Honeywell T8624D Programmable Thermostat INSTALLATION INSTRUCTIONS

Honeywell T8624D Programmable Thermostat  

APPLICATION

The T8624D Chronotherm® IV Deluxe Programmable Thermostat provides electronic control of 24 Vac multistage heating and cooling systems

FEATURES

Full seven-day program capability; different schedules and temperature setpoints may be selected for everyday to match the homeowner’s flexible schedule.  Copy key makes programming easier and faster for the installer and homeowner.  Daylight Savings Time (DST) key for quick change in and out of Daylight Savings Time.  Models available with programmable fan operation for added homeowner comfort.  Easy temporary temperature setpoint changes for current period, vacation hold (1 to 255 days) or indefinite hold adds to the homeowner comfort and energy savings.  Most frequently used keys are located by the Liquid Crystal Display (LCD) for quick and easy access to information.

• Attractive styling complements any decor to the homeowner’s delight.
•  Back lighting the large display makes the LCD very easy to read
• Models available with outdoor temperature sensor capability for homeowner convenience. The sensor is also more accurate than a thermometer.
•  Configurable features allows one model to be used to replace many different models (less inventory, no longer need to carry separate models to get these features).
• °F or °C temperature display;
•  automatic or manual changeover;
•  electric or conventional heat fan operation;
•  adjustable heating cycle rate.
•  Minimum off time for cooling compressors and heat pumps protects the equipment and extends the equipment life.
• Easy installation, setup and system test saves installer time and increases productivity.
•  System test simplifies troubleshooting and saves time by overriding the time delays.1BY7BBHHHHHHHH
•  Adaptive Intelligent Recovery® control brings the room temperature to temperature setpoint at the programmed time, maximizing comfort and energy savings.
•  Setpoints are permanently held in memory (no batteries used) and retained during power outages for increased installer and homeowner convenience.
•  Universal Versaguard™ Thermostat guards available for added security

SPECIFICATIONS

Important
The specifications given in this publication do not include normal manufacturing tolerances. Therefore, this unit might not exactly match the listed specifications. This product is tested and calibrated under closely controlled conditions, and some minor differences in performance can be expected if those conditions are changed

Thermostat Model
T8624D Thermostats provide features listed in Table 1

Changeover	System Selection	Fan Selection	Comments
Automatic	Heat-Off- Cool-Auto	On-Auto	System and fan selections are done by keyboard.

Electrical Rating (Nominal Range):

• 24 Vac, 50/60 Hz.
• 20 to 30 Vac, 50/60 Hz.

Batteries:

• No batteries required.

Loss of Power:

• The thermostat will maintain programmed times and temperatures for the life of the product. The clock and day information is retained for a minimum of thirty minutes.

System Current Load Ratings:

• 6 VA maximum at 30 Vac, 50/60 Hz.

Output Relay Draw:

• See Table 2

Relay	Running (A)	Inrush (A)
Fan	0.5	2.5
Heat (all stages)	1.5	3.5
Cool (all stages)	1.5	7.5

Temperature:

• Ratings:
  • Operating Ambient: 40°F to 110°F (4°C to 43°C).
  • Shipping: -30°F to +150°F (-34°C to +65°C).
• Display Accuracy:
  • ±1°F (±0.5°C).
• Setpoint:
  • Range:
    • Heating: 40°F to 90°F (7°C to 31°C)
    • Cooling: 48°F to 99°F (9°C to 37°C).
    • Differential: 3°F (1.5°C).
    • Default Settings: see Table 3.

Period	Time	Heat Setpoint	Cool Setpoint	Fan Setting
Wake	6:00 AM	70°F (21°C)	78°F (25.5°C)	Auto
Leave	8:00 AM	62°F (16.5°C)	85°F (29.5°C)	Auto
Return	6:00 PM	70°F (21°C)	78°F (25.5°C)	Auto
Sleep	10:00 PM	62°F (16.5°C)	82°F (28°C)	Auto

• Minimum Stage Operation Time:
  • Minimum On (Heat and Cool) (select models): factory setting 2 minutes; option 0 minutes.
  • Minimum Off (Cool and Heat Pump): factory setting 2 minutes; option 0 minutes.
• Humidity Ratings:
  • 5% to 90% RH, noncondensing.
• Clock Accuracy:
  • +1 minute per month.
• Finish:
  • Taupe or Premier White® color.

