Honeywell T8112C User manual

® U.S. Registered Trademark
© 2004 Honeywell International Inc.
All Rights Reserved 69-0862—4
Electronic Programmable
Thermostat
Owner’s Manual

2 69-0862—4
Table of Contents
Programming Your Thermostat ........................................................................ 3
Program Schedule........................................................................................... 5
Set Current Time/Day...................................................................................... 6
Heating Program ............................................................................................. 6
Cooling Program.............................................................................................. 7
Operating Your Thermostat................................................................................ 7
Using Programming Features.......................................................................... 7
Setting Fan Switch........................................................................................... 8
Setting System Switch..................................................................................... 9
Maintaining Your Thermostat ............................................................................ 9
Installing Batteries ........................................................................................... 9
Troubleshooting Guide...................................................................................... 12
Limited One-Year Warranty ............................................................................... 17

3 69-0862—4
Programming Your Thermostat
When batteries are installed, your thermostat
can be programmed in your hand before it is
installed or after it is mounted on the wall. For
instructions on installing or replacing the
batteries, refer to Maintaining Your Thermostat
section.
Refer to the Program Schedule section to
program your time and temperature settings for
various times of the day.
Four time periods are available during
workdays: WAKE, LEAVE, RETURN, and
SLEEP. During weekends, only the WAKE and
SLEEP time periods are available. View these
periods individually on the display when you
press the Set Schedule key.
WAKE is the time the thermostat turns on the
heating/cooling equipment after an energy
saving period. When deciding what time to
set for your WAKE period, include extra lead
time, depending on the outside temperature
and your furnace response time, to give the
furnace a head start to heat the house
before you get up. (This will be a higher tem-
perature during heating season, and a lower
temperature during cooling season.)
LEAVE is the time period you can set for an
energy-saving temperature while you are
away at work or school. (This will be a lower
temperature during heating season, and a
higher temperature during cooling season.)
RETURN is the time the thermostat turns on the
heating/cooling equipment after an energy
saving period. When deciding what time to
set for your RETURN period, include extra
lead time, depending on the outside temper-

4 69-0862—4
ature and your furnace response time, to
give the furnace a head start to heat the
house before you arrive home.
SLEEP is the time period you can set for an
energy-saving temperature while you are
sleeping. (For more comfortable sleeping,
some people choose not to raise the cool
temperature during the night.)
You will set one schedule for weekdays and
another for weekends because your
requirements will probably be different for each.
Fill in the times and temperatures you desire for
weekdays and weekends. If you decide not to
program the thermostat, it automatically
controls heating at 68°F (20°C) and cooling at
78°F (20°C), 24 hours a day. Also, you do not
need to enter a time and temperature program
for all periods if your schedule does not require
it. For example, a house that is occupied during
weekdays would only require programs for
WAKE and SLEEP.
When pressing the keys, use the ball of your
finger or a soft pencil eraser.
NOTE: Use of sharp fingernails or pencil
points can damage the keypad.
If you make an error at any time during
programming, just press the Run Program key,
and continue again at the last step.

5 69-0862—4
Program Schedule
Heating Program Schedule
aWAKE and RETURN start times should include extra lead time, based on outside temperature and furnace
response time, to give your furnace a head start to heat the house.
b The temperatures cannot be set higher than 88°F (26°C) or lower than 45°F (7°C).
Weekdays Start Time Heating TemperaturebCooling Temperatureb
WAKE a
LEAVE
RETURNa
SLEEP
Weekends
WAKE a
SLEEP

6 69-0862—4
NOTE: If you decide not to program the thermostat, it will automatically control heating at 68°F
(20°C), and cooling at 78°F (26°C), 24 hours a day. This guide can be used for program-
ming your new thermostat.
IMPORTANT
Batteries are required for operation
and programming. When inserting
batteries, set the System switch to Off.
Remove the battery door (on the
thermostat left side) using a coin at the
bottom. See Maintaining Your Ther-
mostat section.
Set Current Time/Day
To set time, press and release Set Clock/Day
key once. Press Time keys until current time
shows.
To set the day, press and release the Set
Clock/Day key again. Press Time keys until
current day shows. Press Run Program key.
Heating Program
With the System switch set to Heat, press and
release the Set Schedule key once. WAKE,
Mon-Fri, and SET appear on the display.
Use Time keys to program WAKE time and
Temp keys to program WAKE temperature for
Mon-Fri. Repeat sequence for LEAVE,
RETURN, and SLEEP.

7 69-0862—4
Press Set Schedule key until WAKE, SA SU
and SET appear on the display. Use Time keys
to program WAKE time and Temp keys to
program WAKE temperature for Sat-Sun.
Repeat the sequence for SLEEP.
Cooling Program
WIth System switch at Cool, follow the same
instructions as for the Heating Program.
After programming, adjust the Fan and System
switches, as desired. Press and release Run
Program key to start the program.
Operating Your Thermostat
Using Programming Features
Temporarily Change temperature for current
period only—
Press Temp keys to set desired
temperature. The change cancels itself at
the next scheduled program change; to
cancel sooner, press Run Program key.
M8473
Auto On
Fan Cool Off Heat
System
T U
AM
LE A VE
USE TO
SET CURRENT
DAY AND TIME
USE TO SET
PROGRAM PERIOD
USE TO SET
TIME LATER
USE TO
SET COOLER
TEMPERATURE
USE TO SET
WARMER TEMPERATURE
LCD DISPLAY
USE TO SET
TIME EARLIER RUN
PROGRAM
KEY
HOLD
TEMP
KEY

