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®
T8624D Chronotherm IV  
Deluxe Programmable  
Multistage Thermostats  
INSTALLATION INSTRUCTIONS  
APPLICATION  
The T8624D Chronotherm® IV Deluxe Programmable  
Multistage Thermostats provides electronic control of 24  
Vac single-zone multistage systems.  
Refer to Table 1 for a general description of the  
thermostats. All T8624 thermostats require a common  
wire to supply power.  
Table 1. Description of T8624 Thermostats.  
Fan  
Selection  
T8624 Changeover  
Automatic  
System Selection  
Comments  
D
Heat-Off-Cool-Auto  
On-Auto  
System and fan selections are done by keyboard.  
3.  
Installer must be a trained, experienced service  
technician.  
MERCURY NOTICE  
4. After completing installation, use these instructions  
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.  
to check out the product operation.  
Location  
Contact your local waste management authority  
for instructions regarding recycling and the  
proper disposal of the old control.  
Install the thermostat about 1.5m (5 ft) 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:  
INSTALLATION  
—
—
—
—
—
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.  
When Installing this Product...  
1
.
.
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.  
2
®
U.S. Registered Trademark  
Copyright © 2002 Honeywell •  
• All Rights Reserved  
6
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
Position wallplate horizontally on the wall or on a  
Wallplate Installation  
2
in. x 4 in. (50.8 mm x 101.6) mm wiring box.  
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.  
YES  
NO  
NO  
1
.5 METERS  
5 FEET)  
(
NO  
M10856  
Fig. 1. Typical location of thermostat.  
Position and level the wallplate (for appearance  
only). The thermostat will function correctly even  
when not level.  
1.  
WIRING  
All wiring must comply with local electrical codes and  
ordinances. Refer to Fig. 3 for typical hookup. A letter  
code is located near each terminal for identification.  
2
.
.
Use a pencil to mark the mounting holes. See Fig.  
2
.
3
Remove the wallplate from the wall and drill two  
/16 inch (76 mm) holes in the wall (if drywall) as  
3
marked. For firmer material such as plaster, drill  
two 7/32 inch (5.56 mm) holes. Gently tap anchors  
CAUTION  
(provided) into the drilled holes until flush with the  
Electrical Shock Hazard.  
Can cause electrical shock or equipment  
damage.  
wall.  
4.  
Position the wallplate over the holes, pulling wires  
through the wiring opening.  
Loosely insert the mounting screws into the holes.  
Tighten mounting screws.  
Disconnect power before beginning wiring.  
5
6
.
.
1.  
Loosen the terminal screws on the wallplate and  
connect the system wires. See Fig. 4.  
IMPORTANT  
Use 18 gauge, color-coded thermostat cable for  
WALL  
proper wiring.  
WIRES  
THROUGH WALL  
2.  
3.  
4.  
Securely tighten each terminal screw.  
Push excess wire back into the hole.  
Plug the hole with nonflammable insulation to pre-  
vent drafts from affecting the thermostat.  
WALL  
ANCHORS (2)  
MOUNTING  
HOLES  
MOUNTING  
SCREWS  
M15044  
Fig. 2. Mounting the wallplate.  
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
Mounting Thermostat  
THERMOSTAT  
Y2  
1.  
Engage tabs at the top of the thermostat and wall-  
plate. See Fig. 5.  
RC  
Y1  
G
O
C
B
W2  
W1  
R
OT OT  
2.  
Press lower edge of case to close and latch.  
2
NOTE: To remove the thermostat from the wall, first pull  
out at the bottom of the thermostat; remove top  
last.  
FAN  
RELAY  
COMPRESSOR  
CONTACTOR 2  
HEAT  
RELAY  
2
OUTDOOR  
SENSOR  
COMPRESSOR  
CONTACTOR 1  
COOL  
DAMPER  
HEAT  
DAMPER  
HEAT  
RELAY  
1
3
3
1
L1  
(
L1  
(HOT)  
HOT)  
L2  
1
L2  
COOLING  
TRANSFORMER  
HEATING  
TRANSFORMER  
A. ENGAGE TABS  
AT TOP OF  
THERMOSTAT  
AND WALLPLATE.  
