Honeywell 6400 D Manual

Operating 
Manual
RTH6400
Programmable Thermostat 
69-2211EF-05  

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For assistance with this product please visit http://yourhome.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 © 2013 Honeywell International Inc. All rights reser ved.
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...

RTH6400 Programmable Thermostat
 1 69-2211EF—05
About your new thermostat
  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
About your new thermostatThermostat features ....................................2Programming at a glance ............................3Quick reference to controls .........................4Quick reference to display ...........................5
Programming & OperationSet time and day...

Operating Manual
69-2211EF—05 2
About your new thermostatAbout 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.
•	 Large,	 clear,	backlit	 display	 is	easy	 to	read	 —	even	 in	the	 dark.
•	 Displays	 both...

RTH6400 Programmable Thermostat
 3 69-2211EF—05
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...

Operating Manual
69-2211EF—05 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—05
Quick reference to display screen
Set Clock/Day/
Schedule Auto
W
ake Wed
Fan SystemHeat On
Heat Heat
Setting
Inside
AM
75756:
30
Replace Battery
M28402
In Recovery
Current inside temperature
Current program periodWake/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...

Operating Manual
69-2211EF—05 6M28404
Wed
Set  Day Set Schedule
Done
PM4
:
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 D AY 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...

RTH6400 Programmable Thermostat
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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 heating 
or	cooling	 system	is	on.	 If	set	 to	“On,”	 the	
fan runs continuously. M28405
Set Clock/Day/
ScheduleAuto
Fan
System
Heat
M28406
Set  Clock/Day/
ScheduleOn
Fan
System
Heat 

Operating Manual
69-2211EF—05 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)....