Honeywell T8602D User manual

® U.S. Registered Trademark
Copyright © 2002 Honeywell • • All Rights Reserved
INSTALLATION INSTRUCTIONS
69-1507-2
T8602D Chronotherm® IV
Deluxe Programmable
Thermostats
APPLICATION
The T8602 Chronotherm ®IV Deluxe Programmable Thermostat provides electronic control of 24 Vac single-stage
heating and cooling systems or 750 mV heating and 24 Vac cooling. Refer to Table 1 for a general description of the
thermostat. All T8602 thermostats are powered by batteries.
Table 1. Description of T8602 Thermostats.
MERCURY NOTICE
If this control is replacing a control that contains
mercury in a sealed tube, do not place your old
control in the trash. Dispose of properly.
Contact your local waste management authority
for instructions regarding recycling and the
proper disposal of the old control.
INSTALLATION
When Installing this Product...
1. Read these instructions carefully. Failure to follow
the instructions can damage the product or cause
a hazardous condition.
2. Check the ratings given in the instructions and on
the product to make sure the product is suitable for
your application.
3. Installer must be a trained, experienced service
technician.
4. 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.
See Fig. 1.
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. (50.8 mm x 101.6 mm) wiring box.
Position wallplate horizontally on the wall or on a
2 in. x 4 in. (50.8 mm x 101.6 mm) wiring box.
T8602 System Changeover System Selection
Fan
Selection Comments
D Heat-Cool Automatic Heat-Off-Cool-Auto On-Auto System and fan selections are made on
keyboard.

T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
69-1507—2 2
Fig. 1. Typical location of thermostat.
1. Position and level the wallplate (for appearance
only). The thermostat functions correctly even
when not level.
2. Use a pencil to mark the mounting holes.
See Fig. 2.
3. Remove the wallplate from the wall and drill two
3/16 inch (76 mm) holes in the wall (if drywall) as
marked. For firmer material such as plaster, drill
two 7/32 inch (5.56 mm) holes. Gently tap anchors
(provided) into drilled holes until flush with wall.
4. Position the wallplate over the holes, pulling wires
through the wiring opening.
5. Loosely insert the mounting screws into the holes.
6. Tighten mounting screws.
Fig. 2. Mounting the wallplate.
WIRING
All wiring must comply with local electrical codes and
ordinances. Refer to Fig. 3 and 6 for typical hookup. A
letter code is located near each terminal for identification.
CAUTION
Electrical Hazard.
Can cause electric shock or equipment
damage.
Disconnect power before wiring.
1. Loosen the terminal screws on the wallplate and
connect the system wires. See Fig. 7.
IMPORTANT
Use 18 gauge, color-coded thermostat cable for
proper wiring.
2. Securely tighten each terminal screw.
3. Push excess wire back into the hole.
4. Plug the hole with nonflammable insulation to
prevent drafts from affecting the thermostat.
Fig. 3. Typical hookup in heat application.
5 FEET
[1.5 METERS]
YES NO
NO
NO
M1010
6
WIRES
THROUGH WALL
WALL
MOUNTING
HOLES
M15044
MOUNTING
SCREWS
WALL
ANCHORS (2)
L1
(HOT)
L2
M10409
FAN
RELAY
G
THERMOSTAT
HEAT
RELAY
RW
TRANSFORMER
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
1
1