1
2
3
POWER 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 HEAT  
PUMP SYSTEMS.  
M11309  
Fig. 3. Typical hookup of T8624D  
in a heat pump system.  
B. PRESS LOWER  
EDGE OF CASE  
TO LATCH.  
M14628  
FOR WRAPAROUND  
INSERTION STRIP  
FOR STRAIGHT INSERTION  
STRIP 5/16 IN. (8 MM).  
7
/16 IN. (11 MM).  
Fig. 5. Mounting thermostat on wallplate.  
M4826  
Fig. 4. Correct wiring technique.  
3
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
INCREASE TEMPERATURE  
SETTING OR SCROLL  
FORWARD THROUGH  
INSTALLER SETUP OPTIONS  
INCREASE TIME SETTING  
OR SCROLL FORWARD  
THROUGH INSTALLER SETUP  
AND SYSTEM TEST  
SET WAKE TIMES  
AND SETPOINTS  
SET LEAVE TIMES  
AND SETPOINTS  
SET RETURN TIMES  
AND SETPOINTS  
DECREASE TEMPERATURE  
SETTING OR SCROLL  
BACKWARD THROUGH  
INSTALLER SETUP OPTIONS  
SET CURRENT  
DAY AND TIME  
RETURN TO  
NORMAL  
OPERATIONS  
DISPLAY INFORMATION  
SUCH AS PRESENT  
SETTINGS AND OUTDOOR  
TEMPERATURE  
ENTER  
INDEFINITE  
OR TIMED  
HOLD MODE  
Time  
Set Program  
Leave  
SET SLEEP TIMES  
AND SETPOINTS  
Run  
Program  
Set Current  
Day/Time  
Wake  
Return  
Sleep  
Fan  
Heat/Cool  
Settings  
SELECT FAN  
OPERATION  
Hold Temp  
Day  
System  
SET CURRENT OR  
PROGRAM DAY  
Daylight  
Time  
Copy  
SELECT SYSTEM  
OPERATION  
CHANGE BETWEEN  
DAYLIGHT SAVINGS  
AND STANDARD TIME  
DECREASE TIME SETTING OR  
SCROLL BACKWARD THROUGH  
INSTALLER SETUP AND SYSTEM TEST  
CHANGE BETWEEN  
HEATING AND COOLING  
SETPOINTS  
COPY ONE PROGRAMMED  
DAY TO ANOTHER DAY  
M14624  
Fig. 6. T8624D key locations and descriptions.  
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.  
Time  
Set Program  
Leave  
Return  
Run  
Program  
Set Current  
Day/Time  
Wake  
Sleep  
Fan  
Heat/Cool  
Settings  
System  
System  
Hold Temp  
Day  
Daylight  
Time  
Copy  
Fan  
See Fig. 6 for the location of the keys.  
SETTINGS  
M14625  
Fig. 7. T8624D System and Fan key locations.  
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. 7. The fan settings can be set for  
each program period individually. The system selection is  
for all the program periods.  
NOTE: Always press the keys with your fingertip or  
similar blunt tool. Sharp instruments like a pen  
or pencil point can damage the keyboard.  
Temperature Settings  
System settings control the thermostat operation as  
follows:  
Refer to Table 2 for the default program. If the daytime  
energy savings period is not used, press the period key  
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.  
(
Leave or Return) until the time is blank. The fan setting  
feature is available on select thermostat models. See  
Owners Guide, form number 69-0940, for complete  
instructions on changing the program.  
Table 2. Default Program Settings.  
Fan settings control the system fan as follows:  
Heat  
Setpoint  
Cool  
Setpoint  
Fan  
Setting  
Period  
Time  
On: Fan operates continuously.  
