Page 1
T8501A,B,C,D
Microelectronic Thermostats
INSTALLATION INSTRUCTIONS
APPLICATION
The T8501 Microelectronic Thermostat provides electronic control of 24 Vac single-stage heating and cooling systems.
Refer to Table 1 for a general description of the thermostat. All T8501 Thermostats require a common wire to supply
power.
Table 1. Description of T8501 Thermostats.
T8501 System Changeover
A Heat only None None None —
B Heat only None Heat-Off On-Auto Select models have only a system switch or fan
C Heat-Cool Manual Heat-Off-Cool On-Auto System and fan selections are done by
D Heat-Cool Automatic Heat-Off-Cool-Auto On-Auto System and fan selections are done by
System
Selection
Fan
Selection Comments
switch and some models have both.
switches.
keyboard.
RECYCLING NOTICE
If this control is replacing a control that contains
mercury in a sealed tube, do
control in the trash.
Contact your local waste management authority for
instructions regarding recycling and the proper
disposal of the old thermostat.
not
place your old
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.
Copyright © 1996 Honeywell Inc. • • All Rights Reserved
CAUTION
Disconnect power supply to prevent electrical
shock or equipment damage.
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. wiring box. Position wallplate horizontally
on the wall or on a 2 in. x 4 in. wiring box.
쐃 Position and level the wallplate (for appearance
only). The thermostat will function properly even
when not level.
X-XX UL
69-0959
Page 2
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
WALL
ANCHORS
(2)
NO
WIRES
THROUGH WALL
YES
NO
5 FEET
[1.5 METERS]
Fig. 1. Typical location of thermostat.
WALL
쐏 Position the wallplate over the holes, pulling wires
through the wiring opening.
쐄 Loosely insert the mounting screws into the holes.
쐂 Tighten mounting screws.
WIRING
All wiring must comply with local electrical codes and
ordinances. Refer to Fig. 3 through 5 for typical hookups.
A letter code is located near each terminal for identification.
NO
M10106
MOUNTING
HOLES
MOUNTING
SCREWS
Fig. 2. Mounting the wallplate.
쐇 Use a pencil to mark the mounting holes. See Fig. 2.
쐋 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 or wood, drill two
7/32 inch holes. Gently tap anchors (provided) into
the drilled holes until flush with the wall.
69-0959
M6530
CAUTION
Disconnect power before wiring to prevent
electrical shock or equipment damage.
쐃 Loosen the terminal screws on the wallplate and
connect the system wires. See Fig. 6.
IMPORTANT
Use 18 gauge, color-coded thermostat cable for
proper wiring.
쐇 Securely tighten each terminal screw.
쐋 Push excess wire back into the hole.
쐏 Plug the hole with nonflammable insulation to
prevent drafts from affecting the thermostat.
2
Page 3
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
M4826
FOR WRAPAROUND
INSERTION STRIP
7/16 IN. (11 MM).
FOR STRAIGHT
INSERTION STRIP
5/16 IN. (8 MM).
THERMOSTAT
T
2
OUTDOOR
TEMPERATURE
SENSOR
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
AVAILABLE ON SELECT MODELS.
2
CW
HEATING
RELAY OR
VALVE COIL
1
M4822
L1
(HOT)
L2
Fig. 3. Typical hookup in heat only application.
THERMOSTAT
2
COMPRESSOR
CONTACTOR
HEATING
RELAY OR
VALVE COIL
1
M4821
OUTDOOR
TEMPERATURE
SENSOR
COOL
CHANGEOVER
VALVE OR
DAMPER
HEAT
CHANGEOVER
VALVE OR
DAMPER
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
AVAILABLE ON SELECT MODELS.
2
FAN
RELAY
ROTO
ROTOTCBOGYW
L1
(HOT)
L2
THERMOSTAT
T
OGYC BW
Rc
2
OUTDOOR
TEMPERATURE
SENSOR
COMPRESSOR
CONTACTOR
FAN
RELAY
COOL
CHANGEOVER
VALVE OR
DAMPER
1
L1
(HOT)
L2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
AVAILABLE ON SELECT MODELS.
