can Do

Page 3 lists the headline features. The Lyric T5 Wi-Fi is a connected touchscreen thermostat built around four ideas:

• Flexible scheduling. Choose location-based control (geofencing), smart scheduling, a time-based schedule, or no schedule at all.
• Smart Alerts. The thermostat sends notifications for things like extreme indoor temperatures and reminders for maintenance such as filter changes.
• Automatic heat-to-cool changeover. In Auto mode it decides whether to heat or cool to reach the setpoint.
• Smart Response. The unit learns your heating and cooling cycle times so it reaches the temperature you want at the time you want it.

The Lyric app can manage several thermostats and several people in one household, which matters for the geofencing behavior described later.

Touchscreen, System Modes, and Fan Modes

Three touch keys sit across the top of the display (pages 4 and 8): Mode selects the system mode, Fan selects fan operation, and Menu opens programming and settings. The center shows the current indoor temperature, and the small number is the desired temperature you change with + and -. The screen enters idle mode about 45 seconds after the last touch and may dim depending on the brightness setting.

System modes (page 8): Heat, Cool, Off, Auto (when enabled), and Em Heat (Emergency Heat). The guide is explicit that Em Heat only appears on heat pump systems with an auxiliary/emergency heat stage configured, that Auto mode is disabled by default, and that either mode may not show up depending on the equipment and how the thermostat was installed.

Fan modes (page 9): On runs the blower continuously, Auto runs it only during heating or cooling, and Circ (circulate) runs it at random intervals at least 35% of the time to keep air moving.

Built-in compressor protection (page 9): after a shutdown the compressor waits a few minutes before restarting to prevent damage. During that wait the screen flashes Cool On, or Heat On on a heat pump. The same flashing message also acts as a startup delay after an AC power loss.

Connecting to Wi-Fi and the Lyric App

To control the thermostat remotely it must join your home network through the Lyric app (page 10). The guide’s steps:

1. Put your phone or tablet on a 2.4 GHz Wi-Fi signal. Many routers broadcast both 2.4 and 5.0 GHz; pick the 2.4 GHz one.
2. At the thermostat, press and hold the indoor temperature in the center of the screen for 5 seconds until the screen changes.
3. Install the Lyric app from the App Store or Google Play, open it, and tap SET UP NOW when the thermostat appears under “Thermostat Found.” If it does not appear, tap INSTALL A DEVICE.

A status icon in the upper-right corner shows whether Wi-Fi is connected, disconnected or not set up, or off. To move the thermostat to a new network (page 11), delete it first in the app under Thermostat Configuration, then hold the center temperature for 5 seconds and set it up again; your equipment settings and preferences are retained.

Scheduling and Overrides

Page 13 lays out the four scheduling styles. Location-based control uses your phone’s GPS: the thermostat drops to your Away temperature when you cross the geofence boundary on the way out and returns to your Home temperature when you cross back on the way in. Smart scheduling adds a Sleep period to that behavior. Time-based scheduling uses four periods per day, Wake, Away, Home, and Sleep, and can be the same every day, split weekday/weekend, or set a day at a time. If you do not want a program, select no schedule and adjust manually.

Overrides (pages 6 to 7) are how you depart from the program for a while. A Hold Until temporary hold changes the setpoint for up to 12 hours, or until a time you choose, then the schedule resumes; it is meant for time-based schedules. A Permanent Hold keeps a temperature until you change it or run the schedule again. A Vacation Hold suspends the program for a longer span and, the guide notes, can only be started from the Lyric app. In every case, touching Run Schedule ends the hold and returns to the program.

Main Menu Settings and Reset Options

Page 12 maps the whole menu. From the home screen, touch Menu and arrow through these items:

• Schedule (create or edit a program), Clean Screen (disables the touch layer for 30 seconds so you can wipe it), Temp Scale (Fahrenheit or Celsius), and Screen Lock (limits access to settings).
• Wi-Fi (configure or change the network), Brightness, and Recovery (turn the Smart Response learning feature on or off).
• Clock and Date (only manual when the thermostat is offline; a connected unit sets them itself), EQMT Status (live heating, cooling, and fan status), and Device Info (MAC ID, IP address, date code, model number, and firmware versions).
• Alerts (only present when an active alert shows) and Reset.