ORDERING INFORMATION

When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the TRADELINE® Catalog or price sheets for complete ordering number. If you have additional questions, need further information, or would like to comment on our products or services, please write or phone:

• Your local Home and Building Control Sales Office (check white pages of your phone directory).
• Home and Building Control Customer Relations
• Honeywell, 1885 Douglas Drive North
• Minneapolis, Minnesota 55422-4386

Dimensions

Mounting Means:
The thermostat mounts on a wallplate. The wallplate mounts horizontally on a wall or outlet box with two no. 6 x 32 screws (included).

Accessories:
C7089B Outdoor Temperature Sensors (69-1020). Universal Versaguard™ Thermostat guards

INSTALLATION

When Installing this Product…

• Read these instructions carefully. Failure to follow the instructions can damage the product or cause a hazardous condition.
• Check the ratings given in the instructions and on the product to make sure the product is suitable for your application.
• Installer must be a trained, experienced service technician.
• After completing installation, use these instructions to check out the product operation.

Location

• Install the thermostat about 5 ft (1.5m) above the floor in an area with good air circulation at average temperature.
• Do not install the thermostat where it can be affected by:
•  drafts, or dead spots behind doors and in corners.
•  hot or cold air from ducts.
•  radiant heat from sun or appliances.
•  concealed pipes and chimneys.
•  unheated (uncooled) areas such as an outside wall behind the thermostat.

Wallplate Installation

• The thermostat can be mounted horizontally on the wall or on a 2 in. x 4 in. wiring box. Position wallplate horizontally on the
•  wall or on a 2 in. x 4 in. wiring box.
•  Position and level the wallplate (for appearance only).
• The thermostat will function properly even when not level.
•  Use a pencil to mark the mounting holes.
•  Remove the wallplate from the wall and drill two 3/16 inch holes in the wall (if drywall) as marked. For firmer material such as plaster, drill two 7/32 inch holes.
• Gently tap anchors (provided) into the drilled holes until flush with the wall.
•  Position the wallplate over the holes, pulling wires through the wiring opening.
•  Loosely insert the mounting screws into the holes.
•  Tighten mounting screws.

WIRING
All wiring must comply with local electrical codes and ordinances. Follow equipment manufacturer wiring instructions when available. Refer to Fig. 14 for typical hookup. A letter code is located near each terminal for identification. Refer to Table 4 for terminal designations.

CAUTION

• Disconnect power before wiring to prevent electrical shock or equipment damage.
• Loosen the terminal screws on the wallplate and connect the system wires.

Standard Terminal Designations	Alternate Terminal Designations	Typical Connection	Function	Terminal Type
B	—	Heat damper or changeover valve	Output	24V powered contact
C	Ba, C, X1, X2	Common	Input
G	F	Fan relay	Output	24V powered contact
O	R	Cool damper or changeover valve	Output	24V powered contact
OT, OT	—	Outdoor temperature sensor (C7089B)	Input	—
R	V	24V system or heating transformer	Input	—
RC	—	24V cooling transformer	Input	—
W1	H1, R3	Stage 1 heating relay	Output	24V powered contact
W2	H2, R4, W3, Y	Stage 2 heating relay	Output	24V powered contact
Y1	C1, M, Y	Stage 1 compressor contactor	Output	24V powered contact
Y2	C2, M, Y	Stage 2 compressor contactor	Output	24V powered contact

IMPORTANT

• Use 18 gauge, color-coded thermostat cable forproper wiring.
• Securely tighten each terminal screw.
• Push excess wire back into the hole.
• Plug the hole with nonflammable insulation to prevent drafts from affecting the thermostat.