Auto: Fan operates with equipment.  
Wake  
6:00 AM 70°F  
21°C)  
78°F  
(25.5°C)  
Auto  
(
Leave 8:00 AM 62°F  
85°F  
(29.5°C)  
Auto  
Auto  
Auto  
(
16.5°C)  
Return 6:00 PM 70°F  
78°F  
(25.5°C)  
(
21°C)  
Sleep  
10:00 PM 62°F  
82°F  
(
16.5°C)  
(28°C)  
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
INSTALLER SETUP  
Wait Set Program Set Day/Time Temporary Setting  
Em Heat  
Off  
NOTE: For most applications, the thermostat factory-  
settings will not need to be changed. Review  
the factory settings in Table 2 and if no changes  
are necessary, go to the Installer System Test  
section.  
Recovery  
Hold for  
AM  
PM  
Cool  
Auto  
Filter Em Ht Aux Ht Days  
Fan  
MonTue Wed Thu Fri Sat Sun Repl Batt Room Outdoor  
On  
Wake Leave Return Sleep DST  
Heat Cool  
Auto  
M14559  
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 T8624.  
Fig. 8. Display of all LCD segments..  
A combination of key presses are required to use the  
Installer Setup feature.  
—
To enter the installer setup, press and hold the  
information i 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. See Fig. 8  
and 9.  
INSTALLER SETUP  
NUMBER DISPLAY  
(COLUMN 2 OF TABLE 3)  
FACTORY SETTING OR OTHER  
CHOICE DISPLAY (COLUMN 3  
OR 5 OF TABLE 3)  
M14618  
—
—
—
—
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. 9. Display of Installer Setup number and setting.  
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  
complete, review the settings to confirm that  
they match the system.  
Table 3. Thermostat Installer Setup Options.  
Installer Setup  
Number (Press  
Time ∆ key to  
change)  
Other Choices  
(Press ꢀ or ꢁ key to change)  
Actual  
Factory Setting  
Display Description  
Select  
Display  
Description  
Setting  
Not Used.  
1
2
—
0
—
—
1
—
—
Fan operation.  
Conventional  
Heat pump and electric heat  
applications where  
thermostat controls fan  
operation in heat mode  
applications where  
equipmentcontrols  
fan operation in  
heat mode  
Not Used.  
3
4
—
6
—
—
—
—
—
Heating cycle  
rate.a  
Stage 1  
6—6 cph is fixed for stage 1.  
5
Stage 2  
3 or 9 3—3 cph  
6—6 cph factory setting for  
all stages of system  
—9 cph used for electric  
heat  
9
Not Used.  
6 thru 11  
12  
—
1
—
—
—
—
System setting  
adjustment  
Manual  
changeover  
0 or 2 0—Auto changeover  
2—Fixed auto changeover  
a The cycle rate for the last stage of heat is adjustable with 6 cph as the factory setting.  
5
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
Table 3. Thermostat Installer Setup Options. (Continued)  
Installer Setup  
Number (Press  
Time ∆ key to  
change)  
Other Choices  
(Press ꢀ or ꢁ key to change)  
Factory Setting  
Actual  
Setting  
Select  
Adaptive  
Intelligent  
Recovery™  
control.  
Display  
Description  
Display  
Description  
13  
0
AdaptiveIntelligent  
Recovery™  
control is activated  
(system starts  
1
Conventional recovery  
(system starts recovery at  
programmed time).  
—
early so setpoint is  
reached by start of  
program period).  
Degree  
temperature  
display  
14  
0
Temperature is  
displayed in °F  
1
Temperature is displayed  
in °C  
Not Used.  
15  
16  
—
0
—
—
1
—
—
—
Clock format.  
12-hour clock  
format.  
24-hour clock format.  
Not Used.  
17 thru 18  
19  
—
0
—
—
1
—
Extended fan  
operation in  
heating  
No extended fan  
operation after the  
call for heat ends.  
