Honeywell T8112C Thermostat User Manual

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T8112C,D Electronic  
Programmable Thermostats  
INSTALLATION INSTRUCTIONS  
APPLICATION  
Location  
Install the thermostat about 5 ft. (1.5m) above the floor in  
The T8112C,D thermostats provide electronic  
programmable control for 24 to 30 Vac heating and  
cooling systems.  
an area with good air circulation at average temperature.  
Do not install the thermostat where it can be affected by:  
drafts, or dead spots behind doors and in corners.  
hot or cold air from ducts.  
RECYCLING NOTICE  
 radiant heat from sun or appliances.  
 concealed pipes and chimneys.  
If this control is replacing a control that contains  
mercury in a sealed tube, do not place your old  
control in the trash.  
unheated (uncooled) areas such as an outside wall  
behind the thermostat.  
Contact your local waste management authority  
for instructions regarding recycling and the proper  
disposal of the old thermostat.  
Mounting Plate Installation  
Position mounting plate on the wall. Use a level to make  
sure mounting plate is level. Use a pencil to mark the two  
mounting holes. See Fig. 1.  
INSTALLATION  
WALL ANCHORS (2)  
When Installing this Product…  
WIRES THROUGH  
WALL OPENING  
1.  
Read these instructions carefully. Failure to follow  
them could cause a hazardous condition.  
Check the ratings given in the instructions and on  
the product to make sure the product is suitable for  
your application.  
WALL  
2.  
3
.
.
Installer must be a trained experienced service  
technician.  
After installation is complete, check out product  
operation as provided in these instructions.  
4
MOUNTING  
PLATE  
MOUNTING  
SCREWS (2)  
CAUTION  
M1718  
1.  
Disconnect power supply to prevent electrical  
shock or equipment damage.  
Fig. 1. Mounting plate installation.  
2.  
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.  
®
U.S. Registered Trademark  
Copyright © 1998 Honeywell Inc. •  
All Rights Reserved  
69-0917-2  
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T8112C,D ELECTRONIC PROGRAMMABLE THERMOSTATS  
1
.
Remove mounting plate from the wall, and drill  
/16 inch holes in wall (if drywall) as marked. For  
firmer material such as plaster or wood, drill  
/32 inch holes. Gently tap anchors (provided) into  
IMPORTANT  
When using a high efficiency furnace such as a  
3
90 percent or greater AFUE (Average Fuel  
Utilization Efficiency) unit, adjust screw A out  
one turn and screw B in.  
7
drilled holes until flush with the wall.  
2
.
.
Reposition mounting plate over holes, pulling  
wires through wiring opening. Loosely insert two  
mounting screws into holes.  
THERMOSTAT BACK  
A
B
C
ADJUST SCREWS THROUGH HOLES  
TO SELECT OPERATION DESIRED  
HEATING SYSTEM  
FUEL SWITCH  
POSITION  
WARM AIR  
FURNACE  
A–IN B–IN  
F
F
E
3
Level for appearance only; the thermostat will  
function properly even when not level. Tighten  
mounting screws. See Fig. 2.  
D
HOT WATER A–OUT B–IN  
BOILER  
1 TURN  
ELECTRIC  
FURNACE  
A–IN  
B–OUT  
1 TURN  
FOR HIGH EFFICIENCY FURNACE (90%+ AFUE)  
W
Y
G
ADJUST: SCREW A–OUT 1 TURN  
SCREW B–IN  
FUEL SWITCH – F POSITION  
LEVEL  
FUEL SWITCH  
F
E
R
Rc  
M3669  
Fig. 3. Back view of thermostat.  
Wiring Thermostat  
All wiring must comply with local electrical codes and  
ordinances. Refer to Fig. 4 through 7 for typical hookups. A  
letter code is located near each terminal for identification.  
See Table 1 for terminal cross referencing information.  
M1714A  
Fig. 2. Leveling mounting plate.  
Adjust Fan Operation Switch,  
as Required  
CAUTION  
Disconnect power before wiring to prevent  
electrical shock or equipment damage.  
The Thermostat fan operation switch, labeled FUEL  
SWITCH is factory set in the F position. See Fig. 4. This  
is the correct setting for most systems. If your system is  
an electric heat system, set the switch to E. The E setting  
allows the fan to turn on immediately with the heating or  
cooling in a system where the G terminal is connected.  
