Honeywell RTH6400 Series User manual

Operating
Manual
RTH6400
Programmable Thermostat
69-2211EF-01

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For assistance with this product please visit http://DIYthermostats.honeywell.com
or call Honeywell Customer Care toll-free at 1-800-468-1502
® U.S. Registered Trademark.
US Patent No. D542,677 and other patents pending
Copyright © 2008 Honeywell International Inc. All rights reserved.
M28400
Quick Reference Card
Grasp and pull to see basic
operating instructions at a
glance.
Battery Holder
Press down and pull to
remove batteries.
Batteries should be
replaced once a year
(see page 15).
NOTE: Remove battery holder; model number is on the battery holder.

RTH6400 Programmable Thermostat
1 69-2211EF—01
About your new thermostat
About your new thermostat
Thermostat features...................................2
Programming at a glance .......................... 3
Quick reference to controls.......................4
Quick reference to display ........................5
Programming & Operation
Set time and day........................................6
Select fan setting (auto/on) ......................7
Select system setting (heat/cool)..............8
Using program schedules .........................9
Program schedule overrides ...................12
Auto Changeover .....................................14
Built-in compressor protection ...............16
Smart Response®Technology .................17
Appendices
Battery installation...................................18
Customer assistance ...............................19
In case of difficulty...................................20
Limited warranty ......................................22
This thermostat is ready to go!
Your new thermostat is pre-programmed
and ready to go.
See page 3 to check settings.
Table of contents

Operating Manual
69-2211EF—01 2
About your new thermostat
Congratulations on the purchase of your new Honeywell thermostat. It has been
designed to give you many years of reliable service and easy-to-use, push-button
climate control.
Features
• Separately programmable weekday, Saturday, and Sunday schedules.
• One-touch temp control overrides program schedule at any time.
• EnergyStar®compliant to greatly reduce your heating/cooling expenses.
• Large, clear, backlit display is easy to read — even in the dark.
• Displays both room temperature and temperature setting.
• Removable battery holder for fast, easy replacement.
• Built-in compressor protection.

RTH6400 Programmable Thermostat
3 69-2211EF—01
This thermostat is ready to go!
Your new thermostat is pre-programmed and ready to go. All you have to do is set the
time and day. Then check the settings below and change if needed:
1. Set time and day (required for proper operation).........................See page 6
2. Select fan setting (Auto/On): Preset to Auto.................To change, see page 7
3. Select system setting (Heat/Cool): Preset to Heat ......To change, see page 8
4. Program schedules: Preset to energy-saving levels
while you’re at work or asleep (assumes you wake at
6 am, leave at 8 am, return at 6 pm and go to bed
at 10 pm) ......................................................................To change, see pages 9-11
ONE-TOUCH TEMP CONTROL: You can override the program schedule at any time, and
manually adjust the temperature (see pages 12-13).

Operating Manual
69-2211EF—01 4
Quick reference to controls
M28401
Digital display (see page 5). Battery holder (see page 15).
Temperature buttons
Press to adjust temperature
settings (see pages 11-13).
Hold button
Press to override programmed
temperature control (see page 13).
Function buttons
Press to select the function displayed just above each button.
(Functions change depending on the task.)

RTH6400 Programmable Thermostat
5 69-2211EF—01
Quick reference to display screen
Set Clock/Day/
Schedule
Auto
Wake Wed
Fan System
Heat On
Heat
Heat
Setting
Inside
AM
75
75
6:30
Replace Battery
M28402
In Recovery
Current inside temperature
Current program period
Wake/Leave/Return/Sleep
(see pages 9-11)
Set clock/day/schedule
Press to set time, day or
program schedules (see
pages 6 & 11)
Function buttons
Press the button beneath each function to view or change
settings (functions change depending on the task)
Low battery warning
(see page 15) Current time/day
(see page 6)
Temperature setting
(see pages 11-13)
System status
On when “calling” for
heating or cooling;
flashes when waiting for
compressor restart (see
page 14)
System setting
Heat/Cool/Off
(see page 8)
Fan setting
Auto/On (see page 7)
Smart Response®
technology in effect
(see page 17)