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  
24  
—
0
—
—
1
—
—
—
Outdoor  
No outdoor  
temperature is  
displayed.  
Outdoor temperature is  
displayed. Needs a  
C7089B1000 Outdoor  
Temperature Sensor to  
operate.  
temperature  
display(models  
with OT  
terminals).  
Not Used.  
Deadband  
25 thru 29  
30  
—
3
—
—
—
Heating and  
4 thru 10 Heating and cooling  
setpoints can be set no  
closer than the chosen  
value:  
cooling setpoints  
can be set no  
closer than 3°F  
(
1.5°C).  
4—4°F (2°C)  
5
6
7
8
9
1
—5°F (2.5°C)  
—6°F (3°C)  
—7°F (3.5°C)  
—8°F (4°C)  
—9°F (4.5°C)  
0—10°F (5°C)  
Not Used.  
31 and 32  
33  
—
5
—
—
—
—
Minimum off  
time for the  
compressor.  
5 minutes  
minimum off time  
for the  
0 thru 4  
Minimum number of minutes  
(0 thru 5) the compressor  
will be off between calls for  
the compressor.  
compressor.  
Temperature  
range stops in  
heating.  
34  
35  
36  
90  
45  
—
Highest setpoint  
setting for heating.  
40 to 89 Temperature range (1°F  
increments) of heating  
setpoint settings.  
Temperature  
range stops in  
cooling.  
Lowest setpoint  
setting for cooling.  
46 to 99 Temperature range (1°F  
increments) of cooling  
setpoint settings  
Not Used.  
—
—
—
—
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
Table 3. Thermostat Installer Setup Options. (Continued)  
Installer Setup  
Other Choices  
(Press ꢀ or ꢁ key to change)  
Number (Press  
Time ∆ key to  
change)  
Factory Setting  
Display Description  
Actual  
Setting  
Select  
Display  
Description  
Temperature  
display  
adjustment.  
37  
0
No difference in  
displayed  
temperature and  
actual room  
-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.  
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 0, 1, 3, 4 0 – Off  
run time). 1 – 10 days  
3
4
– 60 days  
– 120 days  
(
Time counted when heat,  
cool or fan is running.)  
Humidifier Pad  
Monitor.  
44  
45  
0
0
Off  
1, 2, 3  
1 – 90 days  
2 – 180 days  
3
– 365 days  
(Time counted by calendar  
days in heat mode.)  
Ultraviolet Air  
Treatment (UV)  
System Lamp  
Monitor.  
Off  
1
1 – 365 days  
(Time counted by calendar  
days in any mode.)  
IMPORTANT  
NOTE: Sun=Sunday, Mon=Monday,  
Tue=Tuesday, Wed=Wednesday,  
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.  
Thu=Thursday, Fri=Friday, Sat=Saturday.  
Set Day/Time  
Time  
Set Program  
Leave  
PM  
Pr Ro g  
u
r
n
am  
S
De at yC / Tu ri mr e  
e
nt  
Wake  
Return  
Sleep  
Fan  
Setting Current Day and Time  
Day  
Hold Temp  
Day  
H
S
e
e
at tt /i Cn go  
s
ol  
System  
Tue  
D Ta yi ml ig  
e
ht  
Copy  
1.  
Press Set Current Day/Time.  
M14620  
NOTE: On initial powerup or after an extended power  
loss, 1:00 pm flashes on the display until a key  
is pressed.  
3. Press Time ∆ or Time ∇ until the current time is dis-  
played.  
NOTE: Tapping the Set Current Day/Time changes the  
time in one-hour increments.  
