Honeywell CHRONOTHERM T8624C User manual

1 68-0134
C.H. • 9-93 • ©Honeywell Inc. 1993 • Form Number 68-0134
The T8624C,D Chronotherm III Program-
mable Fuel Saver Thermostats provide auto-
maticcontrolofmultistageheating/coolingsys-
tems and offer users the highest standard of
comfort and convenience available with energy
savings.
■Different schedules may be selected for week-
days, Saturday and Sunday.
■Can be programmed in hand (with batteries in-
stalled) or on wall to provide up to four tempera-
ture settings per day.
■Large digital clock (liquid crystal display) indi-
cates continuous time, day, current period and
room temperature.
■AdaptiveIntelligentRecovery™brings roomtem-
perature to programmed temperature at pro-
grammed time, maximizing comfort and energy
savings.
■Temperaturecontrolprogram maintainstempera-
ture within 1°F of setpoint.
■Temporary program override available by using:
— WARMER and COOLER keys.
— SKIP next period key.
— CHANGE to last period key.
■HOLD TEMP key provided for indefinite pro-
gram override (vacation/holiday).
■Installer self-test and time delay override save
installation time.
■SYSTEM light-emitting diode (LED) indicates
system is energized.
■Models available with automatic or manual heat/
cool changeover.
■Batteries included provide power to maintain
clock and memory during power failures.
■Switchingsubbase withwiring terminalsincluded.
■Powered directly from control transformer, re-
quiring an extra (24V) wire to thermostat.
■Fan operation switch to select either independent
or direct thermostat control of fan in heating
included on back of select models.
CONTENTS
Specifications .................................................2
Ordering Information.....................................2
Selection/Application .....................................4
Installation .....................................................5
Checkout....................................................... 11
Programming the Thermostat ......................14
Operating the Thermostat ............................18
Troubleshooting ...........................................21
Glossary ....................................................... 22
T8624C,D (5-1-1 Day
Programming) Chronotherm®
III Fuel Saver Thermostats

2
T8624C,D
SPECIFICATIONS • ORDERING INFORMATION
Ordering Information
When purchasing replacement and modernization products from your TRADELINE® wholesaler or your distributor, refer to the
TRADELINE Catalog or price sheets for complete ordering number, or specify—
1. Model number. 3. System, fan switching desired.
2. Number of heat and cool stages desired. 4. Application.
If you have additional questions, need further information or would like to comment on our products or services, please write or
phone:
1. Your local Honeywell Home and Building Control Sales Office (check white pages of your phone directory).
2. Home and Building Control Customer Satisfaction
Honeywell Inc., 1885 Douglas Drive North
Minneapolis, Minnesota 55422-4386 [phone]
In Canada—Honeywell Limited/Honeywell Limitee, 740 Ellesmere Road, Scarborough, Ontario M1P 2V9. International
Sales and Service offices in all principal cities of the world. Manufacturing in Australia, Canada, Finland, France, Germany,
Japan, Mexico, Netherlands, Spain, Taiwan, United Kingdom, U.S.A.
Specifications
IMPORTANT: The specifications given in this publi-
cation do not include normal manufacturing toler-
ances. Therefore, this unit may not exactly match
thelisted specifications.Also, thisproduct istested
under closely controlled conditions, and some mi-
nor differences in performance can be expected if
those conditions are changed.
TRADELINE®MODELS
TRADELINE models (see Table 1) are selected and
packaged to provide ease of stocking and handling
and also maximum replacement value.
LIGHT-EMITTING DIODE (LED): SYSTEM LED
lights during thermostat ON cycle.
VOLTAGE RATING: 15 to 30 Vac.
CURRENT RATING: 1.6A maximum total per stage.
OPERATING HUMIDITY RANGE: 5 to 90 percent
relative humidity, noncondensing.
OPERATING AMBIENT TEMPERATURE RANGE:
40°F to 110°F [4°C to 43°C].
TABLE 1—TRADELINE MODELS.
SETPOINT RANGE: 45°F to 88°F [7°C to 31°C].
CALIBRATION: Self-calibrating thermostat and
thermometer to ±1°F.
SHIPPINGTEMPERATURE:-20°Fto +120°F [-29°C
to +49°C].
CYCLES PER HOUR ADJUSTMENT:
Heating: First stage of 2-stage heat models—fixed at
3 cph. Second stage of 2-stage heat models or heat
stage of single-stage heat models—factory-set at
6 cph; field-adjustable to 1,3,6 or 9 cph.
Cooling: Factory-set at 3 cph (not field adjustable);
minimum off-time of five minutes.
FINISH: Beige matte with decorative brushed metal
faceplate or Premier White™.
DIMENSIONS:Thermostat (mountedonsubbase)—7 in.
[178 mm] long, 5-5/16 in. [135 mm] high, 1-3/4 in.
[44 mm] deep. See Fig. 1 for subbase dimensions.
TYPICAL KEYPAD: See Fig. 2.
ACCESSORIES:
TG586A Locking Cover.
TG512 Versaguard™ Universal Thermostat Guard.
Thermostat
Model Stages Changeover Switching
Number Heat Cool Type System Fan Application
T8624C 2 1 Auto HEAT-AUTO-COOL-OFF ON-AUTO Multistage
T8624D 2 2 Auto HEAT-AUTO-COOL-OFF ON-AUTO Multistage
T8624D 2 2 Manual HEAT-OFF-COOL ON-AUTO Multistage

