This Honeywell TH8110U1003 VisionPro Thermostat Operating Manual guide is for the touchscreen that arrived pre-programmed and only needs a clock set. Everything below is quoted from the 32-page PDF, with the page number attached so you can check it.

Table of Contents

What Is the TH8110U1003?

Plain answer: a touchscreen thermostat for a single-stage system, sold as part of the VisionPro TH8000 Series. The manual calls it “the world’s most advanced, easy-to-use thermostat” (page 2).

One booklet covers three models, and the differences matter. Page 1 prints the list, “This manual covers the following models”:

• “TH8110U: For 1 Heat/1 Cool systems”
• “TH8320U: For up to 3 Heat/2 Cool systems”
• “TH8321U: For up to 3 Heat/2 Cool systems with dehumidification”

The model number decides what the extra menu options do; to find it, “Pull thermostat from wallplate and turn over to find model number” (page 1).

Page 1 also warns: “Never use sharp instruments, such as a pencil or pen, to press touchscreen keys.”

Controls at a Glance

Page 4 prints the screen with every key labelled, and the captions under it say what each key does:

Touchscreen keys, from the quick reference on page 4

Key	What the manual says it does
SCHED	“Press to set program schedule (see page 11)”
HOLD	“Press to override program schedule (see pages 12-14)”
CLOCK	“Press to set clock (see page 6)”
SCREEN	“Press to lock keypad for 30 seconds to clean screen (see page 17)”
MORE	“Press for more options (select models only)”
FAN	“Press to select fan operation (see page 7)”
SYSTEM	“Press to select system type (see page 8)”

Page 5 lists the status line: “Cool On: Cooling system is activated”, “Heat On: Heating system is activated” and “Recovery” — for when “Adaptive Intelligent Recovery in effect (see page 15)”, the feature that lets the thermostat “learn” how long the furnace and air conditioner take “to reach programmed temperature settings”. Heat running early for a wake-up isn’t a bug.

Clock, Fan and System Settings

Set the clock first. Page 6: “To set the current time display, press CLOCK, then press” the up or down arrow, and DONE saves. The note that separates it from a cheap dial: “The real-time clock should never require adjustment since it automatically updates for daylight savings time, and stores all date/time information”. The weekday is set in the advanced functions.

Fan has three modes, and page 7 defines them exactly:

• “On: Fan is always on.”
• “Auto: Fan runs only when the heating or cooling system is on.”
• “Circ: Fan runs randomly, about 35% of the time, not counting any run time with the heating or cooling system.”

Two fine points from that page: “If a fan schedule is programmed, “Auto” will run the fan schedule”, and a forced fan stays put — “the setting you select will remain active until you press FAN again to select Auto”.

Page 8 gives SYSTEM its positions: “Heat: Thermostat controls only the heating system.” “Cool: Thermostat controls only the cooling system.” “Off: Heating and cooling systems are off.” “Auto: Thermostat automatically selects heating or cooling depending on the indoor temperature.” A fifth, Em Heat, is flagged “Select models only”, and its result is blunt: “Compressor is locked out.”

Programming the Schedule

The Honeywell VisionPro thermostat programming instructions begin on page 9, under “Save money by setting program schedules”, which defines the four periods by what you’re doing in them:

• Wake — “Set to the time you awaken and the temperature you want during the morning, until you leave for the day.”
• Leave — “Set to the time you leave home and the temperature you want while you are away (usually an energy-saving level).”
• Return — “Set to the time you return home and the temperature you want during the evening, until bedtime.”
• Sleep — “Set to the time you go to bed and the temperature you want overnight (usually an energy-saving level).”

The factory schedule assumes a conventional day. Page 3 states the presets in one line: “energy-saving levels while you’re at work or asleep (assumes you wake at 6 am, leave at 8 am, return at 6 pm and go to bed at 10 pm)”.

Adjusting a period

Page 11’s steps, in the manual’s own words:

1. “Press SCHED, then EDIT.”
2. “Press day buttons (MON-SUN) to select day(s).”
3. Set that period’s time and its heat and cool temperatures with the up or down arrow.
4. “Press other time periods (LEAVE, RETURN, SLEEP) to set time and temperatures for each.”
5. Press DONE to save, or CANCEL to leave without saving changes.

Two helpers: “You can press CANCEL PERIOD to eliminate any unwanted time period”, and “Press FAN to customize fan settings for any time period (see page 7)”. The day buttons copy one day onto others — the screen prints “OK TO PICK MULTIPLE DAYS” above them. Want two periods instead of four? Advanced function 0540 switches between “Two program periods (Wake, Sleep)” and “Four program periods (Wake, Leave, Return, Sleep)” (page 25).

Temporary, Permanent and Vacation Holds

Temporary. Press the up or down arrow: “This will temporarily override the temperature setting for the current time period.” When the timer expires or you press CANCEL or SCHED, “the program schedule will resume and set the temperature to the level you’ve programmed”.

Permanent. “Press HOLD to permanently adjust the temperature. This will turn off the program schedule.” Page 13: what you set “will be maintained 24 hours a day until you manually change it or press CANCEL (or SCHED) to cancel “Hold” and resume the program schedule.”

Vacation. Page 14 suspends the schedule for a counted run of days: set a temperature and the resume time, then “Press HOLD twice” and pick the count. “Whatever temperature you set will be maintained 24 hours a day for the number of days you select. After this number of days have elapsed, the previously programmed schedule will resume at the time you set.” Back early? CANCEL or SCHED resumes it.

Screen Lock, Cleaning and Humidity

Page 16 covers tampering: “To prevent tampering, the screen can be partially or fully locked.” In partial lock, “the screen displays SCREEN LOCKED for several seconds if a locked key is pressed”, and any unlocked key clears it while that message shows. Full lock is absolute — “When the screen is fully locked, no keys function.” Both come from advanced function 0670 (page 25).

Cleaning has its own key: “Press SCREEN to lock the screen for cleaning. The screen will remain locked for 30 seconds so you can clean the screen without changing any settings” (page 17). On liquids: “Do not spray any liquid directly on the thermostat. Spray liquids onto a cloth, then use the damp cloth to clean the screen.”

Humidity is a select-models feature. “Select models can display the current indoor humidity level” (page 18), and “When humidity increases, the thermostat runs the air conditioner longer to reduce humidity” (page 19). With an outdoor sensor fitted, “the outdoor temperature is shown instead of the humidity level. Press MORE to display the humidity level.”