8 69-0862—4
Hold a temperature indefinitely—Press
Hold Temp key once. Press Temp keys
until display shows desired temperature.
Press Run Program key once to return to
the program.
Check Current Temperature Setting—Press
Run Program key once. If using Temporary
Change or Hold features, pressing this key
cancels your change.
Check Programs—Press Set Schedule key
repeatedly to see each time and tempera-
ture. Press Run Program key once to return
to the program.
Cancel a program—Press Set Schedule key
until the program to cancel shows. Pressing
the two Time keys together cancels the
program.
Permanently Change a program—Repeat the
steps in the Heating Program or Cooling
Program sections, as applicable.
Return to the normal program or the starting
program—Press Run Program key once.
Setting Fan Switch
Fan switching positions are:
Auto: Normal setting for most homes. A single-
speed fan turns on automatically with the air
conditioner or furnace. A two-speed fan
usually runs on high with the air conditioner
and runs on low with the furnace.
On: Fan runs continuously. Use for improved
air circulation during special occasions or for
more efficient electronic air cleaning.

9 69-0862—4
Setting System Switch
System switching positions control thermostat
operation:
Cool: Thermostat controls air conditioning
system.
Off: Both heating and air conditioning systems
are off.
Heat: Thermostat controls heating system.
Maintaining Your Thermostat
Installing Batteries
IMPORTANT
Batteries must be installed for pro-
gramming and operation of the ther-
mostat and heating/cooling system.
1. Purchase two AA alkaline batteries; non-
alkaline batteries do not last as long and
can leak, causing damage to the thermo-
stat or wall surface.
2. Make sure the thermostat is set in the Off
position.
3. Use a coin to remove the battery door.
4. Install the fresh batteries, making sure
the positive and negative terminals are
oriented correctly.
M5783
Auto On
Fan Cool Off Heat
System
FAN SWITCH SYSTEM
SWITCH
T U
AM
LE A VE

10 69-0862—4
5. Replace the battery door.
As batteries are running low, bATLo indicator
flashes for one to two months before batteries
run out completely. Replace batteries as soon
as possible after indicator starts flashing.
After batteries are completely dead, bAtLo
indicator disappears, leaving the display
completely blank and the heating and/or cooling
system not operating.
M5781
INSTALL TWO AA ALKALINE
BATTERIES AS SHOWN
M5782
Auto On
Fan Cool Off Heat
System
FAN SWITCH SYSTEM
SWITCH
T U
AM
LE A VE

11 69-0862—4
To remove batteries, press down on the left
ends. 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 Programming Your
Thermostat section for instructions.

12 69-0862—4
Troubleshooting Guide
If... Then...
Display does not come on. • Set the System switch to Off. Remove batteries. Insert
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 does not go
lower than 45°F (7°C) or higher than
88°F (31°C) during programming.
•The temperature setting limit is reached. The setting
range is 45 to 88°F (7 to 31°C).
Temperature change occurs at the
wrong times.
•Check 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.

13 69-0862—4
Heating does not come on. • Check that System 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.
•If display is blank or displays bAtLo, install fresh
batteries.
•If temperature setting is higher than current
temperature, and System On indicator is lit, contact
your local dealer.
Cooling does not come on. • Check that System 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.
•If display is blank or displays bAtLo, install fresh
batteries.
If... Then...

14 69-0862—4
Cooling does not come on (Cont) • 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 the Cool position. If the air
conditioner comes on, the compressor could have
reached its high-limit temperature protection and shut
down. If air conditioner does not come on after ten
minutes and the System On indicator is lit, contact your
local dealer.
•If two- or four-wire installation, verify that R-Rc jumper
is installed.
If... Then...

15 69-0862—4
Too warm or too cool. • Press Run Program key to check the current
temperature setting.
•If desired, change the temperature setting. See
Programming Your Thermostat section.
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.
Thermostat current temperature
setting does not match the display
temperature to within +/- 1°.
•Check that the wiring hole in the wall behind the
wallplate was plugged with insulation to prevent drafts
that could adversely affect thermostat operation.
•Be aware that it is normal for the current setting and
display temperature to differ occasionally.
•During recovery from setback or setup, setting and
display temperature can differ for up to 30 minutes
after the recovery period.
Incorrect temperature showing on
thermostat display.
•The thermostat is factory-calibrated and cannot be
adjusted.
If... Then...

16 69-0862—4
NOTICE
This equipment is a Class B digital apparatus, which complies with Canadian Radio Interference
Regulations, CRC c.1374.
bAtLo remains on display after fresh
batteries are installed.
•Remove the batteries. Wait one hour. Install fresh
alkaline batteries.
If... Then...

17 69-0862—4
Limited One-Year Warranty
Honeywell warrants this product 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 where 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:
In the U.S:
Honeywell Return Goods, Dock 4, MN 10-3860,
1985 Douglas Drive, Golden Valley, MN 55422.
In Canada:
Honeywell Limited/Honeywell Limitée
35 Dynamic Drive, Scarborough, Ontario M1V 4Z9

18 69-0862—4
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 TWO-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; you may have other rights that vary from state to state.
If you have any questions concerning this warranty, please write Honeywell Customer Care, 1985
Douglas Drive North, Golden Valley, MN 55422 or call 1-800-468-1502.

19 69-0862—4

69-0862—4 J.S. Rev. 10-04 www.honeywell.com/yourhome
Automation and Control Solutions
Honeywell International Inc. Honeywell Limited-Honeywell Limitée
1985 Douglas Drive North 35 Dynamic Drive
Golden Valley, MN 55422 Scarborough, Ontario
M1V 4Z9