3 68-0134
T8624C,D
SPECIFICATIONS
Fig. 1—T8624 Subbase mounting dimensions in in. [mm].
4 [121]
3
4
3 [83]
5
16
7 [179]
1
[46]
13
16
5
[135]
5
16
M5181A
43
32
[104]
131
32
[50]
Fig. 2—Typical thermostat keypad.
SYSTEM
RUN
PROGRAM
WAKE
TIME
TEMPERATURE
PRESENT
SETTING
SKIP
NEXT
PERIOD
CHANGE
TO LAST
PERIOD
SET
PRESENT
DAY/TIME
HOLD
TEMP
DAY
SET
HEAT/COOL SLEEP
LEAVE AHEAD WARMER
BACK COOLER
M2998
WED
LEAVE
AM
HEAT ON
HEAT AUTO COOL ON AUTO
FAN
ROOM
RETURN
OFF
PERIOD

4
T8624C,D
SELECTION/APPLICATION
Selection/Application
The T8624 Thermostat uses the latest microelec-
tronic design and control technology to provide home
and building owners with the highest level of comfort
available and optimal energy savings in a package that is
easy to use and easy to live with.
The following section is a guide to selection and
application of the best thermostat to meet individual
needs.
PROGRAMMING
Does the thermostat selected accommodate the
customer’s daily schedule, lifestyle or work schedule?
Device Programming
Daily
Temperature
Selection
T8624C,D 5-1-1 (Mon-Fri,
Sat, Sun) 4 heat and 4 cool
T8621A,C,D 7-day (each
day different) 4 heat and 4 cool
T8600,01,02,03* 5-1-1 (Mon-Fri,
Sat, Sun) 4 heat and 4 cool
The choices are:
*Model not currently available to control multistage
equipment.
IF NEW CONSTRUCTION APPLICATION, CON-
SIDER:
•Equipmenttype(see manufacturerspecifications).
—Staging required.
—System switching required.
—Fan switching required.
•Control wiring—number of conductors required
to operate equipment and thermostat.
IMPORTANT: The T8624 requires an additional con-
ductor to transformer common to provide continu-
ous 24V power for thermostat operation.
IF RETROFIT/REPLACEMENT APPLICATION,
CONSIDER:
•Equipment requirements.
—Staging (heat stages, cool stages).
—Systemswitching (manual:HEAT-OFF-COOL;
automatic: HEAT-AUTO-COOL-OFF). Emer-
gency heat for heat pump application not pro-
vided on T8624.
—Fan switching; does fan come on automatically
from thermostat on cooling only (typical gas/
oil heating), or on call for cool and heat (typical
electric heat with single speed fan)?
•Existing wiring
—Arethereenoughconductorstooperatethe equip-
ment and the thermostat? Can a new cable be
pulled?
IMPORTANT: The T8624 requires an additional con-
ductor to transformer common to provide continu-
ous 24V power for thermostat operation.
SECURITY
Does the thermostat selected provide access to
Access Typical Application Device
Free access to
programming
and adjustment/
override.
Home or
owner-occupied
commercial
building.
T8624A,C,D
Restricted
access to
device.
Public
building. T8624 with TG512 Locking
Guard or
TG586A
Locking Cover.
programmming and the override features that will best
suit the application? The choices are:
SINGLE-STAGE HEAT PUMPS
If home/building owner has a single-stage heat pump,
one option is to use a T8624C or D (see Fig. 8).
The T8624C is a two-stage heating, one-stage cool-
ing programmable thermostat. The T8624D is a two-
stage heating, two-stage cooling programmable thermo-
stat. What both thermostats have in common is separate
W1 and W2 (first and second stage heat) terminals. In
both cases, the W1 can be used for changeover in heat-
ing.
For single-stage compressor applications (both first-
stage heating and first-stage cooling energized through
the Y terminal), simply jumper Y1 and W1.
Note that the recovery algorithm of the T8624 may
cause the compressor to cycle on and off during recov-
ery.
Although the cycle rate for the first stages of heat and
coolareset forhot watersystems, the secondstage ofthe
T8624 must be adjusted. Turn the cycle rate adjustment
screws to the hot water setting on both the T8624C and
D to achieve the cycle rate appropriate for heat pumps.
If changeover is utilized in the cooling mode, apply a
normally closed relay.
The above application should be used only on single-
stage heat pumps.