Advanced Functions

Entering setup is a two-key trick, not a menu button. Page 21: “1. Press SYSTEM.” then “2. Press and hold blank center key until the display changes.” The blank centre key is the space in the middle of the screen. The Honeywell TH8000 series advanced functions a homeowner needs:

Advanced functions quoted from pages 22-25

Function	Name	Settings in the manual
0160	“Program schedule on/off”	“0 Program schedule is off. Thermostat is non-programmable.” / “4 Program schedule is on (7-day programmable).”
0540	“Program schedule periods”	“2 Two program periods (Wake, Sleep)” / “4 Four program periods (Wake, Leave, Return, Sleep)”
0320	“Temperature format (°F/°C)”	“0 Fahrenheit” / “1 Celsius”
0670	“Screen lock”	“0 Screen is unlocked (fully functional)” / “2 Screen is fully locked”
0500	“Furnace filter change reminder”	“0 Off (no reminder to change furnace filter)” through “6 Reminder after 365-day run time (about 3 years)”
0510	“Humidifier pad change reminder”	“1 Reminder after 3 months” / “2 Reminder after 6 months” / “3 Reminder after 1 year”
0520	“UV lamp change reminder”	“1 Reminder after 1 year”
0120-0150	Year, month and date settings	Four separate functions: the two year digits, month (1-12) and date (1-31)
0330	“Daylight savings time on/off”	“The thermostat is pre-programmed to automatically adjust to daylight savings time.”

Every reminder alert clears the same way: “Press RESET to cancel the alert”.

Batteries and Reset

Page 20 opens with the fact that surprises most owners: “Batteries are optional (to provide backup power) if your thermostat was wired to run on AC power when installed.” When the warning starts, “Install fresh batteries immediately when the LO BATT warning begins flashing.” Even without one, the standing advice is to “replace batteries once a year, or before leaving home for more than a month”, and TH8110U1003 battery replacement takes “3 fresh AAA alkaline batteries”.

There is no factory reset button in this document, so how to reset Honeywell VisionPro thermostat settings comes down to the levers the manual does give. To clear the schedule rather than the power, use function 0160: “0 Program schedule is off. Thermostat is non-programmable.” / “4 Program schedule is on (7-day programmable).” Because the clock “stores all date/time information”, a battery swap shouldn’t cost you the schedule.

In Case of Difficulty

For TH8110U1003 troubleshooting, page 26 opens with “If you have difficulty with your thermostat, please try the following suggestions. Most problems can be corrected quickly and easily.” and names five symptoms. Here is the manual’s own list, with only what this PDF copy prints as readable text:

The manual’s “In case of difficulty” symptoms, pages 26-27

Symptom	What this copy of the manual reads
“Display is blank”	Fixes are in the scrambled block; the readable tail says “batteries are correctly installed (see page 20).”
“No response to key presses (or temperature will not change)”	Listed on page 26; read the bullets under it in your own copy.
“Backlight is dim”	Listed on page 26, followed by the same readable “batteries are correctly installed (see page 20).”
“Heating or cooling system does not respond”	Press SYSTEM once each way: “Make sure the temperature is set higher than the Inside temperature.” / “Make sure the temperature is set lower than the Inside temperature.”
“Heating or cooling system does not respond”	If “Wait” is displayed, the readable tail gives “5 minutes for the system to restart safely, without damaging the compressor (see page 15).”
“Display shows Fan Auto and On or Auto and Circ at the same time”	“If Auto and On is shown, the fan is scheduled for “On” during this period (see page 7).”

That gap is the honest limitation of this run: several pages of this PDF — the feature list on page 2, the preset temperatures on page 10 and most of the troubleshooting on page 26 — use a subset font with no usable text mapping, so they extract as scrambled glyphs. The symptom names above survived because they print in a normal font; the sentences under them did not. For those rows the paper manual is the authority.

Specifications

• Document: Operating Manual, VisionPRO TH8000 Series Touchscreen Programmable Thermostat, number 69-1894EFS-03, 32 pages, © 2011 Honeywell International Inc.
• Schedule: four periods a day, weekday and weekend settings, “7-day programmable” through function 0160.
• Warranty: page 29 heads a “5-year limited warranty”, and the readable exclusion says “This warranty does not cover removal or reinstallation costs.”
• Support: “call Honeywell Customer Care toll-free at 1-800-468-1502”.

FAQ

Can the TH8110U1003 run two stages of heating?

Not per this document, which assigns it one stage each way: “TH8110U: For 1 Heat/1 Cool systems”. The models in the same booklet that handle more are TH8320U and TH8321U, “For up to 3 Heat/2 Cool systems”.

Why does the screen say Wait after I turn the cooling on?

Compressor protection, which page 15 defines as a delay rather than a fault: “This feature forces the compressor to wait a few minutes before restarting, to prevent equipment damage.” Page 27 gives the number: “5 minutes for the system to restart safely, without damaging the compressor”.

Is there a TH8110U1003 wiring diagram in this manual?

No. This operating manual runs from clock setting to humidity control with no terminal chart; the only wiring language here is that the thermostat may have been “wired to run on AC power when installed”.

Does the TH8110U1003 work with an app?

The document never says so. Across all 32 pages there is no mention of Wi-Fi, a network, an app or a portal — your TH8110U1003 VisionPro manual PDF describes keypad-only operation.

What if the display goes blank?

Page 26 lists “Display is blank” first, and its readable fragment points at power: “batteries are correctly installed (see page 20).” The rest of that block is in the pages this copy can’t render as text, so confirm against the paper manual.

The Honeywell RTH7400D Programmable Thermostat Owner’s Guide is a 64-page booklet, document 69-1726-1, dated 08-04 on the back cover. It covers the whole life of the unit in one file. Installation runs from page 3 to page 26, the installer setup menu from page 27 to page 38, and operation from page 39 to page 61. This page follows that booklet and quotes its wording where the wording decides how a step works.

Download the Honeywell RTH7400D Owner’s Guide (PDF)

Download Honeywell RTH7400D Programmable Thermostat Owner’s Guide (PDF)

Table of Contents

• What the Guide Covers
• What Comes in the Box
• Before You Touch the Wires
• Mounting the Wallplate
• Wiring: Conventional and Heat Pump
• Batteries and Mounting the Thermostat
• Setting the Calendar and Clock
• System and Fan Settings
• Installer Setup Numbers
• Programming the Four Periods
• Temporary and Permanent Holds
• Filter Timer
• Adaptive Intelligent Recovery
• Compressor Protection
• Troubleshooting Tips
• Specifications
• Frequently Asked Questions

What the Guide Covers

The contents page lists twelve headings with their page numbers. The file runs straight through in English with no second language, so the printed numbers and the PDF page numbers are the same throughout.

