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Heating or Cooling Thermostat  
and Wallplate or  
Heating/Cooling Thermostat and  
Subbase  
T8090A/191108A, Q682B  
OWNER’S MANUAL
9-0574-2  
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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  
old 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.  
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TABLE OF CONTENTS  
Features Of Your Thermostat ........................................................................................................... 4  
Setting The Temperature .................................................................................................................. 7  
Inserting Clock Batteries ................................................................................................................... 8  
Setting The Clock.............................................................................................................................. 9  
Programming................................................................................................................................... 10  
Troubleshooting .............................................................................................................................. 14  
Servicing The Thermostat ............................................................................................................... 23  
Cycle Rate Adjustment.................................................................................................................... 23  
Thermometer Adjustment................................................................................................................ 24  
Warranty.......................................................................................................................................... 27  
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Features Of Your Thermostat  
1
FLIP-UP COVER. Lift it up to set clock for  
energy savings and normal temperature  
periods.  
8 TEMPERATURE SETTING LEVERS. Left  
(blue mark) controls the low temperature,  
right (red mark) controls the high  
temperature.  
2
3
4
5
THERMOSTAT COVER. Lift up and  
remove to adjust heat anticipator.  
THERMOMETER. Provides accurate room  
temperature reading.  
2
1
CLOCK. This clock provides a 24-hour  
slotted dial to hold the programming pins.  
CLOCK HANDS. Turn minute hand clock-  
wise  
to match the correct AM or PM  
time to the time indicator.  
TIME INDICATOR. Arrow head indicates  
time for 24-hour dial.  
PROGRAM INDEX WHEEL. Controls high  
and low temperature at specific time of day  
as set by program pins.  
6
7
3
M8726  
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9
PROGRAM PINS. Must be inserted into  
4-hour clock dial slots to control program  
index wheel.  
0 PIN SLOTS. Located on 24-hour dial at  
0-minute intervals for program pin  
insertion.  
1 MANUAL PROGRAM ADVANCE BUTTON.  
2
5
4
10  
8
14  
1
1
1
Allows change from comfort to energy  
savings setting and vice versa without  
changing the program.  
1
2 HEAT ANTICIPATOR SCALEPLATE.  
Calibrated to match the heating system  
current draw in amperes.  
1
3 ANTICIPATOR SETTING LEVER. Must be  
adjusted to match the heating system  
primary control current.  
1
4 MERCURY BULB AND BIMETAL  
ELEMENT (2). Provide automatic tempera-  
ture control by switching the heating or  
cooling system on or off.  
9
7
6
11  
12  
13  
M8691  
5
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1
5 191108AJ WALLPLATE. Provides mount-  
ing base and wiring connections for  
heating-only or cooling-only thermostat.  
15  
M2421  
1
6 Q682B SUBBASE. Provides mounting  
base, wiring connections and manual  
switching control for heating/cooling  
thermostat.  
O
B
R
G
W
Y
16  
FAN  
COOL  
ON  
AUTO  
HEAT  
OFF  
M719  
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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 tem-  
perature you want for normal comfort periods.  
HIGH  
LOW TEMPERATURE  
SETTING LEVER  
TEMPERATURE  
SETTING  
LEVER  
(BLUE MARK)  
(RED MARK)  
50  
60 70  
80  
NOTE: You may override the time program by  
setting both the red and blue levers to the  
same temperature set point.  
1
2
7
9
6
10  
5
11  
4
50 60 70 80  
12  
3
1
9
1
3
3
1 2  
4
1 1  
5
1 0  
6
7
9
For Cooling:  
6
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.  
M1520  
Fig. 1—Setting high and low  
temperature levers.  
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Inserting Clock Batteries  
BATTERY LOCATION FOR  
2) AAA BATTERIES;  
INSTALL WITH POSITIVE  
ENDS UP  
(
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 may be installed to  
supply power to the clock if power is inter-  
rupted 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 recommend Energizer batteries.  
M7188  
Fig. 2—Inserting clock batteries.  
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Time ends, move the minute hand carefully in  
a clockwise direction 23 hours. Do NOT  
reverse the minute hand, or damage to timer  
mechanism may occur.  