T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
3 69-1507—2
Fig. 4. Typical hookup in heat and cool system
with one transformer.
Fig. 5. Typical hookup in heat and cool system
with two transformers.
Fig. 6. T8602 typical millivoltage heating circuit.
.
Fig. 7. Correct wiring technique.
Mounting Thermostat
1. Engage tabs at the top of the thermostat and
wallplate. See Fig. 8.
2. Press lower edge of case to close and latch.
NOTE: To remove the thermostat from the wall, first pull
out at the bottom of the thermostat; remove top
last.
Fig. 8. Mounting thermostat on wallplate.
L1
(HOT
)
L2
M10347A
FAN
RELAY
YG
THERMOSTAT
HEAT
RELAY
RW
COMPRESSOR
CONTACTOR
TRANSFORMER
B
HEAT
DAMPER
COOL
DAMPER
O
1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
CAN BE USED FOR CHANGEOVER VALVE ON SINGLE-STAGE HEAT
PUMP SYSTEMS.
AVAILABLE ON SELECT MODELS. OT WIRES MUST HAVE A
SEPARATE CABLE FROM THE THERMOSTAT CABLE.
2
2
2
1
3
OTOT
OUTDOOR
TEMPERATURE
SENSOR
3
RC
L1
(HOT
)
L2
M10348
FAN
RELAY
YG
THERMOSTAT
RC
HEAT
RELAY
RW
L1
(HOT)
L2
COMPRESSOR
CONTACTOR
HEATING
TRANSFORMER
COOLING
TRANSFORMER
B
HEAT
DAMPER
COOL
DAMPER
O
2
1POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
JUMPER RC TERMINAL TO R TERMINAL WHEN INSTALLED ON A
ONE TRANSFORMER SYSTEM.
CAN BE USED FOR CHANGEOVER VALVE ON SINGLE-STAGE HEAT
PUMP SYSTEMS.
AVAILABLE ON SELECT MODELS. OT WIRES MUST HAVE A
SEPARATE CABLE FROM THE THERMOSTAT CABLE.
T8600D MODELS REQUIRE POWER TO R TERMINAL AT ALL TIMES.
2
3
3
1
1
3
4
OTOT
OUTDOOR
TEMPERATURE
SENSOR
4
5
5
M20270
GO B
THERMOSTAT
LIMIT
CONTROL
PILOTSTAT
CONTROL
(IF USED)
MILLIVOLTAGE
GAS CONTROL
MILLIVOLTAGE
GENERATOR
YRW
1AVAILABLE ON SELECT MODELS. OT WIRES MUST HAVE A
SEPARATE CABLE FROM THE THERMOSTAT CABLE.
OTOT
OUTDOOR
TEMPERATURE
SENSOR
1
PP
TH/
PP
TH
M482
6
F
OR WRAPAROUND
I
NSERTION STRIP
7
/16 IN. (11 MM).
FOR STRAIGHT INSERTION
STRIP 5/16 IN. (8 MM).
M1462
8
PRESS LOWER
EDGE OF CASE
TO LATCH.
ENGAGE TABS
AT TOP OF
THERMOSTAT
AND WALLPLATE.
A.
B
.

T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
69-1507—2 4
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 Self-Test,
• display outdoor temperature (select models),
• set the system operation,
• set the fan operation.
See Fig. 9 for location of the keys.
NOTE: Always press the keys with your fingertip or
similar blunt tool. Sharp instruments like a pen
or pencil point can damage the keyboard.
Fig. 9. T8602D key locations and descriptions.
SETTINGS
System and Fan Settings
The system default setting is Heat and the fan default
setting is Auto. Use the System and Fan keys to change
the settings. See Fig. 10. 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:
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:
On: Fan operates continuously.
Auto: Fan operates with equipment.
Fig. 10. Thermostat System and Fan key locations.
M14624
Time Set Program
System Fan
Run
Program
Hold Temp
Set Current
Day/Time Wake Leave Return Sleep
Day Heat/Cool
Settings
Daylight
Time Copy
INCREASE TEMPERATURE
SETTING OR SCROLL
FORWARD THROUGH
INSTALLER SETUP OPTIONS
DECREASE TEMPERATURE
SETTING OR SCROLL
BACKWARD THROUGH
INSTALLER SETUP OPTION
S
DISPLAY INFORMATION
SUCH AS PRESENT
SETTINGS AND OUTDOOR
TEMPERATURE
RETURN TO
NORMAL
OPERATIONS
ENTER
INDEFINITE
OR TIMED
HOLD MODE
SET CURRENT
DAY AND TIME
SET CURRENT OR
PROGRAM DAY
CHANGE BETWEEN
DAYLIGHT SAVINGS
AND STANDARD TIME
I
NCREASE TIME SETTING
O
R SCROLL FORWARD
T
HROUGH INSTALLER SETUP
A
ND SYSTEM TEST
DECREASE TIME SETTING OR
SCROLL BACKWARD THROUGH
INSTALLER SETUP AND SYSTEM TEST
COPY ONE PROGRAMMED
DAY TO ANOTHER DAY
SET WAKE TIMES
AND SETPOINTS
CHANGE BETWEEN
HEATING AND COOLING
SETPOINTS
SET LEAVE TIMES
AND SETPOINTS SET RETURN TIMES
AND SETPOINTS
SET SLEEP TIMES
AND SETPOINTS
SELECT SYSTEM
OPERATION
SELECT FAN
OPERATION
M14625
HoldTemp
Run
Program
Copy
Daylight
Time
Set Current
Day/Time
System Fan
Time Set Program
Day System
Fan
Wake Leave Return Sleep
Heat/Cool
Settings

