Honeywell T8631A User manual

Chronotherm III
for Comfort and Convenience
OWNER'S GUIDE
Residential and Residential and Helping You Control Your World
Building Controls Division Building Controls Division
Honeywell Inc. Honeywell Limited—Honeywell Limitée
1985 Douglas Drive North 740 Ellesmere Road
Golden Valley, Minnesota 55422 Scarborough, Ontario
M1P 2V9
Congratulations! You made a smart choice when you purchased your new Honeywell Communicating
Chronotherm III Thermostat. It’s the smart thermostat that:
■ Keeps you comfortable by automatically calculating exactly when the furnace or air conditioning
should go on to have the house at the desired comfort temperature by the time you wake up.
■ Savesthemaximumamountofenergyandmoney byrememberingtoautomaticallysetbacktheheat
or air conditioning when you leave home.
■ Providestheultimateincomfortandconvenience bycomingtoyoualreadyprogrammed.Butit’syour
choice—use the preprogrammed schedule or set your own.
■ Can be connected to a Honeywell's TotalHome system for external access and control. TotalHome
system devices communicate using HBus, a Honeywell communications protocol.

Features
3Set the cooling temperatures. See
page 7.
4Set the system and fan switches. See
page 12.
1Setthecurrenttimeandday.Seepage1.
2Set the program schedule and heating
temperatures. See page 2.
Simple Four-Step Programming
Of course, you can use the schedule preprogrammed into your new thermostat. See
Glossary,page40-42).But it’saneasymattertoprogramthethermostattofityourlifestyle.
Choose
manual or
programmed
thermostat
operation.
Program up
to four
different time
periods in
each
schedule.
Set different
schedules for
weekdays,
Saturday, and
Sunday.
Choose
system and
fan operation
with the
thermostat
switches (on
subbase).
AUX. HT. and EM. HT. on T8631R.
See Glossary, page 40.
Bypass the
stored
program for
a single
period.
Set the
temperature
warmer or
cooler with the
touch of a key.
Monitor thermostat operation; read
current time and room temperature at
a glance.
Check status light to see if the thermostat
is on, even in the dark.

TABLE OF CONTENTS
Programming Your Thermostat ...........................1-13
Setting the current day and time ............................. 1
Setting the program schedule and heating tempera-
tures....................................................................2
Setting the cooling temperatures ............................ 7
Setting the system and fan switches on the
subbase ............................................................ 12
Operating Your Thermostat ...............................14-20
Temporarily changing the program ....................... 14
Permanently changing the program ......................15
Operating the thermostat manually .......................16
Canceling program settings...................................17
Checking the program times and temperatures .... 18
Checking the current temperature setting .............19
External access and control of thermostat ............20
Maintaining Your Thermostat ............................21-24
Removing the thermostat ......................................21
Replacing the thermostat ...................................... 22
Replacing the batteries..........................................23
Power outages ...................................................... 24
Adaptive Intelligent Recovery™ ........................25-28
Selecting Recovery Setting................................29-30
Heat Pumps with Supplemental Heat................31-32
Answering Common Questions About the Chrono-
therm III Thermostat............................................33-36
Saving Energy Across the U.S...........................37-39
Glossary...............................................................40-42
Your Personal Program ......................................43-44
Troubleshooting Guide.......................................45-46
Quick Reference to the Keys .............................47-48
Index.....................................................................49-50
Warranty.................................................................... 51
i