5 68-0134
Installation
T8624C,D
INSTALLATION
RECYCLING NOTICE
If this control is replacing a control that contains
mercury in a sealed tube, donot place your old control in
the trash. Contact your local waste management author-
ity for instructions regarding recycling and the proper
disposal of your old control.
If you have any questions, call Honeywell Inc. at 1-
800-468-1502.
COMPATIBILITY
The T8624 Thermostats will replace most heating/
cooling system thermostats. As long as ac power is
continuously available to the transformer, the thermostat
will be compatible with any low-volt control system.
IMPORTANT: The T8624 requires an additional con-
ductor to transformer common to provide continu-
ous 24V power for thermostat operation.
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 given on the product to make
sure the product is suitable for your application.
3. Installer must be a trained, experienced service
technician.
4. Allow thermostat to warm to room temperature
before operating.
5. After installation is complete, check out product
operation as provided in these instructions.
CAUTION
Disconnect power supply to prevent electrical
shock or equipment damage.
LOCATION
Installthermostat andsubbase about5ft[1.5m]above
the floor in an area with good air circulation at room
temperature.
Do not install 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 such as an outside wall
behind the thermostat.
REPLACING AN EXISTING THERMOSTAT
Turnoffthermostat powerat furnace orboiler. Atwo-
transformer system may require turning off two switches
!
or disconnects. Remove any existing wallplate or sub-
base from wall. To avoid miswiring later, label each
wire color with the letter or number on the wiring termi-
nal as the wire is removed.
NEW INSTALLATION
Run cable to a hole at the selected wall location for the
thermostat, and pull about 3 in. [76 mm] of wire through
theopening. Color-coded,18-gauge thermostatcablewith
at least one conductor for each wiring terminal is recom-
mended. Good service practice recommends selecting
cable with one or two more conductors than the immedi-
ate application requires.
MOUNTING SUBBASE
IMPORTANT: Before mounting, set the system switch
to the OFF position.
NOTE: The subbase does not require leveling for proper
operation, but only for appearance.
Fig. 3—Removing thermostat from subbase.
HEATAUTOCOOLOFF
ONAUTO
FAN
M 844
Remove thermostat from subbase (Fig. 3).
Mount the subbase directly onto the wall with the
screws and anchors included. If drywall construction,
use plastic anchors. Use the subbase as a template, and
with a pencil, mark the two mounting screw positions
(Fig. 4). Use
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 using the two screws provided.
Gently tighten the screws, level the top surface of the
subbase, and securely tighten the screws.

6
T8624C,D
INSTALLATION
Fig. 4—Mounting subbase on wall.
WIRES THROUGH
WALL OPENING
WALL
WALL
ANCHORS
(2)
SUBBASE
MOUNTING
HOLES
MOUNTING
SCREWS (2)
M846
Fig. 5—Restrict wiring to recessed 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
M 847
WIRING
All wiring must comply with local electrical codes
and ordinances.
Disconnect power before wiring to prevent electrical
shock or equipment damage.
The shape of the terminal barrier permits insertion of
straightor conventionalwraparound wiringconnections.
Either method is acceptable.
Push excess wire back into the hole, and plug the hole
with nonhardening caulk, putty or insulation to prevent
drafts from affecting thermostat operation.
NOTE: Restrict wiring to the recessed area surrounding
the terminals (Fig. 5) to assure thermostat/subbase
contact.
Refer to Figs. 6-8 for typical hookups of subbase and
thermostat.
ADJUSTING CYCLE RATE
To customize the thermostat cycling performance to
various types of heating equipment, cycle rate adjust-
ment screws are provided on the back of the thermostat
to provide optimum room temperature control.
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 furnace or air conditioner.
The heating cycle rate of this thermostat is factory-set
for gas/oil warm air heating. The cooling cycle rate is
factory-set and cannot be adjusted. The heating cycle
rate can be adjusted by turning one or both cycle rate
adjustment screws located on the back of the thermostat.
In multistage heat systems, the cycle rate adjustment
applies to the highest stage of heat only. Screws should
be backed out about one-half to one turn, or be turned in
until tight. See Fig. 9.
TIME/TEMPERATURE CONVERSION
(SOME MODELS)
The display readout may be converted between 12
and 24 hour clock or °C and °F using screws 2A and 2B
as indicated in Fig. 9.
FAN OPERATION OPTION SWITCH
(SELECT MODELS ONLY)
Select models include a fan operation option switch
on the subbase that is visible before the thermostat is
mountedon the subbase.The switchshould bein electric
heat position for electric heating systems that do not
have independent fan control.
INSTALLING BATTERIES
Three AAA alkaline batteries are included to provide
backup to prevent program loss in case of power outage.
Install batteries in back of thermostat as shown in Fig.
10.Without battery backup, the program will remain
about 30 seconds in event of power loss.
IMPORTANT: When batteries are first installed, the
display will flash 1:00 PM and 32 ° . The tempera-
ture will stay at 32
° F until the thermostat is
powered from the system wiring.
When the batteries are low, the display will flash
REPL BAT. Homeowner will have 20-30 seconds to
install new batteries after removing old batteries from
back of thermostat. After 20-30 seconds, it will be nec-
essary to reprogram. REPL BAT indication will disap-

7 68-0134
T8624C,D
INSTALLATION
Fig. 6—T8624C 2-stage heat/1-stage cool thermostat with HEAT-AUTO-COOL-OFF system and AUTO-ON
fan switching.
NOMINAL 24 Vac POWER MUST BE PRESENT BETWEEN R AND C FOR
THERMOSTAT OPERATION.
DENOTES THERMOSTAT TO SUBBASE INTERCONNECTION.
M5233
HEATING
TRANSFORMER
R
C
W1
W2
HEAT RELAY 1
HEAT RELAY 2
COOLING
TRANSFORMER
Y1
G
RC
COOLING
CONTACTOR
FAN RELAY
HEAT 1
HIGH
LIMIT
HIGH
LIMIT
L1
(HOT)
L2
HEAT
AUTO
OFF
SYSTEM
SWITCH
AUTO
ON
FAN
SWITCH
COOL
HEAT 2
2
1
COOL
L1
(HOT)
L2
1
2
1
2
3
4
3
4
SUBBASE
LOGIC/
CONTROL
CIRCUIT
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
FOR SINGLE TRANSFORMER SYSTEM JUMPER R AND RC.
POWER
SUPPLY
THERMOSTAT
LOGIC CIRCUIT