Section	Pages
Prepare for Installation	3
Follow Important Instructions	5
Remove Old Thermostat	6
Follow Special Instructions	7
Label Old Thermostat Wires	10
Mount New Wallplate to Wall	11
Connect Wires to New Wallplate	15
Install Batteries	23
Attach New Thermostat to Wallplate	24
Configure Installer Setup	26
Customer Assistance	62
Limited One-Year Warranty	63

Page 1 states the electrical scope in one sentence: the thermostat provides electronic control of “24 Vac heating and cooling systems or 750 mV heating systems.” No other voltage is mentioned anywhere in the booklet.

One numbering detail explains an apparent gap. The contents page puts Configure Installer Setup at 26, while the numbered step itself opens on page 27, because page 26 finishes the calendar step.

What Comes in the Box

Step 1 asks you to check six items before starting. The guide names them in the parts drawing on page 3:

• Wallplate
• Thermostat
• Mounting screws (2) and wall anchors (2)
• Owner’s guide
• Wire labels
• Caution card

If any of them is missing, the instruction is to call Honeywell Customer Care at 1-800-468-1502 before returning the thermostat to the store. The same page warns to turn off power at the furnace or at the fuse and circuit breaker panel before you begin.

The tool list on page 4 is short and specific:

• Two AA alkaline batteries
• No. 2 Phillips screwdriver and standard pocket screwdriver
• Drill
• Drill bit, 3/16 in. for drywall and 7/32 in. for plaster
• Level (optional)
• Hammer
• Pencil
• Electrical tape

The bit sizes are worth reading twice: 3/16 in. for drywall and 7/32 in. for plaster, with the plaster figure repeated again in the mounting step on page 14.

Before You Touch the Wires

Step 2 is a single rule: do not connect the wires to the new thermostat based on wire colour, because damage can occur to the heating or cooling system. The guide gives the alternative in the same paragraph: the enclosed wire labels mark the wires connected to the old thermostat, and those labels are what the new connections follow.

Step 3 removes the old unit. Power goes off first, at the system or at the fuse and circuit breaker panel. Then the cover comes off, and the old thermostat comes off the wall or wallplate with the wires left in place. Page 6 adds a mercury notice: a thermostat with mercury in a sealed tube does not go in the trash, and your local waste management authority has the recycling and disposal instructions.

The C and C1 wire rules

Step 4 handles the wires that are easy to get wrong. Page 7 gives the two-wire case and page 8 gives the one-wire case:

• Two C and C1 wires on the old thermostat: do not connect them to the new thermostat. Disconnect them, keep them from touching each other or any other wire, and wrap the bare end of each one separately with electrical tape.
• One C or C1 wire: connect that wire to C on the new thermostat.
• Wires not connected to the old thermostat: do not connect them to the new thermostat, and wrap their ends with electrical tape.

Step 5 labels each wire as it is disconnected, using the tags supplied in the box. The page adds a practical warning: do not let the wires fall into the wall opening once they are free.

Mounting the Wallplate

Step 6 is seven numbered moves across pages 11 to 14. Separate the wallplate from the thermostat, pass the labeled wires through the wire hole on the wallplate, then position it with the arrow pointing up.

The level is used for appearance only, and the guide says so in brackets. Mark the two mounting holes with a pencil, move the wallplate aside, and drill at the marks: 3/16 in. for drywall, 7/32 in. for plaster. Tap the wall anchors in until they sit even with the wall surface, set the wallplate over them, insert the two screws, check the level if you want, and tighten.

Wiring: Conventional and Heat Pump

Step 7 starts with a choice rather than a connection. Standard heating and cooling systems use the conventional letter designations. Heat pump systems use the heat pump designations. The guide points to the system-type table on page 30 when you are not sure which one you have.

The jumper between Rc and R

Two rules cover the metal jumper wire on the terminal block:

• If wires are to be connected to both Rc and R, loosen both screw terminals and remove the jumper.
• If only one of the two is to be connected, leave the jumper in place.

Wires go into the holes on the side of the terminal block that match the letter designations, and the screws are tightened afterwards. One limit applies to the whole block: do not connect more than one wire to each terminal.

Conventional systems

Page 18 prints the letter comparison for a conventional system. Each row shows a terminal on the new thermostat and the letters that may appear on the labeled wires from the old one.

Terminal on the new thermostat	Possible letter on the labeled wire
RC	RC or R
R	R or RH, 4, V
W	W or W1, H
Y	Y or Y1, M
G	G or F
C	C or C1, X, B
Y2	Y2
W2	W2

Four numbered notes follow that chart. They are printed on page 19, and the numbers match the triangles in the drawing:

1. If wires go to both RC and R, remove the jumper between them. If only one of the two is used, leave the jumper in place.
2. If the old thermostat had wires on both R and RH, remove the jumper on the new one. Connect the old R to the new RC and the old RH to the new R.
3. If two C and C1 wires were connected to the old thermostat, tape each bare end separately and do not use them.
4. If one C or C1 wire was connected, it goes to the C designation on the new thermostat.

Heat pump systems

Page 20 prints the equivalent chart for a heat pump. This one has nine positions, one more than the conventional block.

Terminal on the new thermostat	Possible letter on the labeled wire
RC	VR or V or R
R	No wire shown; the jumper stays in place
O/B	H or B, O
Y	Y1 or M or Y
G	F or G
C	X or B, C
L	F or L
E	X2 or X, E
AUX	AUX, W1, W or W2

On the heat pump chart the R position carries no wire of its own. The drawing leaves the jumper between RC and R in place, and the first note on page 21 states that instruction directly. The other three notes cover cases that need a decision before wiring continues:

• If the old thermostat had separate wires on both V and VR, some system modification is required. Call your local heating and cooling contractor for assistance.
• If the old thermostat had wires on both O and B, attach the B wire to the C designation on the new thermostat. If another wire is already matched to C, contact Honeywell.
• If the old thermostat had wires on W1, Y1 and W2, some system modification is required. Call your local heating and cooling contractor for assistance.

Step 7 closes by pushing excess wire back into the wall opening and keeping the wires inside the shaded area marked on the drawing.

Batteries and Mounting the Thermostat

Two fresh AA alkaline batteries go on the back of the thermostat, in the holder marked on the casing. The guide then asks for one more move that is easy to miss: remove the tab labeled “Remove during installation” in the lower right corner of the thermostat back.

Mounting is two steps and a power check. Align the screw blocks with the pins on the back of the thermostat, then push the thermostat straight onto the wallplate until it snaps into place. Turn the power back on at the system or at the fuse and circuit breaker panel. If the wires interfere with mounting, push the excess back into the wall opening.