STEP 1
SETTING THE CURRENT
DAY AND TIME
You can program this thermostat
only on the wall with 24 Vac applied
to R and C terminals.
Always press the keys with your
fingertip or similar blunt tool. Sharp
instruments like a pen or pencil
point can damage the keyboard.
NOTE: Check the glossary, page
40, for definitions of unfamiliar
words.
1
2
SET
PRESENT
DAY/TIME
MON
PM
Press and release. The display
shows 1:00 PM Mon.
Press and hold until the current day
appears in the display.
Press and hold until the current time
appears in the display. Be sure AM
or PM appears as desired.
You have programmed the current
day and time. Go on to Step 2.
DAY
AHEAD
BACK
TUE
PM
TUE
PM
STEP 2
SETTING THE PROGRAM
SCHEDULE AND HEATING
TEMPERATURES
Before You Begin…
The schedule form on page 43
provides an opportunity to plan your
schedule.
Now…
Start by programming the WAKE
time and temperature for weekdays.
The thermostat requires a program
for WAKE. You can program
LEAVE, RETURN and SLEEP or
not, as you please.
SET
HEAT/COOL
Press and release. Note that the
display shows WAKE, the
preprogrammed time and tempera-
ture.
If the display reads COOL, press and
release to switch to HEAT.
If display reads SAT or SUN, press
and hold until MON TUE WED THU
FRI appears.
Press and hold until the display
shows the desired starting time. If
using T8631A in Conventional
Recovery ( ■■ visible in display). See
Glossary section. With Convential
Recovery the time should be set 30
or more minutes ahead of desired
comfort time to get the house
comfortable.
WAKE
DAY
AHEAD
BACK
MON TUE WED THU FRI ON HEAT
WAKE
AM
SET
PT
MON TUE WED THU FRI ON HEAT
WAKE
AM
SET
PT
MON TUE WED THU FRI ON HEAT
WAKE
AM
SET
PT
MON TUE WED THU FRI ON HEAT
WAKE
AM
SET
PT
PROGRAMMING YOUR THERMOSTAT

4
3
Program the LEAVE time and
temperature, if desired.
NOTE: You can cancel the LEAVE,
RETURN or SLEEP program by
holding down the key until the
time and temperature disappear
from the display.
PROGRAMMING YOUR THERMOSTAT
AHEAD
BACK
WARMER
COOLER
WARMER
COOLER
MON TUE WED THU FRI ON HEAT
LEAVE
SET
PT
LEAVE
MON TUE WED THU FRI ON HEAT
LEAVE
AM
SET
PT
MON TUE WED THU FRI ON HEAT
LEAVE
AM
SET
PT
Press and release. The display
shows LEAVE, but no time or
temperature.
Press and hold until the display
shows the desired starting time.
Press and hold until the display
shows the desired temperature.
Program the RETURN time and
temperature, if desired. Press and release. The display shows RETURN, but no time or
temperature.
Press and hold until the display
shows the desired starting time.
T8631A using Conventional Recov-
ery ( ■■ visible in display) should be
set 30 or more minutes ahead of
desired comfort time.
Press and hold until the display
shows the desired temperature.
AHEAD
BACK
RETURN
MON TUE WED THU FRI ON HEAT
RETURN
SET
PT
MON TUE WED THU FRI ON HEAT
RETURN
PM
SET
PT
Press and hold until the display
shows the desired temperature.
If the display starts to blink while
you are holding down TEMPERA-
TURE WARMER or COOLER, you
have reached the setting limit.
MON TUE WED THU FRI ON HEAT
WAKE
AM
SET
PT
WARMER
COOLER
MON TUE WED THU FRI ON HEAT
RETURN
PM
SET
PT
Press and release. The display
shows SLEEP, the preprogrammed
time and temperature.
Press and hold until the display
shows the desired starting time.
SLEEP
Program the SLEEP time and
temperature, if desired.
MON TUE WED THU FRI ON HEAT
SLEEP
PM
SET
PT
AHEAD
BACK
MON TUE WED THU FRI ON HEAT
SLEEP
PM
SET
PT