T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
5 69-1507—2
Temperature Settings
Refer to Table 2 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
Owner’s Guide, form number 69-0940, for complete
instructions on changing the program.
Table 2. Default Program Settings.
INSTALLER SETUP
NOTE: For most applications, the thermostat factory-
settings do not require changing. Review
factory settings in Table 2 and if no changes are
necessary, go to the Installer Self-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 3. The table includes all the configuration options
and the factory settings for the T8602.
A combination of key presses are required to use the
Installer Setup feature:
— To enter the installer setup, press and hold the
information ikey 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. See Fig. 11
and 12.
— 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 backward, press
the Time ∇key.
— To exit the Installer Setup, press Run Program.
Fig. 11. Display of all LCD segments.
Fig. 12. Display of Installer Setup number and
setting.
CAUTION
Heat Pump and Electric Heat System
Configuration Hazard.
Can cause equipment damage.
Configure heat pump and electric heat systems to
1 in Installer Setup number 2 to prevent system
running without fan.
IMPORTANT
Only configurable numbers are shown on the
device. Example: If thermostat does not have a
system key, Installer Setup Number 12 will not
be displayed. Review Table 3 factory-settings
and mark any desired changes in the Actual
Setting column. When Installer Setup is com-
plete, review the settings to confirm that they
match the system.
Period Time
Heat
Setpoint
Cool
Setpoint
Fan
Setting
Wake 6:00 AM 70°F
(21°C)
78°F
(25.5°C)
Auto
Leave 8:00AM 62°F
(16.5°C)
85°F
(29.5°C)
Auto
Return 5:00 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
M1455
9
Aux Ht
Set Day/TimeSet Program
Mon
Wake Leave Return Sleep OutdoorRoom
Filter
Wait
System
Fan
Em Hea
t
On
Auto
Of
f
Coo
l
Auto
AM
PM
Hold for
Heat Cool
Repl Batt
Recovery
DST
TueWedThu Fri Sat Sun
Days
Temporary Setting
Em Ht
M14618
INSTALLER SETUP
NUMBER DISPLAY
(COLUMN 2 OF TABLE 3)
FACTORY SETTING OR OTHER
CHOICE DISPLAY (COLUMN 3
OR 5 OF TABLE 3)

T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
69-1507—2 6
Table 3. Thermostat Installer Setup Options.
Select
Installer Setup
Number (Press
Time ∆key to
change)
Factory Setting
Other Choices
(Press or key to change)
Actual
SettingDisplay Description Display Description
Not Used. 1 — — — — —
Fan operationa2 0 Conventional
applications where
equipment controls
fan operation in
heat mode
1 Heat pump or electric heat
applications where
thermostat controls fan
operation in heat mode.
Not Used. 3 — — — — —
Heating cycle
rate.
4 6 6—6 cph used for
conventional heat
1, 3 or 9 1—1 cph used for radiant
floor heat, gravity system
3—3 cph used for hot water
systems or high
efficiency furnaces
9—9 cph used for electric
heat systems
Not Used. 5 thru 11 — — — — —
System setting
adjustment
12 1 Manual
changeover
0 or 2 0—Auto changeover
2—Auto only
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
temperature
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.a
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.a
20 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
Temperature 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)
Not Used. 31 thru 32 — — — — —