Setting the Calendar and Clock

Page 25 states the memory behaviour: once the calendar is set, the thermostat keeps the current time and day in memory for up to ten years under normal use. The calendar is the first screen shown when the unit is powered for the first time.

1. Use the Up or Down arrow to set the Month.
2. Press Next to advance to the Date.
3. Use the Up or Down arrow to set the Date.
4. Press Next to advance to the Year.
5. Use the Up or Down arrow to set the Year.
6. Press Done to advance to the Time.
7. Use the Up or Down arrow to set the Time.
8. Press Done again to reach the home screen.

The clock has its own path once the unit is running. Press Clock & More, set the time with the arrows, and press Done. A footnote on page 48 adds that the day of the week should already be correct, and points back to the installer setup section if it is not.

System and Fan Settings

The three buttons under the display carry the everyday settings. System & Fan selects Heat, Off, Cool and Em Heat, and also selects Fan Auto or On. Schedule selects the programming mode. Clock & More selects time and furnace filter information. The two arrow buttons raise or lower the temperature setting, and in other screens they make selections.

Heat, Off, Cool and Em Heat

• Heat: the thermostat controls the heating system.
• Off: heating and cooling systems are both off.
• Cool: the thermostat controls the cooling system.
• Em. Heat: available on heat pump systems with auxiliary heat. The thermostat controls emergency heat and auxiliary heat if needed, and the heat pump compressor is not operational.

Page 41 prints a caution in the system settings section. It carries an equipment damage hazard and warns that air conditioning compressor damage is possible. It also states that the cooling system should not be operated when the outdoor temperature is below 50°F (10°C).

Fan Auto and On

Press System & Fan, then press the Fan button to choose between two modes. Auto is the setting the guide calls normal for most homes, and the fan runs only when the heating or cooling system is on. On keeps the fan running continuously, for improved air circulation or for more efficient air cleaning.

Installer Setup Numbers

Step 11 is the menu that tells the thermostat what equipment it is connected to. The entry gesture uses two different presses, and the order matters:

1. Press and release the System button.
2. Press and hold the center button for approximately five seconds, until the screen changes.
3. Release the center button when the display matches the drawing on page 28.

Inside the menu, the arrows change the setting, Next advances to the next installer setup number, Done exits and saves, and Go Back returns to the last one. The number sits on the left of the display and the selected value on the right.

Thirteen setup numbers are documented. Three of them, 0180, 0190 and 0240, may not appear at all. The guide says to move to the next page when the number is missing from the left side of the display.

Number	Name	Settings
0120	Date (Year Upper)	First two digits of the calendar year, 20 for 2005
0130	Date (Year Lower)	Last two digits of the calendar year, 05 for 2005
0140	Date (Month)	Number of the current month
0150	Date (Day)	Number of the current date
0170	System Type Selection	1 to 10, listed below
0180	Fan Control in Heating	0 gas or oil heat, 1 electric heat
0190	Heat Pump Changeover Valve	0 changeover in cooling with an O wire, 1 changeover in heating with a B wire
0240	Heating Cycle Rate	5, 9, 3 or 1 by equipment type
0320	Temperature Indication Scale	0 Fahrenheit, 1 Celsius
0330	Daylight Savings	0 off, 1 on
0500	Furnace Filter Change Reminder	0 off, 1 to 6 by interval
0530	Adaptive Intelligent Recovery	0 conventional recovery, 1 adaptive
0640	Clock Format	12 or 24

0170, the system type list

Page 30 lists ten options:

1. Heating and Cooling (Conventional), gas, oil or electric heating with central air conditioning.
2. Single-stage Heat Pump with no back-up or auxiliary heat, where the compressor runs in both heating and cooling.
3. Heat Only with no fan (Conventional), with no wire on the G terminal.
4. Heat Only with fan (Conventional), typically wires R, W and G.
5. Hot Water Heat Only (Conventional), for three wires or for normally closed hot water valves wired to R and Y.
6. Cool Only (Conventional), central air conditioning only.
7. Multistage Heat Pumps, a heat pump with auxiliary or back-up heat.
8. Multistage Conventional Heating and Cooling with 2 stages of heat on W and W2 and 2 stages of cool on Y and Y2.
9. Multistage Conventional Heating and Cooling with 2 stages of heat on W and W2 and 1 stage of cool on Y.
10. Multistage Conventional Heating and Cooling with 1 stage of heat on W and 2 stages of cool on Y and Y2.

0180, 0190 and 0240

Fan control in heating depends on who runs the fan during a heat call. At 0180, 0 means the heating system controls the fan, which is the gas or oil case, and 1 means the thermostat controls it, which is the electric heat case.

Changeover at 0190 follows the wire that was connected to O/B. Use 0 when an O wire went to that terminal, and 1 when a B wire did.

Heating cycle rate at 0240 takes four values, and each one names equipment rather than a number of cycles. Value 5 is a gas or oil furnace under 90% efficient and value 9 is an electric furnace. Value 3 covers gas or oil hot water heat and a gas furnace at 90% or above. Value 1 is gas or oil steam or gravity heat.

Programming the Four Periods

The thermostat runs up to four periods. The guide describes each one by what the household is doing. Wake is the period when you awaken and want the home at a comfortable temperature. Leave is the period away from home, and Return is the period when you come back. Sleep is the period when you are asleep and want an energy-saving temperature. Monday through Friday can share one set of times and temperatures, and Saturday and Sunday are scheduled separately.

1. Press the Schedule button. The View button looks at the schedule without editing it.
2. Press the Edit button.
3. Monday through Friday flashes. Press Select Day to select that block. Checkmarks appear next to the days selected.
4. Press Next Step. Wake flashes to show it is selected.
5. Press Next Step to reach the Wake time, then change it with the arrows.
6. Press Next Step to reach the heating temperature, then change it with the arrows.
7. Press Next Step to reach the cooling temperature, then change it with the arrows.
8. Repeat for Leave, Return and Sleep, then press Done. “Saved” appears on the display while the changes go to the selected days.
9. For Saturday and Sunday, repeat the whole sequence. Use the Down arrow until Sat or Sun flashes, then press Select Day.

The day list is worked with the arrows rather than the Select Day button alone. Up and Down move through the days, and Select Day or DeSelect Day adds or removes the day you are on.

Temporary and Permanent Holds

A temporary hold ends by itself. Press the Up or Down arrow next to the temperature you want to adjust, and “Temporary” appears above the set temperature. The setting holds until the next scheduled period time, and Use Schedule cancels it and resumes the schedule.