Under Reset (page 24) the guide offers four choices: a return to the original settings (the menu item is labeled “Factory reset”), a Schedule reset back to the default Mon-Fri and Sat-Sun program, a HomeKit reset that clears Apple HomeKit credentials, and a Wi-Fi reset that clears the saved router credentials.

Alerts and Maintenance Reminders

Pages 26 and 27 print the alert list. When the alert symbol appears on the home screen, touch Menu then ALERTS; a three-digit code appears by the clock and a description scrolls. Non-critical alerts can be snoozed for up to seven days or dismissed; some critical alerts cannot. Representative codes:

Compatibility Before You Install

Page 28 (“General system information”) carries the constraints that decide whether the Lyric T5 fits your system, plus three cautions. Quote them rather than guessing:

• Compatible with most single-stage and multi-stage conventional and heat pump heating and cooling systems.
• 24 VAC power through a “C” (common) wire is required.
• Does not work with electric baseboard heat (120-240V) or with millivolt systems.
• Remote control through iOS or Android; compatible with Apple HomeKit and Amazon Echo.
• Heat setpoint range 40 to 90 °F (4.5 to 32.0 °C); cool setpoint range 50 to 99 °F (10.0 to 37.0 °C); sensor accuracy ±1.5 °F at 70 °F.

CAUTION: ELECTRICAL HAZARD. Can cause electrical shock or equipment damage. Disconnect power before beginning installation.

CAUTION: EQUIPMENT DAMAGE HAZARD. Compressor protection is bypassed during testing. To prevent equipment damage, avoid cycling the compressor quickly.

CAUTION: MERCURY NOTICE. If the Lyric T5 Wi-Fi thermostat is replacing a thermostat that contains mercury in a sealed tube, do not place the old thermostat in the trash. Contact your local waste management authority for proper recycling or disposal instructions.

Troubleshooting

Page 29 is the guide’s own troubleshooting list, reproduced here with only what the manual states.

Getting Help and Warranty

The guide’s welcome page lists support channels: lyric.honeywell.com, email MyLyric@honeywell.com, and Lyric Technical Support at 1-800-633-3991. Page 33 states a two-year limited warranty on workmanship and materials, with service handled through Honeywell Customer Care at 1-800-468-1502. Before you call, open Menu, then Device Info, and note the model number, MAC ID, and firmware versions, since those are what support will ask for.

If you are uninstalling or handing the home over, use the reset options on page 24 first. The guide is clear that the thermostat keeps your settings and router information in memory even when it is powered off, so clearing the schedule, Wi-Fi, and HomeKit credentials protects your account.

The Honeywell Thermostat CM921 User Manual is a 19-page booklet, document 42011077-103 R1, dated 2006 and published by Honeywell Control Systems Ltd. The CM921 is a 1 day wireless programmable room thermostat that talks to an HC60NG relay box, so no thermostat cable runs between the two. This page follows it through setup, programming, the modes, the holiday function, the user parameters, cooling and the eight faults it prints.

Download the Honeywell CM921 User Manual (PDF)

Table of Contents

• What Is the Honeywell CM921?
• Controls and Display
• Setup: Batteries, Date and Time
• Programming the Six Periods
• Operating Modes and the Holiday Function
• User Parameters, Cooling and the HC60NG
• Troubleshooting: The Eight Entries
• Frequently Asked Questions

What Is the Honeywell CM921?

Page 1 describes the CM921 as a wireless programmable room thermostat designed to control a heating system efficiently, providing comfortable temperatures when you are at home and energy savings when you are away. The link to the boiler is wireless, so the booklet covers no wiring for the thermostat itself; the connections sit at the boiler and the HC60NG relay box. The unit has a backlit LCD, an OK confirm key, six temperature levels per day, a holiday button, automatic summer and winter time change, and a memory that holds the program when the batteries come out. Optimum Start and the OFF-mode frost value are installer settings.