Setting The Clock  
Lift thermostat flip-up cover and you’ll find  
the 24-hour program dial, slotted in 10-minute  
increments. Adjust the clock to the current time  
by moving the minute hand carefully in clock-  
wise  
direction. DO NOT reverse the  
minute hand.  
When time is correctly set, the Time  
Indicator Arrow (see Fig. 3) will point to the  
correct time and corresponding daytime (light)  
or nighttime (dark) band of the program dial.  
MINUTE  
HAND  
EXAMPLE: For 11 PM, the time indicator arrow  
will point directly to dark band. For 11 AM,  
the arrow will point to light band on dial.  
TIME  
INDICATOR  
ARROW  
Daylight Savings Time  
When Daylight Savings Time starts, move  
the minute hand carefully in a clockwise  
direction one hour. When Daylight Savings  
M8561  
Fig. 3—Setting the clock.  
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up to six temperature changes with the pins  
supplied. We recommend at least five hours  
for each energy saving period.  
Programming  
You can program your thermostat to  
automatically lower and raise the temperature  
one or more times every 24 hours.  
24-HOUR PROGRAM DIAL  
(GRAY AREA FOR  
NIGHT SETTINGS)  
Before setting your program:  
FLIP-UP  
COVER  
Lift thermostat flip-up cover and you'll find  
the 24-hour program dial. The slots on the  
program dial (Fig. 4) are for the program pins  
that can be inserted at ten-minute intervals.  
Three red and three blue program pins are  
included with your thermostat. The red pins  
start the high-temperature period; the blue pins  
start the low-temperature period. A heating  
program has been preprogrammed. A red pin  
is inserted at 6:00 AM for high temperature  
PROGRAM  
PINS  
THERMOSTAT  
COVER  
PROGRAM PIN SLOT  
PROGRAM PIN  
STORAGE  
PROGRAM INDEX WHEEL  
(
comfort period); a blue pin is inserted at  
0:00 PM for low temperature (energy saving  
TIME INDICATOR  
ARROW  
MANUAL PROGRAM  
ADVANCE BUTTON  
1
M8692  
period). Two additional sets of pins are located  
in the program pin storage area. You can set  
Fig. 4—Program components.  
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To change the pins or add a new  
energy savings period:  
Decide when you want the energy savings  
period to start and insert a blue pin at the notch  
that corresponds to this time. After the blue pin  
engages, the furnace will be off until room temp-  
erature drops to the energy savings set point.  
To insert a pin, push it straight into the  
selected notch on the program dial until it’s  
completely seated.  
To remove a pin, press against program dial  
and pull the pin straight out. DO NOT attempt  
to change a pin if it is engaged with the  
program index wheel.  
On heating/cooling systems, you must reset the  
pins when the seasons change. You will also  
probably want to change the lever positions.  
WINTER  
PROGRAM  
TEMPERATURE PIN IN  
SUMMER  
PROGRAM  
TEMPERATURE  
PIN IN  
°F  
°C  
CONTROL  
°F  
°C  
CONTROL  
NIGHT  
ENERGY 10:00 PM  
SAVING  
PERIOD 6:00 AM  
DAY  
ENERGY  
SAVING  
PERIOD  
BEGINS  
58  
14  
BLUE  
80  
27  
RED  
BLUE  
RED  
ENDS  
68  
24  
27  
24  
2
0
RED  
BLUE  
RED  
75  
80  
75  
BEGINS  
58  
14  
20  
7:30 AM  
ENDS  
4:00 PM  
68  
BLUE  
Setting the Heating Program:  
Decide when you want the temperature to  
reach the comfort level. Find the notch on the  
dial that’s one-half hour before this time and  
insert a red pin. The half-hour head start gives  
the furnace time to heat the house before you  
wake up or arrive home.  
M1690B  
Fig. 5—Programming examples.  
You can set both a day and a night pro-  
gram. See Fig. 5 for program examples.  
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Setting the Cooling Program:  
Decide when you want the energy savings  
period to start and insert a red pin at the notch  
that corresponds to this time. After the red pin  
engages, the air conditioner will be off until  
room temperature rises to the energy savings  
set point.  