A permanent hold does not end by itself. Set the temperature with the arrows, press Hold, and “Permanent Hold” shows on the display. It stays until it is cancelled, and Use Schedule is the button that cancels it and resumes the schedule.

Filter Timer

The filter timer counts fan run time rather than calendar days. The interval is set at installer setup number 0500. “Change Filter” appears on the display when the timer expires, and pressing Reset restarts it.

The remaining time can be checked without waiting for the reminder. Press Clock & More, press Next, press Reset if you want to restart the timer at that moment, and press Done. The reminder itself is switched on or off at installer setup number 0500.

Adaptive Intelligent Recovery

The feature removes the guesswork of when to start heating or cooling. The guide’s example is a Wake period set for 6:00 AM at 70°F. The thermostat turns the heat on before 6:00 AM so that the house reaches 70°F by 6:00 AM.

Two details make it recognisable in use. The word “Recovery” appears on the screen when the system is coming on before a scheduled time. The learning period is stated as well: about a week to adjust to local weather, your schedule, the construction of your home and your heating or cooling system. Each day adjusts the next day’s recovery start time.

The feature is switched at installer setup number 0530. Value 0 is conventional recovery, where the system starts at the programmed time, and 1 is adaptive, where it starts early enough to reach the setting by the start of the period.

Compressor Protection

The thermostat has a built-in minimum-off timer that prevents the compressor from restarting too early after a shutdown. The timer is activated after the compressor turns off.

If there is a call during that window, the display shows “Wait”. When the timer expires, “Cool On” or “Heat On” appears solidly and the compressor and fan turn on. A footnote on page 58 marks “Heat On” as heat pump only.

Troubleshooting Tips

The troubleshooting section runs across pages 59, 60 and 61 as a two-column table with fourteen entries: four on page 59, six on page 60 and four on page 61. Both columns below are the guide’s own text, and the symptom wording is kept exactly as printed so you can match it to the display in front of you.

If . . .	Then . . .
Display is blank.	Check that fresh AA alkaline batteries are installed as marked on the thermostat.
Temperature settings do not change.	Check that the temperature settings are: Heating 40°F to 90°F (4.5°C to 32°C). Cooling 50°F to 99°F (10°C to 37°C).
Heating system does not turn on.	Set the system to Heat by pressing the System button. Check the heat temperature setting to be sure it is set above the room temperature and “Heat On” shows solidly in the display. Check the circuit breaker to be sure it is not tripped. Check power switch at heating and/or cooling system to be sure it is on. Check the furnace door to be sure it is closed securely. Wait five minutes for the heating system to respond. If all of this was checked, contact your local heating and cooling contractor.
Cooling system does not turn on.	Set the system to Cool by pressing the System button. Check the cool temperature setting to be sure it is set below the room temperature and “Cool On” shows solidly in the display. Check the circuit breaker to be sure it is not tripped. Check the power switch at the heating and/or cooling system to be sure it is on. Check the furnace door to be sure it is closed securely. Wait five minutes for the cooling system to respond. If all of this was checked, contact your local heating and cooling contractor.
Cannot set System setting to Cool.	Check Installer Setup Number 0170, Heating and/or Cooling System Type; make sure the setting matches the installed heating and/or cooling system.
“Heat On” is not shown in the display.	Set the System setting to Heat and set the temperature setting above the room temperature. If “Heat On” is shown solidly in the display, but the heating system does not turn on, see “Heating system does not turn on” in the Troubleshooting Tips.
“Cool On” is not shown in the display.	Set the System setting to Cool and set the temperature setting below the room temperature. If “Cool On” is shown solidly in the display, but the cooling system does not turn on, see “Cooling system does not turn on” in the Troubleshooting Tips.
“Wait” shows in the display.	Compressor minimum-off timer is active. Wait up to five minutes for the cooling or heating system to turn on.
Fan does not turn on in a call for heat (electric furnaces only).	Check Installer Setup Number 0180, Fan Control in Heating, and make sure it is set to Electric Heat.
Heat pump puts out cool air in the heat mode and warm air in the cool mode (heat pumps only).	Check Installer Setup Number 0190, Heat Pump Changeover Valve, and make sure the setting matches the changeover required by the installed heat pump.
Both the heating and cooling systems are running at the same time.	Check Installer Setup Number 0170, Heating and/or Cooling System Type, and make sure the setting matches the installed heating and/or cooling system. Check and make sure the bare portions of the wires are not touching.
Heating system is running in cool mode.	Check Installer Setup Number 0170, Heating and/or Cooling System Type, and make sure the setting matches the installed heating and/or cooling system.
Heating system does not turn off and the heat temperature setting is set below the room temperature (“Heat On” is not shown in display).	Check Installer Setup Number 0170, Heating and/or Cooling System Type, and make sure the setting matches the installed heating and/or cooling system.
Red LED is on in the upper left corner and the Heat Pump is not working.	A system monitor is wired to the thermostat L terminal. See Heating or Cooling system does not turn on in the Troubleshooting Tips.

Six of the fourteen entries end at a setup number rather than at a part, and 0170 accounts for four of them on its own.

Specifications

Item	Detail
Document	69-1726-1, back cover dated 08-04
Length	64 pages, English only
System voltage	24 Vac heating and cooling systems or 750 mV heating systems
Batteries	Two AA alkaline, on the back of the thermostat
Clock memory	Current time and day kept for up to ten years once the calendar is set
Conventional terminals	RC, R, W, Y, G, C, Y2, W2
Heat pump terminals	RC, R, O/B, Y, G, C, L, E, AUX
Setpoint range	Heating 40°F to 90°F (4.5°C to 32°C), cooling 50°F to 99°F (10°C to 37°C)
Warranty	One year, battery excluded

Customer assistance is on page 62, at www.honeywell.com/yourhome or 1-800-468-1502. The warranty on pages 63 and 64 excludes the battery and excludes removal and reinstallation costs. It gives two return routes: back to the retailer with a bill of sale, or by mail with proof of purchase and a short description of the malfunction.

Frequently Asked Questions

You’ve got an RTH2510B on the wall and you need to wire it, set the schedule, or figure out why the display is blank. This guide covers the installation, programming, and troubleshooting steps from the official Honeywell owner’s manual, with a PDF download at the bottom.

What is the RTH2510B?

The RTH2510B is Honeywell’s wired 7-day programmable thermostat for standard 24-volt heating and cooling systems. It comes in the same series as the RTH2410B, which is the cheaper 5-1-1 model (one schedule for weekdays, one for Saturday, one for Sunday). The RTH2510B lets you set a different program for every day of the week, which matters if your weekends don’t look like your weekdays.