2
3
JUMPER Rh TO Rc IN A SINGLE TRANSFORMER SYSTEM.
Fig. 5. Typical hookup in heat and cool
system with two transformers.
HEAT
CHANGEOVER
VALVE OR
DAMPER
HEATING
RELAY OR
VALVE COIL
1
M4820
3
RhOTO
L1
(HOT)
L2
Fig. 4. Typical hookup in heat and cool
system with one transformer.
Mounting Thermostat
쐃 Engage tabs at the top of the thermostat and
wallplate. See Fig. 7.
쐇 Press lower edge of case to close and latch.
Fig. 6. Proper wiring technique.
3
69-0959
Page 4
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
A.
ENGAGE TABS AT TOP OF THERMOSTAT AND WALLPLATE.
B.
PRESS LOWER EDGE OF CASE TO LATCH.
Fan settings control the system fan as follows:
On: Fan operates continuously.
Auto: Equipment controls fan.
The system default setting is Heat and the fan default
setting is Auto. Use the keyboard or system and fan
switches, depending on model, to change to the desired
settings. See Figs. 9 and 10.
i
HEAT OFF COOL
ON AUTO
SYSTEM
Selection for heating or cooling
equipment operation.
Heat - Heating equipment
Off - No equipment
Cool - Cooling equipment
HEAT OFF COOL
ON AUTO
FAN
On - Fan runs continuously
Auto - Fan runs when
heating or cooling
equipment operates
M6798A
Fig. 7. Mounting thermostat on wallplate.
NOTE: To remove the thermostat from the wall, first pull out
at the bottom of the thermostat; remove top last.
Using Thermostat Keys
The thermostat keys are used to:
• set temperature,
•display present setting,
• configure Installer Setup,
• check Self-Test,
•display outdoor temperature (select models).
Select models have keys to:
• set the system operation,
• set the fan operation.
See Fig. 8 for key information.
INCREASE
TEMPERATURE
SETTING
i
DECREASE
TEMPERATURE
SETTING
DISPLAY PRESENT
SETTINGS AND SCROLL
THROUGH INSTALLER
SETUP MODES
(INFORMATION KEY)
M6801
Fig. 8. Thermostat key locations and descriptions.
SETTINGS
System and Fan Settings
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.
M10146
Fig. 9. T8501C system and fan switches location.
i
Fan
System
Press to select
Press to select
heating or cooling
heating or cooling
equipment.
equipment.
Em. Ht.
-Emergency heating
On— Fan runs continuously
Heat—Heating equipment
Auto—Fan runs when
Off — No equipment
Cool—Cooling equipment
Auto—Thermostat
automatically selects
heating and cooling
equipment.
CHECK LIGHT ON SELECT MODELS
1
heating or cooling
equipment operates
System
Fan
1
System
Fan
M10147
Fig. 10. T8501D system and fan keys location.
NOTE: Always press the system and fan keys with your
fingertip or similar blunt tool. Sharp instruments
like a pen or pencil point can damage the
keyboard.
Temperature Settings
The default setpoint for heat is 70°F (21°C) and for cool is
78°F (25.5°C). Press the increase ▲ or decrease ▼ key to
change the present setting. To change between heat and
cool, press the Information i key until the setting to be
changed appears.
INSTALLER SETUP
NOTE: For most applications, the thermostat factory-
settings do not need to be changed. Review the
factory settings in Table 2 and if no changes are
necessary, go to the Installer Self-Test section.
69-0959
4
Page 5
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
The Installer Setup is used to customize the thermostat to
specific systems. Some of the options include temperature
display, changeover, minimum equipment on time and
minimum off time. Installer modes are listed in numerical
order in Table 2. The table includes all the configuration
options and the factory-settings available for the T8501.
IMPORTANT
The Installer Setup must be set correctly for the
HVAC equipment, thermostat and subbase to
operate properly.
A combination of key presses are required to use the
Installer Setup feature.