Mounting Thermostat Wallplate

• The thermostat mounts on the wallplate after they are installed.
• Engage tabs at the top of thermostat and wallplate.
• Press lower edge of case to latch.
• NOTE: To remove the thermostat from the wall, first pull out at the bottom of the thermostat; then remove the top.
• A. ENGAGE TABS AT TOP OF THERMOSTAT AND WALLPLATE
• B. PRESS LOWER EDGE OF CASE TO LATCH.

SETTINGS

Using Thermostat Keys

The thermostat keys are used to:

•  set current day and time,
•  program times and setpoints for heating and cooling,
•  temporarily override program temperatures,
•  display present setting,
•  configure Installer Setup,
•  check System Test,
•  display outdoor temperature (select models),
•  set the system operation,
•  set the fan operation.

System and Fan Settings
The system default setting is Heat and the fan default setting is Auto. Use the System and Fan keys or switches to change the settings. See Fig. 7. The fan settings can be set for each program period individually. The system selection is for all the program periods

System settings control the thermostat operation as follows:

• Heat: The thermostat controls the heating.
• Off: Both the heating and cooling are off.
• Cool: The thermostat controls the cooling.
• Auto: The thermostat automatically changes between heating and cooling operation, depending on the indoor temperature.

Fan settings control the system fan as follows:

• On: Fan operates continuously.
• Auto: Fan operates with equipment.

Temperature Settings
Refer to Table 5 for the default program. If the daytime energy savings period is not used, press the period key (Leave or Return) until the time is blank. The fan setting feature is available on select thermostat models. See Programming Section for complete instructions on changing the program.

Period	Time	Heat Setpoint	Cool Setpoint	Fan Setting
Wake	6:00 AM	70°F (21°C)	78°F (25.5°C)	Auto
Leave	8:00 AM	62°F (16.5°C)	85°F (29.5°C)	Auto
Return	6:00 PM	70°F (21°C)	78°F (25.5°C)	Auto
Sleep	10:00 PM	62°F (16.5°C)	82°F (28°C)	Auto

INSTALLER SETUP

NOTE For most applications, the thermostat factory settings will not need to be changed. Review the factory settings in Table 6 and if no changes are necessary, go to the Installer System Test section.

The Installer Setup is used to customize the thermostat to specific systems. Some of the options include temperature display, changeover and outdoor temperature display. Installer Setup numbers are listed in Table 6. The table includes all the configuration options and the factory settings for the thermostat. A combination of key presses are required to use the Installer Setup feature.

•  To enter the Installer Setup, press and hold the Information  key with the increase ▲ and decrease ▼ keys until the first number is displayed. All display segments appear for approximately three seconds before the number is displayed.
•  To advance to the next Installer Setup, press the Time ▲ key. To change a setting, use the increase ▲ or decrease ▼ key.
•  To scroll the Installer Setup numbers backwards, press the Time ▼ key.
•  To exit the Installer Setup, press Run Program

Thermostat Installer Setup Options

Select	Installer Setup Number (Press Time      key to change)	Factory-Setting		Other Choices (Press ▲ or ▼ key to change)		Actual Setting
		Display	Description	Display	Description
Not used	1 thru 3	—	—	—	—	—
Heating cycle	4	6	Stage 1	3 or 9	3—3 cph used for steam systems 6—6 cph factory setting for all stages of system 9— 9 cph used for electric heat
ratea	5		Stage 2
Not used	6 thru 11	—	—	—	—	—
System setting adjustment	12	1	Manual changeover	0 or 2	0—Auto changeover 2—Fixed auto changeover
Adaptive Intelligent Recovery™ control	13	0	Adaptive Intelligent Recovery™ control is activated (system starts early so setpoint is reached by start of program period)	1	Conventional recovery (system starts recovery at programmed time)	—
Degree tempera- ture display	14	0	Temperature is displayed in °F	1	Temperature is displayed in °C
Not used	15	—	—	—	—	—
Clock format	16	0	12-hour clock format	1	24-hour clock format
Not used	17 and 18	—	—	—	—	—
Extended fan operation in heating	19	0	No extended fan operation after the call for heat ends	1	Fan operation is extended 90 seconds after the call for heat ends.
Extended fan operation in cooling	20	0	No extended fan operation after the call for cool ends	1	Fan operation is extended 90 seconds after the call for cool ends.
Not used	21 thru 23	—	—	—	—	—
Outdoor temperature display (models with OT terminals)	24	0	No outdoor temperature is displayed	1	Outdoor temperature is displayed. Needs a C7089B1000 Outdoor Sensor to operate.
Not used	25 thru 29	—	—	—	—	—
Deadband	30	3	Heating and cooling setpoints can be set no closer than 3°F (1.5°C)	4 thru 10	Heating and cooling setpoints can be set no closer than the chosen value: 4—4°F (2°C) 5—5°F (2.5°C) 6—6°F (3°C) 7—7°F (3.5°C) 8—8°F (4°C) 9—9°F (4.5°C) 10—10°F (5°C)