8
T8624C,D
INSTALLATION
DENOTES THERMOSTAT TO SUBBASE INTERCONNECTION. M3765
HEATING
TRANSFORMER
R
C
W1
W2
HEAT RELAY 1
HEAT RELAY 2
COOLING
TRANSFORMER
Y2
Y1
G
RC
COOLING
CONTACTOR 1
COOLING
CONTACTOR 2
FAN RELAY
HIGH
LIMIT
HIGH
LIMIT
HEAT
AUTO
OFF
SYSTEM
SWITCH
AUTO
ON
FAN
SWITCH
COOL
HEAT 2
COOL 2
COOL 1
SUBBASE
LOGIC/
CONTROL
CIRCUIT
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
FOR SINGLE TRANSFORMER SYSTEM, JUMPER R AND RC.
NOMINAL 24 Vac POWER MUST BE PRESENT BETWEEN
R AND C FOR THERMOSTAT OPERATION.
AVAILABLE ON T8624D MODELS ONLY.
POWER
SUPPLY
THERMOSTAT
LOGIC
CIRCUIT
1
L1
(HOT)
L2
2L1
(HOT)
L2 1
2
3
4
1
2
3
4
HEAT 1
5
5
Fig. 7—T8624D 2-stage heat/2-stage cool thermostat with HEAT-AUTO-COOL-OFF system and AUTO-ON
fan switching.

9 68-0134
T8624C,D
INSTALLATION
Fig. 8—T8624D 2-stage heat/2-stage cool thermostat with HEAT-OFF-COOL system and AUTO-ON fan
switching; auto fan on heat and cool; convertible to auto fan on cool only.
FOR ELECTRIC HEAT APPLICATIONS (AUTO FAN OPERATES WITH W1
AND Y1), USE ONLY ONE TRANSFORMER; JUMPER R AND RC. SET
SWITCH TO ELECTRIC POSITION.
NOMINAL 24 VAC POWER MUST BE PRESENT BETWEEN R AND C FOR
THERMOSTAT OPERATION.
DENOTES THERMOSTAT TO SUBBASE INTERCONNECTION.
M1016D
HEATING
TRANSFORMER
R
C
W1
W2
B
STAGE 1
HEAT RELAY
STAGE 2
HEAT RELAY
HEATING DAMPER OR
CHANGEOVER RELAY
COOLING
TRANSFORMER
O
Y2
Y1
G
RC
STAGE 1
COOLING RELAY
STAGE 2
COOLING RELAY
COOLING DAMPER OR
CHANGEOVER RELAY
FAN RELAY
HEAT 2
HEAT 1
HIGH
LIMIT
HIGH
LIMIT
L1
(HOT) L2
HEAT
OFF
COOL
SYSTEM
SWITCH
COOL 1 COOL 2
AUTO
ON
FAN
SWITCH
L1
(HOT)L2
NON-ELECTRIC
ELECTRIC
FAN
OPERATION
SWITCH
3
2
4
1
3
1
SUBBASE
LOGIC/
CONTROL
CIRCUIT
5
1
2
3
4
5
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
FOR GAS OR OIL APPLICATIONS OR ELECTRIC HEAT APPLICATIONS
WHERE THE FAN OPERATION IS CONTROLLED INDEPENDENTLY OF
THE THERMOSTAT (AUTO FAN OPERATES WITH Y1 ONLY), TWO
TRANSFORMERS MAY BE USED. SET SWITCH TO NONELECTRIC
POSITION.
POWER
SUPPLY
THERMOSTAT
LOGIC CIRCUIT

10
T8624C,D
INSTALLATION
Fig. 9—Cycle rate adjustment.
SYSTEM
GRAVITY
AIR/WATER
HOT
WATER
GAS/OIL
WARM AIR
ELECTRIC
WARM AIR
1A
OUT 1/2
TO 1 TURN OUT 1/2 TO 1 TURN
OUT 1/2
TO 1 TURN
OUT 1/2
TO 1 TURN
1B
IN
IN
(FACTORY SETTING)
IN IN
TIME/TEMP
DISPLAY 2A 2B
24 HR IN
12 HR
o
o
C
F
OUT 1/2
TO 1 TURN
OUT 1/2
TO 1 TURN
IN
M311A
1 SCREWS 2A, 2B AVAILABLE ON SOME MODELS ONLY.
1A
2A 2B
1B
1
CYCLES
PER HOUR
1
3
6
9
pear when thermostat is mounted back on the subbase.
IMPORTANT: For proper thermostat operation, al-
ways replace dead batteries with new alkaline
batteries. We recommend Energizer® batteries.
If batteries are completely dead, the display will go
blank when the thermostat is removed from the subbase.
After replacing the batteries, reprogramming will be nec-
essary.
BATTERY PLACEMENT
(NOTE CORRECT PLUS
AND MINUS DIRECTION)
M 372A
Fig. 10—Battery placement.
POWER OUTAGES
Backup batteries will hold the programming and keep
the display on during most power outages. Once the
power is restored, the system will resume normal opera-
tion.
If the display goes off when power is lost, either the
backup batteries need to be replaced or are not installed.
When power is restored, the display will flash 1:00 PM
as a reminder to reprogram.
MOUNTING THE THERMOSTAT
With system switch set to OFF, hang the thermostat
on the tabs at the top of the subbase (Fig. 11A). Swing
down and press on lower edge until thermostat snaps in
place (Fig. 11B). Open cover and tighten the captive
mounting screws (Fig. 11C).
SETTING DAY AND TIME
Restore 24V power to the thermostat. When power is
applied to the thermostat, the display will read 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 the mounting of the thermostat to the sub-
base. If loose or misaligned, remove thermostat
and reinstall on the subbase, making sure it is
firmly attached.
—Check to see that heat or cool system power is on.
—Check voltage between R and C; it should be 24 to
30 Vac.
SET
PRESENT
DAY/TIME
DAY
AHEAD
BACK