MON TUE WED THU FRI ON HEAT
SLEEP
PM
SET
PT
PROGRAMMING YOUR THERMOSTAT
5
WARMER
COOLER
DAY
LEAVE
RETURN
AHEAD
BACK
WARMER
COOLER
SUN ON HEAT
SLEEP
PM
SET
PT
DAY
SLEEP
WAKE LEAVE
RETURN
AHEAD
BACK
WARMER
COOLER
RUN
PROGRAM
6
Press and hold until the display
shows the desired temperature.
Press and release until SAT appears
on the display.
Press WAKE, LEAVE, RETURN or
SLEEP to select the time period.
Press the AHEAD/BACK keys to set
the time and the WARMER/COOLER
keys to set the temperature.
SAT ON HEAT
SLEEP
PM
SET
PT
Set the SATURDAY schedule. Use
the same procedure as for week-
days.
SLEEP
WAKE
Set the SUNDAY schedule. Use
the same procedure as for week-
days.
Press and hold until SUN appears on
the display.
Press WAKE, LEAVE, RETURN or
SLEEP to select the time period.
Press the AHEAD/BACK keys to set
the time and the WARMER/COOLER
keys to set the temperature.
You have completed setting the
program schedule and heating
temperatures. To set air conditioning,
go to Step 3,
If you do not want to program cool
temperature, skip Step 3 and press
RUN PROGRAM key.

7
8
PROGRAMMING YOUR THERMOSTAT
STEP 3
SETTING THE COOLING
TEMPERATURES
The program times are the same
for both heating and cooling. Only
the cooling temperatures need to
be programmed if you have already
programmed for heating. If you
change program times for cooling,
you are also changing them for
heating! To set times as you
program the cooling temperatures,
use the TIME AHEAD and BACK
keys as described in Step 2.
First program the WAKE tempera-
ture for weekdays.
WAKE Press and release. The display
shows WAKE, the time and tempera-
ture you programmed for heating.
Press and release so COOL shows
on the display, along with the
programmed cooling temperature.
If display reads SAT or SUN, press
and hold until MON TUE WED THU
FRI appears.
SET
HEAT/COOL
DAY
SUN ON HEAT
WAKE
AM
SET
PT
MON TUE WED THU FRI COOL
WAKE
AM
SET
PT
SUN COOL
WAKE
AM
SET
PT
Press and hold until the display
shows the desired temperature.
If the display blinks while you hold
down TEMPERATURE WARMER or
COOLER, you have reached the
setting limit.
WARMER
COOLER
MON TUE WED THU FRI COOL
WAKE
AM
SET
PT
Press and release. The display
shows LEAVE, the time programmed
for heating and 78°F.
Press and hold until the display
shows the desired temperature.
Program the LEAVE temperature, if
desired.
LEAVE
MON TUE WED THU FRI COOL
LEAVE
AM
SET
PT
MON TUE WED THU FRI COOL
LEAVE
AM
SET
PT
WARMER
COOLER
Program the RETURN tempera-
ture, if desired.
RETURN
Press and release. The display
shows RETURN, the time pro-
grammed for heating and 78°F.
MON TUE WED THU FRI COOL
RETURN
PM
SET
PT

PROGRAMMING YOUR THERMOSTAT
9
10
WARMER
COOLER
MON TUE WED THU FRI COOL
RETURN
PM
SET
PT
Press and hold until the display
shows the desired temperature.
Program the SLEEP temperature if
desired. Press and release. The display shows SLEEP, the time programmed
for heating and 78°F.
Press and hold until the display
shows the desired temperature.
SLEEP
MON TUE WED THU FRI COOL
SLEEP
PM
SET
PT
WARMER
COOLER
MON TUE WED THU FRI COOL
SLEEP
PM
SET
PT
Set the cooling temperatures for
the SATURDAY schedule. Use the
same procedure as for weekdays.
Press and hold until SAT appears on
the display.
DAY
SAT COOL
SLEEP
PM
SET
PT
Press WAKE, LEAVE, RETURN or
SLEEP to select the time period.
Press the WARMER/COOLER keys
to set the temperature.
SLEEP
WAKE LEAVE
RETURN
WARMER
COOLER
Set the cooling temperatures for
the SUNDAY schedule. Use the
same procedure as for weekdays. DAY Press and hold until SUN appears on
the display.
Press WAKE, LEAVE, RETURN or
SLEEP to select the time period.
SUN COOL
SLEEP
PM
SET
PT
SLEEP
WAKE LEAVE
RETURN