Select	Installer Setup Number (Press Time                key to change)	Factory-Setting		Other Choices (Press ▲ or ▼ key to change)		Actual Setting
		Display	Description	Display	Description
Not used	31 and 32	—	—	—	—	—
Minimum off time for the compressor	33	5	5 minute minimum off time for the compressor	0 thru 4	Minimum number of minutes (0 thru 5) the compressor will be off between calls for the compressor
Temperature range stops in heating	34	90	Highest setpoint heating can be set to	40 to 89	Temperature range (1°F increments) heating setpoint can be set to
Temperature range stops in cooling	35	45	Lowest setpoint cooling can be set to	46 to 99	Temperature range (1°F increments) cooling setpoint can be set to
Not used	36	—	—	—	—	—
Temperature display adjustment	37	0	No difference in displayed temperature and actual room temperature	-3 thru 3	1—Display adjusts to 1°F higher than actual room temperature 2—Display adjusts to 2°F higher than actual room temperature 3—Display adjusts to 3°F higher than actual room temperature -1—Display adjusts to 1°F lower than actual room temperature -2—Display adjusts to 2°F lower than actual room temperature -3—Display adjusts to 3°F lower than actual room temperature

Setting Current Day and Time

• Press Set Current Day/Time
• Press Day until the current day is displayed
• Press Time ▲ or Time ▼ until the current time is displayed.
• If the current time is Daylight Savings Time, press Daylight Time until DST is displayed
• Press Run Program.

INSTALLER SYSTEM TEST

• Use the Installer System Test to check the thermostat operation. Refer to Table 7 for a list of the available system tests.
• To start the system test
• Press and hold the increase ▲ and ▼ decrease keys, at the same time, until 10 appears. All segments of the display are displayed for three seconds before 10 appears.

Tests Available in Installer System Test.

Test Number	System Test Description
10-19	Heating equipment can be turned on and off
30-39	Cooling equipment can be turned on and off
40-49	Fan equipment can be turned on and off
60 0 to 60 19	Keyboard keys test
70-79	Thermostat information including date code and software versions are displayed

Installer System Test Options

Key to Press	Test Number	Description
Heating Equipment System Test
Time	10	Enter heating equipment system test.
▲	11	Stage-one heat comes on. The system fan is also energized.
▲	12	Stage-two heat comes on. Stage-one heat and system fan remain on.
▼	11	Stage-two heat turns off.
▼	10	Stage-one heat and system fan turn off.
Cooling Equipment System Test
Time	30	Change from heating to cooling equipment system test.
▲	31	Stage-one cool and system fan come on.
▲	32	Stage-two cool comes on. Stage-one cool and system fan remain on.
▼	31	Stage-two cool turns off.
▼	30	Stage-one cool and system fan turn off.
Fan Equipment SystemTest
Time	40	Change from cooling to fan equipment system test.
▲	41	Fan comes on.
▼	40	Fan turns off.
Key Operation System Test
Time	60 2	Change from fan to key operation system test.

