Honeywell t8501A User manual

X-XX UL
INSTALLATION INSTRUCTIONS
Copyright © 1996 Honeywell Inc. • • All Rights Reserved
T8501A,B,C,D
Microelectronic Thermostats
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.
RECYCLING NOTICE
If this control is replacing a control that contains
mercury in a sealed tube, do
not place your old
control in the trash.
Contact your local waste management authority for
instructions regarding recycling and the proper
disposal of the old thermostat.
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.
T8501 System Changeover System Selection Fan Selection Comments
AHeat only None None None —
BHeat only None Heat-Off On-Auto Select models have only a system switch or fan
switch and some models have both.
CHeat-Cool Manual Heat-Off-Cool On-Auto System and fan selections are done by
switches.
DHeat-Cool Automatic Heat-Off-Cool-Auto On-Auto System and fan selections are done by
keyboard.
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.
쐃Position and level the wallplate (for appearance
only). The thermostat will function properly even
when not level.
69-0959

69-0959 2
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Fig. 1. Typical location of thermostat.
Fig. 2. Mounting the wallplate.
쐇Use a pencil to mark the mounting holes. See Fig. 2.
쐋Remove 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.
쐏Position the wallplate over the holes, pulling wires
through the wiring opening.
쐄Loosely insert the mounting screws into the holes.
쐂Tighten 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 identifica-
tion.
CAUTION
Disconnect power before wiring to prevent
electrical shock or equipment damage.
쐃Loosen 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.
쐇Securely tighten each terminal screw.
쐋Push excess wire back into the hole.
쐏Plug the hole with nonflammable insulation to
prevent drafts from affecting the thermostat.
WIRES
THROUGH WALL
WALL
MOUNTING
HOLES
MOUNTING
SCREWS
M6530
WALL
ANCHORS
(2)
5 FEET
[1.5 METERS]
YES
NO
NO
NO
M10106

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T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Fig. 3. Typical hookup in heat only application.
Fig. 4. Typical hookup in heat and cool
system with one transformer.
Mounting Thermostat
쐃Engage tabs at the top of the thermostat and
wallplate. See Fig. 7.
쐇Press lower edge of case to close and latch.
Fig. 5. Typical hookup in heat and cool
system with two transformers.
Fig. 6. Proper wiring technique.
L1
(HOT)
L2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
AVAILABLE ON SELECT MODELS.
1
HEATING
RELAY OR
VALVE COIL
M4821
COMPRESSOR
CONTACTOR
FAN
RELAY
RO T O T CBOGYW
OUTDOOR
TEMPERATURE
SENSOR
COOL
CHANGEOVER
VALVE OR
DAMPER
HEAT
CHANGEOVER
VALVE OR
DAMPER
THERMOSTAT
1
2
2
M4826
FOR WRAPAROUND
INSERTION STRIP
7/16 IN. (11 MM).
FOR STRAIGHT
INSERTION STRIP
5/16 IN. (8 MM).
L1
(HOT)
L2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
AVAILABLE ON SELECT MODELS.
JUMPER Rh TO Rc IN A SINGLE TRANSFORMER SYSTEM.
1
HEATING
RELAY OR
VALVE COIL
M4820
COMPRESSOR
CONTACTOR
FAN
RELAY
RhO T O T OGYCBW
OUTDOOR
TEMPERATURE
SENSOR
COOL
CHANGEOVER
VALVE OR
DAMPER
HEAT
CHANGEOVER
VALVE OR
DAMPER
THERMOSTAT
1
3
2
2
3
1
L1
(HOT)
L2
Rc
L1
(HOT)
L2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
AVAILABLE ON SELECT MODELS.
1
HEATING
RELAY OR
VALVE COIL
M4822
RO T O T CW
OUTDOOR
TEMPERATURE
SENSOR
THERMOSTAT
1
2
2

