Honeywell T8535L User manual

X-XX UL
INSTALLATION INSTRUCTIONS
®U.S. Registered Trademark
Copyright © 1999 Honeywell Inc. • • All Rights Reserved
T8535L
Microelectronic Communicating
Nonprogrammable Thermostat
APPLICATION
The T8535 is an electronic, nonprogrammable room thermostat that supports single-stage or multi-stage, single-zone or
multiple-zones in conventional applications. The T8535 uses the Low End SubSystem Topology (LESST), a low-cost,
wired communications protocol.
Table 1. Description of T8535 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.
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.
1. Position and level the wallplate (for appearance
only). The thermostat functions properly even when
not level.
69-1307-1
aAutomatic changeover is not available with wired zoning applications.
T8535 System Changeover System Selection Fan Selection Comments
LHeat-Cool Automatic
a
/
Manual Heat-Off-Cool-Auto On-Auto System and fan selections are done by keyboard.

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T8535L MICROELECTRONIC COMMUNICATING NONPROGRAMMABLE THERMOSTAT
Fig. 1. Typical location of thermostat.
Fig. 2. Mounting the wallplate.
2. Use a pencil to mark the mounting holes. See Fig. 2.
3. Remove the wallplate from the wall and drill two
3/16 in. (5 mm) holes in the wall (if drywall) as
marked. For firmer material such as plaster or wood,
drill two 7/32 in. (5.5 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 the mounting screws.
WIRING
All wiring must comply with local electrical codes and
ordinances. Refer to Fig. 3 for a typical hookup. A letter
code is located near each terminal for identification.
CAUTION
Disconnect power before wiring to prevent
electrical shock or equipment damage.
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
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.
5 FEET
[1.5 METERS]
YES
NO
NO
NO
M10106
WIRES
THROUGH WALL
WALL
MOUNTING
HOLES
MOUNTING
SCREWS
M13223
WALL
ANCHORS
(2)

69-1307—1
3
T8535L MICROELECTRONIC COMMUNICATING NONPROGRAMMABLE THERMOSTAT
Fig. 3. T8535 typical hookup.
M4826
FOR WRAPAROUND
INSERTION STRIP
7/16 IN. (11 MM).
FOR STRAIGHT INSERTION
STRIP 5/16 IN. (8 MM).
Fig. 4. Proper wiring technique.
Mounting Thermostat
1. Engage tabs at the top of the thermostat and
wallplate. See Fig. 5.
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.
Using Thermostat Keys
The thermostat keys are used to:
•set temperature,
•display present setting,
•configure Installer Setup,
•perform System Test,
•set the system operation,
•set the fan operation.
See Fig. 6 for key information.
M6798A
B. PRESS LOWER EDGE OF CASE TO LATCH.
A. ENGAGE TABS AT TOP OF THERMOSTAT AND WALLPLATE.
M6801A
DISPLAY PRESENT
SETTINGS AND SCROLL
THROUGH INSTALLER
SETUP (INFORMATION KEY)
iDECREASE
TEMPERATURE
SETTING
INCREASE
TEMPERATURE
SETTING
Fig. 5. Mounting thermostat on wallplate.
Fig. 6. 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.
NOTE: Auto setting not available in wired zoning
applications.
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 Off and the fan default setting
is Auto. Use the keyboard to change to the desired
settings. See Fig. 7.
TRANSFORMER PRIMARY. PROVIDE DISCONNECT
MEANS AND OVERLOAD PROTECTION AS REQUIRED.
TRANSFORMER SECONDARY.
MAXIMUM WIRE LENGTH BETWEEN FARTHEST
DEVICES IS 300 FT (91M). M13325A
ELECTRONIC
FAN TIMER
THERMOSTAT SUBBASE
DC
L1
L2
1
2
3
3
1
2
XFMR
NEUTRALS
C
RD
COM
24 VAC
2
69
1
5
4
8
3
7
LINE
R

