T8631A,R Communicating
Chronotherm III Thermostats
J.H . • Rev. 3-93 • © Honeywell Inc. 1993 • Form Number 69-0689—2
Application
T8631A,R can be connected to Honeywell's TotalHome
system for external access and control. TotalHome system
devices communicate using HBus, a Honeywell communi-
cations protocol.
These thermostats, powered directly from the control
transformer, provide energy saving control for a 24 Vac
conventional heating/cooling or multistage heat pump
heating/cooling system as indicated in Table 1.
As long as AC power is continuously available to the
transformer, the thermostat will be compatible with most
control systems.
The T8631A,R models include a SYSTEM LED near
the top of the thermostat face. The SYSTEM LED lights
when the thermostat is signaling for heating or cooling.
T8631R includes AUX. HT. and EM. HT LEDs near the
bottom center of the subbase. The AUX. HT. LED lights
whenever the thermostat is calling for operation of the
backup or auxiliary heater. Backup (auxiliary) heat is more
expensive to operate than the heat pump and typically is
used only when the heat pump is unable to handle the load.
The EM. HT. LED lights whenever the thermostat system
switch is in the EM. HT. position. The EM.HT. LED may
also light on some systems if the heat pump is malfunction-
ing. The system switch needs to be moved to EM.HT. on
these heat pumps.
Heat and cool anticipation is fixed in both models; no
adjustment is necessary. T8631A has adjustable cycle rate
for heating; T8631R cycle rate is adjustable only for
auxiliary heat.
Installation
WHEN INSTALLING THIS PRODUCT…
1. Read these instructions carefully. Failure to follow
them could damage the product or cause a hazardous
condition.
2. Check the ratings on the product to make sure the
product is suitable for your application.
3. Installer must be a trained, experienced service tech-
nician.
4. After installation is complete, check out product
operation as provided in these instructions.
5. Allow thermostat to warm to room temperature
before operating.
IMPORTANT: After wiring is complete, push excess wire
back into the hole, and plug hole with nonhardening
caulk, putty or insulation to prevent drafts from
affecting thermostat operation.
LOCATION
Install thermostat and subbase about 5 ft [1.5 m] above
the floor in an area with good air circulation at room
temperature.
Do not install the thermostat where it may be affected by:
— drafts or dead spots behind doors, in corners or under
cabinets.
— hot or cold air from ducts.
— radiant heat from sun or appliances.
— concealed pipes and chimneys.
— unheated (uncooled) areas behind the thermostat,
such as an outside wall.
WIRING TO HEATING/COOLING SYSTEM
The T8631 requires connection to both sides of the
heating transformer secondary for power.
If Replacing An Existing Thermostat
Turn off power to thermostat at furnace or heat pump.
A two-transformer system may require turning off two
switches or disconnects. Remove any existing wallplate or
subbase from wall. Label each wire with, or write down,
the letter or number on the wiring terminal as the wire is
removed, to avoid miswiring later.
If New Installation
Run cable to a hole at the selected wall location, and
pull about 3 in. [76 mm.] of wire through the opening.
Color-coded, 18-gauge thermostat cable with one conduc-
tor for each wiring terminal, excluding H terminals, is
recommended. Good service practice recommends select-
ing cable with one or two more conductors than the
immediate application requires.
WIRING TO TOTALHOME SYSTEM
The HBus connection requires an unshielded cable with
3 twisted pairs of #22 AWG solid wire. Use Belden #8742,
Alpha #1304 or equivalent wire. Route this cable with the
thermostat cable to the utility room. Do not connect the
HBus cable to the T8631 until the other TotalHome devices
are connected.
TABLE I—THERMOSTAT MODELS.
Stages Switching
Thermostat Heat Cool System Fan Program
T8631A 1 1 HEAT-OFF-COOL ON-AUTO 5-1-1
T8631R 2 1 EM. HT.-HEAT-OFF-COOL ON-AUTO 5-1-1
Disconnect power before wiring to prevent electrical
shock or equipment damage.
The shape of the terminal barrier permits insertion of
straight or conventional wraparound wiring connections.
Either method is acceptable.
Refer to Figs. 3-5 for typical hookups of subbase and
thermostat.
NOTE: Keep all wiring restricted to ribbed area surround-
ing terminals to assure thermostat/subbase contact. See
Fig. 6.