Thermostat Information

•  Press the Time ▲ key to access the thermostat information
• Press the increase ▲ key to display the production date code. The first two large digits are the month and the third digit is the last digit of the year (Example: 027=February 1997
• Press the increase ▲ key again to display the software identification code. (Example: 02 = software ID code 2)
• Press the increase ▲ key again to display the software revision number (Example: 001=Revision number 1).
• Press the increase ▲ key again to display the EEPROM identification code. (Example: 314 = EEPROM ID 314)
• Press the Run Program key to exit the system test. The system test times out after four minutes without any key presses

PROGRAMMING

The keyboard is located behind the thermostat cover with three frequently used keys by the display. The thermostat display shows day, time, program period, temperature, system and fan operation selection. The thermostat can be set for four times and up to eight temperatures for each day of the week (28 independent time and 56 temperature settings). The ▲ and ▼ keys provide quick temporary temperature changes to increase comfort. The Hold Temp key provides energy efficient operation for extended periods of time. Before starting the programming procedure, use Table 9 to organize the program schedule. The factory preprogrammed time, temperature and fan settings are shown in brackets. If a daytime energy savings period is not used, press the period key (Leave or Return) until the time is blank. The fan setting feature is available on select thermostat models.

Default Time, Setpoints and Fan Settings.

Period

Start Time

Heat Setpoint

Cool Setpoint

Fan Setting

MONDAY

Wake	[6:00 AM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Leave	[8:00 AM]	[62°F (16.5°C)]	[85°F (29.5°C)]	[Auto]
Return	[6:00 PM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Sleep	[10:00 PM]	[62°F (16.5°C)]	[82°F (28°C)]	[Auto]

TUESDAY

Wake	[6:00 AM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Leave	[8:00 AM]	[62°F (16.5°C)]	[85°F (29.5°C)]	[Auto]
Return	[6:00 PM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Sleep	[10:00 PM]	[62°F (16.5°C)]	[82°F (28°C)]	[Auto]

WEDNESDAY

Wake	[6:00 AM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Leave	[8:00 AM]	[62°F (16.5°C)]	[85°F (29.5°C)]	[Auto]
Return	[6:00 PM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Sleep	[10:00 PM]	[62°F (16.5°C)]	[82°F (28°C)]	[Auto]

THURSDAY

Wake	[6:00 AM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Leave	[8:00 AM]	[62°F (16.5°C)]	[85°F (29.5°C)]	[Auto]
Return	[6:00 PM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Sleep	[10:00 PM]	[62°F (16.5°C)]	[82°F (28°C)]	[Auto]

FRIDAY

Wake	[6:00 AM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Leave	[8:00 AM]	[62°F (16.5°C)]	[85°F (29.5°C)]	[Auto]
Return	[6:00 PM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Sleep	[10:00 PM]	[62°F (16.5°C)]	[82°F (28°C)]	[Auto]

SATURDAY

Wake	[6:00 AM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Leave	[8:00 AM]	[62°F (16.5°C)]	[85°F (29.5°C)]	[Auto]
Return	[6:00 PM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Sleep	[10:00 PM]	[62°F (16.5°C)]	[82°F (28°C)]	[Auto]

SUNDAY

Wake	[6:00 AM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Leave	[8:00 AM]	[62°F (16.5°C)]	[85°F (29.5°C)]	[Auto]
Return	[6:00 PM]	[70°F (21°C)]	[78°F (25.5°C)]	[Auto]
Sleep	[10:00 PM]	[62°F (16.5°C)]	[82°F (28°C)]	[Auto]

Setting the Current Day and Time

• • Press Set Current Day/Time
  • Press Day until the current day is displayed.
  • Press Time ▲ or Time ▼ until the current time is displayed
  • NOTE: If the current time is Daylight Savings Time, press Daylight Time until DST is displayed
  • Press Run Program.