— To enter the Installer Setup mode, press and hold the
Information i key with the increase ▲ and decrease
▼ keys until the first mode number is displayed. All
display segments appear for approximately three
seconds before the mode number is displayed. See
Figs. 11 and 12.
— To advance to the next Installer Setup mode, press
the Information i key.
— To change a setting, use the increase ▲ or de-
crease ▼ key.
— To exit the Installer Setup mode, press and hold the
Information i key until the display returns to normal
(approximately three seconds). The display scrolls the
Mode Numbers backwards to get to the normal
display. The Installer Setup mode is automatically
exited if no key presses are made for five minutes.
NOTE: Only configurable Mode Numbers are shown.
Em Ht Temporary Setting
Aux Ht
Repl
Wait
Batt
System Fan
Em HeatOffCool Auto Only
Fig. 11. Display of all the segments of the LCD.
Fig. 12. Display of Installer Setup mode and setting.
CAUTION
Heat pump and electric heat systems must be
configured to 01 in Installer Setup mode 02 to
prevent equipment damage caused by the system
running without the fan.
Table 2. Thermostat Installer Setup Options.
Select
Mode Number
(Press i key
to change)
Factory-Setting
(Press ▲ or ▼ key to change)
Display Description Display Description
Not used 01 — — — —
Fan operationa02 00 Conventional applica-
tions where equipment
controls fan operation in
heat mode
01 Heat pump and electric heat
Not used 03 — — — —
Heating cycle rate 04 06 6 cph used for
conventional systems
01, 03,
or 09
Not used 05 thru 11 — — — —
Changeover
(T8501D only)
a
Available on select models.
12 01 Automatic changeover 00 Manual changeover
Remote
Room
%Humid
Heat Cool
Outdoor
OnAuto
M4844
MODE NUMBER DISPLAY
(COLUMN 2 OF TABLE 2)
FACTORY SETTING OR
OTHER CHOICE DISPLAY
(COLUMN 3 OR 5 OF TABLE 2)
M10105
Other Choices
applications where thermostat
controls fan operation in heat
mode
01—1 cph used for radiant floor
heat, gravity systems
03—3 cph used for hot water
systems or high efficiency
furnaces
09—9 cph used for electric heat
systems
(Continued)
5
69-0959
Page 6
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Table 2. Thermostat Installer Setup Options (continued).
Select
Mode Display
(Press i key
to change)
Factory-Setting
Display Description Display Description
Not used 13 — — — —
Degree tempera-
ture display
14 00 Temperature is
displayed in °F
Not used 15 thru 18 — — — —
Extended fan
operation in
a,b
heating
Extended fan
operation in
a
cooling
19 00 No extended fan
20 00 No extended fan
operation after the call
for heat ends
operation after the call
for cool ends
Not used 21 thru 23 — — — —
Outdoor
temperature
a
display
24 00 No outdoor temperature
is displayed
Not used 25 thru 32 — — — —
Minimum off time
for the
compressor
Heating setpoint
range stop
Cooling setpoint
range stop
System On
a
display
Temperature
display
adjustment
a
Available on select models.
b
Mode 02 must be set to 01 to extend fan operation.
c
T8501D is 48°F.
33 05 5 minute minimum off
34 90 Heating setpoint can be
a
35 45
a
36 00 LCD On symbol is
37 00 No difference in
time for the compressor
set no higher than 90°F
c
Cooling setpoint can be
set no lower than 45°F
displayed when system
is energized
displayed temperature
and actual room
temperature
(Press ▲ or ▼ key to change)
01 Temperature is displayed in °C
01 Fan operation is extended
01 Fan operation is extended
01 Outdoor temperature is displayed.
00, 01,
02, 03 or
04
40 thru90Number can be set anywhere
45c thru99Number can be set anywhere
c
01 Display is disabled, usually set for
01 thru
06
Other Choices
90 seconds after the call for
heat ends
90 seconds after the call for
cool ends
Needs a C7089B1000 Outdoor
Sensor to operate.