11 68-0134
T8624C,D
INSTALLATION • CHECKOUT
Fig. 11—Mounting thermostat on subbase.
M3764
PM
RETURN
MON HEAT ON
SYSTEM
AUTO
PM
RETURN
MONHEATON
SYSTEM
RUN
PROGRAMTIME
TEMPERATURE
PRESENT
SETTING
SKIP
NEXT
PERIOD
CHANGE
TOLAST
PERIOD
SET
PRESENT
DAY/TIME
HOLD
TEMP
AHEADWARMER
BACKCOOLER
A. B.
C.
HEATAUTOCOOLOFF
ONAUTO
FAN
PERIOD
WAKE
SLEEPRETURN
LEAVE
DAY
SET
HEAT/COOL
Checkout
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 (both stages if multistage), and the fan should run
(may be a short delay on forced air systems). Press
COOLER key until the setting is about 10°F [6°C]
below room temperature. The heating equipment should
shut off, followed by the fan.
NOTE: On an AUTO changeover thermostat, the cool-
ing temperature must be set at least 3°F [2°C] above
the heating temperature, or display will flash.
COOLING
CAUTION
Do not operate cooling if outdoor temperature
is below 50°F [10°C]. Refer to manufacturer
recommendations.
NOTE: When cooling setting is changed, thermostat
will wait up to five minutes before turning on the
cooling equipment. This delay is to protect the com-
pressor.
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
equipment and fan should start (both stages if multi-
stage). Press WARMER key until the setting is about
10°F [6°C] above room temperature. The cooling
equipment and fan equipment should stop.
NOTE: On an AUTO changeover thermostat, the heat-
ing temperature must be set at least 3°F [2°C] below
the cooling temperature, or display will flash.
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, the fan operates directly
with the thermostat call for cooling and also with the
!

12
System Press Look For This Response
Switch
Position This Key Key
Down Key Released
OFF 06 Blank
02 Blank
05 Blank
04 Blank
01 Blank
00 Blank
(CHECK
EACH
POSITION)
12 See note A
OFF 08 Blank
13 Microprocessor
mask no. and
revision no.
09 Blank
14 Blank
HEAT or
AUTO 14 1st stage heating and SYSTEM
LED on.
14 2nd stage heating
also on.
14 2nd stage heating
off.
14 1st stage heating
and SYSTEM
LED off.
NOTE: If single-stage heating system, press key twice
instead of four times; once to turn on heating and
SYSTEM LED, second time to turn off.
OFF 10 Blank
11 Normal operating
display.
END SELF-TEST
A
SUN MON TUE WED THU FRI SAT COOL ON HEAT ON
WAKE LEAVE RETURN SLEEP TEMPORARY
REPL
BAT
AM
PM
SET
PT
M410C
(continued)
RUN
PROGRAM
RUN
PROGRAM
SET
HEAT/COOL
DAY
SLEEP
BACK
COOLER
AHEAD
LEAVE
WARMER
RETURN
WAKE
T8624C,D
CHECKOUT
1
SET
PRESENT
DAY/TIME
SET
PRESENT
DAY/TIME
SET
PRESENT
DAY/TIME
SET
PRESENT
DAY/TIME
SET
PRESENT
DAY/TIME
System Press Look For This Response
Switch
Position This Key Key
Down Key Released
OFF 03 Blank
07 Blank
15 Blank
COOL or
AUTO
(with fan in
15 1st stage cooling,
fan and SYSTEM
LED on.
AUTO) 15 2nd stage cooling
also on.
15 2nd stage cooling
off.
15 1st stage cooling,
fan and SYSTEM
LED off.
NOTE: If single-stage cooling system, press key twice
instead of four times; once to turn on cooling, fan
and SYSTEM LED, second time to turn off.
CHANGE
TO LAST
PERIOD
SKIP
NEXT
PERIOD
PRESENT
SETTING
PRESENT
SETTING
PRESENT
SETTING
PRESENT
SETTING
PRESENT
SETTING
HOLD
TEMP

13 68-0134
T8624C,D
CHECKOUT
Third
Digit Manual or Auto Changeover System Switch Position
0 Manual HEAT or OFF
1 Auto HEAT or OFF
3 Auto AUTO
4 Manual COOL
5 Auto COOL
Fourth
Digit Degrees Clock (hrs) System Switch Position
0 F 12 COOL, AUTO
or OFF
1 F 24 COOL, AUTO
or OFF
2 F 12 HEAT
3 F 24 HEAT
4 C 12 COOL, AUTO
or OFF
5 C 24 COOL, AUTO
or OFF
6 C 12 HEAT
7 C 24 HEAT
Second Stages of
Digit Heat Cool
021
122
211
312
402
510
620
First Digit
Cycle Rate Setting (cph at 50% on
time for stage 1 on 1-heat models,
stage 2 on 2-heat models)
01
13
29
36
M5734