 

Programming the First Day
Start by programming the Wake time and temperature (and fan operation on select models) for any one day

• Press Wake.
• Press Day until the desired day is displayed
• Press Time ▲ or Time ▼ until the desired Wake time is displayed.
• Press increase ▲ or decrease ▼ key until the desired Wake temperature is displayed
• Press Heat/Cool Settings to switch to other system temperature setpoint.
• Press increase ▲ or decrease ▼ key until the other desired temperature setpoint is displayed.
• Press Leave, Return or Sleep and repeat steps 3, 4, 5 and 6 for programming the rest of the day. The first day is now programmed
• Press Run Program when all days are programmed

Copying a Day

• Press Wake.
• Press Day to select the day to be copied if different from the day displayed.
• Press Copy.
• Press Day until the day to be copied to is displayed
• Press Copy
• Repeat steps 2 through 5 for all the days desired.
• Press Run Program

Clearing Program Period

• Press Wake, Leave, Return or Sleep
• Press Day until the desired day is displayed
• Press Leave, Return or Sleep until the start time and temperature setting are cleared (approximately 3 seconds).
• Repeat steps 2 and 3 for all the periods to be cleared.
• Press Run Program

Changing Temperature Setting Indefinitely

• Press Hold Temp
• Press increase ▲ or decrease ▼ key to change the setting, if desired
• Press Heat/Cool Settings to change between heat and cool settings.
• Press increase ▲ or decrease ▼ key to adjust temperature settings.
• Press Run Program to cancel the Hold and to return to  the program.

Changing Temperature Setting Until a Designated Day and Period

• Press Hold Temp twice
• Press Time ▲ or Time ▼ until the desired number of days is displayed (1 to 256 days). (Example: 18 = Hold will override the daily programs for 18 days)
• Press Wake, Leave, Return or Sleep to select the period the program will start. (Example: Return = thermostat will stop the Hold at the Return period start time)
• Press increase ▲ or decrease ▼ key to adjust the temperature setting, if desired. (Example: Heat 54° = heating equipment will operate when the room temperature is below 54°F)
• Press Heat/Cool Settings to change between heat and cool settings.
• Press increase ▲ or decrease ▼ key to adjust the temperature setting, if desired. (Example: Cool 84° = cooling equipment will operate when the room temperature is above 84°F)

Setting Temporary Fan Operation
Press Fan until the desired fan operation is selected. This fan setting will be in effect until the next regularly scheduled period starts.

Using Daylight Savings Time Feature
This feature allows you to change in and out of Daylight Savings Time with a key press. When Daylight Time is pressed in the fall, the time will go back one hour. In the spring, the time will go ahead one hour and the display will show DST. See the Setting the Current Day and Time section for initial setting instructions.

Displaying the Outdoor Temperature
If your thermostat is equipped with an outdoor sensor, you can check the temperature at the sensor by pressing i once.

OPERATION

P+I Control
The thermostat microprocessor-based control requires that the user understands temperature control and thermostat performance. A conventional electromechanical or electronic thermostat does not control temperature precisely at setpoint. Typically, there is an offset (droop) in the control point as the system load changes. This is a phenomenon that most people in the industry know and accept. Many factors contribute to offset including switch differential, thermal lag, overshoot, cycle rates and system load. The thermostat microprocessor simultaneously gathers, compares and computes data. Using this data, it controls a wide variety of functions. The special proprietary algorithm (program) in the thermostat eliminates the factors causing offset. This makes temperature control more accurate than the conventional electromechanical or electronic thermostats. The temperature control algorithm is called proportional plus integral (P+I) control. The thermostat sensor, located on the thermostat or remote, senses the current space temperature. The proportional error is calculated by comparing the sensed temperature to the programmed setpoint. The deviation from the setpoint is the proportional error. The thermostat also determines integral error, which is a deviation based on the length of error time. The sum of the two errors is the (P+I) error. The cycle rate used to reach and maintain the setpoint temperature is computed using the P+I. The addition of the integral error is what differentiates the thermostat from many other electronic and electromechanical thermostats.