What you get, per the manual:

• Backlit display that shows the room temperature at all times
• Four periods per day: Wake, Leave, Return, Sleep
• Temporary and permanent hold to override the schedule
• Early Start: the heat or AC kicks in before the scheduled time so the room hits your target exactly when you want it
• A 5-minute compressor protection delay that prevents short-cycling
• Runs on two AAA batteries, so the schedule survives a power outage

What it works with (and what it doesn’t)

Systems it works with

The manual lists these as compatible:

• Gas, oil, or electric furnace
• Central air conditioner
• Hot water system with or without pump
• Millivolt systems (wall furnaces, gas fireplaces)
• Central heating and cooling
• Heat pump without auxiliary/backup heat
• Heat pump with auxiliary/backup heat (requires Advanced Installation setup, below)

What it doesn’t work with

The manual is explicit about two things this thermostat can’t handle:

• Multistage systems (two-stage compressors, variable-speed air handlers)
• Line-voltage systems (120V/240V baseboard heaters, electric radiators). The thermostat runs on 24V or 750mV, not 120/240V.

No C-wire needed. This thermostat runs on batteries. If you happen to have a spare C wire in the wall, cap it with a wire nut and tuck it away. The installation guide explicitly says “do not use C or X.”

Replacing an old thermostat and not sure what you have? Take a photo of the existing wiring before you disconnect anything. Then go look at the labels on the HVAC control board to confirm what each wire does.

Before you touch any wires

Shut off the breaker that controls your furnace or air handler. The thermostat itself is low-voltage, but the control board behind it isn’t. Don’t skip this.

1. Label every wire before you pull it. Stick a small piece of tape on each wire with the terminal letter it came from: R, Rh, Rc, W, Y, G, B, O. Wire colors are not a standard. The letters are what matter.
2. Check whether you have a heat pump. If you see wires going to both O and B terminals, you’ve got a heat pump. The RTH2510B handles basic heat pumps, and it can also run a heat pump with auxiliary/backup heat strips — but you have to tell the thermostat what system you have in the Advanced Installation menu (see below).
3. Mount the wallplate. Run the wires through the center hole, level it, and drive the screws.
4. Don’t run AC below 50°F outside. The manual spells this out as an equipment-damage hazard. The compressor can be hurt if you run the cooling system when it’s colder than 50°F (10°C) outdoors.

Wiring the RTH2510B

For a conventional (non-heat-pump) system, match your labeled wires to the terminals below.

Terminal	Typical color*	What it does
R / Rh	Red	24V hot, heating transformer
Rc	Red	24V hot, cooling transformer
W / AUX	White	Heating relay. Doubles as the auxiliary/backup heat terminal on heat-pump systems.
Y	Yellow	Compressor contactor. On heat-pump systems without aux heat, a factory jumper ties Y and W together.
G	Green	Fan relay
B / O	Blue / Orange	Heat pump reversing valve. Connect to whichever matches your system; don’t use both.
C / X	—	Not used. Tape off and tuck away.

* Colors are a rough guide. Always wire by the terminal label, not the wire color.

The R/Rc jumper

The thermostat ships with a small metal jumper connecting R and Rc. Leave it in place if you have just one red wire. If you’ve got two red wires (one on R, one on Rc), pull the jumper out before inserting both.

Once the wires are in, give each one a gentle tug to make sure it’s seated. Push the extra wire back into the wall, snap the thermostat onto the wallplate, and flip the breaker back on.

The Fan Operation switch

On the back of the thermostat there’s a small switch. Set it to Gas or Oil for forced-air furnaces where the fan comes on with the call for heat. Set it to Electric or Heat Pump if the thermostat controls the fan directly through the G terminal.

Telling the thermostat what system you have

This is the step most people miss. After wiring, you have to enter the Advanced Installation menu so the thermostat knows whether it’s controlling a conventional furnace, a heat pump without aux heat, or a heat pump with backup strips:

1. Hold down the Set button and both the Up and Down arrows at the same time for about 5 seconds, until the display changes.
2. Function 1 picks the system type: 0 = gas/oil/electric heat with central AC (or heat pump without aux); 1 = heat pump with auxiliary/backup heat.
3. Function 5 picks the heat source: 5 = gas/oil forced air; 6 = electric furnace; 3 = heat pump or hot water.
4. You can also set Early Start on/off (Function 13), °F vs °C (Function 14), compressor protection on/off (Function 15), and the filter-change reminder (Function 21).
5. Press Run to save and exit. Changes also save automatically after 60 seconds with no button press.

If you have a heat pump with backup heat and you skip this step, the emergency heat strips won’t work when they’re supposed to.

Setting up the 7-day schedule

The thermostat comes pre-loaded with energy-saving settings, so it’ll work out of the box. But you’ll want to adjust the times to match your actual routine.

Default factory schedule

Period	Time	Heat	Cool
Wake	6:00 AM	70°F	78°F
Leave	8:00 AM	62°F	85°F
Return	6:00 PM	70°F	78°F
Sleep	10:00 PM	62°F	82°F

Programming steps

1. Flip the SYSTEM switch to Heat or Cool first. You have to program heating and cooling separately.
2. Press SET until the display says “Set Schedule.”
3. The Wake time flashes. Use Up/Down to set it, then press SET.
4. The Wake temperature flashes. Set it, press SET.
5. Repeat for Leave, Return, and Sleep.
6. When you finish a day, the display jumps to the next day. Keep going until you’ve set every day you want to customize.
7. Press RUN to save and exit.

If your weekdays are all the same, just program Monday and leave the defaults for Tuesday through Friday. Customize Saturday and Sunday separately. No need to do all seven days from scratch.

An example workweek schedule

Period	Time	Heat (winter)	Cool (summer)
Wake	6:30 AM	68°F	76°F
Leave	8:00 AM	60°F	85°F
Return	5:30 PM	70°F	76°F
Sleep	11:00 PM	62°F	78°F

Buttons and switches you’ll use daily

Heat / Cool / Off

The SYSTEM switch on the side picks the mode. Heat calls for warmth below setpoint, Cool calls for AC above setpoint, Off shuts everything down.

Temporary hold

Tap Up or Down to nudge the temperature. The screen shows “Temporary” and the current period flashes. This override only lasts until the next scheduled period, then it goes back to the program.

Permanent hold

Press HOLD to lock in one temperature indefinitely. Useful on vacation days or when you’re home sick. Press RUN when you want the schedule back.

“Cool On” flashing

Don’t panic. That’s the 5-minute compressor protection delay. The AC will start once the timer runs out. It’s there so the compressor doesn’t short-cycle, which is what kills compressors early.

