Honeywell T8631A User Manual

T8631A,R Communicating

Chronotherm III Thermostats

Application

T8631A,R can be connected to Honeywell's TotalHome
system for external access and control. TotalHome system
devices communicate using HBus, a Honeywell communi­cations 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.

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

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 tech­nician.

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.

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 malfunction­ing. 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.

— 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 conduc­tor for each wiring terminal, excluding H terminals, is
recommended. Good service practice recommends select­ing 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.

J.H . • Rev. 3-93 • © Honeywell Inc. 1993 • Form Number 69-0689—2

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 construc­tion, 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.

S

Y

S

T

E

M

HEAT

AUTO

COOL

OFF

F
A

N

O

N

A

U
T

O

AUX. HEAT

M3060

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.

Fig. 2—Mounting subbase on wall.

WALL

WIRES THROUGH
WALL OPENING

WALL
ANCHORS
(2)

MOUNTING
HOLES

SUBBASE

SWITCH UP DISCONNECTS THE HBUS.

1
2

FAN CAN BE SET FOR ELECTRIC HEAT OR CONVENTIONAL.

1
HBUS
SWITCH

2
FAN
OPERATIONAL
SWITCH FOR
T8631A ONLY

MOUNTING
SCREWS (2)

M3061

Fig. 3—T8631A 1-stage heat/1-stage cool thermostat with HEAT-OFF-COOL system and ON-AUTO fan
switching.

POWER

3

SUPPLY

FAN
SWITCH

STAT
LOGIC
CIRCUIT

H3

TRANS­CEIVER

POWER
SUPPLY

1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
JUMPER R AND RC FOR SINGLE TRANSFORMER SYSTEM.

2
3

DENOTES THERMOSTAT TO SUBBASE INTERCONNECT.

4

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.

5

FOR SINGLE STAGE HEAT PUMP APPLICATIONS, JUMPER W TO Y FOR SINGLE COMPRESSOR CONTACTOR

6

OPERATION.

BUS IN

H3

H4
H4
H1

H2

BUS OUT

13.7 VDC

+

_

4

BUS
POWER
SUPPLY

SUBBASE
LOGIC/
CONTROL
CIRCUIT

ELEC.

ON

AUTO

SYSTEM
SWITCH

HEAT

OFF

COOL

HEAT/

HIGH
LIMIT

COOL

5

CONV.

R

C

B

HEAT DAMPER OR
CHANGEOVER RELAY

W

G

6

O

COOL DAMPER OR
CHANGEOVER RELAY

Y

RC

1

HEATING SYSTEM
TRANSFORMER

HEAT RELAY

2

FAN RELAY

5

COMPRESSOR
CONTACTOR

1

COOLING
SYSTEM
TRANSFORMER

M3066A

2

L1
(HOT)

L2

L2
L1

(HOT)

Fig. 4—T8631A 1-stage oil heat/1-stage cool. Oil Primary has its own transformer.

HEATING-COOLING WALLPLATE

O G

1

RELAY

T

T

OIL PRIMARY

COOLING
DAMPER/
COOLING
CHANGE­OVER

1

L1
(HOT)

L2

Fig. 5—T8631R 2-stage heat/1-stage cool thermostat with EM. HT.-HEAT-OFF-COOL system and ON-AUTO
fan switching.

L1
(HOT)

L2

1

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.

C B

FAN
RELAY

RW

HEATING
DAMPER/
HEATING
CHANGE­OVER

AIR
COND.
EQUIP.

Y

M3089

3

POWER
SUPPLY

FAN

STAT
LOGIC
CIRCUIT

SUBBASE
LOGIC/
CONTROL
CIRCUIT

POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS

1

REQUIRED.
REMOVE JUMPER ( IF PRESENT) FOR SYSTEM WITH ISOLATED STAGE 1 HEATING

2

AND COOLING CONNECTIONS.
DENOTES THERMOSTAT TO SUBBASE INTERCONNECT.

3

DO NOT CONNECT H BUS WIRES TO THERMOSTAT UNTIL OTHER TotalHome

4

DEVICES ARE CONNECTED.

SWITCH

SYSTEM
SWITCH

ON

AUTO

HIGH
LIMIT

OFF

COOL

HEAT/
COOL 1

E. HEAT
HEAT

E. HEAT
RED

HIGH
LIMIT

AUX.
HEAT
GREEN

HEAT 2

R

C

L

W2

E

W1

G

O

B

Y1

TRANS­CEIVER

POWER
SUPPLY

MONITOR

2

H3
H3

H4
H4
H1
H2

TRANSFORMER

AUXILIARY
HEAT RELAY

EMERGENCY
HEAT RELAY

STAGE 1
HEAT RELAY

FAN RELAY

CHANGEOVER
RELAY (COOL)

CHANGEOVER
RELAY (HEAT)

COMPRESSOR
CONTACTOR

BUS IN

BUS OUT

13.7 VDC

+

_

4

BUS

POWER

SUPPLY

M3065A

1

L1
(HOT)

L2

3 69-0689—2