Honeywell T8131A User manual

169-0887—1
OWNER’S GUIDE
69-0887-1
T8131A,B Programmable Thermostat
Weekday/Weekend (5-day/ 2-day)
Programmable Heat and/or Cool
Low Voltage (20 to 30 Vac)
Thermostat and Mounting Plate

269-0887—1
Welcome to the world of comfort and energy
savings with your new Honeywell program-
mable thermostat.
By following the programing instructions in this
manual, your new thermostat will automatically
control the temperature in your home, keeping
you comfortable while saving energy.
Direct any questions concerning the application
of this thermostat to Honeywell Customer
Assistance at 1-800-468-1502, Monday-Friday
7:00 a.m.-5:30 p.m., Central time.

369-0887—1
Table of Contents
Page
Prepare for Installation .................................................................................................................... 5
Remove Old Thermostat ................................................................................................................. 7
Replacing a ClockThermostat that has C or C1 Clock Terminals .................................................. 8
Install Batteries................................................................................................................................ 9
Program the Thermostat ................................................................................................................. 11
Adjust Fan Operation Switch........................................................................................................... 20
Adjust System On-Time, °F/°C........................................................................................................ 20
Mount Thermostat Mounting Plate .................................................................................................. 22
Wire Thermostat Terminals ............................................................................................................. 24
Mount Thermostat ........................................................................................................................... 28
Check Thermostat Operation After Programming and Installing..................................................... 29
Set Fan and System Switches ........................................................................................................ 31
Troubleshooting Guide .................................................................................................................... 32
Limited One-Year Warranty.................................................................................... Inside Back Cover

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RECYCLING
If this thermostat is replacing a thermo-
stat that contains mercury in a sealed
tube, do
not place your old thermostat
in the trash. See Fig. 1. Contact your
local waste management authority for
instructions regarding recycling and the
proper disposal of your old thermostat.
If you have questions, call Honeywell
Inc. at 1-800-468-1502.
Fig. 1.Typical location of a mercury switch
in a thermostat.
M3701
MERCURY
SWITCH

569-0887—1
Prepare for Installation
ACheck Table 1 to make sure this thermostat is compatible with your system. For more
information, call Honeywell Customer Assistance, toll-free 1-800-468-1502.
Table 1. Compatibility Chart.
System Type Compatible With T8131
Gas—Standing Pilot Yes
Gas—Electronic Ignition Yes
Gas-Fired Boilers Yes
a,b
Gas—Millivolt No
Oil-Fired Boilers Yes
a,b
Oil-Fired Furnace Yes
Electric Furnace Yes
Electric Air Conditioning Yes
Baseboard Electric (120/240 Line Volt) No
Heat Pumps/Multistage Equipment No
NOTE: Not compatible with any 120/240 volt circuit.
aCompatible with 2-wire Honeywell zone valves. Isolating relay required for 3-wire thermostats for zone valves.
Not compatible with 2-wire White-Rodgers no. 1361Valves.
bCompatible with
hot water baseboard systems. Will not work efficiently on steam or gravity systems.

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2Acquire tools and items (below) as needed.Also purchase two AA alkaline batteries; we
recommend Energizer® batteries.
M878B
CROSS-RECESSED
SCREWDRIVER HAND OR POWER
DRILL WITH 3/16 INCH
DRILL BIT, IF NEEDED TO
DRILL HOLES IN WALL
WIRE CUTTER/STRIPPER OR SHARP
KNIFE, IF NEEDED TO STRIP WIRES MASKING TAPE, IF
NEEDED TO LABEL WIRES
AS DISCONNECTED FROM
OLD THERMOSTAT
LEVEL, IF NEEDED TO LEVEL
THERMOSTAT FOR APPEARANCE

769-0887—1
Remove Old Thermostat
ATest to make certain that your heating
and cooling systems are working
properly. If either does not work, contact
your local heating/air conditioning dealer.
To avoid compressor damage, do not
operate the cooling system when outdoor
temperature is below 50°F (10°C).
2Turn off power to the system at the
furnace, or at the fuse/circuit breaker
panel.
3Carefully unpack your new thermostat
and mounting plate; save the package of
screws, the instructions and the receipt.
4Remove the cover from the old thermo-
stat. If it does not snap off when pulled
firmly from the bottom, check for a screw
used to lock on the cover.
5Loosen screws holding thermostat to
subbase, wallplate or wall, and lift away.
6Disconnect wires from old thermostat or
subbase. As you disconnect each wire,
use masking tape to label it with the old
terminal designation. If there are only two
wires, they do not require labeling. If
there is an extra wire that is not con-
nected to your old thermostat, you
also
will not be connecting
it to your new
thermostat. Keep the wires from falling
back into the wall by wrapping them
around a pencil as shown.
WIRES THROUGH
WALL OPENING
M5136