1. Connect the system wires to the thermostat. See  
Fig. 8. A letter code is located near each terminal  
for identification.  
NOTE: Hold the thermostat as shown in Fig. 9 to  
minimize need for wire extenders.  
Adjust System On-time, as Required  
The system on-time is factory-set for a warm air, gas or  
oil heating system. If you are installing it on another type  
of system, the system on-time must be adjusted  
accordingly by setting screws A and B on the back of the  
thermostat. Use the heating system table shown in Fig. 3  
as a guide. The system on-time should be optimized  
according to the type of system to minimize room  
temperature swings. Setting the screw out one turn  
means turning the screw approximately 360° or one  
complete turn. Setting the screw in means tightening the  
screw completely down.  
2
3
4
.
.
.
Securely tighten each terminal screw.  
Push excess wire back into the hole.  
Plug hole with nonflammable insulation to prevent  
drafts from affecting the thermostat.  
Table 1.Typical Wire Colors and Functions  
Thermostat  
Terminal  
Connect to  
Wire Color  
Green  
Yellow  
White  
a
Function  
Fan  
In the event that you want longer furnace on-time,  
readjust the screws A and B as follows:  
G
Y
Cooling  
Warm Air Furnaceset at the Hot Water setting (A—  
out one turn, Bin).  
W
Rc  
R
Heating  
Blue  
Air Cond. Power  
Furnace Power  
Electric FurnaceLeave at the Warm Air Furnace  
setting (Ain, Bin).  
Red  
a
Wire colors are typical; verify at heating/cooling  
equipment connection.  
NOTE: This thermostat does not have a setting for  
steam/gravity air. Cycles would not be long  
enough for accurate temperature control.  
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T8112C,D ELECTRONIC PROGRAMMABLE THERMOSTATS  
2-WIRE HEAT-ONLY (JUMPER INTACT)  
5-WIRE HEAT/COOL (JUMPER REMOVED)  
A
C
A
C
B
D
B
D
W
Y
G
JUMPER  
W
Y
G
R
Rc  
R
Rc  
HEATING  
RELAY OR  
VALVE COIL  
FAN  
RELAY  
HEATING  
RELAY OR  
VALVE COIL  
L1  
(
HOT)  
1
L2  
COOLING  
CONTACTOR  
COIL  
1
1
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
M1709B  
L1  
HOT)  
L1  
(HOT)  
L2  
(
L2  
Fig. 4.Typical hookup in two wire lead  
only (jumper intact) application.  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
M1711B  
Fig. 6.Typical hookup in five wire heat  
and cool (jumper removed) application.  
4-WIRE HEAT/COOL (JUMPER INTACT)  
A
C
B
D
3-WIRE COOL-ONLY (JUMPER INTACT)  
W
Y
G
JUMPER  
A
B
C
D
R
Rc  
W
Y
G
JUMPER  
HEATING  
RELAY OR  
VALVE COIL  
COOLING  
CONTACTOR  
COIL  
R
Rc  
FAN  
RELAY  
L1  
COOLING  
CONTACTOR  
COIL  
(
HOT)  
L2  
FAN  
RELAY  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
L1  
(HOT)  
L2  
M1710B  
Fig. 5.Typical hookup in four wire heat  
and cool (jumper intact) application.  
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND  
OVERLOAD PROTECTION AS REQUIRED.  
M848A  
Fig. 7.Typical hookup in three wire cool  
only (jumper intact) application.  
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T8112C,D ELECTRONIC PROGRAMMABLE THERMOSTATS  
T8112C  
JUMPER (FACTORY-  
INSTALLED) REMOVE  
IF 5-WIRE SYSTEM  
INSERT  
STRAIGHT  
UNDER  
SCREW HEAD  
5
(
/16 in.  
8 mm)  
STRIP  
A. ENGAGE TABS AT TOP OF  
THERMOSTAT AND MOUNTING PLATE.  
B. PRESS LOWER EDGE  
OF CASE TO LATCH.  
c R  
R
AM  
TULEAVE  
END OF WIRE  
VISIBLE HERE  
G
W
Y
M1712A  
Fig. 8. Proper wiring technique.  
M5780  
T8112D  
A. ENGAGE TABS AT TOP OF  
B. PRESS LOWER EDGE  
THERMOSTAT AND MOUNTING PLATE.  