PROGRAMMING YOUR THERMOSTAT
11
12
Press the WARMER/COOLER keys
to set the temperature.
You have completed programming
the cooling temperatures.
Press and release to start the
program.
Go to Step 4.
WARMER
COOLER
RUN
PROGRAM
TUE
LEAVE
PM
SET
PT
STEP 4
SETTING THE SYSTEM AND FAN
SWITCHES ON THE SUBBASE
The T8631A does not have the EM.
HT. switch position. Note the
positions provided on your sub-
base, then set the switch(s) as
desired.
First set the fan switch.
Then set the system switch.
FAN ON: Use for improved air
circulation during special occasions
or for more efficient electronic air
cleaning. The fan runs continuously.
FAN AUTO: Normal setting for most
homes and businesses. T8631A: the
fan starts and stops with the air
conditioner and with the heating
equipment when the fan switch (4A)
is set for electric heat. When 4A is
set for conventional heat, the fan is
controlled by the heating equipment.
T8631R: the fan starts and stops with
the compressor in heat pump
systems when the system switch is
set to HEAT or COOL. When system
switch is set to EM. HT., the fan
operates with the auxiliary heat (on
some models).
EM. HT. (T8631R only): The thermo-
stat controls only the backup heat.
The heat pump is off.
FAN
AUTOON
FAN
AUTO
ON
EM. HT. HEAT OFF COOL

13
14
PROGRAMMING YOUR THERMOSTAT
EM. HT. HEAT OFF COOL
EM. HT. HEAT OFF COOL
EM. HT. HEAT OFF COOL
Now, while you enjoy precision
temperature control, read on to
learn about the operating flexibility
that makes this thermostat THE
SMART CHOICE.
OPERATING YOUR THERMOSTAT
TEMPORARILY CHANGING
THE PROGRAM
These features let you tailor the
program for those times when
someone comes home early, or
you’re staying up late, or you plan
to be out for the evening.
SKIP
NEXT
PERIOD
TUE
LEAVE RETURN
PM
TUE
WAKE TEMPORARY
PM
Press and release. The name of the
period to be skipped will flash in the
display until the next regularly
scheduled period starts.
Press and release. The display will
show the name of the previous
period and flash TEMPORARY until
the next regularly scheduled periods
starts.
HEAT: The thermostat controls your
heating system.
OFF: Both your heating and cooling
systems are off.
COOL: The thermostat controls your
cooling system.
You have finished programming your
thermostat.
CHANGE
TO LAST
PERIOD

15
To temporarily raise or lower the
temperature for the current period
only.
If you change your mind.
WARMER
COOLER
TUE
LEAVE
PM
SET
PT
RUN
PROGRAM
AHEAD
BACK
RUN
PROGRAM
WARMER
COOLER
SLEEP
WAKE LEAVE
RETURN
DAY
Press and hold until the desired
temperature is reached. The display
will flash TEMPORARY until the next
programmed time period starts.
Press and release to cancel any of
the temporary settings.
Press and release the desired period
key.
Press and hold until the desired day
schedule shows on the display.
PERMANENTLY CHANGING THE
PROGRAM
If your schedule changes or you
want a different temperature, you
can update any setting without
affecting the rest of the program.
Press and hold the Time or Tem-
perature keys until the display shows
the desired new program.
Press and release to return to
normal operation.
OPERATING THE THERMOSTAT
MANUALLY
This feature lets you set one
temperature that the thermostat will
hold continuously. Your preset
schedule will resume when you
push the RUN PROGRAM key.
Press and release.
Press and hold to change the
temperature setting. After a few
seconds, the display will show the
current temperature.
Press and release to check the
temperature setting.
Press and release to cancel hold.
ON HEAT
SET
PT
ON HEAT
SET
PT
PRESENT
SETTING
RUN
PROGRAM
HOLD
TEMP
WARMER
COOLER
ON HEAT
SET
PT
OPERATING YOUR THERMOSTAT
TUE
LEAVE
PM
16