MOUNTING SUBBASE
The subbase does not require leveling for proper opera-
tion, but only for appearance.
Remove thermostat from subbase. See Fig. 1.
The subbase mounts directly onto the wall with the
screws and anchors included in the package. Use the
subbase as a template, and with a pencil, mark the two
mounting screw positions. See Fig. 2. If drywall construc-
tion, plastic anchors must be used; select 3/16 in. bit to
drill holes for anchors. Gently tap anchors into holes until
they are flush with the wall surface. Thread wires through
the center opening of the subbase. Then, mount the subbase
by using two screws provided. Gently tighten screws, level
top surface of subbase and then securely tighten screws.
WIRING
All wiring must comply with local electrical codes and
ordinances.
Fig. 1—Removing thermostat from subbase.
AUX. HEAT
HEAT
AUTO
COOL
OFF
O
N
A
U
T
O
F
A
N
M3060
S
Y
S
T
E
M
Fig. 2—Mounting subbase on wall.
WIRES THROUGH
WALL OPENING
WALL
WALL
ANCHORS
(2)
SUBBASE
MOUNTING
HOLES
MOUNTING
SCREWS (2)
M3061
HBUS
SWITCH
FAN
OPERATIONAL
SWITCH FOR
T8631A ONLY
1
2
1
2
SWITCH UP DISCONNECTS THE HBUS.
FAN CAN BE SET FOR ELECTRIC HEAT OR CONVENTIONAL.
Fig. 3—T8631A 1-stage heat/1-stage cool thermostat with HEAT-OFF-COOL system and ON-AUTO fan
switching.
2
AUTO
ON
FAN
SWITCH
POWER
SUPPLY
COOL
HEAT
SYSTEM
SWITCH
OFF
SUBBASE
LOGIC/
CONTROL
CIRCUIT
STAT
LOGIC
CIRCUIT
HEAT/
COOL
HIGH
LIMIT
B
W
O
RC
L2
2
COOL DAMPER OR
CHANGEOVER RELAY
C
HEAT RELAY
G
FAN RELAY
R
Y
HEAT DAMPER OR
CHANGEOVER RELAY
L1
(HOT)
5
BUS IN
POWER
SUPPLY
TRANS-
CEIVER
BUS OUT
BUS
POWER
SUPPLY
+
_
13.7 VDC
H2
H1
H3
H3
H4
H4
4
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
JUMPER R AND RC FOR SINGLE TRANSFORMER SYSTEM.
DENOTES THERMOSTAT TO SUBBASE INTERCONNECT.
DO NOT CONNECT H BUS WIRES TO THERMOSTAT UNTIL OTHER TotalHome DEVICES ARE CONNECTED.
FAN OPERATION SWITCH (4A) IN ELEC. POSITION, USE ONE SYSTEM TRANSFORMER AND JUMPER R TO RC.
FOR SINGLE STAGE HEAT PUMP APPLICATIONS, JUMPER W TO Y FOR SINGLE COMPRESSOR CONTACTOR
OPERATION.
1
4
2
3
M3066A
L2
L1
(HOT)
COMPRESSOR
CONTACTOR
COOLING
SYSTEM
TRANSFORMER
HEATING SYSTEM
TRANSFORMER
1
5
5
3
1
ELEC.
CONV.
6
6
Fig. 4—T8631A 1-stage oil heat/1-stage cool. Oil Primary has its own transformer.
Fig. 5—T8631R 2-stage heat/1-stage cool thermostat with EM. HT.-HEAT-OFF-COOL system and ON-AUTO
fan switching.
3 69-0689—2
W2
AUTO
ON
FAN
SWITCH
O
W1
CHANGEOVER
RELAY (COOL)
C
MONITOR
G
FAN RELAY
SYSTEM
SWITCH
R
CHANGEOVER
RELAY (HEAT)
L2
L1
(HOT)
POWER
SUPPLY
SUBBASE
LOGIC/
CONTROL
CIRCUIT
STAT
LOGIC
CIRCUIT
2
BUS IN
POWER
SUPPLY
TRANS-
CEIVER
BUS OUT
BUS
POWER
SUPPLY
+
_
13.7 VDC
H2
H1
H3
H3
H4
H4
4
Y1
COOL
HEAT
OFF
HEAT/
COOL 1
B
AUXILIARY
HEAT RELAY
EMERGENCY
HEAT RELAY
STAGE 1
HEAT RELAY
COMPRESSOR
CONTACTOR
E
HIGH
LIMIT
L
E. HEAT
HIGH
LIMIT
TRANSFORMER
E. HEAT
RED
AUX.
