RTH111 69-2061EFS-01 11/09 1/8

1.1 Controls

1.2 Display screen

1.3 System switch

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).

1.4 Fan switch

Use the Fan switch to select the fan operation.
•Auto: The fan runs only when heating or cooling is actually taking
place (commonly used setting).
•On: The fan runs continuously. Use this setting for improved air
circulation or for more efficient air cleaning.

1.5 Temperature adjustment

Press the S or T button once to display the setpoint temperature.
Press either button more than once to change the setpoint.
The ambient (measured) temperature is normally displayed. To view
the setpoint temperature, press either of the temperature adjustment
buttons once. The setpoint temperature will appear for five seconds.

1.6 Built-in compressor protection

Your thermostat has a feature that helps prevent damage to the
compressor of your air conditioning system. Because damage can
occur if the compressor is restarted too soon after shutdown, this
feature forces the compressor to wait five minutes before restarting.
During the wait time, the message Cool On flashes on the screen.
When the safe wait time has elapsed, the message stops flashing
and the compressor turns on.
Set the System switch to Off before removing the
batteries. Otherwise, the heating/cooling system could
remain activated even when batteries are removed.
Install two fresh AAA batteries when the low-battery icon flashes on
the screen. The icon appears for 60 days before the batteries are
depleted. Replace batteries once a year, or when you will be away for
more than a month.
The settings are stored in non-volatile (permanent) memory and are
thus saved when the thermostat is without batteries.
nOperation
1.
System switch
Fan switch
Temperature
adjustment buttons
1 When Cool On is flashing, this means the compressor protection is engaged (see
section 1.6).
Temperature
System status
• Cool On: Cooling is
activated. 1
• Heat On: Heating is
activated.
Low-battery warning
Setpoint indicator
Appears when the
setpoint temperature
is displayed.
oBattery replacement
2.
pIn case of difficulty
3.
Screen is blank. • Ensure two fresh AAA alkaline batteries are
correctly installed.
Temperature settings
cannot be changed.
• The System switch is off.
• You are setting the temperatures outside
their allowable ranges:
• Heat: 40 °F to 90 °F (4.5 °C to 32 °C).
• Cool: 50 °F to 99 °F (10 °C to 37 °C).
Cool On is flashing. • The compressor protection delay has been
activated. Cooling will not be activated until
the delay ends (maximum of five minutes).
HI appears on the
screen.
• The ambient (measured) temperature is
above 122 °F (50 °C).
LO appears on the
screen.
• The ambient (measured) temperature is
below 32 °F (0 °C).
E1 appears on the
screen.
• The temperature sensor circuit is opened.
Replace the thermostat.
E2 appears on the
screen.
• The temperature sensor circuit is shorted.
Replace the thermostat.
RTH111

User Guide

Non-programmable Thermostat

400-631-001-A (RTH111 User 69-2061EFS).book Page 1 Tuesday, June 5, 2007 2:24 PM
69-2061EFS-01