69-1307—1 4
T8535L MICROELECTRONIC COMMUNICATING NONPROGRAMMABLE THERMOSTAT
Fig. 7. T8535 System and Fan key locations.
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 Lor decrease Mkey to
change the present setting. To change between heat and
cool, press the Information key until the setting to be
changed is displayed.
DISCOVERY MODE
The thermostat receives information from the LESST
Electronic Fan Timer or Integrated Furnace Control to set
equipment type and the number of stages to be controlled.
The discovery mode automatically sets the cycle rate for
each heating and cooling stage and other designated
control parameters.
During installation and powerup, the thermostat enters into
the discovery mode and temporarily displays
Wait .
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 System Test
section.
Fig. 8. LCD display of all segments.
Em HeatOffCool Auto Only
Heat Cool
OnAuto
System Fan
Room
Outdoor
Em Ht Temporary Setting
Wait
%Humid
Aux Ht Remote
Repl
Batt
M4844
M10105B
INSTALLER SETUP
NUMBER DISPLAY
(COLUMN 1 OF TABLE 2)
FACTORY SETTING OR
OTHER CHOICE DISPLAY
(COLUMN 3 OR 5 OF TABLE 2)
Fig. 9. Installer Setup display.
The Installer Setup is used to customize the thermostat to
specific systems. Some of the options include temperature
display and minimum equipment 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 T8535.
A combination of key presses is required to use the
Installer Setup feature.
—To enter the Installer Setup, press and hold the
Information  key with the increase ▲and decrease
▼keys until the first mode number is displayed. All
display segments appear for approximately three
seconds before the number is displayed. See Fig. 8
and 9.
—To advance to the next Installer Setup, press the
Information key.
—To change a setting, use the increase ▲or decrease
▼key.
—To exit the Installer Setup, press the Fan key. The
Installer Setup is automatically exited if no key
presses are made for five minutes.
NOTE: Only configurable numbers are shown.
M13224
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

69-1307—1
5
T8535L MICROELECTRONIC COMMUNICATING NONPROGRAMMABLE THERMOSTAT
Table 2. Thermostat Installer Setup Options.
aScope indicates whether the setting is shared with other thermostats connected on the LESST Bus (GLOBAL), or if
the setting affects only the thermostat where the installer setup is changed (LOCAL).
Installer
Setup
Number
(Press i
key to Factory-Setting Other Choices
(Press ▲or ▼ key to change)
change) Scope
a
Description Display Description Display Description
1Local Zone Number. 0 Set for zone 0
(single zone). 1 to 15 Zone numbers can be set to zones 1 through 15.
14 Global Temperature
indication scale
(°F or °C).
0Temperature
indicated in °F. 1Temperature indicated in °C.
19 Global Fan overrun in
heating. 00seconds of fan operation after
heating turns off.
190 seconds of fan operation
after heating turns off.
20 Global Fan overrun in
cooling. 00Seconds of fan operation after
cooling turns off.
190 seconds of fan operation
after cooling turns off.
30 Global Minimum
deadband
between
heating and
cooling.
3Heating and cooling
setpoints can be set
no closer than 3°F
(1.5°C).
4°F to 10°F Heating and cooling setpoints
can be set no closer than the
chosen value between 4°F and
10°F (2°C and 5°C).
33 Global Minimum off for
cooling and
compressor.
55minute minimum
off time for the
compressor.
0 through 4 Choose 0, 1, 2, 3 or 4 minute
minimum off time for the
compressor.
34 Global Maximum
setpoint range
stop for
heating.
90°F
(32°C) Heating setpoint range can be set no
higher than 90°F.
40°F
through
90°F
(4.5°C to
32°C).
Maximum setpoint range stop
can be set anywhere between
40°F and 90°F in 1°F (0.5°C)
increments.
35 Global Minimum
setpoint range
stop for cooling.
45°F
(7°C) Cooling setpoint range can be set no
lower than 45°F.
45°F
through
99°F (7°C
to 37°C).
Minimum setpoint range stop
can be set anywhere between
45°F and 99°F in 1°F (0.5°C)
increments.
36 Global System on
display (flame
and snowflake
icons for
heating or
cooling on).
0Icons are displayed
when thermostat
calls for cooling or
heating.
1Display is disabled (usually
used for zoned systems).
37 Local Field calibration
adjustment. 0No difference between displayed
temperature and
actual room
temperature.
-3 through
301—display adjusts to 1°F higher than room temerature.
02—display adjusts to 2°F
higher than room temperature.
03—display adjusts to 3°F
higher than room temperature.
-01—display adjusts to 1°F
lower than room temperature.
-02—display adjusts to 2°F
lower than room temperature.
-03—display adjusts to 3°F
lower than room temperature.

