14
Table 4 — Thermostat Output Assignments
LEGEND
*
Intelligent heat option.
† Y1/W2 is on without W/W1.
OPERATION
Hold, Fan, and Mode Button Operation —
Pressing the Hold button disables the time and temperature
schedule and holds the current desired temperature set point.
When a Hold is active, the HOLD indicator is displayed on the
thermostat screen. To release the Hold, press the Hold button a
second time.
The Fan button selects fan operation. When the fan is set to
ON, the fan will run continuously. When the fan is set to
AUTO, the fan will run during heating and cooling operation
only.
The Mode button selects the operating mode of the thermo-
stat. 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 heat-
ing set point). If COOL is selected, the thermostat will only en-
ter Cooling mode (if the room temperature is above the cooling
set point). If AUTO is selected, the thermostat will enter Heat-
ing or Cooling mode based on the room temperature and the
heating and cooling set points. Heat pumps also have an
E HEAT selection. If E HEAT is selected and there is a heating
demand, the thermostat will turn on the O/W2 output when the
AC/HP DIP Switch C is set to the AC position or O/W2 output
when the AC/HP DIP Switch C is set to the HP position. The
indicator for each selection will be displayed on the thermostat
when selected.
Outdoor Temperature —
When the Up and Down
Arrow buttons are pressed at the same time, the display will
show the temperature of the sensor wired to the thermostat at
S1 and S2. The temperature is displayed for 4 seconds with the
letters “od.” The display then returns to normal. If a sensor is
not connected or the reading is out of range, then “--” is dis-
played. The valid temperature range for the outdoor-air sensor
is –38 to 145 F.
Thermostat Output Assignments —
The thermo-
stat output assignments, based on configuration, are shown
in Table 4.
Five-Minute Compressor Timeguard —
This tim-
er prevents the compressor from starting until it has been off
for at least 5 minutes. The 5-minute timer can be disabled (for
one cycle only) by simultaneously pressing the Fan and Up Ar-
row buttons together (increase temperature).
Fifteen-Minute Cycle Timer —
This timer prevents
the start of a heating or cooling cycle until at least 15 minutes
after the last start of the same cycle. Its function is to assure that
equipment is not cycled more than 4 times per hour. This timer
is defeated for 1 cycle when the desired temperature is manual-
ly changed. It can also be defeated for 1 cycle by simultaneous-
ly pressing the Fan and Up Arrow buttons together (increase
temperature).
Fifteen-Minute Staging Timer —
When multi-stage
heating or cooling is used, the staging timer prevents any
higher stage from energizing until at least 15 minutes has
passed from the start of the previous stage. The timer is dis-
abled if the temperature demand is greater than 5 degrees.
Three-Minute Minimum On Time —
In nor-
mal operation, when a stage is energized, it must remain on for
at least 3 minutes.
Heating/Cooling Set Points —
A minimum differ-
ence of 3 degrees is enforced between the heating and cooling
set points. The thermostat will not allow the set points to be set
within 3 degrees of each other.
Auto-Changeover Timer —
The thermostat will not
change from heating to cooling or cooling to heating until an
opposite demand has existed for a minimum of 20 minutes.
The timer is disabled if the heating or cooling set point is
changed.
Power-On Check —
When power is applied to the ther-
mostat, all possible display indicators are turned on for a few
seconds. The thermostat then indicates the current mode and
configuration information with a 2-digit code. The following
codes can be displayed:
AC — 1-speed air conditioner
HP — 1-speed heat pump
A2 — 2-speed air conditioner
H2 — 2-speed heat pump
HS — Intelligent heat staging with a variable-speed fan coil
and 1-speed heat pump
MODEL
P274-
OUTDOOR
UNIT
AC/HP
SWITCH
C
STAGING
SWTICH
D
THERMOSTAT OUTPUT
24v
HOT
COMMON
FAN
HEAT
STAGE
1
HEAT
STAGE
2
HEAT
STAGE
3
HEAT
STAGE
4
COOL
STAGE
1
COOL
STAGE
2
REVERSE
VALVE
1100
AC
EITHER
EITHER
R
C
G
W/W1
N/A
N/A
N/A
Y/Y2
N/A
N/A
1200
HP
OFF
EITHER
Y/Y2
W/W1
N/A
N/A
Y/Y2
N/A
O/W2
AC
ON
EITHER
W/W1
O/W2
N/A
N/A
Y/Y2
N/A
N/A
1300
2S AC
ON
EITHER
W/W1
O/W2
N/A
N/A
Y1/W2
Y/Y2
N/A
2S HP
OFF
OFF
Y1/W2
Y/Y2
W/W1
N/A
Y1/W2
Y/Y2
O/W2
1S HP
*
OFF
ON
Y/Y2
W/W1
Y1/
W2†
W/W1,
Y1/W2
Y/Y2
N/A
O/W2
1S
—
1-Speed
2S
—
2-Speed
AC
—
Air Conditioner
C
—
Terminal C
G
—
Terminal G
HP
—
Heat Pump
N/A
—
Not Available
R
—
Terminal R