Minimum number of minutes
(0 thru 5) the compressor will be
off between calls for the
compressor
between 40 and 90 in 1°F
increments
between 45
increments
c
and 99 in 1°F
01 for a zoned system
01—Display adjusts to 1°F higher
than actual room temperature
02—Display adjusts to 2°F higher
than actual room temperature
03—Display adjusts to 3°F higher
than actual room temperature
04—Display adjusts to 1°F lower
than actual room temperature
05—Display adjusts to 2°F lower
than actual room temperature
06—Display adjusts to 3°F lower
than actual room temperature
69-0959
6
Page 7
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
INSTALLER SELF-TEST
Use the Installer Self-Test to check the thermostat
configurations and operation. Refer to Table 3 for a list of
the available self-tests.
To start the self-test:
NOTE: The minimum off time for compressors is
bypassed during the Installer Self-Test.
Press and hold the increase ▲ and decrease ▼ keys, at
the same time, until two zeros appear. All segments of the
LCD are displayed before the two zeros appear.
Em Ht Temporary Setting
Aux Ht
Repl
Wait
Batt
System Fan
Em HeatOffCool Auto Only
Key to
Press
Heating Equipment Self-Test
▲ 11 Heat comes on. When Installer Setup mode number 02 is 01, the system fan is also
▼ 10 Heat and system fan turn off.
Cooling Equipment Self-Test
▲ 31 Cool and system fan come on.
▼ 30 Cool and system fan turn off.
Fan Equipment Self-Test (T8501D only)
▲
▼
Test
Mode
Number Description
i
i
i
10 Enter heating equipment self-test. (Set system switch to HEAT on switch models.)
30 Change from heating to cooling equipment self-test. (Set system switch to COOL on switch
40 Change from cooling to fan equipment self-test.
41 Fan comes on.
40 Fan turns off.
TEST MODE
NUMBER
Heat Cool
energized.
models.)
Remote
Room
%Humid
Outdoor
OnAuto
M4844
M6792
Table 4. Installer Self-Test Options.
Table 3. Tests Available In The Installer
Test
Number Self-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 (T8501D only) can be turned
60-69 System key or system switch position test
70-79 Thermostat information including date code
Refer to Table 4 for the directions and results of the
specific tests.
IMPORTANT
Models with system and fan switches must set
the switches to the equipment that is being
checked for the equipment to operate.
NOTE: Press and hold the increase ▲ and decrease ▼
keys for three seconds to exit the self-test mode.
The self-test times out after five minutes without
any key presses.
Self-Test Mode.
on and off.
(not available on T8501A)
and software versions are displayed
(Continued)
7
69-0959
Page 8
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Table 4. Installer Self-Test Options. (Continued)
Key to
Press
Key or Switch Operation Self-Test
IMPORTANT
SYSTEM KEY OR SWITCH SELF-TEST (When system switch is used, move switch to see Test Mode Numbers.)
System 61 Heat Test Mode Number is displayed. (Set system switch to HEAT.)
System 62 Off Test Mode Number is displayed. (Set system switch to OFF.)
System 63 Cool Test Mode Number is displayed. (Set system switch to COOL.)
System 64 Auto Test Mode Number is displayed.
FAN KEY SELF-TEST (Fan switch cannot be tested)
Fan 68 Fan on Test Mode Number is displayed.
Fan 69 Fan off Test Mode Number is displayed.
a
Available on select models.
Test
Mode
Number Description
Test Mode Numbers will only be displayed when the system is configured for the selected function.
EXAMPLE: Numbers 60, 61 and 62 are the only numbers that will be displayed when a system
is configured for heat only.
i
60 Change from cooling or fan to key operation self-test.
a
Thermostat Information
쐃 Press the Information i key to access the thermo-
stat information.
M4864
쐇 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: 026 = February 1996)
M4865
쐋 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)
M4866
M6791
69-0959
8
Page 9
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Press the increase ▲ key again to display the
EEPROM identification code.