Batteries

Two AAA alkalines. When “Lo Batt” starts flashing, you’ve got about 60 days before they die. Change them once a year, or before any trip longer than a month. Always flip SYSTEM to Off before pulling the batteries. The clock and day will need re-setting, but your programmed temperatures are stored permanently.

Troubleshooting

Problem	Likely cause	Fix
Display is blank	Furnace door not closed; dead batteries	Make sure the furnace blower door is fully shut. Put in fresh AAA batteries. Check that the thermostat is snapped onto the wallplate.
Heat or AC won’t turn on	Wrong switch position; setpoint too close to room temp	Set SYSTEM to Heat and raise the setpoint above room temp, or to Cool and lower it below. Wait up to 5 minutes for the compressor delay.
“Cool On” or “Heat On” keeps flashing	Compressor protection active	Wait 5 minutes. If it’s still flashing after 15 minutes, the problem is in the wiring or the HVAC system, not the thermostat.
Can’t set temperature below/above a value	Outside the allowed range	Heat range is 40–90°F. Cool range is 50–99°F. The thermostat won’t accept values outside these.
“Heat On” never shows	Setpoint not above room temp; loose W wire	Raise the heat setpoint a few degrees. If still nothing, check that the W (white) wire is seated.
“Cool On” never shows	Setpoint not below room temp; outdoor below 50°F	Lower the cool setpoint. Don’t run AC when it’s below 50°F outside.
Room temp reading looks off	Sensor still settling after install	Give it 10–15 minutes. The thermostat should be on an interior wall, not in direct sun, near a vent, or on an outside wall.
Schedule resets after battery change	Only clock/day memory is volatile	Expected. Re-set the time and day. Your temperatures are still there.
“Lo Batt” flashing	Batteries low	Replace both AAA batteries within 60 days. Set SYSTEM to Off first.

If nothing above fixes it, the issue is almost certainly at the furnace control board, the wiring, or the HVAC equipment itself. Call a licensed HVAC tech at that point.

Specifications

Model	RTH2510B (7-day); RTH2410B (5-1-1) in same series
Programmability	7 days, 4 periods per day
Power	24 VAC (or 750 mV millivolt systems), backed by 2 AAA batteries
Load rating	1 A @ 24 VAC per output
Heat range	40–90°F (4.5–32°C)
Cool range	50–99°F (10–37°C)
System type	Single-stage heat/cool; conventional furnace, millivolt, or heat pump (with or without backup heat, set in Advanced Installation)
Compressor delay	5 minutes minimum
Warranty	1-year limited

FAQ

Do I need a C-wire?

No. It runs on two AAA batteries. If you have a spare C wire in the wall, just cap it with a wire nut and leave it alone.

How do I reset it to factory defaults?

The manual doesn’t include a dedicated factory-reset button. To clear a custom schedule, press RUN. For a deeper reset, pull the batteries out for several minutes, then re-set the clock and day. For anything more, check the troubleshooting section in the official PDF.

RTH2510B vs RTH2410B, what’s the difference?

RTH2510B lets you set a separate schedule for every day. RTH2410B does weekdays, Saturday, and Sunday as three groups. The wiring and physical hardware are identical.

Why does “Cool On” flash before the AC starts?

Compressor protection. It forces a 5-minute wait after shutdown before the compressor can restart. This prevents short-cycling. It’s normal, not a fault.

Will it work with a heat pump?

Yes, including heat pumps with auxiliary/backup heat strips. The key is you have to enter the Advanced Installation menu (hold Set + Up + Down for 5 seconds) and set Function 1 to 1. Skip that and the backup strips won’t trigger.

How long do the batteries last?

About a year. The “Lo Batt” light starts flashing around 60 days before they’re dead.

This guide is based on the official Honeywell/Resideo RTH2510/RTH2410 documentation (doc numbers 69-2420 and 69-2726). Always shut off the breaker before wiring, and call a licensed HVAC technician if you’re not sure about a step.

Skip to PDF content

Search for the Honeywell Thermostat TH8320U1008 Install Manual and you will most often reach Honeywell’s official VisionPRO TH8000 Series Installation Guide (document number 69-2693). That single manual covers the touch-screen programmable models TH8110U, TH8320U, and TH8321U, so the wiring, installer setup, and safety guidance you need for the TH8320U are all inside it. The TH8320U is rated in the guide “for up to 3 Heat / 2 Cool systems” and can be configured for either multi-stage conventional or heat pump systems.

Here is what that manual covers, how it is organized, the safety notices to read before you start, and where to turn for help. It is written for homeowners, DIY installers, and HVAC technicians. One boundary worth stating early: Honeywell’s 69-2693 document is an installation and setup manual. Everyday front-panel operation, such as setting the schedule from the touch screen or adjusting comfort setpoints, is closely related but often published as a separate homeowner guide, so if you only need day-to-day operating steps, download both documents from the official support site.

The model number is not printed on the front. As the manual instructs, pull the thermostat from the wallplate and turn it over to find the model number. That confirms you have the correct TH8320U manual before you follow any wiring step.

Key Features

The TH8000 Series is a touch-screen, wall-mounted programmable thermostat built around staging control. The features below are drawn from the installation guide’s terminal tables, installer-setup function list, and “Special functions” page. Almost all of them live in the protected Installer Setup menu, which is separate from the homeowner screens.

System and staging capability

• Up to 3 heat / 2 cool stages. Installer options cover multistage conventional and heat pump configurations (setup function 0170 offers system types such as 2 heat/2 cool multistage conventional and 3 heat/2 cool heat pump with auxiliary heat).
• Conventional and heat pump systems. The wiring section provides two distinct terminal maps: one for conventional systems (W, W2, Y, Y2) and one for heat pumps (Y, Y2, Aux/E, O/B, L).
• Wide system-type support. The guide lists gas/oil/electric heat with air conditioning, warm air, hot water and high-efficiency furnaces, heat pumps, steam, gravity, two-wire zone-valve systems (Series 20), cool only, and 750 mV heating systems.

Comfort and intelligence features

• Adaptive Intelligent Recovery™ (function 0530) lets the thermostat “learn” how long your furnace and air conditioner take to reach a programmed temperature, so the space arrives at setpoint at the scheduled time.
• Automatic or manual changeover (functions 0300 and 0310). In auto mode the thermostat picks heat or cooling based on indoor temperature; the guide notes heat and cool settings must be at least 2°F apart (at least 5°F if dehumidification is enabled).
• Programmable schedule. Setup function 0160 selects 7-day programming or non-programmable, and function 0540 chooses either 4 program periods (Wake, Leave, Return, Sleep) or 2 periods (Wake, Sleep).
• Maintenance reminders. Furnace filter (0500), humidifier pad (0510), and UV lamp (0520) change reminders with selectable run-time or calendar intervals.
• Optional sensors. Terminals S1/S2 support an optional outdoor or remote indoor temperature sensor (function 0340) for display-only or control use.
• Compressor protection. Function 0580 forces a short delay (factory default 5 minutes) before the compressor restarts; during this delay the guide says the message “Wait” flashes on the display.
• Keypad lock. Function 0670 lets you partially or fully lock the touch screen, which is handy for property managers and rentals.