Operating Manual
69-2211EF—01 6
M28404
Wed
Set Day Set Schedule
Done
PM
4:30
Set Clock/Day/
Schedule
Auto
Fan System
Heat
M28403
Set the time and day
1. Press the SET CLOCK/DAY/SCHEDULE
button, then press s or t to set
the clock time.
2. Press the SET DAY button, then
press s or t to select the day of
the week.
3. Press DONE to save & exit.
Note: If the SET CLOCK/DAY/SCHEDULE
option is not displayed, press DONE or
RUN SCHEDULE.
Note: If the display flashes Set Clock, the
thermostat will follow your settings for
the weekday “Wake” time period until you
reset the time and day.
Press SET CLOCK/DAY/SCHEDULE, then adjust time
Press SET DAY, then select current day

RTH6400 Programmable Thermostat
7 69-2211EF—01
Select the fan setting
Press the FAN button to select Auto or On.
In “Auto” mode (the most commonly used
setting), the fan runs only when the heat-
ing or cooling system is on. If set to “On,”
the fan runs continuously.
M28405
Set Clock/Day/
Schedule
Auto
Fan System
Heat
M28406
Set Clock/Day/
Schedule
On
Fan System
Heat

Operating Manual
69-2211EF—01 8
Select the system setting
Press the SYSTEM button to select Heat, Cool
or Off.
• Heat: Thermostat controls only the
heating system.
• Cool: Thermostat controls only the
cooling system.
• Off: Heating and cooling systems are off.
• Auto: Thermostat automatically selects
heating or cooling depending on the
indoor temperature.
CAUTION: EQUIPMENT DAMAGE
HAZARD. To prevent possible
compressor damage, do not operate
cooling system when outdoor
temperature is below 50°F (10°C).
Note: The Auto setting may not
appear, depending on how your
themostat was installed.
M28407
Set Clock/Day/
Schedule
Auto
Fan System
Heat
M28408
Set Clock/Day/
Schedule
Auto
Fan System
Cool

RTH6400 Programmable Thermostat
9 69-2211EF—01
Save money by setting program schedules
It’s easy to program your system for maximum energy savings. You can program four
time periods each day, with different settings for weekdays, Saturday and Sunday.
Set to the time you awaken and the temperature you want
during the morning, until you leave for the day.
Set to the time you leave home and the temperature you
want while you are away (usually an energy-saving level).
Set to the time you return home and the temperature you
want during the evening, until bedtime.
Set to the time you go to bed and the temperature you want
overnight (usually an energy-saving level).
WAKE
6:00 am
70 °
LEAVE
8:00 am
62 °
RETURN
6:00 pm
70 °
SLEEP
10:00 pm
62 °

Operating Manual
69-2211EF—01 10
EnergyStar®settings for maximum cost savings
This thermostat is pre-set to use EnergyStar®program settings. We recommend these
settings, since they can reduce your heating/cooling expenses by as much as 33%.
(See next page to adjust times and temperatures of each time period.)
Wake
(6:00 am)
Leave
(8:00 am)
Return
(6:00 pm)
Sleep
(10:00 pm)
Cool (Mon-Fri)Heat (Mon-Fri) Heat (Sat-Sun) Cool (Sat-Sun)
70 °75 °70 °75 °
62 °83 °62 °
[Or cancel period]
83 °
[Or cancel period]
70 °75 °70 °
[Or cancel period]
75 °
[Or cancel period]
62 °78 °62 °78 °

RTH6400 Programmable Thermostat
11 69-2211EF—01
To adjust program schedules
1. Press SET CLOCK/DAY/SCHEDULE, then SET
SCHEDULE.
2. Press s or t to set your weekday Wake
time (Mon–Fri), then press NEXT.
3. Press s or t to set the temperature for this
time period, then press NEXT.
4. Set time and temperature for the next time
period (Leave). Repeat steps 2 and 3 for each
weekday time period.
5. Press NEXT to set Saturday time periods.
6. Press NEXT to set Sunday time periods, then
press DONE to save & exit.
Note: Make sure the thermostat is set to the system
you want to program (Heat or Cool).
Note: You can press CANCEL PERIOD to eliminate
unwanted time periods (except Wake).
M28409
Set Clock/Day/
Schedule
Auto
Fan System
Heat
Set Day Set Schedule
Done
Mon Tue Wed Thu FriLeave
Set Schedule
Heat
Setting
AM
62
8:00
Done CancelPeriod Next

Operating Manual
69-2211EF—01 12
M28410
Heat
Setting
Inside
AM
69
75
6:30
Temporary
Run Schedule
Auto
Fan System
Heat
Program schedule override (temporary)
Press s or tto immediately adjust
the temperature. This will temporarily
override the temperature setting for the
current time period.
The new temperature will be
maintained only until the next
programmed time period begins (see
page 10). For example, if you want to
turn up the heat early in the morning, it
will automatically be lowered when you
leave for the day.
To cancel the temporary setting at any
time, press RUN SCHEDULE.
Press to cancel temporary setting and
resume program schedule.
Note: Make sure the thermostat is set
to the system you want to control (heat
or cool).
Press to temporarily adjust temperature.