OF CASE TO LATCH.  
M3002A  
Fig. 9. Holding thermostat while installing.  
C. SWING COVER OPEN TO  
CHECK OPERATION.  
Mounting Thermostat on Mounting Plate  
1.  
Engage tabs at the top of thermostat and mounting  
plate. See Fig. 10.  
2.  
Press lower edge of case to latch.  
NOTE: To remove the thermostat from the wall, first  
pull out at the bottom of the thermostat; remove  
top last.  
M13063  
Fig. 10. Mounting thermostat on mounting plate.  
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T8112C,D ELECTRONIC PROGRAMMABLE THERMOSTATS  
As the batteries are running low, a bAt Loindicator flash  
for one to two months before batteries run out completely.  
Replace the batteries as soon as possible after the  
indicator starts flashing. If the batteries are not replaced  
sometime during the flashing bAt Lo,the indicator  
eventually stops flashing. bAt Lowill stay on without  
flashing, indicating the thermostat and heating/cooling  
system have stopped working and the batteries are almost  
completely dead.  
Installing Batteries  
IMPORTANT  
Batteries must be installed for programming and  
operation of the thermostat and heating/cooling  
system.  
1.  
Use two AA alkaline batteries; nonalkaline  
batteries will not last as long, and can leak,  
causing damage to the thermostat or wall surface.  
Energizer batteries are recommended.  
After the batteries are completely dead, the bAt Lo”  
indicator disappears, leaving a completely blank display.  
2.  
3.  
4.  
Make sure the thermostat is set in the OFF position.  
Use a coin to remove the battery door. See Fig. 11.  
To remove, press down on left ends of batteries. If the  
new batteries are installed within 20 to 30 seconds of  
removing the old ones, the thermostat does not have to  
be reprogrammed. If the display is blank, the batteries  
are dead or incorrectly installed and the thermostat has  
to be reprogrammed. See Owners Manual for  
programming instructions.  
Install the new batteries making sure positive and  
negative terminals are oriented correctly. See  
Fig. 12.  
5.  
Replace battery door.  
SETTINGS  
Current Time/Day  
To set time, press and release the Set Clock/Day key  
once. Press the Time keys until the current time shows.  
To set day, press and release the Set Clock/Day key  
again. Press the Time keys until the current day shows.  
Press Run Program key.  
See Owners Manual for complete programming  
instructions.  
M5781  
Fan Switch  
FAN AUTO: Normal setting for most homes. A single-  
speed fan turns on automatically with the air conditioner  
of furnace. A two-speed fan usually runs on high with  
the air conditioner and on low with the furnace.  
Fig. 11. Removing battery door.  
INSTALL TWO AA ALKALINE  
BATTERIES AS SHOWN  
NOTE: When Fan Operation Switch on the back of the  
thermostat is in E position, the fan operates with  
the furnace only.  
AM  
TU  
LEAVE  
FAN ON: The fan runs continuously. Used for improved  
air circulation during special occasions or for more  
efficient electronic air cleaning.  
Fan Auto On  
System Cool Off Heat  
System Switch  
System switching positions control thermostat operation  
as follows:  
FAN SWITCH  
SYSTEM  
SWITCH  
COOL: The thermostat controls the air conditioning  
system.  
OFF: Both the heating and air conditioning systems  
are off.  
M5782  
Fig. 12. Installing batteries.  
HEAT: The thermostat controls the heating system.  
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T8112C,D ELECTRONIC PROGRAMMABLE THERMOSTATS  
CHECKOUT  
Heating  
Fan  
Move the thermostat system switch to OFF and the fan  
switch to ON. The fan should run continuously. With the  
system switch still in the OFF position, move the fan  
switch to AUTO; the fan should stop.  
Do not check heating system operation by jumpering  
thermostat terminals at the primary control such as the  
gas valve, zone valve, or oil burner control This will  
damage the thermostat. Instead, you could jumper R  
and R wires at the thermostat.  
Move the system switch to HEAT and the fan switch  
to AUTO.  
Press key until the setting is about 10°F (6°C) above room  
temperature. Heating should start and the fan should run  
after a short delay (immediately if fan operation switch is  
set in E position).  