17
18
OPERATING YOUR THERMOSTAT
CANCELING PROGRAM
SETTINGS
The thermostat requires time and
temperature settings in the WAKE
period, but any of the other periods
can be canceled. Weekday,
Saturday and Sunday settings are
canceled separately.
Press and hold the desired period
key until the time and temperature
clear from the display (about 3
seconds).
Press and release to return to
normal operation.
SLEEP
LEAVE
RETURN
RUN
PROGRAM
MON TUE WED THU FRI ON HEAT
LEAVE
MON
RETURN
PM
CHECKING THE PROGRAM
TIMES AND TEMPERATURES
You can check all the stored
settings without affecting the
permanent program.
SLEEP
WAKE Press and release the desired
period key. The start time and
temperature setting will appear on
the display.
Press and release to display the
next daily time and temperature for
that period.
Press and release to return to
normal operation.
LEAVE
RETURN
MON TUE WED THU FRI ON HEAT
SLEEP
PM
SET
PT
SAT ON HEAT
SLEEP
PM
SET
PT
RUN
PROGRAM
MON
RETURN
PM
DAY

19
20
CHECKING THE CURRENT
TEMPERATURE SETTING
Press a single key to compare
current room temperature to the
setting at any time.
PRESENT
SETTING Press and release. The display will
show the current temperature setting
for several seconds, then revert to
the room temperature.
ON HEAT
SET
PT
ACCSING EXTERNAL SYSTE
OPERATING YOUR THERMOSTAT
EXTERNAL ACCESS AND
CONTROL OF THERMOSTAT
The T8631 Communicating
Chronotherm III Thermostat can
be connected to a Honeywell
TotalHome system for external
access and control.
A TotalHome system allows you
to change thermostat settings
from the system's user interface
panels. depending on the system
chosen, you can also use a
touchtone phone to adjust your
setting. Whenever the thermostat
is controlling to TotalHOme
system setting, a ▲▲appears
under the room temperature
display.
You can easily make temporary
temperature setting changes by
pushing the
WARMER or
COOLER key on the T8631. The
temporary override setting lasts
until the next period starts. To
permanently change the tempera-
ture set point, push the desired
period key, then the
WARMER or
COOLER key. Use the RUN
PROGRAM
key to change from
external system control to thermo-
stat control of program times and
temperatures until a new command
is received from the TotalHome
system.
The T8631 Thermostat can
communicate on an HBus network
over four-wire conductor cables.
This cable connects to the H1, H2,
H3 and H4 terminals on the
thermostat.
HBus is a Honeywell proprietary
communications protocol.
For assistance, call Consumer
Services, 1-800-468-1502, Monday-
Friday, 7:30 a.m. to 5:00 p.m.,
Central time.
MON
WAKE
AM
SET
PT

22
REMOVING THE THERMOSTAT
1 Loosen the two captive screws at
the bottom corners of the case. 2 Pull out the thermostat from the
bottom. 3 Lift the thermostat up and off the
base.
AUX. HEAT
HEAT AUTO COOL OFF
ONAUTO
FAN
M5066
SYSTEM
EM.HT.HEATOFF
ON AUTO
FAN
M5013
COOL
EM.HT.AUX.HEAT
SYSTEM
PM
RETURN
MONHEATON
SYSTEM
M5062
RUN
PROGRAMTIME
TEMPERATURE
PRESENT
SETTING
SKIP
NEXT
PERIOD
CHANGE
TOLAST
PERIOD
SET
PRESENT
DAY/TIME
HOLD
TEMP
DAY
SET
HEAT/COOLSLEEP
LEAVEAHEADWARMER
RETURNBACKCOOLER
WAKE
PERIOD
3 Tighten the captive screws.
M5014
HEATAUTOCOOLOFF
ONAUTO
FAN
EM.HT.AUX.HEAT
PM
RETURN
MON HEAT ON
SYSTEM
AUTO
M5063
REPLACING THE THERMOSTAT
1 Hang the thermostat on the tabs
at the top of the subbase. 2 Swing down and press bottom
edge until thermostat snaps in
place.
21
MAINTAINING YOUR THERMOSTAT
PM
RETURN
MONHEATON
SYSTEM
M5075
RUN
PROGRAMTIME
TEMPERATURE
PRESENT
SETTING
SKIP
NEXT
PERIOD
CHANGE
TOLAST
PERIOD
SET
PRESENT
DAY/TIME
HOLD
TEMP
DAY
SET
HEAT/COOLSLEEP
LEAVEAHEADWARMER
RETURNBACKC
OOLER
WAKE
PERIOD

