Honeywell T8621A User manual

1 68-0058—1
T8621A,C,D
Chronotherm™ III Fuel
Saver Thermostats
C. H. • Rev. 8-92 • ©Honeywell Inc. 1992 • Form Number 68-0058—1
■Fullseven-dayprogramcapability;differentsched-
ules may be selected for every day.
■Can be programmed in hand (with batteries in-
stalled)oronwalltoprovideuptofourtemperature
settings per day.
■Large digital clock (liquid crystal display) indi-
cates continuous time, day, current period and
room temperature.
■Adaptive Intelligent Recovery™ brings room
temperature to programmed temperature at pro-
grammed time, maximizing comfort and energy
savings.
■Temperature control program maintains tempera-
ture within 1°F of setpoint.
■Temporaryprogramoverrideavailablebyusing—
—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.
■Switchingsubbasewithwiringterminalsincluded.
■Powereddirectlyfromcontroltransformer,requir-
ing an extra (24V) wire to thermostat.
■Fanoperationswitch includedonback ofSUPER
TRADELINE models to select either indepen-
dentordirect thermostatcontroloffan inheating.
■Models available with separate sensor for remote
mounting.
CONTENTS
Specifications ............................................... 2
Ordering Information................................... 2
Selection/Application ................................... 5
Installation ................................................... 7
Checkout..................................................... 17
Programming the Thermostat .................... 19
Operating the Thermostat .......................... 25
Operation ................................................... 28
Troubleshooting ......................................... 29
Glossary ..................................................... 30
Table of Contents ....................................... 31
The T8621A,C,D Chronotherm III Program-
mable Fuel Saver Thermostats provide auto-
matic control of single or multistage heating/
cooling systems and offer users the highest
standard of comfort and convenience available
with energy savings.

2
T8621A,C,D
SPECIFICATIONS • ORDERING INFORMATION
Specifications
IMPORTANT:Thespecificationsgiveninthispublica-
tion do not include normal manufacturing toler-
ances. Therefore, this unit may not exactly match
the listed specifications. Also, this product is
tested under closely controlled conditions, and
some minor differences in performance can be
expected if those conditions are changed.
SUPER TRADELINE MODEL
SUPER TRADELINE controls, see Table 1, offer fea-
tures not available on TRADELINE models and are
designedto replace a wide range of Honeywell and
competitive controls.
SUPER TRADELINE FEATURE: Fan operation switch
on back of thermostat to select either independent or
direct thermostat control of fan in heating.
TRADELINE MODELS
TRADELINE models, see Table 2, are selected and pack-
aged 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.
TABLE 1—SUPER TRADELINE MODEL.
Thermostat
Model Stages Changeover Switching
Number Heat Cool Type System Fan Application
T8621D 2 2 Manual HEAT-OFF-COOL ON-AUTO Multistage
Ordering Information
When purchasing replacement and modernization products from your TRADELINE® wholesaler or distributor, refer to the
TRADELINE Catalog or price sheets for complete ordering number, or specify—
1. Model number; SUPER TRADELINE, if desired. 4. Remote temperature sensing, if desired.
2. Number of heat and cool stages desired. 5. Application.
3. System, fan switching desired.
Ifyou haveadditional questions,need furtherinformation orwould 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.

3 68-0058—1
T8621A,C,D
SPECIFICATIONS
TABLE 2—TRADELINE MODELS.
Thermostat
Model Stages Changeover Switching
Number Heat Cool Type System Fan Application
T8621A* 1 1 Auto HEAT-AUTO- ON-AUTO Single stage
COOL-OFF
T8621C 2 1 Auto HEAT-AUTO- ON-AUTO Multistage
COOL-OFF
T8621D* 2 2 Auto HEAT-AUTO- ON-AUTO Multistage
COOL-OFF
*Model available with separate sensor for remote mounting.
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].
SETPOINT RANGE: 45°F to 88°F [7°C to 31°C].
CALIBRATION:Self-calibrating thermostat and ther-
mometer to ±1°F.
SHIPPING TEMPERATURE: -20°Fto+120°F[-29°Cto
+49°C].
CYCLES PER HOUR ADJUSTMENT:
Heating:Firststageof2-stageheatmodels—fixedat
3 cph. Second stage of 2-stage heat models or
heat stage of single-stage heat models—factory-
set at
6 cph; adjustable for other systems.
Cooling: Factory-set at 3 cph (not field adjustable);
minimum off-time of five minutes.
FINISH:Beigemattewithdecorativebrushedmetalface-
plate.
DIMENSIONS: Thermostat (mounted on subbase)—7
in.[178 mm] long, 5-5/16 in. [135 mm] high, 1-3/
4 in. [44 mm] deep. See Fig. 1 for subbase dimen-
sions and Fig. 2 for sensor dimensions.
TYPICAL KEYPAD: See Fig. 3.
ACCESSORIES:
TG586A Locking Cover.
TG512 Versaguard Universal Thermostat Guard.
REPLACEMENT PARTS:
202905AA Remote Temperature Sensor Assembly.
Includessensor,screws,anchorsandinstructions.See
Fig. 2 for dimensions.
Fig. 1—T8621 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]

4
T8621A,C,D
SPECIFICATIONS • SELECTION/APPLICATION
Fig. 2—202905AA Remote Temperature Sensor dimensions in in. [mm].
43
32
[104]
FRONT
131
32
[50]
SIDE
M5244
2
[51]
131
32 [50]
41
64 [16]
3
8
1
19
64
9
64
1
2
[8]
[4]
DIA.
[13]
[35]
1[25]
BACK
Fig. 3—Typical thermostat keypad.
SYSTEM
RUN
PROGRAM
PERIOD
TIME
TEMPERATURE
PRESENT
SETTING
SKIP
NEXT
PERIOD
CHANGE
TO LAST
PERIOD
SET
PRESENT
DAY/TIME
HOLD
TEMP
DAY
SET
HEAT/COOL CANCEL
PERIOD
COPY
FROM AHEAD WARMER
BACK COOLER
M5360
WED
MIDDAY
AM
HEAT ON
HEAT OFF COOL ON AUTO
FAN
ROOM
COPY
TO

10
Fig. 9—T8621C 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
T8621A,C,D
INSTALLATION