Controls and Display

Page 2 prints a numbered drawing of fifteen parts. The instructions use the slider switch with its five positions, DATE, PROG, AUTO, MAN and OFF; the up and down temperature arrows; the green OK button; the left and right program arrows; the enquiry button marked with an i; the holiday button marked with a suitcase; and the plus and minus time buttons.

Setup: Batteries, Date and Time

Step 1: Fitting the Batteries

Follow these steps only if the screen is blank, with no symbols or digits displayed.

1. Lift up the front cover to reveal the battery cover.
2. Remove the battery cover by pressing down and sliding it out.
3. Insert the two AA LR6 alkaline batteries supplied with the thermostat, watching the orientation on page 2; the screen then displays information and the unit is ready.
4. Replace the cover by sliding it firmly back.

The cells are alkaline LR6, and used ones are to be disposed of carefully.

Step 2: Setting the Date and Time

Move the slider to DATE. SET THE DAY appears and the day digits flash; the up or down arrow shows DAY OK? while pressed, and the green button confirms. The month and year follow the same way, and an invalid date returns the thermostat to the start of the mode.

The time digits then flash with SET THE TIME. Each press moves one minute, and holding the button changes the time slowly and then progressively quicker. CHANGES SAVED appears, then DATE COMPLETE; moving the slider before that point discards the changes.

Step 3: First Run

With the date and time set, move the slider to AUTO and the built-in program runs. The booklet describes no pairing or commissioning procedure for the radio link.

Programming the Six Periods

The built-in program has six temperature level changes, settable between 3.00am and 2.50am, each level between 5°C and 35°C in 0.5°C increments. The default program is printed on page 5.

Move the slider switch to PROG and use the left and right arrows to move between the six periods; a flashing square at the bottom of the screen marks the current one.

Changing a Period

The screen shows SET TIME 1 with the time flashing. Press an arrow and TIME 1 OK? appears; holding the button changes the time quickly, and if the next change period flashes, that next change is pushed forward if you keep pressing. The green button confirms and SET TEMP 1 follows; adjust until TEMP 1 OK? appears, confirm, and SET TIME 2 follows. Repeat for all six periods, or move the slider to AUTO at any point. Ten minutes without input brings MOVE THE SLIDER on screen.

Any period from 2 to 6 can be disabled. In PROG, reach it with the left and right arrows, check the flashing square, then hold the enquiry button for at least 2 seconds. To restore one, navigate to it, where the screen shows DISABLED, and hold the same button until ENABLED appears.

Operating Modes and the Holiday Function

AUTO, MAN and OFF

AUTO follows the temperature program, default or personalised, which the booklet calls the best way to maintain comfort while maximising energy savings. MAN acts as a simple thermostat with a fixed setpoint, adjustable from 5°C to 35°C and held until another mode or temperature is selected. OFF controls to 5°C by default as frost protection, a value adjusted by calling your installer.

Room, Target and Frost Temperature

In AUTO and MAN the display shows the room temperature with ROOM TEMP. Pressing the enquiry button flashes the target temperature with TARGET TEMP for 5 seconds; in OFF the same button shows FROST TEMP. The up or down arrow overrides the programmed temperature for 5 seconds, ending at the next programmed change. The plus or minus buttons adjust the clock, confirmed with the green button.

The Holiday Function

The holiday function holds a constant temperature, 10°C by default, for 1 to 99 days, saving energy and related costs while the home is empty. In AUTO or MAN, press the holiday button: the day after the current day is selected with RETURN DATE OK?, and the plus or minus buttons set 1 to 99 days. The green button confirms, then TEMP OK? allows 5°C to 35°C. HOLIDAY MODE stays displayed until the return date, the counter dropping by one at midnight, and the thermostat resumes the mode set on the slider. Press the holiday button again, or move the slider, to cancel.

