Honeywell T8501 User Manual
T8501
Microelectronic Thermostats
INSTALLATION INSTRUCTIONS
APPLICATION
The T8501 Microelectronic Thermostats 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.
System Changeover System Selection
Heat-Cool Automatic Heat-Off-Cool-Auto On-Auto System and fan selections are done by
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 1.5m (5 ft) above the floor in
an area with good air circulation at average temperature.
See Fig. 1.
Fan
Selection Comments
keyboard.
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.
1. Position and level the wallplate (for appearance
only). The thermostat will function properly 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 the drilled holes until flush with the
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.
® U.S. Registered Trademark
Copyright © 2004 Honeywell • • All Rights Reserved
69-0925-4
T8501 MICROELECTRONIC THERMOSTATS
NO
NO
Fig. 1. Typical location of thermostat.
WALL
WIRES
THROUGH WALL
WALL
ANCHORS
(2)
MOUNTING
HOLES
MOUNTING
SCREWS
M6530A
Fig. 2. Mounting the wallplate.
WIRING
All wiring must comply with local electrical codes and
ordinances. Refer to Fig. 3 and 5 for typical hookup. A
letter code is located near each terminal for identification.
YES
5 FEET
[1.5 METERS]
NO
M10106
CAUTION
Electrical Shock Hazard.
Can cause electrical shock and equipment
damage.
Disconnect power before wiring.
1. 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.
2. Securely tighten each terminal screw.
3. Push excess wire back into the hole.
4. Plug the hole with nonflammable insulation to pre-
vent drafts from affecting the thermostat.
THERMOSTAT
T
2
OUTDOOR
TEMPERATURE
SENSOR
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
AVAILABLE ON SELECT MODELS.
2
Fig. 3. Typical hookup in heat only application.
C W
HEATING
RELAY OR
VALVE COIL
1
M4822
ROTO
L1
(HOT)
L2
69-0925—4 2
THERMOSTAT
A
A
TOT
OUTDOOR
TEMPERATURE
SENSOR
HEAT
CHANGEOVER
VALVE OR
DAMPER
1
2
CBO GYW
2
COMPRESSOR
CONTACTOR
COOL
CHANGEOVER
VALVE OR
DAMPER
FAN
RELAY
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
AVAILABLE ON SELECT MODELS.
HEATING
RELAY OR
VALVE COIL
1
M4821
RO
L1
(HOT)
L2
T8501 MICROELECTRONIC THERMOSTATS
.
FOR WRAPAROUND
INSERTION STRIP
7/16 IN. (11 MM).
FOR STRAIGHT INSERTION
STRIP 5/16 IN. (8 MM).
M4826
Fig. 6. Correct wiring technique.
Mounting Thermostat
1. Engage tabs at the top of the thermostat and wallplate. See Fig. 7.
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.
.
ENGAGE TABS AT TOP OF THERMOSTAT AND WALLPLATE.
Fig. 4. Typical hookup in heat and cool system with
T OT O GYCBW
2
OUTDOOR
TEMPERATURE
SENSOR
COOL
CHANGEOVER
VALVE OR
DAMPER
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
Rc
FAN
RELAY
1
one transformer.
THERMOSTAT
COMPRESSOR
CONTACTOR
two transformers.
HEAT
CHANGEOVER
VALVE OR
DAMPER
HEATING
RELAY OR
VALVE COIL
3
RhO
B.
PRESS LOWER EDGE OF CASE TO LATCH.
M6798
Fig. 7. Mounting thermostat on wallplate.
1
L1
OT)
(H
L2
M4820
3 69-0925—4
T8501 MICROELECTRONIC THERMOSTATS
Using Thermostat Keys
The thermostat keys are used to:
• set the temperature,
• display present setting,
• configure Installer Setup,
• check System-Test,
• display outdoor temperature (select models),
Select models have keys to:
• set the system operation,
• set the fan operation.
NOTE: Always press the keys with your fingertip or sim-
ilar blunt tool. Sharp instruments like a pen or
pencil point can damage the keyboard.
See Fig. 8 for key locations.
INCREASE
TEMPERATURE
SETTING
i
DECREASE
TEMPERATURE
SETTING
DISPLAY PRESENT
SETTINGS AND SCROLL
THROUGH INSTALLER
SETUP (INFORMATION KEY)
M6801A
Fig. 8. Thermostat key locations and descriptions.
SETTINGS
System and Fan Settings
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.
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 Fig. 9.
i
System
Press to select
heating or cooling
equipment.
Em. Ht.
-Emergency heating
HeatÑ Heating equipment
Off Ñ No equipment
CoolÑCooling equipment
AutoÑ Thermostat
automatically selects
heating and cooling
equipment.
1
LED INDICATOR.
Fan
Press to select
heating or cooling
equipment.
OnÑ Fan runs continuously
AutoÑ Fan runs when
heating or cooling
equipment operates
System
Fan
1
System
Fan
M10147C
Fig. 9. T8501 System and Fan key locations.
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.
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 factorysettings for the T8501.
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. 11 and 12.
— To advance to the next Installer Setup, press the
i key.
— To change a setting, use the increase ! or
decrease # key.
— To exit the Installer Setup, press and hold the
Information i key until the display returns to normal
(approximately three seconds). The display scrolls the
numbers backward to get to the normal display. The
Installer Setup is automatically exited if no key
presses are made for five minutes.
NOTE: Only configurable number are shown.
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