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T8501A,B,C,D MICROELECTRONIC THERMOSTATS
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.
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.
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.
Fig. 9. T8501C system and fan switches location.
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.
M6798A
B. PRESS LOWER EDGE OF CASE TO LATCH.
A. ENGAGE TABS AT TOP OF THERMOSTAT AND WALLPLATE.
M10147
i
Press to select
heating or cooling
equipment.
Em. Ht. -Emergency heating
Heat—Heating equipment
Off — No equipment
Cool—Cooling equipment
Auto—Thermostat
automatically selects
heating and cooling
equipment.
Press to select
heating or cooling
equipment.
On—Fan runs continuously
Auto—Fan runs when
heating or cooling
equipment operates
System
System
System
Fan
Fan
Fan
1
1CHECK LIGHT ON SELECT MODELS
M6801
DISPLAY PRESENT
SETTINGS AND SCROLL
THROUGH INSTALLER
SETUP MODES
(INFORMATION KEY)
i
DECREASE
TEMPERATURE
SETTING
INCREASE
TEMPERATURE
SETTING
M10146
i
HEAT OFF COOL
ON AUTO
HEAT OFF COOL
ON AUTO
SYSTEM
Selection for heating or cooling
equipment operation.
Heat - Heating equipment
Off - No equipment
Cool - Cooling equipment
FAN
On - Fan runs continuously
Auto - Fan runs when
heating or cooling
equipment operates

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5
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Mode Number
(Press i key Factory-Setting Other Choices
(Press ▲or ▼key to change)
Select 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
applications where thermostat
controls fan operation in heat
mode
Not used 03 — — — —
Heating cycle rate 04 06 6 cph used for
conventional systems 01, 03, or 09 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
Not used 05 thru 11 — — — —
Changeover
(T8501D only) 12 01 Automatic changeover 00 Manual changeover
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.
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.
aAvailable on select models.
(Continued)
M10105
MODE NUMBER DISPLAY
(COLUMN 2 OF TABLE 2)
FACTORY SETTING OR
OTHER CHOICE DISPLAY
(COLUMN 3 OR 5 OF TABLE 2)
Em HeatOffCool Auto Only
Heat Cool
OnAuto
System Fan
Room
Outdoor
Em Ht Temporary Setting
Wait
%Humid
Aux Ht Remote
Repl
Batt
M4844

69-0959 6
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Table 2. Thermostat Installer Setup Options (continued).
aAvailable on select models.
b Mode 02 must be set to 01 to extend fan operation.
cT8501D is 48°F.
Mode Display
(Press i key Factory-Setting
Other Choices
(Press ▲or ▼key to change)
Select to change) Display Description Display Description
Not used 13 — — — —
Degree tempera-
ture display 14 00 Temperature is displayed in °F 01 Temperature is displayed in °C
Not used 15 thru 18 — — — —
Extended fan
operation in
heating
a,b
19 00 No extended fan
operation after the call
for heat ends
01 Fan operation is extended
90 seconds after the call for
heat ends
Extended fan
operation in
cooling
a
20 00 No extended fan
operation after the call
for cool ends
01 Fan operation is extended
90 seconds after the call for
cool ends
Not used 21 thru 23 — — — —
Outdoor
temperature
display
a
24 00 No outdoor temperature
is displayed 01 Outdoor temperature is displayed. Needs a C7089B1000 Outdoor
Sensor to operate.
Not used 25 thru 32 — — — —
Minimum off time
for the
compressor
33 05 5 minute minimum off
time for the compressor 00, 01, 02, 03 or
04
Minimum number of minutes
(0 thru 5) the compressor will be
off between calls for the
compressor
Heating setpoint
range stop
a
34 90 Heating setpoint can be
set no higher than 90°F 40 thru 90 Number can be set anywhere between 40 and 90 in 1°F
increments
Cooling setpoint
range stop
a
35 45
c
Cooling setpoint can be
set no lower than 45°F
c
45
c
thru
99 Number can be set anywhere between 45
c
and 99 in 1°F
increments
System On
display
a
36 00 LCD On symbol is
displayed when system
is energized
01 Display is disabled, usually set for
01 for a zoned system
Temperature
display
adjustment
37 00 No difference in
displayed temperature
and actual room
temperature
01 thru
06
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