User Parameters, Cooling and the HC60NG

The Three User Parameters

Move the slider to OFF, then hold the enquiry button for about 5 seconds; CLOCK SELECT appears with the current setting.

The up or down arrow selects each value, the display flashes, and the green button confirms it; move the slider to exit. Selecting 1 on RESET PROGRAM restores the built-in program and discards the personalised one, and clock select changes how the time is displayed, not the time itself.

Switching to Cooling

Cooling needs a correctly set up system. Press the up and down arrows together for 5 seconds in any mode and COOLING appears. The cooling program uses the same six times with its own temperatures, edited through PROG:

The HC60NG Relay Box

The HC60NG is the relay box that receives the radio signal, with a push button and relay status LEDs. The green LED indicates normal operation of the radio frequency system, on when the boiler is on. A red LED, steady or flashing, means radio communication has been lost, which the location of the thermostat may explain, or a radio fault, which is a call to the installer. While communication is lost the boiler can be switched with the push button.

Troubleshooting: The Eight Entries

Pages 12 and 13 print eight entries in three columns, Symptom, Possible Cause and Remedy, four on each page, several with more than one cause. They appear in the booklet’s order and grouping, with icons named as the battery, flame and spanner symbols.

Frequently Asked Questions

The Honeywell CT87K Owner’s Manual is the official installation-and-operation booklet for Honeywell’s classic “The Round” non-programmable, dial-operated room thermostat. The document number is 69-1959EFS-02, a 16-page trilingual guide (English on pages 1-5, French on 6-10, Spanish on 11-15). It covers two physically similar models together: the CT87K for 24 VAC heating systems, and the CT87N for 24 VAC heating and cooling systems. If your wall dial only has an R and a W connection and no system or fan switch, the CT87K sections are the ones you need.

The CT87K is a mechanical setpoint dial, not a digital programmable thermostat. You set the temperature by rotating the round face; there is no schedule, no app, and no keypad. That simplicity is exactly why it is still installed in a lot of homes and small commercial spaces, and why the manual itself is short. The whole booklet fits on five English pages: package contents, removal of the old unit, wallplate mounting, wiring by terminal, two small configuration switches, and a one-line operating instruction.

Before wiring anything, verify you have the right model. The manual warns that if your old thermostat has four or more wires (not counting C or C1), you may have bought the wrong replacement for a CT87K. In that situation it tells you to stop and call Honeywell at 1-800-468-1502 for advice.

Key Features of the CT87K

The CT87K’s feature set is deliberately small. Honeywell’s Owner’s Manual and the corresponding retail listing describe a non-programmable, single-stage heat-only dial thermostat with a 24 VAC control circuit, 1-year limited warranty, Premier White housing, 3.69 in x 3.69 in x 1.09 in (94 x 94 x 28 mm) dimensions, and an optional decorative cover plate for hiding old marks. The owner-facing details that matter day to day are:

• Rotary setpoint dial. Turn the round cover to the temperature you want; the ring shows current and desired indoor temperature.
• Heat-only operation. The CT87K controls a single heating stage. It has no System switch and no Fan switch; those live on the CT87N sibling.
• Two configuration switches inside the base. The pair of cycle-rate switches is set once during installation to match your heating equipment (see the table below).
• Terminal block for R, W, and Y. The CT87K uses Y as the third conductor on a 3-wire hot-water heat-only valve circuit, not for cooling.
• Optional decorative cover plate. Fits behind the base to hide marks left by the previous thermostat.
• 24 VAC control power only. The Owner’s Manual lists the CT87K as being for 24 VAC heating systems. Do not install it on a line-voltage electric baseboard circuit.

The CT87N, which shares the manual, is the version to buy when you need heat, cool, and a fan switch as well as the dial.

Document Structure

The English portion of 69-1959EFS-02 runs in a fixed order. Knowing the layout is quicker than scrolling through a preview.