23
24
MAINTAINING YOUR THERMOSTAT
REPLACING THE BATTERIES
Your thermostat uses three AAA alkaline batteries. The
display will flash REPL BAT when the batteries get low.
You won’t have to reprogram the thermostat if you
insert the new batteries within 20-30 seconds of taking
out the old ones.
To replace:
■Set the system switch to OFF.
■Remove the thermostat from the wall. See page 21.
■Lift the batteries out of the holder.
■Insert the new batteries, making sure the positive (+)
terminals all face toward the right.
■Replace the thermostat on the wall. See page 22.
■Reprogram, if necessary.
M5065
POWER OUTAGES
Backup batteries will hold the programming and keep
on the display during most power outages. Once the
power is restored, the system will resume normal
operation.
If the display goes off when power is lost, either the
backup batteries need to be replaced or were not
installed. When power is restored, the display will flash
1:00 PM to remind you to reprogram. If the colon is not
flashing, there is no AC power or the thermostat is not
properly connected to the subbase.

25
26
ADAPTIVE INTELLIGENT RECOVERY™
M 168
ADAPTIVE INTELLIGENT
RECOVERY™—BREAK-
THROUGH TECHNOLOGY
SENSES TEMPERATURE MORE
LIKE YOU DO
Your new thermostat is so smart,
it’s almost human. ■
Your body perceives temperature from a variety of sources, not only from
the air in the room, but also from your surroundings—walls, windows and
furnishings.
■
Human beings feel differences in temperature as slight as two degrees
Fahrenheit.
■
Common household thermometers and standard thermostats sense only
air temperature, which may or may not reflect how hot or cold the room
actually
feels to a human being.
■
Your new thermostat reads both the temperature of the wall and the air—
and responds to temperature changes as little as one degree Fahren-
heit—so room temperature is more likely to
feel right to you and your
family.

27
28
AM
PM
SUN MON TUE WED THU FRI SAT COOL ON HEAT ON
WAKE LEAVE RETURN SLEEP TEMPORARY UNOCCUIPIED
REPL
BAT
SET
PT
AM
PM
SUN MON TUE WED THU FRI SAT COOL ON HEAT ON
WAKE LEAVE RETURN SLEEP TEMPORARY UNOCCUIPIED
REPL
BAT
SET
PT
AM
PM
SUN MON TUE WED THU FRI SAT COOL ON HEAT ON
WAKE LEAVE RETURN SLEEP TEMPORARY UNOCCUIPIED
REPL
BAT
SET
PT
AM
PM
SUN MON TUE WED THU FRI SAT COOL ON HEAT ON
WAKE LEAVE RETURN SLEEP TEMPORARY UNOCCUIPIED
REPL
BAT
SET
PT
System Operating
in Energy Savings Mode
Recovery Begins Recovery Continues
System Operating
in Comfort Mode
ENERGY
SAVINGS
PERIOD RECOVERY FROM ENERGY SAVINGS COMFORT
PERIOD
TIME
TEMPERATURE
THE THERMOSTAT USES THE SAME SCHEME TO RETURN GRADUALLY
TO LOWER COMFORT TEMPERATURE DURING THE COOLING SEASON.
M 171
THE OPTIMUM COMFORT AND
ENERGY SAVINGS SOLUTION
■
This thermostat is actually a small but powerful computer . When calculat-
ing the exact time to turn on your furnace or air conditioner, it considers
(1) air temperature, (2) temperature of the wall and (3) when you want
the comfort temperature established.
■
During the Adaptive Intelligent Recovery setting, the thermostat in-
creases the control temperature gradually and turns the equipment on
and off
several times to save energy by avoiding overshooting the
comfort temperature. You can see the current control temperature
anytime during recovery by pressing the PRESENT SETTING key.
■
This smart control learns from experience . Each day it checks how
closely it
hit the target and adjusts the recovery start time accordingly.
■
It typically takes four to eight days after installation for this thermostat to
adjust
to the weather, your life style, home construction and heating/
cooling system. The thermostat calculates the LEAVE/RETURN recovery
separately from the SLEEP/WAKE recovery.
■
With the T8631A, you can choose whether you want to use Adaptive
Intelligent Recovery™ or conventional recovery. Use the Adaptive
Intelligent Recovery setting if you want to choose the exact time that the
room reaches your
comfort temperature. Use conventional recovery if
you prefer to choose the exact time your furnace or air conditioner
comes
on
to start recovery.
ADAPTIVE INTELLIGENT RECOVERY™