Decide when you want the temperature to  
reach the comfort level. Find the notch on the  
dial that’s one-half hour before this time and  
insert a blue pin. The half-hour head start gives  
the air conditioner time to cool the house  
before you wake up or arrive home.  
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Start Or End Programs With Manual Program  
Advance Button  
IMPORTANT:To prevent damage to the program  
advance mechanism, DO NOT use the  
Press the button to immediately begin an  
energy savings period or return to the normal  
setting. After pressing the button, check the  
program indicator to ensure the system is in  
the desired mode. If the program indicator  
shows blue, the lower temperature is in effect;  
if it shows red, the higher temperature is in  
effect. Using the manual advance button will  
not affect the stored program.  
program advance button within a 30-minute  
period before or after a program change.  
The manual program advance button  
enables immediate, one-time-only program  
changes to accommodate temporary schedule  
changes.  
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Troubleshooting  
Your Honeywell thermostat requires little or no attention. Most problems can generally be  
traced to the following:  
Problem  
No heat.  
Check  
Action  
— system switch. May be in OFF or  
Move system switch to HEAT position.  
COOL position.  
1
fuse or circuit breaker.  
If blown or tripped, replace fuse or reset  
breaker.  
furnace power switch. May be Off. Move switch to ON.  
pilot flame. May be out. Relight pilot flame per furnace manufacturers  
instructions.  
R and W thermostat connections. Turn Off power to furnace. Check for correct  
terminal hookups. Repair any frayed or  
broken wires. Firmly tighten all terminal  
screws. Turn On power.  
other problem.  
Contact a qualified service technician for  
assistance.  
(continued)  
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Troubleshooting (continued)  
Problem  
Check  
Action  
Energy savings  
temperature program  
— program dial for proper day or  
night phase.  
Turn timer ahead 12 hours. Move setting  
knob clockwise  
only.  
12 hours off.  
Rooms do not warm  
up at programmed  
— timer program for heating system. Move red pin one-half hour earlier on the  
May need more time to warm up  
rooms.  
program dial.  
time.  
2
Temperature change — programs pins for correct time  
Relocate pins to desired settings.  
occurs at the wrong  
time.  
locations.  
Room temperatures  
are not correct.  
— positions of thermostat setpoint  
levers.  
Reset to desired temperatures.  
position of subbase system  
switch.  
Move to desired operating position.  
(continued)  
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Troubleshooting (continued)  
Problem  
Check  
thermostat circuits.  
Action  
Room temperatures  
are not correct  
continued).  
HEATING-ONLY SYSTEM—Move  
temperature setting levers 5°F (3°C)  
above room temperature. Heating system  
should start. If the system does not  
operate, call a qualified technician.  
COOLING ONLY SYSTEM–Move  
temperature setting levers 5°F (3°C)  
below room temperature. Cooling system  
should start. If the system does not  
operate, call a qualified technician.  
HEATING/COOLING SYSTEM—With  
system switch at HEAT, move  
(
temperature setting levers 5°F (3°C)  
above room temperature. Heating  
system should start.  
(continued)  
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Troubleshooting (continued)  
Problem  
Check  
Action  
Room Temperatures  
are not correct  
With system switch at COOL, move  
temperature setting levers 5°F (3°C) below  
room temperature. Cooling system should  
start. If the systems do not operate, call a  
qualified technician.  
(
continued).  
Burner-on time too  
short.  
anticipator setting. (See figure on Increase anticipator setting by 0.05.  
page 23 for anticipator location.) Observe burner operation.  
Burner-on time too  
long.  
anticipator setting. (See figure on Decrease anticipator setting by 0.05.  
page 23 for anticipator location.) Observe burner operation.  
No cooling.  
1
system switch. May be in OFF or Move switch to COOL position.  
HEAT position.  
fuse or circuit breaker.  
If fuse is blown or breaker tripped, replace or  
reset.  
(continued)  
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Troubleshooting (continued)  
Problem  
Check  
Action  
Move to ON position.  
No cooling  
continued)  
1
condenser switch position.  
Located outdoors and may be  
turned OFF.  
(
thermostat connections. Check  
for correct terminal hookups.  