Operation Sequence The thermostat energizes specific terminals depending what the Fan and System are set to. The LCD will display the time, room temperature, system and fan selection. Symbols will be displayed when the heating, cooling or fan is energized. See Table 10 for specific information

Selection		Call	Energize	Display
Fan	System
Auto	Off	None	None	None
On	Off	None	G
Auto	Cool	None	O	None
Auto	Cool or Auto	Stage 1 Cooling	O, G and Y1	and
Auto	Cool or Auto	Stage 2 Cooling	O, G, Y1 and Y2	and
Auto	Heat	None	B	None
Auto	Heat or Auto	Stage 1 heating	B, Ga and W1	and
Auto	Heat or Auto	Stage 2 heating	B , Ga, W1 and W2	and
Auto	Auto	None	O or Bb	None

Equipment Protection As part of the operational sequence, the thermostat microprocessor also incorporates minimum off time for all heating and cooling stages. Using the minimum off time assures that rapid cycling of equipment does not occur, which extends equipment life. Minimum off times are set in the Installer Setup.

Thermostat Operation Startup When power to the thermostat is turned on, a startup and initialization program begins. The startup occurs only on initial powerup. After total loss of power for an extended period, the current time and day may need to be set, but the user program is held. See Table 11 for the default values.

Period	Time	Heat Setpoint	Cool Setpoint	Fan Setting
Wake	6:00 AM	70°F (21°C)	78°F (25.5°C)	Auto
Leave	8:00 AM	62°F (16.5°C)	85°F (29.5°C)	Auto
Return	6:00 PM	70°F (21°C)	78°F (25.5°C)	Auto
Sleep	10:00 PM	62°F (16.5°C)	82°F (28°C)	Auto

Adaptive Intelligent Recovery® Feature Adaptive Intelligent Recovery® control assures that the comfort setting is achieved at the programmed time regardless of weather conditions. Conventional recovery, however, starts recovery at the beginning of the programmed time period and used the equipment to achieve the comfort settings as soon as possible. Adaptive Intelligent Recovery® control calculates the recovery ramp based on the number of degrees away from the desired setpoint, previous equipment performance, and weather history to initiate recovery at the optimal time to achieve the comfort setting at the desired time. Once the recovery ramp is intersected, the setpoint changes from the setback setpoint to the comfort setpoint. This change snaps on both stages of the equipment and runs both stages until the setpoint is reached. If the setpoint is reached too early or too late, the ramp is adjusted for the next days’ recovery.

TROUBLESHOOTING

Symptom	Possible Cause	Action
Display will not come on.	Thermostat is not being powered.	•      Check for 24 Vac between R and C terminals. —    If missing 24 Vac: —    check if the circuit breaker is tripped—reset the circuit breaker. —    check if the system fuse is blown—replace the fuse. —    check if the power switch on the HVAC equipment is in the Off position—set to the On position. —    check wiring between thermostat and HVAC equipment—replace any broken wires and tighten any loose connections. —    If 24 Vac is present, proceed with troubleshooting.
Temperature display is incorrect.	Room temperature display has been reconfigured.	Enter Installer Setup number 37 and reconfigure the display.
	Thermostat is configured for °F or °C display.	Enter Installer Setup number 14 and reconfigure the display.
	Bad thermostat location.	Relocate the thermostat.
Temperature settings will not change. (Example: Cannot set the heating higher	The upper or lower temperature limits were reached.	Check the temperature setpoints: •      Heating limits are 40 to 90°F (7 to 31°C) •      Cooling limits are 48 to 99°F (9 to 37°C) .
or the cooling lower.)	The setpoint temperature range stops were configured.	Check Installer Setup numbers 34 and 35 and reconfigure the setpoint stops.
Heating or cooling come on momentarily and shut off	Heat or cool circuit is opening up or becoming high impedance.	Add resistor in parallel with load or install interface relay.
System on indicator (flame=heat, snowflake=cool) is displayed, but no warm or cool air is coming from the registers.	Heating or cooling equipment is not operating.	Verify operation of heating or cooling equipment in system test.
Heating will not come on.	No power to the thermostat.	•      Check for 24 Vac between R and C terminals. —    If missing 24 Vac: —    check if the circuit breaker is tripped—reset the circuit breaker. —    check if the system fuse is blown—replace the fuse. —    check if the power switch on the HVAC equipment is in the Off position—set to the On position. —    check wiring between thermostat and HVAC equipment—replace any broken wires and tighten any loose connections. —    If 24 Vac is present, proceed with troubleshooting.
	Thermostat minimum off time is activated.	Wait up to five minutes for the system to respond.
	System selection is not set to Heat.	Set system selection to Heat.
	Heating setpoint is below room temperature.	Check heating setpoint. Set heating setpoint to desired temperature.