1. Getting started (page 1). Package contents (thermostat, cover plate, wall anchors and screws, wire labels) and required tools: No. 2 Phillips and small pocket screwdrivers, hammer, level, pencil, and a drill bit sized 3/16 in for drywall or 7/32 in for plaster.
2. Remove your old thermostat (page 1). Turn off power, remove the cover, leave the old wallplate in place, and check for a sealed mercury tube.
3. Label wires and remove the old wallplate (page 2). Wrap each wire with the letter label that matches the old terminal, then remove the old wallplate. Includes the “wrong replacement” wire-count check and a table mapping common old-terminal letters to CT87N and CT87K terminals.
4. Mount the base and connect wires (pages 2-3). Mark screw holes, drill and insert anchors, thread the wires, and tighten the terminal screws. Includes the notes about removing the R-Rc jumper, choosing O versus B on a heat pump, and taping off unused conductors.
5. Configure the switches (page 4, CT87N sections apply when present). The fan-operation switch has an E and F position; the cycle-rate switches 1 and 2 have a four-row setting table for steam, high-efficiency, gas/oil, and electric systems.
6. Finish installation (page 4). Snap the thermostat onto the base, restore power.
7. Operation (page 5). The CT87N has a System switch (Cool, Heat, Off) and a Fan switch (On, Auto). Both models set temperature by rotating the dial.
8. Warranty. The Owner’s Manual closes with the one-year limited warranty statement.

Wiring and Configuration

The CT87K terminal block carries R, W, and Y. The manual maps the older Honeywell or generic terminal letters to those three. Existing labels connect as follows:

• R, Rh, 4, or V → new R terminal.
• W, W1, or H → new W terminal.
• Y or Y1 or M → new Y terminal.
• C, X, or B → not used on the CT87K. Wrap the bare end with electrical tape and leave it disconnected.

The manual gives two wiring recipes for the heat-only model. A two-wire heat-only system uses only R and W. A three-wire hot-water heat-only system uses R to R, W to W, and Y to Y, which drives an open/close zone valve. Do not rely on wire color; label by the terminal letter on the old unit.

Cycle rate switches

Inside the base are two small switches, labeled 1 and 2, that set how often the thermostat cycles the equipment. The Owner’s Manual gives one row per heating type:

Set both switches before you snap the cover on, because they are not reachable from the front. If you are replacing an identical CT87K, note the old switch positions in a photo before you remove the wires.

Setting the Temperature

Operation is a single action: rotate the round face to the number that matches the temperature you want the room to hold. The ring shows both the current indoor reading and the setpoint. There is no program, no hold, and no schedule to cancel; the CT87K keeps calling for heat until the room reaches where you turned the dial. If you need a heat/cool/off selection or a fan On/Auto switch, that is the CT87N’s System and Fan switch page in the same manual, not the CT87K.

Important Safety Notices

The CT87K Owner’s Manual carries four safety statements that are worth reading before the screwdriver comes out:

• Turn the power off first. Step 1 of the removal procedure reads: “CAUTION: TURN OFF POWER to system at the furnace, or at the fuse/circuit breaker panel before you begin.” Do not remove or touch low-voltage wiring until you have confirmed power is off at the equipment.
• Mercury disposal. The manual’s MERCURY NOTICE says that if your old thermostat contains mercury, you should contact your local waste-management authority for proper disposal instructions rather than placing it in the trash.
• Lithium / perchlorate cell. The Owner’s Manual states the thermostat contains a lithium battery that may contain perchlorate material and that special handling may apply; it points to the California DTSC perchlorate guidance.
• Cooling low-temperature caution. The CT87N version of the manual adds: “CAUTION: EQUIPMENT DAMAGE HAZARD (CT87N). Do not operate cooling system when outdoor temperature is below 50°F (10°C).” The CT87K is heat only and does not have that feature, but the same rule applies to any connected cooling equipment.