Turn OFF power to cooling system.  
Repair any frayed or broken wires.  
Firmly tighten all terminal screws.  
other.  
Contact a qualified service technician for  
assistance.  
level position of thermostat.  
Reinstall thermostat wallplate or subbase.  
Use a spirit level.  
Thermostat setting  
and thermometer  
reading disagree.  
area around thermostat for drafts  
or radiant heat.  
Thermostat should be about 5 ft (1.5m)  
above floor on an inside wall. Contact  
qualified service technician for change of  
location.  
(continued)  
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Troubleshooting (continued)  
Problem  
Check  
Action  
Thermostat setting  
and thermometer  
reading disagree  
calibration of thermometer.  
See instructions on page 24.  
(continued).  
Clock does not run.  
thermostat connections at  
the two C terminals. If no  
connections, clock needs  
batteries in order to run.  
Install as shown on page 8.  
3
Replace with two new AAA alkaline batteries  
as shown on page 8.  
Batteries may not have been  
installed.  
Batteries may need replacement  
if new batteries are installed and  
clock still does not run.  
Replace thermostat.  
voltage across the two C  
terminals.  
Remove thermostat from the wallplate or  
subbase and measure the voltage. Refer to  
the table on page 22 for cause and reaction.  
(continued)  
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Troubleshooting (continued)  
Problem  
Check  
pins in program dial. If pins are  
Action  
Clock does not run  
continued).  
Push down on pins to make sure they are  
(
not completely seated in program completely seated in program dial.  
dial, jamming with index wheel  
may occur.  
Clock loses time.  
power. May be interrupted.  
Make sure power is on. Reset clock.  
high limit control. If clock powered Wire separate transformer to power clock, or  
through system transformer,  
power to clock and equipment  
may be off on safety.  
install backup batteries as shown on page 8.  
Replace filter and reset clock.  
filter. May be clogged. Safety  
limit on equipment may cut off  
power to system.  
(continued)  
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Troubleshooting (continued)  
Problem  
Check  
batteries may need replacement.  
Action  
Clock loses time  
continued).  
Replace with two new AAA alkaline batteries  
as shown on page 8. We recommend  
(
®
Energizer batteries.  
1
2
Not applicable on model used in heating-only system.  
Not applicable on model used in cooling-only system.  
3
If clock is not battery powered, clock may still use batteries for backup.  
If this Troubleshooting section has not solved the problem, call your qualified heating service  
technician or Honeywell Customer Assistance Center, 1-800-468-1502, Monday-Friday, 7:00 AM to  
:30 PM, Central time, for additional assistance.  
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Voltage At Clock Terminals  
AC Voltge at  
C-C Terminals  
Check  
Action  
0
Vac.  
1. System power off.  
1. Restore power.  
2. Replace wiring.  
2.  
Short in clock power supply  
wiring.  
3.  
.
Free or replace limit switch.  
Replace transformer.  
3
.
.
Limit switch contacts stuck open.  
4
4
Transformer supplying power is  
burned out.  
Up to 15 Vac.  
1. System transformer used to power 1. Use additional (separate) transformer.  
the clock is inadequate.  
2.  
Install transformer with proper secondary  
voltage.  
2.  
Additional (separate) transformer  
used to power the clock has  
inadequate voltage.  
15 to 30 Vac.  
1. Spring fingers o thermostat not  
making proper contact with  
subbase terminals.  
1. Rebend spring fingers to a 45 degree  
angle to ensure proper contact.  
2. Replace thermostat.  
2. Clock has failed.  
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Servicing The Thermostat  
Cycle Rate Adjustment  
The equipment should cycle on and off just  
enough to keep the room temperature close to  
the temperature lever settings.  
If the thermostat seems to cycle the heating  
system too fast or too slow, adjust the cycle  
rate by moving the anticipator setting lever one  
indicator mark at a time (Fig. 6). Observe the  
heating system operation after each adjust-  
ment.  
ANTICIPATOR  
SCALEPLATE  
ANTICIPATOR  
SETTING LEVER  
NOTE: Most hot water systems require a  
setting of 1.2A.  