SELECTING RECOVERY SETTING
29
30
Your T8631A Thermostat includes a screw on the back
marked 2A, allowing for the Adaptive Intelligent Recov-
ery™/Conventional Recovery choice.
Your thermostat was shipped from the factory with the
screw positioned for Adaptive Intelligent Recovery
setting. Your installer may have left the screw in this
position, or may have changed it to Conventional
Recovery. Before programming, you must know which
recovery method your thermostat has been set for.
• With the Adaptive Intelligent Recovery setting, the
dwelling will reach the comfort temperature at the
exact time you have programmed into the thermo-
stat.
• With Conventional Recovery, the programmed time
will be the time your furnace comes on to start
recovery; therefore, you should program the start
time to be earlier than the desired comfort time. It
may require some trial and error for you to arrive at
the best starting time, and the best starting time will
vary as the seasons change.
SYSTEM
GRAVITY
AIR/WATER
HOT
WATER
GAS/OIL
WARM AIR
ELECTRIC
WARM AIR
1A
OUT
1 TURN OUT 1 TURN
OUT
1 TURN
OUT
1 TURN
1B
IN
IN
(FACTORY SETTING)
IN
IN
M3064
1A 1B
2A 2B
DISPLAY TEMPERATURE
2B
o
C
F
o
OUT
IN
2B
2A
OUT
IN
2A
RECOVERY OPTION
ADAPTIVE
CONVENTIONAL
HEAT
CYCLE RATE
To determine which type of recovery is
set into your T8631A Thermostat,
make sure your thermostat is mounted
and powered on the wall.
Press key. Check thermostat display.
• If the ■■shows in the lower right-
hand corner (see illustration), the
thermostat is set for Conventional
Recovery. If you would rather have
the Adaptive Intelligent Recovery
setting, remove thermostat from
wall, turn screw 2A (on back of
thermostat) clockwise until it
bottoms. DO NOT OVERTIGHTEN.
• If the ■■does not show, the
thermostat is set for Adaptive
Intelligent Recovery™. If you would
rather have Conventional Recov-
ery, remove thermostat from wall,
turn screw 2A (on back of thermo-
stat) out 1/2 to 1 turn.
MON
WAKE
AM
M5058
INDICATES
THERMOSTAT IS SET FOR
CONVENTIONAL RECOVERY
RUN
PROGRAM

HEAT PUMP WITH SUPPLEMENTAL HEAT
HEAT PUMPS ARE DIFFERENT (T8631R)
■
Heat pump systems usually have a supplemental,
second stage heating system that operates only
when necessary
. The Honeywell Chronotherm III
Thermostat for heat pumps is designed to minimize
the more expensive second-stage operation,
indicated by the green AUX light on the switching
subbase.
■
With your Chronotherm III Thermostat, you will
notice that your compressor operates continuously
during the recovery period
. This may appear to
waste energy, but it is actually more efficient.
Multiple ON-OFF cycles are neither necessary to
achieve comfort, nor as efficient for heat pump
systems. By reducing the number of cycles, you
reduce the strain on your system and extend
equipment life.
AUXILIARY
HEATING
ELEMENT
OFF
OUTDOOR
AIR
INDOOR
AIR
HEAT
TRANSFER
INDOORSOUTDOORS
AUXILIARY
HEATING
ELEMENT
ON
OUTDOOR
AIR
INDOOR
AIR
HEAT
TRANSFER
INDOORSOUTDOORS
MILD WEATHER SEVERE WEATHER
■ In mild weather, almost all of the demand for heat in
buildings can be met by the heat pump compressor.
This first stage process of moving heat indoors is
very economical. As the air becomes colder outside,
the first stage may be unable to deliver enough heat
to maintain the desired comfort level in the building.
■
During high heat demand, the thermostat will call for
additional second stage power from the auxiliary
heat system
. This auxiliary heat is commonly
electric
resistance heat and is two to three times
more expensive to operate than the compressor.
31
32
HEAT PUMPS ARE TWO SYSTEMS IN ONE