HEAT
GREEN
HEAT 2
M3065A
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS
REQUIRED.
REMOVE JUMPER ( IF PRESENT) FOR SYSTEM WITH ISOLATED STAGE 1 HEATING
AND COOLING CONNECTIONS.
DENOTES THERMOSTAT TO SUBBASE INTERCONNECT.
DO NOT CONNECT H BUS WIRES TO THERMOSTAT UNTIL OTHER TotalHome
DEVICES ARE CONNECTED.
1
4
2
3
1
3
RW
COOLING
DAMPER/
COOLING
CHANGE-
OVER
RELAY
Y
AIR
COND.
EQUIP.
O G
FAN
RELAY
C B
HEATING
DAMPER/
HEATING
CHANGE-
OVER
L1
(HOT)
L2
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
1
M3089
HEATING-COOLING WALLPLATE
L1
(HOT)
L2
T
OIL PRIMARY
T
4
Fig. 6—Keep wiring restricted to ribbed area
surrounding terminals.
FOR STRAIGHT
INSERTION –
STRIP 5/16 in. [8 mm]
FOR WRAPAROUND –
STRIP 7/16 in. [11 mm]
RESTRICT
WIRING TO
THIS AREA
WIRING TO BE BELOW
THIS SURFACE
TOP SURFACE
OF SUBBASE
FRONT VIEW OF
TERMINAL AREA
CROSS-SECTIONAL VIEW OF
TERMINAL AREA
M3062
Fig. 7—T8631R cycle rate adjustment.
M3063A
1A
2A
2B
1B
NORMAL
FASTER
1B
IN
OUT
1 TURN
(FACTORY
SETTING)
DISPLAY TEMPERATURE
2B
o
C
F
o
OUT
IN
NOT USED
2B
CYCLE RATE
AUXILIARY HEAT
Fig. 8—T8631A cycle rate adjustment.
SYSTEM
GRAVITY
AIR/WATER
HOT
a
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
M3064A
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
a
SOME HIGH EFFICIENCY FURNACES OPERATE BETTER IF ADJUSTED
TO HOT WATER SETTING.
CYCLE RATE ADJUSTMENT
NOTE: MOST APPLICATIONS WILL NOT REQUIRE
A CHANGE IN CYCLE RATE.
The room air temperature will normally vary slightly
from the comfort temperature setting with the cycling of
the heat pump, auxiliary heater, furnace or air conditioner.
The cycle rate of the T8631R Thermostat is factory-set for
heat pumps. The heat pump compressor cycle rate can not
be adjusted. The auxiliary heat cycle rate can be adjusted
by turning the cycle rate adjustment screw located on the
back of the thermostat. See Fig. 7.
T8631A has a factory-set cycle rate of six cycles per
hour in heating and three cycles per hour in cooling. For
high efficiency furnaces, it can be necessary to change the
cycle rate to the hot water setting. Cooling cycle rate is not
adjustable, but heating can be adjusted by turning one or
both 1A and 1B screws on the back of the thermostat. See
Fig. 8 for adjustments. The screw should only be backed
out about one-half turn, or be turned in until tight.
ADAPTIVE INTELLIGENT RECOVERY™/CON-
VENTIONAL RECOVERY CONVERSION
The T8631A and T8631R are factory-set for Adaptive
Intelligent Recovery™, but the T8631A can be converted
to Conventional Recovery by using the screw 2A on the
back of the thermostat as indicated in Fig. 8.
With the Adaptive Intelligent Recovery setting, the
room will reach the comfort temperature at the exact time
programmed into the thermostat. The control temperature
will increase gradually and turn the equipment on and off
several times to reach the comfort temperature slowly and
on time.
With Conventional Recovery, the start time should be
programmed to be earlier than the desired comfort time. It
may require some trial and error to arrive at the best starting
time. A ■ will appear on the display when using Conven-
tional Recovery.