14
Programming the Thermostat
IMPORTANT: With Adaptive Intelligent Recovery™,
program the times for when the homeowner wants
the home comfortable. The thermostat will decide
how early to begin the temperature changes.
NOTE: Some models will show 32°F instead of the
current temperature, indicating the thermostat is op-
erating on backup batteries until the thermostat is
mounted on the wallplate and the system is powered.
STEP 1
SET THE CURRENT DAY AND
TIME
This thermostat can be programmed either
on the wall or in hand. SEE PAGE 5 TO
FIND OUT HOW TO REMOVE THE
THERMOSTAT FROM THE SUBBASE.
Always press the keys with fingertip or
similar blunt tool. Sharp instruments like a
pen or pencil point can damage the key-
board.
NOTE: Check the glossary, page 22, for
STEP 2
SET THE PROGRAM SCHEDULE
AND HEATING TEMPERATURES
Before Beginning…
Theschedule form onpage 22provides the
homeowner an opportunity to plan the
schedule.
Now…
Start by programming the WAKE time
and temperature for weekdays.
The thermostat requires a program for
WAKE. You can program LEAVE, RE-
TURN and SLEEP or not, as desired.
Press and release. Note that
thedisplay showsWAKE and
the preprogrammed time and
temperature.
If the display reads COOL,
press and release to switch to
HEAT.
If display reads SAT or SUN,
press and hold until MON
TUEWEDTHUFRI appears.
Press and hold until the dis-
play shows the desired start-
ing time.
Press and hold until the dis-
play shows the desired tem-
perature.
If the display starts to blink while holding down TEM-
PERATURE WARMER or COOLER, the setting limit
has been reached. If the thermostat can switch automati-
cally between heating and cooling, the heating tempera-
ture must be at least three degrees below the air condi-
tioning temperature. For example, if the cooling setting
definitions of unfamiliar
words.
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.
MON
PM
M5015
TUE
PM
M5017
TUE
M5016
PM
MON TUE WED THU FRI ON HEAT
WAKE
AM
SET
PT
M5018
MON TUE WED THU FRI ON HEAT
WAKE
AM
SET
PT
M5018
MON TUE WED THU FRI ON HEAT
WAKE
AM
SET
PT
M5018
MON TUE WED THU FRI ON HEAT
WAKE
AM
SET
PT
M5019
T8624C,D
PROGRAMMING THE THERMOSTAT
SET
PRESENT
DAY/TIME
DAY
BACK
AHEAD
WAKE
SET
HEAT/COOL
DAY
BACK
AHEAD
WARMER
COOLER
MON TUE WED THU FRI ON HEAT
WAKE
AM
SET
PT
M5020

15 68-0134
temperaturedisappearfrom
the display.
Pressandrelease. Thedisplay
shows LEAVE, but no time
or temperature.
Press and hold until the dis-
play shows the desired starting time.
is 75°F, the maximum heating setting is
72°F.
Program the LEAVE time and tempera-
ture, if desired.
NOTE: The LEAVE, RETURN or SLEEP
program may be canceled by holding
down the period key until the time and
LEAVE
T8624C,D
PROGRAMMING THE THERMOSTAT
BACK
AHEAD
WARMER
COOLER
MON TUE WED THU FRI ON HEAT
LEAVE
SET
PT
M5021
MON TUE WED THU FRI ON HEAT
LEAVE
AM
SET
PT
M5022
MON TUE WED THU FRI ON HEAT
LEAVE
AM
SET
PT
M5023
MON TUE WED THU FRI ON HEAT
RETURN
SET
PT
M5024
MON TUE WED THU FRI ON HEAT
RETURN
PM
SET
PT
M5025
BACK
AHEAD
Pressand release.The display
shows RETURN, but no time
or temperature.
Press and hold until the dis-
play shows the desired start-
ing time.
Press and hold until the dis-
play shows the desired tem-
perature.
MON TUE WED THU FRI ON HEAT
RETURN
PM
SET
PT
M5026
WARMER
COOLER
Program the SLEEP time and temperature, if desired.
Press and release. The dis-
play shows SLEEP and the
pre-programmed time and
temperature.
Press and hold until the dis-
play shows the desired start-
ing time.
SLEEP
RETURN
MON TUE WED THU FRI ON HEAT
SLEEP
PM
SET
PT
M5027
Press and hold until the display shows the
desired temperature.
Program the RETURN time and tempera-
ture, if desired.
BACK
AHEAD
MON TUE WED THU FRI ON HEAT
SLEEP
PM
SET
PT
M5060
WARMER
COOLER
MON TUE WED THU FRI ON HEAT
SLEEP
PM
SET
PT
M5028
Press and hold until the display shows the
desired temperature.
DAY
SAT ON HEAT
SLEEP
PM
SET
PT
M5029
Set the SATURDAY sched-
ule. Use the same procedure
as for weekdays.
Pressand releaseuntil SATap-
pears on the display.
Press WAKE, LEAVE, RE-
TURN or SLEEP to select the
time period.
Use the AHEAD/BACK keys
SLEEP
WAKE LEAVE
RETURN
BACK
AHEAD
WARMER
COOLER
tosetthe timeandtheWARMER/COOLER
keys to set the temperature.
DAY
Set the SUNDAY schedule.
Use the same procedure as for
weekdays. SUN ON HEAT
SLEEP
PM
SET
PT
M5030