T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
7 69-1507—2
aNumber 2 must be set to 1 to extend fan operation.
IMPORTANT
Review the settings to confirm that they match
the system. Press Run Program to exit the
Installer Setup. The thermostat has saved the
Installer Setup changes and initiated a reset in
order to operate using the new settings. Be sure
to set the current day and time immediately.
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 is
off between calls for the
compressor.
Temperature
range stops in
heating.
34 90 Highest heating
setpoint setting.
40 to 89 Temperature range (1°F
increments) of heating
setpoint settings.
Temperature
range stops in
cooling.
35 45 Lowest cooling
setpoint setting.
46 to 99 Temperature range (1°F
increments) of cooling
setpoint settings.
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.
Furnace Air
Filter Timer.
43 2 30 days (System
run time)
0, 1, 3, 4 0 – off
1 – 10 days
3 – 60 days
4 – 120 days
(Time is counted when heat,
cool or fan is running.)
Humidifier Pad
Monitor.
44 0 Off 1, 2, 3 1 – 90 days
2 – 180 days
3 – 365 days
(Time is counted by calendar
days in heat mode.)
Ultraviolet (UV)
Air Treatment
System Lamp
Monitor.
45 0 Off 1 1 – 365 days
(Time is counted by calendar
days in any mode.)
Table 3. Thermostat Installer Setup Options. (Continued)
Select
Installer Setup
Number (Press
Time ∆key to
change)
Factory Setting
Other Choices
(Press or key to change)
Actual
SettingDisplay Description Display Description

T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
69-1507—2 8
Setting Current Day and Time
1. Press Set Current Day/Time.
NOTE: On initial powerup or after an extended power
loss, 1:00 pm flashes on the display until a
key is pressed.
2. Press Day until the current day is displayed.
NOTE: Sun=Sunday, Mon=Monday,
Tue=Tuesday, Wed=Wednesday,
Thu=Thursday, Fri=Friday, Sat=Saturday.
3. Press Time ∆or Time ∇until the current time is
displayed.
NOTE: Tapping the Set Current Day/Time changes the
time in one hour increments.
NOTE: If the current time is Daylight Savings Time,
press Daylight Time until DST is displayed.
4. Press Run Program.
View or Reset Timer Settings
When the thermostat activates a timer, the thermostat
flashes Filter until the timer resets.
1. Reset the timer by pressing the ikey until the
expired timer is displayed.
2. Press the Time ∆key to reset the timer.
3. Press the Run Program key.
NOTE: You can view the number of days remaining at
any time by pressing the i key three or four
times. If more than one timer is active, all active
timers show sequentially when pressing the
i key several times.
M1461
9
Time Set Program
System Fan
Run
Program
Hold Temp
Set Current
Day/Time
Set Current
Day/Time Wake Leave Return Sleep
Day Heat/Cool
Settings
Daylight
Time Copy
Set Day/Time
Mon
PM
M1462
0
Time Set Program
System Fan
Run
Program
Hold Temp
Set Current
Day/Time Wake Leave Return Sleep
Day
Day Heat/Cool
Settings
Daylight
Time Copy
Set Day/Time
PM
Tue
M1462
1
Time Set Program
System Fan
Run
Program
Hold Temp
Set Current
Day/Time Wake Leave Return Sleep
Day
Time
Heat/Cool
Settings
Daylight
Time Copy
Set Day/Time
AM
Tue
M1462
2
Time Set Program
System Fan
Run
Program
Hold Temp
Set Current
Day/Time Wake Leave Return Sleep
Day Heat/Cool
Settings
Daylight
Time
Daylight
Time
Copy
Set Day/Time
AM
DST
Tue
M1462
3
Time Set Program
System Fan
Run
Program
Run
Program Hold Temp
Set Current
Day/Time Wake Leave Return Sleep
Day Heat/Cool
Settings
Daylight
Time Copy Wake Room
System
Fan
Heat
Auto
AM
DST
Tue
M2024
3
Filter Days
M2024
4
Filter Days