Symptom	Possible Cause	Action
Cooling will not come on.	No power to the thermostat.	•      Check for 24 Vac between R and C. —      If missing 24 Vac: —      check if the circuit breaker is tripped—reset the circuit breaker. —      check if the system fuse is blown—replace the fuse. —      check if the power switch on the HVAC equipment is in the Off position—set to the On position. —      check wiring between thermostat and HVAC equipment—replace any broken wires and tighten any loose connections. —      If 24 Vac is present, proceed with troubleshooting.
	Thermostat minimum off time is activated.	•      Wait up to five minutes for the system to respond. •      Enter Installer Setup number 33. Reconfigure minimum off time (if required).
	System selection is not set to Cool.	Set system selection to Cool.
	Cool setpoint is above room temperature.	Check cooling setpoint. Set cooling setpoint to desired temperature.
Outdoor temperature not displayeda	Option not activated.	Enter Installer Setup number 24 and set to 1. Thermostat must have OT terminals and a C7089B1000 installed.
Outdoor temperature display is incorrecta	Outdoor sensor is connected incorrectly.	Refer to C7089B1000 installation instructions and check wiring between the thermostat and sensor.
	Wrong sensor.	Replace sensor with C7089B1000 sensor.

CROSS-REFERENCE

Model Number	Description	TRADELINEÒ Replacement	Remarks
T8624C	Two-stage heat and two-stage cool conventional thermostat; powered direct from 24 Vac transformer; manual changeover; system switch—HEAT-OFF-COOL-AUTO; fan switch—ON-AUTO; O and B terminals
T8624C1008	Trane; Premier WhiteÒ color; part no. TAYSTAT302A.	T8624D2004	Wiring differences (old=new): B=C; jumper R to Rc; taupe color.
T8624D	Two-stage heat and two-stage cool conventional thermostat; powered direct from 24 Vac transformer; automatic changeover; system switch—HEAT-OFF-COOL-AUTO; fan switch—ON-AUTO; O and B terminals
T8624D1006	TRADELINEÒ thermostat; Honeywell logo.	T8624D2004	Configure changeover to auto in Installer Setup 12.
T8624D1014	Carrier Weathermaker.	T8624D2004	Configure changeover to auto in Installer Setup 12.
T8624D1022	Carrier Zone Perfect.	T8624D2004	Configure changeover to auto in Installer Setup 12.
T8624D1030	TRADELINEÒ thermostat; Honeywell logo; Premier WhiteÒ color.	T8624D2004	Configure changeover to auto in Installer Setup 12; taupe color.
T8624D1055	York logo.	T8624D2004	Configure changeover to auto in Installer Setup 12.
T8624D1063	Trane; Premier WhiteÒ color.	T8624D2004	Wiring differences (old=new): B=C; jumper R to Rc; taupe color.

WIRING DIAGRAM

HONEY WELL

Home and Building Control

• Honeywell Inc.
• Honeywell Plaza
• P.O. Box 524
• Minneapolis MN 55408-0524

Honeywell Latin American Region

• 480 Sawgrass Corporate Parkway
• Suite 200
• Sunrise FL 33325

Honeywell T8624D Programmable Thermostat INSTALLATION INSTRUCTIONS

Honeywell T8624D Programmable Thermostat INSTALLATION INSTRUCTIONS