M7317  
Fig. 6—Heat anticipator setting.  
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Thermometer Adjustment  
The thermometer has been accurately calibrated at the factory and should only need adjust-  
ment if it has been dropped or mishandled.  
If the set point lever and the thermometer reading do not agree, follow the procedure below.  
Remove thermostat cover and open the flip-up cover.  
Set the thermostat cover on a table near thermometer of known accuracy.  
Allow at least five minutes for cover ther-  
mometer to sense area temperature, then  
compare the readings. Be careful not to touch  
thermometer or breathe on it.  
THERMOMETER  
BACKSIDE OF  
SLOT  
FLIP-UP COVER  
If the readings are the same, replace cover  
and put the system into operation.  
If the readings are different, insert a small  
screwdriver in the thermometer slot, shown  
in Fig. 7, and turn it until both thermometers  
read the same.  
INSERT AND TURN  
SCREWDRIVER  
Replace thermostat cover and put the  
system into operation.  
M1810  
Fig. 7—Thermometer adjustment.  
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25  
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If you have questions regarding the installation and programming of your Honeywell  
thermostat, please contact the Honeywell Customer Assistance Center at 1-800-468-1502,  
Monday-Friday, 7:00 AM to 5:30 PM, Central time. Before you call, please have the following  
information available: make and model of furnace, old thermostat and air conditioner.  
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26  
Limited One-Year Warranty  
Honeywell warrants this product, excluding battery, to be free from defects in the workmanship or materials, under normal use and service, for a period  
of one (1) year from the date of purchase by the consumer. If, at any time during the warranty period, the product is defective or malfunctions, Honeywell  
shall repair or replace it (at Honeywell’s option) within a reasonable period of time.  
If the product is defective,  
(i) return it, with a bill of sale or other dated proof of purchase, to the dealer or contractor from which you purchased it, or  
(ii) package it carefully, along with proof of purchase (including date of purchase) and a short description of the malfunction, and mail it, postage  
prepaid, to the following address:  
Honeywell Inc.  
in Canada  
Returned Goods Department  
Honeywell Limited/Honeywell Limitee  
740 Ellesmere Road  
1050 Berkshire Lane  
Plymouth, MN 55441-4437  
Scarborough, Ontario M1P2V9  
This warranty does not cover removal or reinstallation costs. This warranty shall not apply if it is shown by Honeywell that the defect or malfunction was  
caused by damage which occurred while the product was in the possession of a consumer.  
Honeywell’s sole responsibility shall be to repair or replace the product within the terms stated above. HONEYWELL SHALL NOT BE LIABLE FOR ANY  
LOSS OR DAMAGE OF ANY KIND, INCLUDING ANY INCIDENTAL OR CONSEQUENTIAL DAMAGES RESULTING, DIRECTLY OR INDIRECTLY  
FROM ANY BREACH OF ANY WARRANTY, EXPRESS OR IMPLIED, OR ANY OTHER FAILURE OF THIS PRODUCT. Some states do not allow the  
exclusion or limitation of incidental or consequential damages, so this limitation may not apply to you.  
THIS WARRANTY IS THE ONLY EXPRESS WARRANTY HONEYWELL MAKES ON THIS PRODUCT. THE DURATION OF ANY IMPLIED  
WARRANTIES, INCLUDING THE WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, IS HEREBY LIMITED TO  
THE ONE YEAR DURATION OF THIS WARRANTY. Some states do not allow limitations on how long an implied warranty lasts, so the above limitation  
may not apply to you.  
This warranty gives you specific legal rights, and you may have other rights which vary from state to state.  
If you have any questions concerning this warranty, please write our Customer Assistance Center, Honeywell Inc., P.O. Box 524, Minneapolis, MN 55440-  
0524 or call 1-800-468-1502, Monday-Friday, 7:00 a.m. to 5:30 p.m., Central time.  
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Automation and Control Solutions  
Honeywell International Inc. Honeywell Limited—Honeywell Limitée  
985 Douglas Drive North  
Golden Valley, MN 55422  
1
35 Dynamic Drive  
Scarborough, Ontario M1V 4Z9  
Rev. 1-95 Form N um ber 69-0574—2