Set Day/Time  
Time  
Set Program  
Leave  
Return  
PM  
Time  
S
De at yC / Tu ri mr e  
e
nt  
Wake  
Sleep  
Fan  
Set Current  
Day/Time  
PrRo  
g
u
r
n
am  
Hold Temp  
Day  
H
S
e
e
at tt /i Cn g  
o
s
ol  
System  
Mon  
Set Day/Time  
D Ta yi ml ight  
e
Copy  
AM  
M14619  
Pr Ro g  
u
r
n
am  
S
De at yC / Tu ri mr e  
e
nt  
Time  
Wake  
Leav  
S
e
et Progra mR eturn  
Sleep  
Fan  
Hold Temp  
Day  
H
S
e
e
at tt /i Cn g  
o
s
ol  
System  
Tue  
D Ta yi ml ig  
e
ht  
Copy  
2.  
Press Day until the current day is displayed.  
M14621  
7
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
NOTE: If the current time is Daylight Savings Time,  
press Daylight Time until DST is displayed.  
To start the system test:  
CAUTION  
The minimum off time for compressors is  
Set Day/Time  
bypassed during the Installer System Test.  
Equipment damage can occur if the compressor  
is cycled too quickly.  
AM  
Time  
Set Program  
Leave  
Daylight  
Time  
Pr Ro g  
u
r
n
am  
S
De at yC / Tu ri mr e  
e
nt  
Wake  
Return  
Sleep  
Fan  
Hold Temp  
ay  
H
S
e
e
at tt /i Cn go  
s
ol  
System  
Tue  
D Ta yi ml ig  
e
ht  
Copy  
DST  
M14622  
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. 10 and 11.  
4.  
Press Run Program.  
System  
Heat  
Table 4. Tests Available In Installer System Test.  
AM  
Time  
Set Program  
Leave  
Run  
Program  
Pr Ro g  
u
r
n
am  
S
De at yC / Tu ri mr e  
e
nt  
Wake  
Return  
Sleep  
Fan  
Test Number  
System Test Description  
Hold Temp  
Day  
H
S
e
e
at tt /i Cn g  
o
s
ol  
System  
Fan  
Tue  
Wake  
Room  
D Ta yi ml ig  
e
ht  
Copy  
DST  
Auto  
M14623  
10-19  
Heating equipment can be turned on  
and off.  
3
0-39  
Cooling equipment can be turned on  
and off.  
Viewing or Resetting Timer Settings  
When the thermostat activates a timer, the thermostat  
40-49  
Fan equipment can be turned on and  
off.  
flashes Filter until the timer resets.  
60 0 to 60 19 Keyboard keys test.  
1.  
Reset the timer by pressing the i key until the  
expired timer is displayed.  
70-79  
Thermostat information including date  
code and software versions are  
displayed.  
Wait Set Program Set Day/Time Temporary Setting  
Filter  
Days  
Em Heat  
Off  
Recovery  
Hold for  
AM  
PM  
Cool  
Auto  
M20243  
Filter Em Ht Aux Ht Days  
Fan  
2.  
Press the Time skey to reset the timer.  
MonTue Wed Thu Fri Sat Sun Repl Batt Room Outdoor  
On  
Wake Leave Return Sleep DST  
Heat Cool  
Auto  
M14559  
Fig. 10. Display of all the segments of the LCD.  
Filter  
Days  
M20244  
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.  
M14612  
Fig. 11. Display of test number.  
Refer to Table 5 for the directions and results of the  
specific tests.  
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.  
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  
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
Table 5. Installer System Test Options.  
Keys to  
Press  
Test  
Number  
Description  
Heating Equipment System Test  
Time ∆  
10  
11  
12  
11  
10  
Enter heating equipment System Test.  
ꢀ
ꢀ
ꢁ
ꢁ
Stage-one heat comes on. The system fan is also energized.  
Stage-two heat comes on. Stage-one heat and system fan remain on.  
Stage-two heat turns off.  
Stage-one heat and system fan turn off.  
Cooling Equipment System Test  
Time ∆  
30  
31  
32  
31  
30  
Change from heating to cooling equipment System Test.  
Stage-one cool and system fan come on.  