69-1307—1 6
T8535L MICROELECTRONIC COMMUNICATING NONPROGRAMMABLE THERMOSTAT
INSTALLER SYSTEM TEST
Use the Installer System Test to check the thermostat
configurations and operation. Refer to Table 3 for a list of
the available system tests.
To start the system test:
NOTE: The minimum off time for compressors is
bypassed during the Installer System Test.
Press and hold the increase ▲and decrease ▼ keys at
the same time until two zeros appear. All LCD segments
are displayed before the two zeros appear.
Em HeatOffCool Auto Only
Heat Cool
OnAuto
System Fan
Room
Outdoor
Em Ht Temporary Setting
Wait
%Humid
Aux Ht Remote
Repl
Batt
M4844
Table 3. Available Tests in the Installer System Test.
M6792A
TEST NUMBER
Refer to Table 4 for the directions and results of the specific tests.
NOTE: Press and hold the increase ▲and decrease ▼keys for three seconds to exit the system test mode. The system
test times out after five minutes without any key presses.
Table 4. Installer System Test Options.
Key to
Press Test Number Description
Heating Equipment System Test
i 10 Enter heating equipment system test. (Set System switch to Heat on switch models.)
▲11 First stage heat turns on.
▲12 Second stage heat turns on.
▲11 Second stage heat turns off.
▼10 First stage heat turns off.
Cooling Equipment System Test
i 30 Change from heat to cooling equipment system test.
▲31 First stage cool and system fan turn on.
▼30 First stage cool and system fan turn off.
Fan Equipment System Test
i 40 Change from cooling to fan equipment system test.
▲41 Fan turns on.
▼40 Fan turns off.
Key Operation System Test
System Key (When System switch is used, move switch to see Test Numbers.)
i 60 Change from cooling or fan to key operation system test.
▲60 5 is displayed.
▼60 4 is displayed.
System 60 2 is displayed.
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.
60-69 System key test.
70-79 Thermostat information, including date code
and software versions, is displayed.

69-1307—1
7
T8535L MICROELECTRONIC COMMUNICATING NONPROGRAMMABLE THERMOSTAT
Thermostat Information
1. Press the Information  key to access the thermo-
stat information.
M4864
M4865
M4866
M4867
M6791
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: 026 = February 1996)
3. Press the increase ▲key again to display the
software identification code. (Example: 02 =
software ID code 2)
4. Press the increase ▲key again to display the
software revision number. (Example: 001 = revision
number 1)
5. Press the increase ▲key again to display the
EEPROM identification code. (Example: 222 =
EEPROM ID 222)
6. Press the Fan key to exit the system test mode;
Wait is displayed. The system test times out after
five minutes without any key presses.

69-1307—1 8
T8535L MICROELECTRONIC COMMUNICATING NONPROGRAMMABLE THERMOSTAT
Home and Building Control
Honeywell Limited-Honeywell Limitée
155 Gordon Baker Road
North York, Ontario
M2H 3N7
69-1307—1 G.H. Rev. 8-99
Home and Building Control
Honeywell Inc.
Honeywell Plaza
P.O. Box 524
Minneapolis, MN 55408-0524
www.honeywell.com/yourhome
TROUBLESHOOTING GUIDE
Printed in U.S.A. on recycled
paper containing at least 10%
post-consumer paper fibers.
Symptom Possible Cause Action
Display does not
turn on. Thermostat is not powered. Check for 24 Vac between C and R terminals; if missing 24 Vac: — Check if the circuit breaker is tripped; if so, reset the circuit
breaker.
— Check if the system fuse is blown; if so, replace the fuse.
— Check if the power switch on the HVAC equipment is in the Off
position; if so, set to the On position.
— Check wiring between the 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 two minutes. After two 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. Enter Installer Setup mode number 14 and reconfigure the display.
Bad thermostat location. Relocate the thermostat.
Temperature
settings will not
change. (Example:
The upper or lower
temperature limits were
reached.
Check the temperature setpoints:
• Heating limits are 40°F to 90°F (4.5°C to 32°C).
• Cooling limits are 45°F to 99°F (7°C to 37°C).
Cannot set the
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 does not
turn on. No power to the thermostat. Check for 24 Vac between C and R terminals; if missing 24 Vac: — Check if the circuit breaker is tripped; if so, reset the circuit
breaker.
— Check if the system fuse is blown; if so, replace the fuse.
— Check if the system switch at the equipment is in the Off
position; if so, 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.
— Check connection to D terminal.
Heating does not
turn on. 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.
Cooling does not
turn on. No power to the thermostat. Check for 24 Vac between C and R terminals; if missing 24 Vac: — Check if the circuit breaker is tripped; if so, reset the circuit
breaker.
— Check if the system fuse is blown; if so, replace the fuse.
— Check if the system switch at the equipment is in the Off
position; if so, 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.
— Check connection to D terminal.
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.