Part Number P274-0150
MODE BUTTON OPERATION — The Mode button selects
the operating mode of the thermostat. If OFF is selected, the
thermostat will not enter Heating or Cooling mode. If HEAT is
selected, the thermostat will only enter Heating mode (if the
room temperature is below the heating set point). If COOL is
selected, the thermostat will only enter Cooling mode (if the
room temperature is above the cooling set point). If AUTO is
selected, the thermostat will enter Heating or Cooling mode
based on the room temperature and the heating and cooling set
IMPORTANT: Read entire instructions before pro-
gramming the thermostat.
Totaline® thermostats are wall-mounted, low-voltage ther-
mostats which maintain room temperature by controlling the
operation of an HVAC (heating, ventilation and air condition-
ing) system using separate heating and cooling set points and
Batteries are not required. During power interruption the
internal memory stores set points indefinitely.
Auto-Changeover — When the thermostat mode is set
to AUTO, the thermostat will provide automatic changeover
from Heating to Cooling mode and Cooling to Heating mode
when required. The thermostat will automatically switch to
maintain the desired temperature setting. The thermostat does
not need to be manually changed from heating to cooling or
cooling to heating operation.
When the auto-changeover mode is selected, a change from
heat to cool (or vice versa) will not occur until an opposite
mode demand has existed for 20 minutes. If the set point is
changed, the 20-minute requirement is ignored.
Thermostat Display — The thermostat display is locat-
ed in the top center of the thermostat. See Fig. 1. The following
information can be displayed on the screen:
mode (OFF, COOL, AUTO, or HEAT)
fan setting (ON or AUTO)
NOTE: It is recommended that auto-changeover mode not be
used if the outdoor temperature is consistently lower than 50 F
or greater than 80 F. In these cases, select Heating or Cooling
clean filter status
outdoor temperature (optional)
Thermostat Buttons and Operation — The Up and
Down Arrows are used to change the current, desired tempera-
ture set point. The Up and Down Arrows are accessible from
the outside of the thermostat. Press the up or down arrow. The
LCD readout will be illuminated and the heating or cooling
temperature set point will be displayed, but will not change.
HEAT, or COOL next to the temperature display indicates
which temperature set point is being displayed. Continue to
press up or down arrows until desired heating or cooling tem-
perature set point is displayed. Press the Mode button to select
the second temperature setting (either HEAT or COOL).
Reset Filter — The CLEAN FILTER icon reminds the
user when it is time to change or clean the filter of the unit. The
Reset Filter function is initiated by Pressing the RESET
FILTER button after you have changed or cleaned your filter to
restart the timer. The Reset Filter function is used to clear the
CLEAN FILTER icon on the display screen.
Display Outdoor-Air Temperature — When the Up
and Down Arrows are pressed at the same time, the display
will show the temperature of the sensor wired to the thermo-
stat. The display then returns to normal. If a sensor is not con-
nected, then “--” is displayed.
The valid temperature range for the outdoor-air sensor is
–38 to 145 F.
NOTE: Your COOL setting must be at least 2 degrees higher
than the HEAT setting. The thermostat will automatically
change the previously set temperature to maintain that
POWER OUTAGE — An internal power source maintains the
desired temperature settings indefinitely.
FAN BUTTON OPERATION — The Fan button selects fan
operation. When the fan is set to ON, the fan will run continu-
ously for improved air circulation. The FAN icon will be dis-
played on the LCD. When the fan is set to AUTO, the fan will
run during heating and cooling operation only and provides
System Error — The temperature sensor failure indicator
sends a -- reading to the LCD display. This indicates your ther-
mostat’s internal or outdoor temperature sensor is no longer
able to measure temperatures. An E2 reading on the LCD dis-
play means there is not enough voltage for the system to
Manufacturer reserves the right to
discontinue, or change at any time,
specifications or designs without notice
and without incurring obligations.
REPLACEMENT COMPONENTS DIVISION
© CARRIER CORPORATION 1106 6-01
PRINTED IN U.S.A.
LITERATURE NUMBER P274-6SO
CATALOG NUMBER 570-458