Lennox XC20-036-230-01 Installation And Service Procedure page 40

PUMP DOWN
Figure 17. Pump-Down Jumper
4. Shut off the liquid line service valve to stop the flow of
refrigerant into the indoor coil.
5. After a three-second delay, the compressor and out­
door fan will ramp up to 100% capacity. (Indoor fan will
remain OFF.)
Display and action (normal operation)
Display
No Change - idle (*)
No Change - idle (*)
Enter or exit field test and program mode.
Solid .
Solid A
Puts unit in diagnostic mode. (Displays ambient, coil, liquid sensor temperatures and any active error codes.)
Solid c
Clears error history (**)
Solid E
Enter diagnostic recall mode. Displays up to 10 error codes in memory.
Solid F
Starts outdoor fan.
String P U
Enter unit code programming.
*No change indicates the display will continue to show whatever is currently being displayed for normal operations.
**Note once the error history is deleted it cannot be recovered. After the history is deleted, the unit will reset itself.
Display and action (normal operation)
Display
Idle mode — decimal flashes at 1 Hertz > 0.5 second ON, 0.5 second OFF
.
C
Cooling operation. Shows C and the cooling demand percentage. Example: C 5 0 pause F 7 0 0 pause A 7 5
F
Fan RPM. Shows F and the current fan RPM. Example: H 5 0 pause F 6 0 0 pause A 4 5
E E
in the display string represents the active error code(s) in the outdoor unit.
Example: C 5 0 pause F 7 0 0 pause E 4 4 1 pause E 4 4 2 pause A 7 5 pause
A A
in the display string represents the outdoor ambient temperature in F at the outdoor sensor on the outdoor unit.
Example: C 5 0 pause F 7 0 0 pause A 7 5
c
If enabled,
Example: C 5 0 pause F 7 0 0 pause A 7 5 pause c 4 5 pause. Air conditioning units do not require an outdoor coil sensor. A 10K
resistor, across pins 5 and 6 on the outdoor control sensor harness, prevents false outdoor coil sensor codes. The 10K resistor
causes the 7-segment display to show a constant 77ºF coil (c) temperature value.
L
If enabled,
Example: C 5 0 pause F 7 0 0 pause A 7 5 pause c 4 5 pause pause L 1 0 5 pause
P d
P D displays when system is in pump down mode.
TYPICAL 7-SEGMENT ACTIVE COOLING OR HEATING DEMAND DISPLAY STRING
C 5 0 F 7 0
COOLING AT
OUTDOOR
50% DEMAND
FAN RPM
BY DEFAULT, COOLING OR HEATING, DEMAND, OUTDOOR FAN RPM, ACTIVE ERROR CODES
AND OUTDOOR AMBIENT TEMPERATURE ARE DISPLAYED.
* Air conditioning units do not require an outdoor coil sensor. A 10K resistor, across pins 5 and 6 on the outdoor control sensor harness, prevents
false outdoor coil sensor codes. The 10K resistor causes the 7-segment display to show a constant 77ºF coil (c) temperature value.
XC20
ON
OFF
PUMP DOWN
Table 8. Field Test, Diagnostic Recall and Program Menu Options
Table 9. Normal Operation Character Display String
c
in the display string represents the outdoor coil temperature in F at the sensor on the outdoor unit.
L
in the display string represents the outdoor liquid line temperature in F at the sensor on the outdoor unit.
0 E 4 4 2
ACTIVE ERROR
CODE (IF PRESENT)
Figure 18. Typical 7-Segment Demand Display String
6. Monitor the low-side pressure at the outdoor unit. The
internal vacuum protection in the compressor and/or
one of the pressure switches prevents full recovery of
ON
the refrigerant into the outdoor unit. When the system
OFF
reaches this condition, the suction line service valve
should be shut off and the Pump-Down Jumper
moved back to the OFF position.
NOTE - The outdoor control will stay in pump-down mode
for five minutes, after which the outdoor control initiates a
compressor shutdown sequence.
7. Use a refrigerant recovery machine to recover the re­
maining refrigerant on the indoor side of the system.
Display and action (configuration and test mode)
A 7 7
OUTDOOR
AMBIENT AIR
TEMP
40
c 7 7 L 1 0 7
OUTDOOR
OUTDOOR LIQUID
COIL TEMP(*)
OUTDOOR COIL AND LIQUID LINE TEMPERATURES CAN BE
MANUALLY ENABLED. IF SYSTEM POWER IS RECYCLED, DISPLAY
STRING REVERTS BACK TO DEFAULT (SEE FIGURE 19 TO ENABLE)
LINE TEMP