(Example: 222 = EEPROM ID 222)
M4867
쐂 Press and hold the increase ▲ and decrease ▼
keys together, until the room temperature is
displayed, to exit the self-test mode. The self-test
times out after five minutes without any key presses.
CHECKOUT
Outdoor Temperature Sensor
(Where Applicable)
Allow the outdoor temperature sensor to soak in the
outdoor air for a minimum of five minutes before taking a
reading. With an accurate thermometer (±1°F [±0.5°C]),
measure the temperature at the sensor location, allowing
time for the thermometer to stabilize before reading. Match
the thermometer reading to the outdoor temperature
display at the thermostat.
TROUBLESHOOTING GUIDE
Symptom Possible Cause Action
Display will not
come on.
Temperature
display is incorrect.
Temperature
settings will not
change. (Example:
Cannot set the
heating higher or
the cooling lower.)
Heating will not
come on.
a
Available on select models.
Thermostat is not being
powered.
Thermostat microprocessor is
locked up.
Room temperature display has
been reconfigured.
Thermostat is configured for °F
or °C display.
Bad thermostat location. Relocate the thermostat.
The upper or lower temperature
limits were reached.
The setpoint temperature range
stops were configured.
No power to the thermostat. • Check that C terminal is connected to the system
a
•Check that C terminal is connected to the system
transformer.
•Check for 24 Vac between C and R or RH 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.
Remove the thermostat from the wallplate for 2 minutes. After
2 minutes, replace the thermostat on the wallplate.
Enter Installer Setup mode number 37 and reconfigure the
display.
Enter Installer Setup mode number 14 and reconfigure the
display.
Check the temperature setpoints:
•Heating limits are 40 to 90°F (7 to 31°C)
•Cooling limits are 45 to 99°F (9 to 37°C) except T8501D
cooling limits are 48 to 99°F
Check Installer Setup mode numbers 34 and 35 and
reconfigure the setpoint stops.
transformer.
•Check for 24 Vac between C and R or RH 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 system switch at the equipment is in the
Off position—set to 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.
(Continued)
9
69-0959
Page 10
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
TROUBLESHOOTING GUIDE (Continued)
Symptom Possible Cause Action
Heating will not
come on.
(Continued)
Cooling will not
come on.
System On
indicator is lit, but
no heat is being
delivered.
Outdoor
temperature
not displayed
Outdoor
temperature
display is incorrect
a
Available on select models.
Thermostat minimum off time is
activated.
System selection is not set to
Heat.
No power to the thermostat. • Check that C terminal is connected to the system
Thermostat minimum off time is
activated.
System selection is not set to
Cool.
Fan operation set for 00
(conventional heat) when it
should be set for 01 (electric
heat).
Conventional heating
equipment turns on the fan
when the furnace has
warmed up to a setpoint.
Heating equipment is not
operating.
Option not activated. Enter Installer Setup mode number 24 and set to 01.
a
Outdoor sensor is connected
incorrectly.
a
Wrong sensor. Replace sensor with C7089B1000 sensor.
Wait up to five minutes for the system to respond.
Set system selection to Heat.
transformer.
• Check for 24 Vac between C and 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 system switch at the 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.
• Wait up to five minutes for the system to respond.
• Enter Installer Setup mode number 33. Reconfigure
minimum off time (if required).
Set system selection to Cool.
Enter Installer Setup mode number 02 and reconfigure the fan
operation.
Wait a minute after seeing the On indicator and then check the
registers.
Verify operation of heating equipment in self-test.
Thermostat must have OT terminals and a C7089B1000
installed.
Refer to C7089B1000 installation instructions and check wiring
between the thermostat and sensor.
69-0959
10
Page 11
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
11
69-0959
Page 12
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Home and Building Control
Honeywell Inc.
Honeywell Plaza
P.O. Box 524
Minneapolis, MN 55408-0524
69-0959
69-0959 J.H. 10-96 Printed in Taiwan R.O.C.
Home and Building Control
Honeywell Limited-Honeywell Limitée
155 Gordon Baker Road
North York, Ontario
M2H 2C9
12
www.honeywell.com/yourhome
Loading...