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Replacing a Clock Thermostat that
has C or C1 Clock Terminals?
If you are replacing a Honeywell Chronotherm®
Thermostat, you may find one or two wires that
go to the C or C1 clock terminals on the
Chronotherm® Thermostat wiring wallplate.Do
not allow them to touch, or you can damage
your transformer. Disconnect the wires and wrap
them
separately, using electrical tape. Do not
wrap them together
.Place the wires where they
do not interfere with the operation of the new
thermostat. Record the colors and terminal
designation labels of the remaining wires.
Six or More Wires?
If there are six or more wires (excluding clock
wires attached to terminals), you most likely
have a variation of a heat pump or multistage
system.This thermostat is
not compatible with
such systems. If you would like information
about which programmable thermostats will
work with your system, call Honeywell Customer
Assistance at 1-800-468-1502.
Three Thermostat Wires?
If you have three wires for heating only and
can operate the fan using the fan ON switch,
this thermostat will work with your system;
however, some hot water (zoned) heating
systems have three thermostat wires. The
thermostat will not work without installing an
isolating relay on these systems. For details,
call Honeywell Customer Assistance at 1-800-
468-1502.

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Install Batteries
IMPORTANT
Batteries must be installed for pro-
gramming and operating the thermo-
stat and heating/cooling system.
AUse two AA alkaline batteries; non-
alkaline batteries will not last as long,
and can leak, causing damage to the
thermostat or the wall surface. We
recommend Energizer® batteries.
2Make sure the thermostat is set to the
OFF position.
3Use a coin to remove the battery door.
4Install the fresh batteries as shown,
making sure positive and negative
terminals are oriented correctly.
5Replace the battery door.
As the batteries are running low, a
bAt Lo
indicator flashes for one to two months before
the batteries run out completely.Replace the
batteries as soon as possible after the indicator
starts flashing. If you do not replace the bat-
teries sometime during the flashing
bAt Lo , the
M1719C
REMOVING
BATTERY
DOOR

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indicator eventually stops flashing. bAt Lo stays
on without flashing to indicate the thermostat and
heating/cooling system have stopped working
and the batteries are almost completely dead.
After the batteries are completely dead, the
bAt
Lo
indicator disappears, leaving a completely
blank display.
Press down on the left ends of
batteries to remove them. If you
insert the new batteries within
20 to 30 seconds of removing
the old ones, you do not need
to reprogram the thermostat.
However, if the display is blank,
the batteries are dead or
incorrectly installed and you
need to reprogram. See
pages 16 to 19 to reprogram.
IMPORTANT
Although the thermostat has a low
battery indicator, replace the batteries
once a year to prevent the thermostat
and heating/cooling system from
shutting down due to lack of battery
power.
As a precaution, when
leaving home for longer
than a month, change the
batteries before you leave
to prevent the system
from shutting down due to
lack of battery power.
INSTALL TWO AA ALKALINE
BATTERIES AS SHOWN
M1713

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Program the Thermostat
When batteries are installed, your thermostat
can be programmed in your hand, before it is
mounted on the wall.
If you would prefer to program the thermostat
after it is mounted on the wall, go to page 22,
and return later to this programming section.
Refer to the personal Program Schedule
(pages 14 and 15) to program your time and
temperature settings for various times of the
day.
Four time periods are available during week-
days—WAKE, LEAVE, RETURN, and SLEEP.
During weekends, only the WAKE and SLEEP
time periods are available.These periods can
be seen individually on the display as you
press the Set Schedule key.
WAKE is the time period you want the house at
a comfortable temperature when you get up
and while you get ready for work or school.
When deciding what time to set for your WAKE
period, include extra lead time, depending on
the outside temperature and your furnace
response time, to give the furnace a head start
to heat the house before you get up. (This will
be a higher temperature during heating
season, or a lower temperature during cooling
season.)
LEAVE is the time period you can set for an
energy-saving temperature while you are away

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at work or school. (This will be a lower tem-
perature during heating season, or a higher
temperature during cooling season.)
RETURN is the time period you want the
house at a comfortable temperature for
activities before bedtime. When deciding what
time to set for your RETURN period, include
extra lead time, depending on the outside
temperature and your furnace response time,
to give the furnace a head start to heat the
house before you arrive home. (Again, higher
for heating or lower for cooling.)
SLEEP is the time period you can set for an
energy-saving temperature while you are
sleeping. (Again, lower for heating or higher for
cooling. For more comfortable sleeping, some
homeowners choose not to raise the cool
temperature during the night.)
You will set one schedule for weekdays and
another for weekends, because your require-
ments are probably different for each.
Fill in the times and temperatures you desire
for weekdays and weekends. If you decide not
to program the thermostat, it automatically
controls heating at 68°F (20°C), and cooling at
78°F (26°C), 24 hours a day. Also, you do not
need to enter a time and temperature program
for all periods if your schedule does not require

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it. For example, a house that is occupied
during weekdays would only require programs
for WAKE and SLEEP.
Before programming, remove the clear plastic
overlay covering the display.
When pressing the keys, use the ball of your
finger or a soft pencil eraser.
NOTE: Using sharp fingernails or pencil
points can damage the keypad.
If you make an error at any time during
programming, press the Run Program key and
continue again at the last step.