TEMPERATURE CONVERSION
The display readout can be converted between °C and
°F using screw 2B. See Figs. 7 and 8.
HBUS SWITCH
The subbase has a switch that you can move to disconnect
the thermostat from the external control device. See Fig. 2.
INSTALLING BATTERIES
Three AAA alkaline batteries are provided as backup to
prevent program loss in event of power outage. Batteries
are included with thermostat. Install batteries in back of
thermostat. See Fig. 9.
Without battery backup, the program will remain about
20 seconds in event of power loss.
Fig. 9—Battery placement.
BATTERY PLACEMENT
(NOTE CORRECT PLUS
AND MINUS DIRECTION
)
M3058
When the batteries are low, the display will flash REPL
BAT. REPL BAT indication will disappear when thermo-
stat is mounted back on the powered subbase with fresh
batteries. This may take up to 15 minutes to occur.
If batteries are completely dead, the display will go
blank when the thermostat is removed from subbase.
MOUNTING THE THERMOSTAT
With system switch set to OFF, hang the thermostat on
the tabs at the top of the subbase. See Fig. 10A. Swing
down and press on lower edge until thermostat snaps into
place. See Fig. 10B. Open cover and tighten the captive
mounting screws. See Fig. 10C.
SETTING DAY AND TIME
NOTE: Thermostat must be mounted on powered subbase
to program.
Restore 24V power to the thermostat. When power is
applied to the thermostat, the display will read 1:00 PM and
32° for a minute or less, followed by 1:00 PM and room
temperature. It will go off for a few seconds, then begin to
flash on and off. Set present day and time.
Press .
Press to set the current day. Each press of
the DAY key advances the display one day.
Press TIME or to set the current time.
If the display will not come on:
— check mounting of thermostat to subbase. If loose
or misaligned, remove thermostat and reinstall on
the subbase, making sure it is firmly attached.
— check to see that system power is on.
— check to see that voltage between R and C is 20 to
30 Vac.
Fig. 10—Mounting the thermostat on subbase.
M3059
PM
RETURN
MON
HEAT ON
SYSTEM
A
U
T
O
P
M
RETURN
MON
HEAT ON
SYSTEM
R
U
N
P
R
O
G
R
A
M
T
I
M
E
T
E
M
P
E
R
A
T
U
R
E
P
R
E
S
E
N
T
S
E
T
T
I
N
G
S
K
I
P
N
E
X
T
P
E
R
I
O
D
C
H
A
N
G
E
T
O
L
A
S
T
P
E
R
I
O
D
S
E
T
P
R
E
S
E
N
T
D
A
Y
/
T
I
M
E
H
O
L
D
T
E
M
P
D
A
Y
S
E
T
H
E
A
T
/
C
O
O
L
S
L
E
E
P
L
E
A
V
E
A
H
E
A
D
W
A
R
M
E
R
R
E
T
U
R
N
B
A
C
K
C
O
O
L
E
R
W
A
K
E
A.
B.
C.
H
E
A
T
A
U
T
O
C
O
O
L
O
F
F
O
N
A
U
T
O
F
A
N
E
M
.
H
T
.
A
U
X
.
H
E
A
T
BACK
AHEAD
SET
PRESENT
DAY/TIME
DAY
5 69-0689—2
Checkout
CAUTION
During cold weather, some heat pumps will re-
quire that crankcase heater be energized several
hours before operating heat pump. Refer to
manufacturer’s recommendations.
HEATING
Move the system switch to HEAT and the fan switch to
AUTO. Press WARMER key until the setting is about
10° F [6° C] above room temperature. Heating should start
and the fan should run (there may be a delay of 5-10
minutes before heat turns on). Press COOLER key until the
setting is about 10° F [6° C] below room temperature. The
heating equipment and fan should shut off. The fan will run
a short time after equipment shuts off with T8631A unless
fan operation switch set for electric.
COOLING
CAUTION
Do not operate cooling if outdoor temperature is
below 50° F [10° C]. Refer to manufacturer’s
recommendations.
NOTE: When cooling setting is changed, thermostat can
wait up to five minutes before turning on the cooling
equipment. This delay is to protect the compressor.
!
!
