Honeywell RTH221 Series User manual

69-2388ES-03
RTH221
1-day Programmable Thermostat
Operating
Manual

Read and save these instructions.
CAUTION: EQUIPMENT DAMAGE HAZARD
To prevent possible compressor damage, do not use Cooling mode when the
outdoor temperature is below 50°F (10°C).
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.

Programmable Thermostat RTH221
Overview
Thermostat features ..............................2
Quick start .............................................3
Quick reference to controls ...................4
Quick reference to display.....................5
Programming & Operation
Setting the clock....................................6
System switch (Heat/Cool)....................7
Fan switch (Auto/On).............................8
Using the schedule...........................9-11
Temporary schedule override..............12
Permanent schedule override .............13
Compressor protection........................14
Appendices
Battery replacement ........................... 15
In case of difficulty .............................. 16
Customer assistance .......................... 17
One-year limited warranty .................. 18
Table of contents
Your new thermostat is pre-programmed
and ready to go!
See page 3 for quick start.

Operating Manual
2
Your new thermostat has been designed to give you many years of reliable service and
easy-to-use, push-button climate control.
Features
• Displays ambient (measured) temperature at all times
• One-touch access to setpoint temperature
• Daily heating/cooling schedule to greatly reduce your heating/cooling expenses
• Temporary and permanent override of schedule
• Built-in compressor protection
About your new thermostat

Programmable Thermostat RTH221
3
Simply perform the three steps below and the thermostat is in operation:
1 Set the clock ................................................................................................ See page 6
2 Select whether to heat or cool...................................................................... See page 7
3 Select whether to run the fan continuously or only when needed................ See page 8
Your thermostat is pre-programmed with a daily heating/cooling schedule. If you do not
wish to use these settings, you can:
Modify the schedule ....................................................................................See page 11
Temporarily override the schedule ............................................................. See page 12
Permanently override the schedule............................................................ See page 13
This thermostat is ready to go

Operating Manual
4
Quick reference to controls
System switch (see page 7)
•Cool: System is in Cooling mode.
•Off: System is off.
•Heat: System is in Heating mode.
Fan switch (see page 8)
•On: Fan runs continuously.
•Auto: Fan runs only when
heating or cooling is activated.
Up/Down buttons
Press to adjust temperature.
Press to set clock, day or
schedule (see pages 6 & 11).
Press to override schedule and
hold temperature (see page 13).
Press to run (follow) schedule
(see page 9).

Programmable Thermostat RTH221
5
Quick reference to display
* When Heat On or Cool On is flashing, compressor protection is engaged (see page 14).
Temperature
The ambient (measured) temperature is
normally displayed. To view the setpoint
temperature, press the Up or Down
button once. The setpoint temperature
will appear for five seconds.
System status
• Cool On: Cooling is activated. *
• Heat On: Heating is activated. *
Low-battery warning
(see page 15)
Setpoint indicator
Appears when the setpoint
temperature is displayed.
Clock
Schedule period
Permanent schedule override
(see page 13)
Temporary schedule override
(see page 12)

Operating Manual
6
1 Press the Set button. Set Time will appear on the screen and the
time display will flash.
2 Press the Up or Down button to set the time.
3 Press the Run button to save the changes & exit. (The changes
are also saved if you do not press any button for 60 seconds.)
NOTE: The clock has lost its settings when the time display flashes. If the thermostat is
following the schedule, it will use the temperature settings programmed for the Wake
period until you readjust the clock.
Set the clock

Programmable Thermostat RTH221
7
System switch (Heat/Cool)
Use the System switch to place the system in
one of the following modes:
•Cool: System is in Cooling mode.
•Off: System is off.
•Heat: System is in Heating mode.
CAUTION: EQUIPMENT DAMAGE HAZARD.
Do not use Cooling mode when the outdoor temperature is below 50°F (10°C).

Operating Manual
8
Fan switch (Auto/On)
Use the Fan switch to select the fan operation.
•Auto: The fan runs only when heating or
cooling is activated (commonly used setting).
•On: The fan runs continuously.