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T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Table 4. Installer Self-Test Options.
Table 3. Tests Available In The Installer
Self-Test Mode.
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.
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.
(Continued)
Em HeatOffCool Auto Only
Heat Cool
OnAuto
System Fan
Room
Outdoor
Em Ht Temporary Setting
Wait
%Humid
Aux Ht Remote
Repl
Batt
M4844
M6792
TEST MODE
NUMBER
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
on and off.
60-69 System key or system switch position test
(not available on T8501A)
70-79 Thermostat information including date code
and software versions are displayed
Key to
Press
Test
Mode
Number Description
Heating Equipment Self-Test
i 10 Enter heating equipment self-test. (Set system switch to HEAT on switch models.)
▲11 Heat comes on. When Installer Setup mode number 02 is 01, the system fan is also
energized.
▼10 Heat and system fan turn off.
Cooling Equipment Self-Test
i 30 Change from heating to cooling equipment self-test. (Set system switch to COOL on switch
models.)
▲31 Cool and system fan come on.
▼30 Cool and system fan turn off.
Fan Equipment Self-Test (T8501D only)
i 40 Change from cooling to fan equipment self-test.
▲41 Fan comes on.
▼40 Fan turns off.

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T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Table 4. Installer Self-Test Options. (Continued)
aAvailable on select models.
쐇Press 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)
쐋Press 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)
Thermostat Information
쐃Press the Information i key to access the thermo-
stat information.
M6791
M4864
M4865
M4866
Key to
Press
Test
Mode
Number Description
Key or Switch Operation Self-Test
a
IMPORTANT
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.
SYSTEM KEY OR SWITCH SELF-TEST (When system switch is used, move switch to see Test Mode Numbers.)
i 60 Change from cooling or fan to key operation self-test.
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.

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T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Press the increase ▲key again to display the
EEPROM identification code.
(Example: 222 = EEPROM ID 222)
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.
쐂Press 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.
M4867
TROUBLESHOOTING GUIDE
aAvailable on select models.
(Continued)
Symptom Possible Cause Action
Display will not
come on. Thermostat is not being powered. •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.
Thermostat microprocessor is
locked up. Remove the thermostat from the wallplate for 2 minutes. After 2 minutes, replace the thermostat on the wallplate.
Temperature
display is incorrect. Room temperature display has been reconfigured. Enter Installer Setup mode number 37 and reconfigure the display.
Thermostat is configured for °F
or °C display.
a
Enter Installer Setup mode number 14 and reconfigure the
display.
Bad thermostat location. Relocate the thermostat.
Temperature
settings will not
change. (Example:
Cannot set the
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 45 to 99°F (9 to 37°C) except T8501D
cooling limits are 48 to 99°F
heating higher or
the cooling lower.) The setpoint temperature range
stops were configured. Check Installer Setup mode numbers 34 and 35 and reconfigure the setpoint stops.
Heating will not
come on. No power to the thermostat. • 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 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.

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T8501A,B,C,D MICROELECTRONIC THERMOSTATS
TROUBLESHOOTING GUIDE (Continued)
aAvailable on select models.
Symptom Possible Cause Action
Heating will not
come on. Thermostat minimum off time is activated. Wait up to five minutes for the system to respond.
(Continued) System selection is not set to
Heat. Set system selection to Heat.
Cooling will not
come on. No power to the thermostat. • Check that C terminal is connected to the system 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.
Thermostat minimum off time is
activated. • Wait up to five minutes for the system to respond. • Enter Installer Setup mode number 33. Reconfigure
minimum off time (if required).
System selection is not set to
Cool. Set system selection to Cool.
System On
indicator is lit, but
no heat is being
delivered.
Fan operation set for 00
(conventional heat) when it
should be set for 01 (electric
heat).
Enter Installer Setup mode number 02 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 equipment is not
operating. Verify operation of heating equipment in self-test.
Outdoor
temperature
not displayed
a
Option not activated. Enter Installer Setup mode number 24 and set to 01.
Thermostat must have OT terminals and a C7089B1000
installed.
Outdoor
temperature Outdoor sensor is connected
incorrectly. Refer to C7089B1000 installation instructions and check wiring between the thermostat and sensor.
display is incorrect
a
Wrong sensor. Replace sensor with C7089B1000 sensor.

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T8501A,B,C,D MICROELECTRONIC THERMOSTATS

69-0959 12
T8501A,B,C,D MICROELECTRONIC THERMOSTATS
Home and Building Control
Honeywell Limited-Honeywell Limitée
155 Gordon Baker Road
North York, Ontario
M2H 2C9
69-0959 J.H. 10-96 Printed in Taiwan R.O.C.
Home and Building Control
Honeywell Inc.
Honeywell Plaza
P.O. Box 524
Minneapolis, MN 55408-0524
www.honeywell.com/yourhome