16
T8624C,D
PROGRAMMING THE THERMOSTAT
SLEEP
WAKE
Press and hold until SUN ap-
pears on the display.
Press WAKE, LEAVE, RE-
TURN or SLEEP to select
the time period.
Usethe AHEAD/BACKkeys
to set the time and the
LEAVE
RETURN
BACK
AHEAD WARMER
COOLER
WARMER/COOLER keys to set the temperature.
This completes setting the program schedule and heat-
ing temperatures. To set air conditioning, go to Step 3.
Firstprogramthe WAKEtem-
perature for weekdays.
Press and release. The display shows WAKE and the
time and temperature pro-
grammed for heating.
Press and release so COOL
shows on the display, along
withthepreprogrammed cool-
ing temperature.
If display reads SAT or SUN,
press and hold until MON
TUEWED THUFRIappears.
Press and hold until the dis-
play shows the desired temperature.
If the display blinks while holding down TEMPERA-
TURE WARMER or COOLER, the setting limit has
been reached. If the thermostat can switch automatically
between heating and cooling, the cooling temperature
must be at least three degrees higher than the corre-
sponding heating temperature. For example, if the heat-
ing setting is 70°F, the mini-
If cooling temperatures are not being pro-
grammed, skip Step 3 and press the RUN
PROGRAM key.
STEP 3
SET THE COOLING TEMPERA-
TURES
The program times are the same for both
heating and cooling. Only the cooling tem-
peratures need to be programmed if the
thermostat has already been programmed
for heating. To set times as the cooling
temperaturesareprogrammed, usetheTIME
AHEAD and BACK keys as described in
Step 2. If the times are changed for cooling,
they are also being changed for heating.
WAKE
SUN COOL
WAKE
AM
SET
PT
M5032
MON TUE WED THU FRI COOL
WAKE
AM
SET
PT
M5033
SET
HEAT/COOL
DAY
WARMER
COOLER
MON TUE WED THU FRI COOL
WAKE
AM
SET
PT
M5034
SUN ON HEAT
WAKE
AM
SET
PT
M5031
LEAVE
mum cooling setting is
73°F. If a lower cooling temperature is desired, the heating tempera- ture first must be lowered ac-
cordingly.
Programthe LEAVEtempera-
ture, if desired.
Press and release. The display
MON TUE WED THU FRI COOL
LEAVE
AM
SET
PT
M5035
WARMER
COOLER
MON TUE WED THU FRI COOL
LEAVE
AM
SET
PT
M5036
shows LEAVE, the time programmed for
heating, and
78°F.
RETURN
MON TUE WED THU FRI COOL
RETURN
PM
SET
PT
M5037
Press and hold until the dis-
play shows the desired tem-
perature.

17 68-0134
T8624C,D
PROGRAMMING THE THERMOSTAT
Program the RETURN tem-
perature, if
desired.
MON TUE WED THU FRI COOL
RETURN
PM
SET
PT
M5038
WARMER
COOLER
Press and release. The display shows RE-
TURN, the time programmed for heating, and 78°F.
Press and hold until the
displayshowsthe desiredtem-
perature.
Programthe SLEEPtempera-
MON TUE WED THU FRI COOL
SLEEP
PM
SET
PT
M5039
MON TUE WED THU FRI COOL
SLEEP
PM
SET
PT
M5040
WARMER
COOLER
ture, if desired.
Press and release.
DAY
Press and hold until the dis-
play shows the desired tem-
perature.
Set the cooling temperatures
for the SATURDAY schedule.
Use the same procedure as for
weekdays.
Press and hold until SAT ap-
SAT COOL
SLEEP
PM
SET
PT
M5041
LEAVE
RETURN
SLEEP
WAKE
WARMER
COOLER
DAY
pears on the display.
PressWAKE, LEAVE, RETURNor SLEEP
to select the time period.
Use the WARMER/COOLER
keys to set the temperature.
Set the cooling temperatures for
theSUNDAY schedule.Use the
sameprocedureasfor weekdays.
Press and hold until SUN ap-
pears on the display.
Press WAKE, LEAVE, RE-
TURN or SLEEP to select the
time period.
SUN COOL
SLEEP
PM
SET
PT
M5042
SLEEP
WAKE LEAVE
RETURN
WARMER
COOLER
RUN
PROGRAM TUE
LEAVE
PM
SET
PT
M5043
SLEEP

