Honeywell RTH6400 Series User manual

Operating
Manual
RTH6400
Programmable Thermostat
69-2211ES-01

Read and save these instructions.
Need Help?
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 69-2211ES—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
69-2211ES—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 69-2211ES—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
69-2211ES—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 69-2211ES—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
69-2211ES—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 69-2211ES—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
69-2211ES—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