Dehumidification control (function 0380) is present in this shared manual but is specified for the TH8321U model, which the guide describes as the version “with dehumidification.” If the guide shades or flags a feature as TH8321-specific, assume it does not apply to your TH8320U.

Installer Setup functions at a glance

The features above are configured through Installer Setup. Use this index to jump to the right function number:

Feature	Installer Setup function
System type	0170
Schedule format / program periods	0160 / 0540
Adaptive Intelligent Recovery	0530
Manual / Auto changeover	0300 / 0310
Compressor protection (“Wait”)	0580
Maintenance reminders (filter / humidifier pad / UV lamp)	0500 / 0510 / 0520
Keypad lock	0670
Remote / outdoor sensor (terminals S1/S2)	0340
Factory reset	0710

Document Structure

Homeowners, installers, and service technicians each go to a different part of the 69-2693 guide, so it helps to know the order things appear in. The guide is compact and mostly diagram-driven. Its sections run in this sequence (numbering follows the printed installation guide).

1. Cover & model scope. Lists the models covered (TH8110U / TH8320U / TH8321U), supported system types, the lithium/perchlorate battery notice, and the “Need Help?” contact block.
2. Wallplate installation. How to separate the wallplate from the thermostat and mount it, including drill sizes (3/16″ for drywall, 7/32″ for plaster), wire hole, mounting screws, and wall anchors.
3. Power options. Explains connecting the 24 VAC transformer common to the “C” terminal and inserting the supplied batteries for primary or backup power.
4. Wiring — terminal designations. Side-by-side Conventional and Heat Pump terminal definitions (R, Rc, C, W, W2, Y, Y2, G, L, Aux/E, O/B, S1, S2).
5. Wiring guides by system. Diagrams for conventional systems (1H/1C one- and two-transformer, heat only, heat only with fan, Series 20 zone valve, cool only, 2H/2C) and heat pump systems (1H/1C, 2H/1C and 2H/2C, 3H/2C with auxiliary heat), each with numbered notes such as “remove jumper for 2-transformer systems.”
6. Mount & set date/time. Removing the tab, snapping the thermostat onto the wallplate, and setting the real-time clock.
7. Installer setup. How to enter the setup menu (press SYSTEM, then hold SYSTEM + HEAT until the display changes) and a function table (0120 through 0710) covering year/date, system type, fan control, changeover valve, cycle rates, backlight, deadband, temperature unit, daylight savings, lockouts, reminders, keypad lock, and reset.
8. Installer system test. A “Test” mode that energizes cooling, fan, heating, and emergency-heat circuits so an installer can verify each output.
9. Special functions. Plain-language notes on auto changeover, remote sensor, Adaptive Intelligent Recovery, compressor protection (“Wait”), dehumidification, and heat pump temperature lockouts.
10. Accessories & replacement parts. Lists optional part numbers, including the outdoor temperature sensor (C7089U1006) and remote indoor sensor (C7189U1005).
11. Specifications. Temperature ranges (heat 40–90°F, cool 50–99°F), operating and shipping temperatures, and electrical ratings per terminal (for example, W and Y rated 20–30 VAC).

A homeowner usually needs only section 6 (mounting and setting date/time); the daily schedule itself lives in Installer Setup (functions 0160 and 0540). An installer works from sections 3 through 5 (power, terminal designations, and the wiring guides) plus the setup table in section 7. For diagnosis, section 8 (installer system test) together with the terminal list in section 4 and the specs in section 11 answer most questions.

Important Safety Notices

The manual opens with several requirements that people tend to skim. The lines below are quoted from the installation guide; follow them rather than working from memory.

• Qualified installer required. The guide states the product “Must be installed by a trained, experienced technician,” and that “Failure to follow these instructions can damage the product or cause a hazardous condition.”
• Electrical hazard — disconnect power. “CAUTION: ELECTRICAL HAZARD. Can cause electrical shock or equipment damage. Disconnect power before beginning installation.” Treat the low-voltage circuit as live until you have confirmed power is off at the equipment.
• Mercury disposal. The manual’s Mercury Notice says that if you are replacing a control that contains mercury in a sealed tube, you must not put the old control in the trash; contact your local waste-management authority for recycling and disposal instructions.
• Lithium / perchlorate battery. The guide warns the thermostat “contains a Lithium battery which may contain Perchlorate material,” and that special handling may apply (it points to the California DTSC perchlorate page for guidance).
• Compressor test hazard. During system test the guide warns: “CAUTION: EQUIPMENT DAMAGE HAZARD. Compressor protection is bypassed during testing. To prevent equipment damage, avoid cycling the compressor quickly.”
• Wiring specifics that affect safety and equipment. The notes direct you to remove the factory jumper only for two-transformer systems, and warn that if the L terminal is used, the 24 VAC common (terminal C) must be connected. Following these prevents mis-staging and back-feed between transformers.

When to stop and call a professional: if you find damaged or unlabeled wires, no clean way to provide a proper common (C) connection, gas or oil equipment you are not licensed to service, or any sign of moisture at the wall opening. This article summarizes the official manual; when a step is unclear, refer to the original document or contact Honeywell/Resideo support rather than guessing.

Getting Help

The manual’s own “Need Help?” block gives the primary support path: for assistance with this product, Honeywell directs users to visit customer.honeywell.com or call Honeywell Customer Care toll-free at 1-800-468-1502. Because these Honeywell Home thermostats are now supported under the Resideo brand, official documentation and product support for the VisionPRO 8000 series can also be found by searching the Honeywell Thermostat TH8320U1008 Operating Manual page or the manufacturer’s support site for the model number.

Before you call, write down the model number (found inside the unit, as noted above), your system type (conventional or heat pump, and how many heat/cool stages), and the wiring you have. Take a photo of the wiring before anything is disconnected. If you are a homeowner who only needs operating help, ask specifically for the VisionPRO 8000 Homeowner/Owner’s Manual so you get the front-panel programming guide in addition to the installation guide.

Download PDF: Honeywell Thermostat TH8320U1008 Installation Manual.pdf