33
34
ANSWERING COMMON QUESTIONS ABOUT THE CHRONOTHERM III THERMOSTAT
3. Why does the T8631 follow a schedule not
programmed into the thermostat?
When the ▲▲ is displayed, the thermostat is control-
ling to the setting in your TotalHome system.
4. How many hours in advance of my WAKE time
should the furnace come on?
The time will vary, up to 24 minutes per degree
Fahrenheit difference between the energy saving
and comfort temperatures, depending on outside
temperature and performance during the past 24
hours. A microchip computer with Adaptive Intelligent
Recovery™ allows the thermostat to
think for itself
and adjust the furnace or air conditioning recovery
time to reach your desired comfort temperature at
the programmed time. Whenever the temperature is
more than one degree hotter or colder than the
comfort temperature at the programmed time, the
system turns on earlier the next day. This approach
ensures the temperature won’t over- or under-shoot
the set point and allows the proper amount of time
for recovery.
5. What does the HOLD key do?
It bypasses
all program settings and holds the
temperature at the present setting. To increase or
decrease the temperature while on HOLD, use the
WARMER-COOLER keys. Pressing the thermostat’s
RUN PROGRAM key or entering a change at the
external system will return the device to programmed
operations.
6. How long does the HOLD key hold?
Forever! The HOLD key will hold the temperature
indefinitely. The only way to release it is to press the
RUN PROGRAM key or enter a change at the
TotalHome system.
7. How can the T8631A Thermostat save energy
when it comes on and off so many times early in
the morning hours?
Two ways. First, it
saves energy (and money) by
setting back the temperature for
blocks of time
during the day or night. Second, it
conserves energy
by recovering gradually to the desired temperature.
1. The temperature displayed on the Chronotherm III
Thermostat doesn’t always match the room
temperature on another thermometer located
right next to it. Why?
The Chronotherm III Thermostat is a
very accurate
instrument designed to sense both air temperature
and wall temperature, like your body does. It gives an
average reading over a period of time. Because it
adjusts itself, it will take a few days after installation
to adjust to your home.
2. A ▲▲triangle symbol is on the display sometimes.
What does it mean?
The T8631 Communicating Chronotherm III Thermo-
stat can be connected to a Honeywell TotalHome
system for external access and control. Whenever
the thermostat is controlling to TotalHome system
settings, a ▲▲appears under the room temperature
display.
This prevents
overshooting your comfort set point
(and wasting energy) or
under-shooting the comfort
set point (and forcing you to change the thermostat
setting, also wasting energy).
Honeywell experts have invested years of engineer-
ing and in-home testing to assure that this is the
most effective way to set back and save energy
while optimizing your comfort.
8. Sometimes my Chronotherm III Thermostat
doesn’t allow the house temperature to drop to
my SLEEP setting before it starts bringing the
furnace on. Why?
Many factors affect your comfort and energy
savings. If those factors, such as weather, humidity,
etc. were
always consistent, an unchanging program
would work just fine. But factors
change . The whole
point of Adaptive Intelligent Recovery™ is to save
energy
without sacrificing comfort. If necessary, the
Adaptive Intelligent Recovery™ will
override your
temperature settings to assure accurate temperature
recovery with optimum comfort and energy savings
for the
current conditions.