Honeywell 6400 D Manual

RTH6400 Programmable Thermostat
 9 69-2211EF—05
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...

Operating Manual
69-2211EF—05 10
Energy saving settings for maximum cost savings
This thermostat is pre-set to use energy saving program settings. We recommend these 
settings, since they can reduce your heating/cooling expenses. (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 °...

RTH6400 Programmable Thermostat
 11 69-2211EF—05
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 &...

Operating Manual
69-2211EF—05 12
M28410
Heat
Setting
Inside
AM
69756:
30
Te mporary
Run Schedule
Auto
Fan
System
Heat
Program schedule override (temporary)
Press s or t to 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...

RTH6400 Programmable Thermostat
 13 69-2211EF—05
M28411
Heat
Setting
Inside
AM
69756:
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	 pro-
gram 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...

Operating Manual
69-2211EF—05 14
Use this feature in climates where both air conditioning and heating are used on t\
he 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 permanently) 
the thermostat will automatically adjust the cooling and heating settings to mai\
ntain a 
3-degree separation between the cool and heat settings.
For example, if...

RTH6400 Programmable Thermostat
 15 69-2211EF—05
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/Coo l
Heat
Setting
Inside
PM
73731:
05
Te mporary
M27477
Press Select Heat/Cool to...

Operating Manual
69-2211EF—05 16
M28412
 
Cool On Coo
l
Setting
Inside
AM75756:
30
Set  Clock/Day/
Schedule Auto
Fan
System
Cool
Built-in compressor protection
This feature helps prevent damage to the com-
pressor 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...

RTH6400 Programmable Thermostat
 17 69-2211EF—05
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...

Operating Manual
69-2211EF—05 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 bat-
teries 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...