RTH6400 Programmable Thermostat
13 69-2211EF—01
M28411
Heat
Setting
Inside
AM
69
75
6:30
Run Schedule
Auto
Fan System
Heat
Hold
Program schedule override (permanent)
Press HOLD to permanently adjust
the temperature. This will override
the temperature settings for all time
periods.
The “Hold” feature turns off the
program schedule and allows you
to adjust the thermostat manually,
as needed.
Whatever temperature you set will
be maintained 24 hours a day until
you manually change it, or press
RUN SCHEDULE to cancel “Hold” and
resume the programmed schedule.
Press to cancel “Hold” setting and
resume program schedule.
Note: Make sure the thermostat is set
to the system you want to control (heat
or cool).
Press to permanently adjust temperature.

Operating Manual
69-2211EF—01 14
Use this feature in climates where both air conditioning and heating are used on the
same day. When the system mode is in Auto, the thermostat automatically selects
heating or cooling depending on the indoor temperature.
While in the Auto mode, if a schedule override takes place (temporarily or perma-
nently) the thermostat will automatically adjust the cooling and heating settings to
maintain a 3-degree separation between the cool and heat settings.
For example, if the heat temperature is raised to where it gets within 3-dgrees of the
cool setting, the display will show an up arrow next to “cool” to show the thermostat
is raising the cool setting up to maintain a 3-dgreee separation.
Press the Select Heat/Cool button to select between the heat and cool to view/adjust
either mode.
Auto Changeover

RTH6400 Programmable Thermostat
15 69-2211EF—01
If the cool temperature is lowered to where it gets close to the heat setting, an arrow
next to heat will show the thermostat is lowering the heat setting down to maintain a
3-degree separation.
Auto Changeover
CAUTION: To avoid possible compressor damage, do not use Auto
Changeover if the outside temperature drops below 50ºF (10ºC).
Run Schedule
Auto
Cool
Fan Select
Heat/Cool
Heat
Setting
Inside
PM
73
73
1:05
Temporary
M27477
Press Select Heat/Cool to set the heat or cool
temperature.
The triangle indicates the cool temperature is
increasing to maintain 3 degrees between heat
and cool settings.

Operating Manual
69-2211EF—01 16
M28412
Cool On
Cool
Setting
Inside
AM
75
75
6:30
Set Clock/Day/
Schedule
Auto
Fan System
Cool
Built-in compressor protection
This feature helps prevent damage to the
compressor in your air conditioning or heat
pump system.
Damage can occur if the compressor is
re-started too soon after shutdown. This
feature forces the compressor to wait a few
minutes before restarting.
During the wait time, the display will flash
the message Cool On (or Heat On if you have
a heat pump). When the safe wait time has
elapsed, the message stops flashing and the
compressor turns on.
Message flashes until safe restart
time has elapsed.

RTH6400 Programmable Thermostat
17 69-2211EF—01
Smart Response®Technology: This feature
allows the thermostat to “learn” how long
the furnace and air conditioner take to reach
programmed temperature settings, so the
temperature is reached at the time you set.
For example: Set the Wake time to 6 am, and
the temperature to 70°. The heat will come
on before 6 am, so the temperature is 70°
by the time you wake at 6. The message “In
Recovery” is displayed when the system is
activated before a scheduled time period.
Smart Response®Technology
M27476
Cool On
Cool
Setting
Inside
AM
75
75
6:38
Set Clock/Day/
Schedule
Auto
Fan System
Cool
In Recovery
Displays when Smart Response is active.

Operating Manual
69-2211EF—01 18
About your new thermostat
M28414
M28413
Replace Battery
Battery replacement
Install fresh batteries immediately when the
REPLACE BATTERY warning begins flashing. The
warning flashes about two months before the
batteries are depleted.
Even if the warning does not appear, you
should replace batteries once a year, or before
leaving home for more than a month.
If batteries are inserted within two minutes, the
time and day will not have to be reset. All other
settings are permanently stored in memory and
do not require battery power.
Press down and pull to remove.
Insert fresh AA alkaline
batteries, then reinstall
battery holder.