If you are not comfortable removing the old thermostat, if the wire labels do not line up with the CT87K terminals, or if your existing wiring uses more conductors than the CT87K expects, stop. Call Honeywell at the number in the manual or hire a licensed HVAC technician rather than guessing at a low-voltage connection.

Getting Help

The Owner’s Manual itself directs users to 1-800-468-1502 when the wire count does not match the CT87K’s expected two- or three-conductor heat-only circuit. Honeywell Home (a Resideo brand) also publishes the 69-1959EFS document and a companion Range Stops PDF on its support site under “The Round Non-Programmable Thermostat” listing. If you need the exact English wording for a warranty claim, note the model number (CT87K1004 or your variant), the date of purchase, and the terminal layout you used.

Download PDF: Honeywell The Round CT87K Owner’s Manual.pdf

This Honeywell VisionPRO TH8000 Series Installation Manual is the 12-page guide for the touch-screen TH8321U1097, the only model listed on page 1. It covers wiring for conventional, heat pump, and IAQ systems, plus 70+ installer setup functions and system tests. The document is form 69-2389-03, © 2011 Honeywell International Inc.

Download Manual (PDF)

Table of Contents

What the Manual Covers

Page 1 lists one model: “TH8321U1097: For up to 3 Heat/2 Cool heat pump or up to 2 Heat/2 Cool conventional systems with dehumidification, humidification, or ventilation”. To find your model number, “(Pull thermostat from wallplate and turn over to find model number)”. This VisionPRO TH8000 wiring guide covers the TH8321U installation for touch-screen programmable control.

The manual opens with three notices: a perchlorate warning for the lithium battery, a mercury notice if replacing an old control, and an electrical hazard caution: “Can cause electrical shock or equipment damage. Disconnect power before beginning installation.” The guide states: “Must be installed by a trained, experienced technician”.

Before You Install

Page 2 covers wallplate installation. “Separate wallplate from thermostat.” Mount it with “Drill 3/16″ holes for drywall. Drill 7/32″ holes for plaster.” After wiring, “Push excess wire back into the wall opening. Plug wall opening with non-flammable insulation.”

Page 6 shows how to mount the thermostat: “Remove tab. Align pins on back of thermostat with slots in wallplate, then push gently until thermostat snaps into place.” Then set the date and time before entering installer setup.

TH8000 Series Terminal Designations

Page 3 defines terminals for conventional and heat pump systems. Both share R (system power), C (common), S1/S2 (optional outdoor sensor), and U1/U1 (optional IAQ device). These TH8000 Series terminal designations apply to all wiring configurations.

Wiring Diagrams for Conventional Systems

Page 4 shows six conventional configurations for VisionPRO TH8000 wiring. Each lists the terminals used and any notes.

Notes: “[1] Power supply. Provide disconnect means and overload protection as required.” “[2] Optional 24VAC common connection.” “[6] Only works with single transformer systems.”

Heat Pump Wiring Diagrams

Page 5 covers four heat pump configurations for VisionPRO TH8000 heat pump wiring systems.

Notes: “[3] O/B set to control as either O or B in installer setup.” “[4] If L terminal is used, 24VAC common (terminal C) must be connected.” “[5] Heat pump reset (powered continuously when thermostat is set to Em. Heat; system monitor when set to Heat, Cool, or Off).”

IAQ Wiring (Humidification, Dehumidification, Ventilation)

Page 5 also shows six IAQ device configurations, all using the U1/U1 terminals. These indoor air quality connections let you integrate humidifiers, dehumidifiers, and ventilators with the thermostat’s control logic.

Notes: “[7] Terminals are normally open dry contacts.” “[8] Equipment must include dehumidification terminal for low-speed fan.”

