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Table 3. Heat Pump Control (A175) Jumper and Terminal Descriptions
Control ID
Label
Description
E12
PSC Fan
240VAC output connection for outdoor fan.
E16
PSC Fan
240VAC input connection for outdoor fan.
E18
W
24VAC output for defrost auxiliary heat output.
L
Thermostat service light connection.
Y2
24VAC thermostat input/output for second stage operation of the unit.
Y1
24VAC thermostat input for first stage operation of the unit.
O
24VAC thermostat input for reversing valve operation
DS
Humiditrol Input
C
24VAC system common
i−
Input/Output − RSBus data low. Used in communicating mode only with compatible indoor thermostat.
i+
Input/Output − RSBus data high. Used in communicating mode only with compatible indoor thermostat.
R
24VAC system power input
E19 and E20
O OUT
24VAC output connection for reversing valve.
E21 and E22
LO−PS
Connection for low−pressure switch (2.4 milliamps @ 18VAC)
E31 and E32
Y1 OUT
24VAC common output, switched for enabling compressor contactor.
E24 and E25
HS−PS
Connection for high−pressure switch.
E26
FAN 1
First−stage basic and precision dehumidification ECM fan motor 24VDC output connection 1.
E27
FAN 2
Second−stage basic and precision dehumidification ECM fan motor 24VDC output connection 2.
E28
FAN C
ECM common connection for ECM fan.
E30
Six position square pin header. P4 provides connections for the temperature sensors.
DIS (YELLOW)
PINS 5 and 6
(RT28)
DIS 5 Discharge line temperature sensor supply.
DIS 6 Discharge line temperature sensor return.
Range is −35ºF to +310ºF. Sensor is clipped on a 1/2" copper tube.
AMB (BLACK)
Pins 3 and 4
(RT13)
AMB 3 Outdoor ambient temperature sensor supply.
AMB 4 Outdoor ambient temperature return.
Range is −40ºF to +140ºF
COIL (BROWN)
Pins 1 and 2
(RT21)
COIL 1 Outdoor coil temperature sensor supply.
COIL 2 Outdoor coil temperature sensor return
Range is −40ºF to +140ºF. Sensor is clipped on a 5/16" copper return bend.
E33
Field Test
This jumper allows service personnel to defeat the timed−off control, initiate or terminate a defrost cycle, and
field programming of unit capacity feature.
E34
Y2 SOLENOID
Keyed plug header used for second−stage compressor output.
E37
Comp Shift Delay
Two position square pin header. When jumper is installed, a 30−second compressor shift delay is implemented.
It de−energizes the compressor contactor, second−stage solenoid (if on) and the ECM fan outputs. After the timer
expires, the compressor contactor and ECM fan outputs are energized. If no jumper is installed, it changes the
reversing valve direction and de−energizing the outputs immediately.
E47
50*
70
90
100
Seven position square pin header. Provides selection of the defrost terminate temperature based on the position
of the selection jumper. The defrost termination temperature is measured by the coil temperature sensor
(RT21). The jumper termination pin is factory set at 50°F (10°C). If the temperature jumper is not installed, the
default termination temperature is 90°F (32°C).
E48
55
50
45
40
NO JUMPER*
Five position square pin header. If the 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 outputs will be energized without the Y2 input. Factory default is no jumper present on E48, which sets
the control to no second stage lock−in.
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.
W1
DS To R
Cut for Humiditrol (EDA) application. This sets the outdoor fan speed to predefined speed. See table 15 for set
speed based on unit size. Use only in two−stage units.
* Factory default setting