T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
9 69-1507—2
INSTALLER SYSTEM TEST
Use the Installer System Test to check the thermostat
operation. Refer to Table 4 for a list of the available
system tests.
CAUTION
Equipment Damage Hazard.
Minimum compressor off-time is bypassed
during Installer System Test.
Avoid cycling compressor quickly.
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 will be displayed before the 10 appears.
See Fig. 12 and 13.
Table 4. Tests Available In Installer System Test.
Fig. 13. Display of all LCD segments.
Fig. 14. Display of test number.
Refer to Table 5 for the directions and results of the
specific tests.
NOTE: Press Time ∆to advance to the next test and
Time ∇to go back to the previous test. Press
Run Program to exit the system test.
Table 5. Installer System Test Options.
NOTE: Press any key and the displayed numbers change. Press Time ∇to go to the previous test and Time ∆to go to
the next test. The Run Program key will not exit this test. Press Time ∆or Time ∇and then the
Run Program key to exit.
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.
M1455
9
Aux Ht
Set Day/TimeSet Program
Mon
Wake Leave Return Sleep OutdoorRoom
Filter
Wait System
Fan
Em Hea
t
On
Auto
Of
f
Coo
l
Auto
AM
PM
Hold for
Heat Cool
Repl Batt
Recovery
DST
TueWedThu Fri Sat Sun
Days
Temporary Setting
Em Ht
M1461
2
Keys to
Press
Test
Number Description
Heating Equipment System Test
Time ∆10 Enter heating equipment system test.
11 Heat comes on. When Installer Setup number 2 is 1, the system fan is also energized.
10 Heat and system fan turn off.
Cooling Equipment System Test
Time ∆30 Change from heating to cooling equipment system test.
31 Cool and system fan come on.
30 Cool and system fan turn off.
Fan Equipment System Test
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.

T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
69-1507—2 10
THERMOSTAT INFORMATION
1. Press the Time ∆key to access the thermostat
information.
2. 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).
3. Press the increase key again to display the soft-
ware identification code.
(Example: 02 = software ID code 2).
4. Press the increase key again to display the soft-
ware revision number.
(Example: 001 = Revision number 1).
5. Press the increase key again to display the
EEPROM identification code.
(Example: 314 = EEPROM ID 314).
6. Press the Run Program key to exit the System
Test. The System Test times out after four minutes
without any key presses.
CHECKOUT
Outdoor Temperature Sensor
(Select Models)
Allow the outdoor temperature sensor to absorb the
outdoor air for a minimum of five minutes before taking a
reading.
M1461
3
M1461
4
M1461
5
M1461
6
M1461
7

T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
11 69-1507—2
TROUBLESHOOTING GUIDE
Table 6. Troubleshooting Guide.
Symptom Possible Cause Action
Display does not
come on.
Thermostat is not being
powered.
• Check if batteries are present and installed correctly.
— If batteries are present and installed correctly, replace
thermostat.
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 do not
change. (Example:
Cannot set the
heating higher or
the cooling lower.)
The upper or lower temperature
limits were reached.
Check the temperature setpoints:
• Heating limits are 40 to 90°F (4.5 to 32°C)
• Cooling limits are 48 to 99°F (7 to 37°C)
The setpoint temperature range
stops were configured.
Check Installer Setup numbers 34 and 35 and reconfigure the
setpoint stops.
Heating does not
come on.
No power to the thermostat. • Check for 24 Vac between R and W terminals (check for
750 mV on PowerPile®Systems).
— 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.
Cooling does not
come on.
No power to the thermostat. • Check for 24 Vac between R or RC and Y 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.
• 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.

69-1507—2 G.H. Rev. 12-02 www.honeywell.com/yourhome
T8602D CHRONOTHERM® IV DELUXE PROGRAMMABLE THERMOSTATS
Printed in U.S.A. on recycled
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post-consumer paper fibers.
Automation and Control Solutions
Honeywell Honeywell Limited-Honeywell Limitée
1985 Douglas Drive North 35 Dynamic Drive
Golden Valley, MN 55422 Scarborough, Ontario
M1V 4Z9
System on indicator
(flame=heat,
snowflake=cool) is
displayed, but no
warm or cool air is
coming from the
registers.
Fan operation set for 0
(conventional heat) when it
should be set for 1 (electric
heat)
Enter Installer Setup number 2 and reconfigure the fan
operation.
Conventional heating equipment
turns on the fan when the
furnace has warmed up to a
setpoint.
Wait a minute after seeing the on indicator and then check the
registers.
Heating or cooling equipment is
not operating.
Verify operation of heating or cooling equipment in self-test.
Outdoor tempera-
ture 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.
Thermostat
backlight appears
dim.
Backlight can fade over the life
of the batteries.
• Wait until Replace Battery indicator is illuminated and
replace batteries.
• Replace batteries now.
aSelect models.
Table 6. Troubleshooting Guide. (Continued)
Symptom Possible Cause Action