Page 34
506601−01
High Discharge Line Temperature Sensor (RT28)
See table 10 for sensor range. The high discharge line
temperature sensor (location shown in figure 1 monitors
temperature range and open/short conditions. See figure
31 for the high discharge line temperature sensor
sequence of operation.
Table 10. Sensor Temperature / Resistance Range
Sensor
Temperature
Range °F (°C)
Resistance values
range (ohms)
Pins/Wire
Color
Discharge
(RT28)
−35 (−37) to 310
(154)
41,000 to 103
1 and 2
(Yellow)
Outdoor
(Ambient)
(RT13)
−40 (−40) to 140
(60)
280,000 to 3750
3 and 4
(Black)
Coil (RT21)
−40 (−40) to 140
(60)
280,000 to 3750
5 and 6
(Brown)
NOTE
Sensor resistance decreases as sensed temperature
increases (see tables 11 and 12).
W Input Fault or Miswire
In case of a W input fault or possible miswire, the system
will function as listed in the sequence of operation in figure
32.
SECOND−STAGE OPERATION
If the control receives a call for second−stage compressor
operation
Y2
in heating or cooling mode and the first-stage
compressor output is active, the second-stage
compressor solenoid output will be energized by the heat
pump control system operation function.
NOTE
Figure 15 illustrates the correct
Y2
field wiring
configuration.
NOTE
The heat pump control system operation monitor
has a five second delay between
Y2
being powered and
the solenoid energizing.
Second Stage Lock−in (E48)
If first-stage compressor output is active in heating mode
and the outdoor ambient temperature is below the selected
compressor lock−in temperature, the second-stage
compressor solenoid output will be energized even without
a
Y2
room thermostat input.
If the jumper is not connected to one of the temperature
selection pins on
E48
(40, 45, 50, 55°F), the second stage
lock−in feature is inactive. Factory default is no jumper
present.
FACTORY DEFAULT
IS NOT JUMPER −
SECOND STAGE
LOCK−IN INACTIVE.
55
50
DEGREE
TARGET
45
DEGREE
TARGET
40
DEGREE
TARGET
55 50 45 40
55 50 45 40
55 50 45 40
55 50 45 40
DEGREE
TARGET
NOTE Earlier produce units will have a default factory
setting (jumper present) for 40ºF. Later produce units will
have no jumper by default present on E48.
Figure 25. Second Stage Lock−in (E48) Settings
The heat pump control de−energizes the second-stage
compressor solenoid output immediately when the
Y2
signal is removed or the outdoor ambient temperature is
5°F above the selected compressor lock−in temperature,
or the first-stage compressor output is de−energized for
any reason.
Shift Delay (E37)
The heat pump control has a field−selectable function to
reduce occasional sounds that may occur while the unit is
cycling in and out of the defrost mode. When a jumper is
installed on the DELAY pins (E37), the compressor will be
cycled off for 30 seconds going in and out of the defrost
mode. Units are shipped with jumper installed on DELAY
pins.
FACTORY DEFAULT OR WHEN
JUMPER IS MISSING
30
0
*30
SECOND DELAY
SECOND DELAY
0
Figure 26. Shift Delay Settings