Cooling  
To avoid possible compressor damage, do not operate  
the cooling system when outside temperature is below  
5
0°F (10°C). See compressor manufacturer instructions  
Press key until setting is about 10°F (6°C) below room  
temperature. The heating equipment should shut off.  
for further information.  
NOTE: When cooling setting is changed, thermostat  
can delay up to five minutes before turning on  
the air conditioner. This delay protects the  
compressor.  
Move the system switch to COOL and the fan switch  
to AUTO.  
Press key until setting is about 10°F (6°C) below room  
temperature. The cooling equipment and fan should start.  
Press key until the setting is about 10°F (6°C) above room  
temperature. The cooling equipment and fan should stop.  
Move the system switch to OFF and the fan switch to  
AUTO. The system and fan should be off.  
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T8112C,D ELECTRONIC PROGRAMMABLE THERMOSTATS  
TROUBLESHOOTING GUIDE  
If…  
Then…  
Display will not come on.  
Set the system switch to OFF. Remove batteries. Insert batteries  
backward for at least five seconds to reset thermostat. Correctly replace  
batteries. Display should come on.  
Make sure batteries are fresh and installed correctly.  
Gently clean battery contacts using a soft pencil eraser. Do not use  
anything abrasive on the clips.  
Temperature display will not go lower  
than 45° F (7° C) or higher than 88° F  
The temperature setting limit is reached. The setting range is 45° F to  
88° F (7° C to 31°C).  
(31° C) during programming.  
Temperature change occurs at the  
wrong times.  
Check the program times for the period in question. Be sure that AM and  
PM indications are correct. Make sure the current day and time are  
correct. Reprogram if necessary.  
Heating will not come on.  
Check that switch on thermostat is set to HEAT. Allow a minimum of five  
minutes for time guard protection to expire.  
Check the system fuse or circuit breaker and replace or reset if  
necessary.  
Check for correct wiring and good connections.  
Disconnect and jumper wires R and W. If heat does not come on, check  
out the heating system.  
If display is blank or says bAt Lo,install fresh batteries.  
Cooling will not come on.  
Check that switch on thermostat is set to COOL. Allow a minimum of five  
minutes for time guard protection to expire.  
Check the system fuse or circuit breaker and replace or reset if  
necessary.  
Check for correct wiring and good connections.  
Disconnect and jumper wires R and Y. If cooling does not come on,  
check out the cooling system.  
If display is blank or says bAt Lo,install fresh batteries.  
The thermostat has a built-in time delay on cooling. Allow at least five  
minutes after changing the setting before the air conditioner starts.  
Make sure outdoor disconnect is engaged (on).  
If temperature setting is lower than current temperature, and SYSTEM  
ON indicator is lit, move system switch from COOL to OFF for ten  
minutes. After ten minutes, return switch to COOL position. If air  
conditioner comes on, compressor could have reached its high limit  
temperature protection and shut down.  
If 2- or 4-wire installation, verify that R-Rc jumper is installed  
Too warm or too cool.  
Press Run Program key to check the current temperature setting.  
If desired, change the temperature setting. See the Owners Manual.  
SYSTEM ON indicator is lit, but no heat  
is coming from the registers.  
Allow time for the furnace to heat up and the fan to come on before  
checking for heat at the register. (Check to make sure the Cycle Rate in  
the Installation section is correct.)  
Thermostat current temperature setting  
does not match the display temperature  
to within ± 1°.  
Check that the wiring hole in the wall behind the wallplate has been  
plugged with insulation to prevent drafts that might adversely affect  
thermostat operation.  
Be aware that it is normal for the current setting and display temperature  
to differ on occasion.  
During recovery from setback or setup, setting and display temperatures  
can differ for up to 30 minutes after recovery period.  
bAtLo remains on display after batteries Remove batteries. Wait one hour. Install fresh Alkaline batteries.  
are installed.  
NOTICE  
This equipment is a Class B digital apparatus, which complies with Canadian Radio Interference Regulations, CRC  
c.1374.  
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Home and Building Control  
Honeywell Inc.  
Honeywell Plaza  
Home and Building Control  
Honeywell Limited-Honeywell Limitée  
155 Gordon Baker Road  
North York, Ontario  
P.O. Box 524  
Minneapolis, MN 55408-0524  
M2H 3N7  
69-09172 G.H. Rev. 4-98 Printed in Mexico  
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