18
T8624C,D
PROGRAMMING THE THERMOSTAT • OPERATING THE THERMOSTAT
ON
AUTOON
M3763
AUTO
FAN
FAN
SET THE SYSTEM AND FAN
SWITCHES ON THE SUB-
BASE.
Depending on thermostat model,
someof theswitchpositions shown
may not be available on the ther-
mostat.Notethepositions provided
on the subbase, then set the
switch(es) as desired.
First set the fan switch.
FAN ON: The fan runs continuously. Use for improved
air circulation during special occasions or for more effi-
cient electronic air
FAN AUTO: Normal setting
for most homes. The fan goes
on and off with the air condi-
tionerin summer.In winter,the
fan on most
systems starts a few minutes
after the furnace comes on. It
stops a few minutes after the
furnace goes off. The fan starts
and stops with the furnace in
some electric heat systems and
with the compressor in heat
pump systems.
Then set the system switch.
HEAT:The thermostatcontrols
your heating system.
AUTO (select models only): The thermostat controls
either your heating or cooling system, depending on
room temperature.
COOL: The thermostat controls your cooling system.
AUTOHEAT OFF
COOL
HEAT OFF
COOL
AUTO
HEAT OFFCOOLAUTO
M3762
HEAT OFFCOOLAUTO
OFF: Both the heating and cooling systems are off.
This completes the programming of the thermostat.
If the thermostat is removed from the wall to program, replace it following the procedure on page 5.
Operating the Thermostat
TEMPORARILY CHANGING THE PROGRAM
These features allow the program to be customized for
those times when someone comes home early, or stays
up late, or plans to be out for the evening.
To keep the current temperature through the
next program period:
SKIP
NEXT
PERIOD
Press and release. The name
of the period to be skipped
will flash in the display until
the next regularly scheduled
period starts.
To go back to the temperature of the previ-
ous program period:
CHANGE
TO LAST
PERIOD
Press and release. The dis-
play will show the name of
the previous period and flash
TEMPORARY until the next
regularly scheduled period starts.
Use the WARMER/COOLER keys to set the tempera-
ture.
You have completed programming the cooling tempera-
tures.
Press and release to start the program.
Go to Step 4.
STEP 4
cleaning.
TUE
LEAVE RETURN
PM
M5044
TUE
WAKE TEMPORARY
PM
M5045

19 68-0134
T8624C,D
OPERATING THE THERMOSTAT
WARMER
COOLER
To temporarily raise or lower the tempera-
ture for the current period only:
TEMPORARY
M5046
ON HEAT
Press and hold until the de-
sired temperature is reached.
The display will flash TEM-
PORARY until the next pro-
grammed time period starts.
With the system switch at the
AUTO position, press and
hold down the key to alter-
natebetweenheating andcool-
ing temperature settings for
temporary override.
Press and release to cancel
anyof thetemporary settings.
PRESENT
SETTING
RUN
PROGRAM TUE
LEAVE
PM
M5047
MANUALLY OPERATING THE
THERMOSTAT
This feature is particularly useful when on
vacation or other extended absences. It does
not cancel the program.
HOLD
TEMP 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 hold down to alter-
nate between heating and
cooling temperature settings.
Press and release to cancel
hold.
ON HEAT
SET
PT
M5048
ON HEAT
SET
PT
M5049
ON HEAT
SET
PT
M5050
WARMER
COOLER
PRESENT
SETTING
PERMANENTLY CHANGING THE
PROGRAM
If the schedule changes or a different tem-
perature is desired, any setting can be up-
dated without affecting other program set-
tings.
SLEEP
WAKE
Press and release the desired
period key.
Press and hold until the desired
day schedule shows on the dis-
play.
Pressandhold theTimeor Tem-
perature keys until the display
showsthe desirednew program.
Press and release to return to
normal operation.
LEAVE
RETURN
DAY
AHEAD
BACK
WARMER
COOLER
RUN
PROGRAM
TUE
LEAVE
PM
M5051
RUN
PROGRAM

20
day and Sunday settings are
canceled separately.
Pressand holdthedesired pe-
riod key until the time and temperature clear from the
display (about three seconds).
Press and release to return to
T8624C,D
OPERATING THE THERMOSTAT
SLEEP
NOTE: Moving the system switch also can-
cels hold.
CANCELING THE PROGRAM
SETTINGS
The thermostat requires time and tempera-
ture settings in the WAKE period, but any of
the others can be canceled. Weekday, Satur-
LEAVE
RETURN
MON TUE WED THU FRI ON HEAT
LEAVE
M5052
RUN
PROGRAM MON
RETURN
PM
M5053
normal operation.
CHECKING THE PROGRAM TIMES
AND TEMPERATURES
SLEEP
WAKE
Check all the stored settings without affecting the per-
manent program.
Press and release the desired
periodkey. Thestart timeand
temperature setting will appear on the display.
Press and release to display
the next daily time and tem-
perature for that period.
Press and release to return to
MON TUE WED THU FRI ON HEAT
SLEEP
PM
SET
PT
M5054
LEAVE
RETURN
SAT ON HEAT
SLEEP
PM
SET
PT
M5055
DAY
MON
M5056
RETURN
PM
RUN
PROGRAM
Press and release. The dis-
play will show the current
temperature setting for sev-
eral seconds, then revert to the room temperature.
To check the heating and cooling settings with the sys-
tem switch at the AUTO position, press and hold down
to alternate between the heating and cooling settings.
During recovery from energy savings, the setting dis-
played will not match the programmed setting. This is
because the thermostat gradually changes the tempera-
turesetting during recoveryto providemost efficientuse
of the heating or cooling equipment.
normal operation.
CHECKING THE CURRENT
TEMPERATURE SETTING
Press a single key to compare current room
temperature to the current temperature set-
ting at any time.
PRESENT
SETTING ON HEAT
SET
PT
M5057
PRESENT
SETTING