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Program Schedule
HEATING PROGRAM SCHEDULE
Weekdays Start Time HeatingTemperature
WAKE
LEAVE
RETURN
SLEEP
Weekends
WAKE
SLEEP
WAKE and RETURN start times should include extra lead time, based on outside temperature
and furnace response time, to give your furnace a head start to heat the house.
The temperatures cannot be set any higher than 88°F (31°C) or any lower than 45°F (7°C).
12
1
1
1
2

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COOLING PROGRAM SCHEDULE
Weekdays Start Time CoolingTemperature
WAKE
LEAVE
RETURN
SLEEP
Weekends
WAKE
SLEEP
WAKE and RETURN start times should include extra lead time, based on outside temperature
and furnace response time, to give your furnace a head start to heat the house.
The temperatures cannot be set any higher than 88°F (31°C) or any lower than 45°F (7°C).
NOTE: If you decide not to program the thermostat, it automatically controls heating at 68°F
(20°C), and cooling at 78°F (26°C), 24 hours a day.
12
1
1
1
2

16 69-0887—1
This guide can be used for programming your new thermostat.
NOTE: Batteries are required for operation and programming. When inserting batteries, set the
system switch to OFF. Remove the battery door (on the thermostat left side) using a coin
at the bottom. Follow the instructions on pages 9 and 10.
Set Current Time/Day
To set the time, press and release once, until current time shows;to set day, press
and release again, until current day shows; then press .
Heating Program
With system switch at HEAT, press and release once.WAKE, MON-FRI and SET appear on
the display.
Set
Clock/Day
Set
Clock/Day
Time
Ahead
Back
Ahead
Back
Time
Run
Program
Set
Schedule

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Ahead
Back
Time
Warmer
Cooler
Temp
Use to program WAKE time and to program WAKE temperature for Mon-Fri.
Repeat sequence for LEAVE, RETURN, and SLEEP.
Press until SAT, SUN, WAKE and SET appear on the display. Use to program
WAKE time and to program WAKE temperature for SAT-SUN. Repeat sequence for SLEEP.
Cooling Program
With system switch at COOL, follow the same instructions as for the Heating Program.
After programming, adjust fan and system switches, as desired. Press and release to start
the program.
Set
Schedule
Ahead
Back
Time
Warmer
Cooler
Temp
Run
Program

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A quick guide for operating or making changes follows:
NOTE: Set system switch to Heat or Cool to perform the following:
Temporarily Change temperature
for current period only —press ; TEMPORARY
indicator shows on display; this is cancelled at next scheduled change, or to cancel sooner,
press .
Hold a temperature indefinitely (such as when you are on vacation)—press , ;
HOLD appears on display; to cancel, press .
Check CurrentTemperature Setting—press . (When using TEMPORARILY CHANGE or
HOLD, pressing this cancels your change.)
Warmer
Cooler
Temp
Run
Program
Warmer
Cooler
Temp
Hold
Temp
Run
Program
Run
Program

19 69-0887—1
Set
Schedule
Run
Program
Check Programs—press repeatedly to see each time and temperature; then press .
Cancel a program—press until program to cancel shows; then press together.
Permanently Change a program—Repeat steps in Heating Program or Cooling Program (page 16
and 17), as applicable.
Return to normal program or start program—press .
Set
Schedule
Ahead
Back
Time
Run
Program
Questions?
Call Honeywell
Customer Assistance
1-800-468-1502.

20 69-0887—1
Adjust Fan Operation Switch
AThe thermostat fan operation switch,
labeled FUEL SWITCH (see illustration on
page 21), is factory-set in the F position.
This is the correct setting for most
systems. If your system is an electric heat
system, set the switch to E.The E setting
allows the fan to turn on immediately with
the heating or cooling in a system where
the G terminal is connected.
Adjust System On-Time, ° F/ ° C
AThe thermostat on-time is factory-set for
a warm air, gas or oil heating system. If
you are installing it on another type of
system, adjust the on-time accordingly by
setting screws A and B on the back of
the thermostat. Use the heating system
table shown in the illustration (page 21)
as a guide.
Optimize the system on-time according to the
type of system to minimize room temperature
swings. Setting the screw
out one turn means
turning the screw approximately 360°counter-
clockwise, or about one complete turn.
In the unlikely event that you want a longer
furnace on-time, readjust screws A and/or B as
follows:
First, turn in both screws completely, then
adjust for system type:
• Warm Air Furnace—set at the HotWater
setting (A—out one turn, B—leave in).