ꢀ
ꢁ
ꢁ
ꢁ
Stage-two cool comes on. Stage-one cool and system fan remain on.  
Stage-two cool turns off.  
Stage-one cool and system fan turn off.  
Fan Equipment System Test  
Time ∆  
40  
41  
40  
Change from cooling to fan equipment System Test.  
ꢀ
ꢁ
Fan comes on.  
Fan turns off.  
Key Operation System Test  
Time ∆ 60 Change from fan to key operation System Test.  
NOTE: Press any key and the displayed numbers will 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.  
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
4.  
Press the increase ꢀ key again to display the soft-  
ware revision number (Example: 001 = Revision  
number 1).  
THERMOSTAT INFORMATION  
1.  
Press the Time ∆ key to access the thermostat  
information.  
M14616  
Press the increase ꢀ key again to display the  
EEPROM identification code. (Example: 314 =  
EEPROM ID 314)  
5.  
M14613  
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 (Exam-  
ple: 027 = February 1997).  
M14617  
Press the Run Program key to exit the system test.  
The system test times out after four minutes with-  
out any key presses.  
6.  
M14614  
Press the increase ꢀ key again to display the soft-  
ware identification code. (Example: 02 = software  
ID code 2)  
3.  
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.  
M14615  
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
TROUBLESHOOTING GUIDE  
Table 6. Troubleshooting Guide.  
Possible Cause  
Symptom  
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  
Room temperature display has Enter Installer Setup number 37 and reconfigure the display.  
display is incorrect. been reconfigured.  
Thermostat is configured for °F Enter Installer Setup number 14 and reconfigure the display.  
or °C display.  
Bad thermostat location.  
Relocate the thermostat.  
Temperature  
The upper or lower temperature Check the temperature setpoints:  
limits were reached. • Heating limits are 40 to 90°F (7 to 31°C).  
• Cooling limits are 48 to 99°F (9 to 37°C).  
settings will not  
change. (Example:  
Cannot set the  
heating higher or  
the cooling lower.)  
The setpoint temperature range Check Installer Setup numbers 34 and 35 and reconfigure the  
stops were configured.  
setpoint stops.  
Heating will not  
come on.  
No power to the thermostat.  
• Check for 24 Vac between R and W 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 Wait up to five minutes for the system to respond.  
activated.  
System selection is not set to  
Heat.  
Set system selection to Heat.  
Heating setpoint is below room Check heating setpoint. Set heating setpoint to desired  
temperature.  
temperature.  
Cooling will not  
come on.  
No power to the thermostat.  
• Check for 24 Vac between R or RC.  
— 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 • Wait up to five minutes for the system to respond.  
activated.  
• 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.  
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T8624D CHRONOTHERM® IV DELUXE PROGRAMMABLE MULTISTAGE THERMOSTATS  
Table 6. Troubleshooting Guide. (Continued)  
Symptom  
System on indicator Heating or cooling equipment is Verify operation of heating or cooling equipment in self-test.  
flame=heat, not operating.  
Possible Cause  
Action  
(
snowflake=cool) is  
displayed, but no  
warm or cool air is  
coming from the  
registers.  
Outdoor tempera- Option not activated.  
ture not displayed  
Enter Installer Setup number 24 and set to 1. Thermostat must  
have OT terminals and a C7089B1000 installed.  
a
Outdoor  
temperature  
display is incorrect  
aSelect models.  
Outdoor sensor is connected  
incorrectly.  
Refer to C7089B1000 Installation Instructions and check wiring  
between the thermostat and sensor.  
a
Wrong sensor.  
Replace sensor with C7089B1000 Sensor.  
Automation and Control Solutions  
Honeywell Honeywell Limited-Honeywell Limitée  
985 Douglas Drive North  
Golden Valley, MN 55422  
1
35 Dynamic Drive  
Scarborough, Ontario  
M1V 4Z9  
69-1412—1 G.H. Rev. 12-02  
www.honeywell.com/yourhome