Installer Setup Functions

Pages 7-10 list 70+ VisionPRO TH8000 installer setup functions (0120-0710). The most critical are:

The full list includes date/time (0120-0160), schedule format (0160), energy saving (0165), heat pump type (0173), auxiliary heat (0200), fossil fuel kit (0210), 2nd/3rd stage cycle rates (0230, 0260), backlight (0280), auto changeover deadband (0310), temperature display (0320), daylight savings (0330), remote sensor (0340), dual fuel control (0345-0347), heat pump lockouts (0350-0360), humidification control (0372-0374), dehumidification (0379-0394), ventilation (0401-0432), filter reminders (0500-0520), UV lamp (0520), adaptive recovery (0530), program periods (0540), clock format (0640), extended fan timer (0650-0660), keypad lock (0670), temperature control (0680-0690), display offset (0700-0701), and reset (0710).

Each VisionPRO TH8000 installer setup function controls a specific aspect of system operation. The manual prints factory defaults in bold throughout pages 7-10, so you can see at a glance which settings need changing for your particular installation.

Installer System Test

Pages 10-11 describe seven system tests. Enter test mode by pressing the system button repeatedly until “Test” appears.

The manual warns: “CAUTION: EQUIPMENT DAMAGE HAZARD. Compressor protection is bypassed during testing. To prevent equipment damage, avoid cycling the compressor quickly.”

Pages 11-12 explain special functions. Auto Changeover (0300) requires heat/cool settings at least 2°F apart (5°F if dehumidification is on).

Remote Sensor (0340) can display outdoor temperature or use a remote indoor sensor. Adaptive Intelligent Recovery (0530) learns how long the system takes to reach setpoints. Compressor Protection (0580) forces a wait before restart.

Dehumidification (0380) on TH8321 models can lower temperature up to 3°F below the cool setting. Heat pump control (0350-0360) sets compressor and auxiliary lockout temperatures. Ventilation (0400-0432) can be locked out by outdoor temperature. Dehumidification Away Mode (0390-0394) controls humidity when the home is unoccupied.

TH8000 Series Specifications and Accessories

Page 12 lists TH8000 Series specifications:

• Temperature ranges: Heat 40° to 90°F (4.5° to 32°C), Cool 50° to 99°F (10° to 37°C)
• Operating ambient: 0° to 120°F (-18° to 48.9°C)
• Shipping: -30° to 150°F (-34° to 66°C)
• Humidity: 5% to 90% (non-condensing)
• Dimensions: 4-9/16 in. H x 6 in. W x 1-3/8 in. D (116 mm H x 152 mm W x 35 mm D)

Accessories include outdoor sensor C7089U1006, remote indoor sensor C7189U1005, discharge air sensor C7735A1000, ventilators ER200B2006/HR200B1005, fresh air damper EARD6, humidifiers HE265A1007/HM512W1005, and cover plate 32003796-001.

FAQ

How do I find the model number?

“(Pull thermostat from wallplate and turn over to find model number)”. Page 1 lists TH8321U1097 for this TH8321U installation.

What’s the difference between conventional and heat pump terminals?

Heat pump systems add E/Aux (auxiliary/emergency heat), L (heat pump reset/monitor), and O/B (changeover valve). Conventional systems use W/W2 for heat stages and Y/Y2 for cooling stages.

How do I wire an outdoor sensor?

Connect to S1/S2 terminals. In installer setup, set function 0340 to 1 (outdoor sensor display only), 2 (outdoor sensor for control with lockouts), or 4 (discharge air sensor for desert humidity control).

What does the L terminal do?

The L terminal provides “Heat pump reset (powered continuously when System is set to Em Heat; system monitor when set to Heat, Cool or Off).” The wiring notes make the common connection mandatory when this terminal is used.

How do I set up dehumidification?

Set function 0371 to 2 for dehumidification control. For TH8321 models, function 0380 can activate cooling to reduce humidity by up to 3°F below the cool setting. For whole-house dehumidification, wire to U1/U1 and set function 0379 to 3.

What’s the compressor protection setting?

Function 0580 defaults to 5 minutes. The manual states: “Forces the compressor to wait a few minutes before restarting, to prevent damage. During this time, the message ‘Wait’ is displayed.” Options are 0-5 minutes.