Honeywell TRADELINE T8090A User manual

169-0628B—1
69-0628B-1
Heating or Cooling Thermostat and
Wallplate or Heating/Cooling
Thermostat and Subbase
T8090A/191108AJ, Q682
OWNER’S MANUAL

269-0628B—1
M3375
Welcome to the world of energy savings with your new Honeywell fuel saver thermostat. The
Honeywell name is your assurance of accurate control and reliable operation for years to come.
Your new thermostat will automatically lower and raise the temperature in your home one or
more times every 24 hours. This allows you to significantly lower your fuel costs, while awakening
(or returning home) to a comfortable temperature.
Read this manual to learn how to use your new thermostat.
Recycling Notice
This control contains mercury in a sealed tube. Do not place control in the trash at the end of its
useful life.
If this control is replacing a control that contains mercury in a sealed tube, do not place your
control in the trash.
Contact your local waste management authority for instructions regarding recycling and the
proper disposal of this control, or of an old control containing mercury in a sealed tube.
If you have questions, call Honeywell Inc. at 1-800-468-1502.

369-0628B—1
Table of Contents
PAGE
Features of Your Thermostat ............................................................................................................ 4
Setting the Temperature ................................................................................................................... 7
Setting Subbase Switches ................................................................................................................ 8
Inserting Clock Batteries ................................................................................................................... 9
Setting the Clock ............................................................................................................................. 10
Programming................................................................................................................................... 11
Troubleshooting .............................................................................................................................. 14
Servicing the Thermostat ................................................................................................................ 23
Cycle rate adjustment ................................................................................................................ 23
Thermometer adjustment ........................................................................................................... 24
Warranty.......................................................................................................................................... 27

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2
1
3
M8895
Features of Your Thermostat
1 FLIP-UP COVER. Lift it up to set clock for
energy savings and normal temperature
periods.
2THERMOSTAT COVER. Lift up and
remove to adjust heat anticipator.
3THERMOMETER. Provides accurate room
temperature reading.
4CLOCK. This clock provides a 24-hour
slotted dial to hold the programming pins.
5CLOCK HANDS. Turn minute hand clock-
wise  to match the correct AM or PM
time to the time indicator.
6TIME INDICATOR. Arrow head indicates
time for 24-hour dial.
7PROGRAM INDEX WHEEL. Controls high
and low temperature at specific time of day
as set by program pins.
8TEMPERATURE SETTING LEVERS.
Left (blue mark) controls the low tempera-
ture; right (red mark) controls the high
temperature.

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58
976 11 12 13
10 14
M8896
4
9PROGRAM PINS. Must be inserted into
24-hour clock dial slots to control program
index wheel.
10 PIN SLOTS. Located on 24-hour dial at
10-minute intervals for program pin
insertion.
11 MANUAL PROGRAM ADVANCE BUTTON.
Allows change from comfort to energy
savings setting and vice versa without
changing the program.
12 HEAT ANTICIPATOR SCALEPLATE.
Calibrated to match the heating system
current draw in amperes.
13 ANTICIPATOR SETTING LEVER. Must be
adjusted to match the heating system
primary control current.
14 MERCURY BULB AND BIMETAL ELE-
MENT (2). Provide automatic temperature
control by switching the heating or cooling
system on or off.

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AUTO OFF COOL HEATON
FAN
B
O
W
Y
R
G
M 719
16
M2421
15
15 WALLPLATE. Provides mounting base and
wiring connections for heating-only or
cooling-only thermostat.
16 SUBBASE. Provides mounting base, wiring
connections and manual switching control
for heating/cooling thermostat.

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8
9
10
12
11
1
2
3
4
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8
9
10
12
11
1
2
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4
5
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7
12
6
3
9
HIGH
TEMPERATURE
SETTING LEVER
(RED MARK)
LOW TEMPERATURE
SETTING LEVER
(BLUE MARK)
M1691
Setting the Temperature
For Heating
Set the left lever (blue mark) to the energy
savings temperature you want when you are
sleeping or your home is unoccupied.
Set the right lever (red mark) to the tempera-
ture you want for normal comfort periods.
NOTE: You may override the time program by
setting both the red and blue levers to the
same temperature setpoint.
For Cooling
Set the left lever (blue mark) to the tempera-
ture you want for normal comfort periods.
Set the right lever (red mark) to the energy
savings temperature you want when you are
sleeping or your home is unoccupied.
Fig. 1—Setting High and Low Temperature
Setting Levers.

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Setting Subbase Switches
(If applicable)
The subbase system switch controls system
operation as follows:
HEAT—Heating system is controlled by the
thermostat. Cooling system is off.
COOL—Cooling system is controlled by the
thermostat. Heating system is off.
OFF—Both the heating and cooling systems
are off. If the fan switch is at the AUTO
position, the fan is also off.
AUTO—In a cooling only application, only
cooling operates. In a heating only applica-
tion, only heating operates.
The subbase fan switch controls fan operation
as follows:
ON—Fan operates continuously.
AUTO—Fan operates with cooling equipment
as controlled by the thermostat or with the
heating equipment as controlled by the
plenum fan switch. In electric heat, heat
pump, and fan coil systems, the fan is
controlled by the thermostat in heating and
cooling.
To switch positions, use thumb or index
finger to slide lever to desired position. For
proper circuit operation, stop switch lever in the
detent over desired function indicator mark.

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BATTERY LOCATION FOR
(2) AAA BATTERIES;
INSTALL WITH POSITIVE
ENDS UP
M7188
Inserting Clock Batteries
Power is supplied to the clock by the 24 Vac
transformer, by two AAA alkaline batteries
(included), or by the heating or cooling control
circuit. Backup batteries can be installed to
supply power to the clock if power is interrupted
when using 24 Vac powering method. Install
batteries in thermostat as shown in Fig. 2. Once
a year or when batteries are dead, replace with
two new AAA alkaline batteries. We recom-
mend Energizer®batteries.
Fig. 2—Inserting Clock Batteries.

10 69-0628B—1
TIME
INDICATOR
ARROW
MINUTE
HAND
M8561
Setting the Clock
Lift thermostat flip-up cover and you will find
the 24-hour program dial, slotted in ten minute
increments. Adjust the clock to the current time
by moving the minute hand carefully in a clock-
wise direction. DO NOT reverse the
minute hand.
When time is correctly set, the Time Indica-
tor Arrow (see Fig. 3) points to the correct time
and corresponding daytime (light) or nighttime
(dark) band of the program dial.
EXAMPLE: For 11 PM, the time indicator arrow
points directly to dark band. For 11 AM, the
arrow points to the light band on the dial.
Daylight Savings Time
When Daylight Savings Time starts, carefully
move the minute hand in a clockwise
direction one hour. When Daylight Savings Time
ends, carefully move the minute hand in a
clockwise direction 23 hours. Do NOT
reverse the minute hand, or damage to the timer
mechanism can occur.
Fig. 3—Setting the Clock.