Move the system switch to COOL and the fan switch to
AUTO. Press COOLER key until the setting is about
10° F [6° C] below room temperature. The cooling equip-
ment and fan should start. Press WARMER key until the
setting is about 10° F [6° C] above room temperature. The
cooling equipment and fan should stop.
FAN
Move the system switch to OFF, and the fan switch to
ON. The fan should run continuously. When the fan switch
is in the AUTO position, fan cycles with the heating or
cooling system.
EXTERNAL ACCESS AND CONTROL
A triangle ▲ symbol is displayed on the lower right
corner of the LCD when the T8631 setting has been
adjusted through the TotalHome system. See Fig. 11.
INSTALLER SELF-TEST (OPTIONAL)
NOTE: Thermostat must have AC power to perform
self-test.
Perform the following test as a check of all thermostat
functions. If thermostat does not respond as indicated,
thermostat must be replaced.
1. Press AHEAD and BACK keys at the same time.
While holding keys down, all segments of the display
should be on. See Fig. 11.
2. Set system switch to OFF. Press AHEAD and BACK
and PRESENT SETTING keys at the same time to enter
self-test.
3. Press each key as listed below, and look for re-
sponses listed as key is held down and released.
Look For This Response
Press This Key Key Down Key Released
PRESENT SETTING 15 see note
a
following
SKIP NEXT PERIOD 07 blank
CHANGE TO LAST 03 blank
PERIOD
COOLER 02 blank
WARMER 06 serial number
transmitted
on HBus
BACK 04 blank
AHEAD 05 blank
RETURN 00 blank
LEAVE 01 control micro-
processor mask
number and
revision number
SLEEP 08 blank
WAKE 12 see note
b
following
SET HEAT/COOL 09 blank
DAY 13 interface
micro-
processor
mask number
and revision
number
HOLD TEMP 10 blank
SET PRESENT 14 see note
c
DAY/TIME following
RUN PROGRAM 11 normal operat-
ing display
NOTES:
a
If the system switch is in COOL, the following se-
quence will occur:
6
Fig. 11—All segments on display.
SUN MON TUE WED THU FRI SAT COOL ON HEAT ON
WAKE LEAVE RETURN SLEEP TEMPORARY
REPL
BAT
AM
PM
SET
PT
M410C
Third System Switch
Digit Position
0 OFF
1 COOL
2 HEAT
4 EM.HT.
c
If the system switch is in HEAT, the following se-
quence will occur:
Fourth Digit: Not used.
CAUTION
Do NOT operate heating until heat pump warmup
procedure is followed. Refer to manufacturer’s
recommendations.
T8631A:
First press—1st stage heating and SYSTEM LED on.
Second press—heating and SYSTEM LED off.
T8631R:
First press—1st stage heating and SYSTEM LED on.
Second press—2nd stage heating also on.
Third press—2nd stage heating off.
Fourth press—1st stage heating and SYSTEM LED off.
(If system switch is in EM. HT., operation is as above,
except 1st stage heating is locked out.)
REFER TO OWNER’S MANUAL FOR PROGRAM-
MING INSTRUCTIONS AND HOMEOWNER
TROUBLESHOOTING.
7 69-0689—2
!
This equipment is a Class B digital apparatus which complies with Canadian Radio Interference Regulations, CRC c. 1374.
CAUTION
Do NOT operate cooling if outdoor temperature
is below 50° F [10° C]. Refer to manufacturer’s
recommendations.
First press—cooling system and SYSTEM LED on.
Second press—cooling system and SYSTEM LED off.
b
A four-digit code number will appear when the key is
released. The four digits of the code represent the
following options:
First T8631A T8631R
Digit CPH CPH
01 3
23 3
49 6
66 6
Second Recovery
Digit Model Degrees Type
0 T8631R F A.I.R.
a
1 T8631R C A.I.R.
a
2 T8631A F Conventional
3 T8631A C Conventional
4 T8631R F A.I.R.
a
5 T8631R C A.I.R.
a
6 T8631A F A.I.R.
a
7 T8631A C A.I.R.
a
!
a
Adaptive Intelligent Recovery™
Home and Building Control Home and Building Control
Honeywell Inc. Honeywell Limited—Honeywell Limitée
1985 Douglas Drive North 740 Ellesmere Road
Golden Valley, Minnesota 55422 Scarborough, Ontario
M1P 2V9
Printed in Taiwan R.O.C.
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