24
C6.1.6/0117-1017/E
be connected to the XCM25D. There are additional terminals available in the unit which allow for
easy connection of additional hardware if required. The wiring diagram also shows these optional
features. The liquid line solenoid valve Y3 can be connected on terminals X1.N & X1.8. The terminals
X1.9 & X1.10 can be used for a room thermostat (connected to
DI3
).
If a temperature sensor is preferred the analog input
AI7
can be used (Caution: controller settings
are not preconfigured for temperature sensor). For details about alternative options please see
Chapters 2.14.3 "Pump-down with room thermostat" and 2.14.4 "Internal pump-down with
temperature sensor (case temperature)".
In any case there are limitations for the cut-out values of the compressors given by the envelopes.
The minimum cut-out settings are shown in
Table 21
below. Those values are also applicable in
case pump-down is carried out by means of an additional low pressure switch. Operation of the unit
below the suction pressures shown in the table could result in tripping of the compressor internal
motor protector (Klixon, error code E28). The envelopes are in accordance with Select software
available at
Unit family
R134a
R404A/R507
R407A
R407F
ZXME
-20°C = 0.3 bar rel
-20°C = 2 bar rel
-23°C* = 1.1bar rel -25°C = 1 bar rel
ZXLE
[-]
-40°C = 0.3 bar rel
-40°C = 0 bar rel
-40°C = 0 bar rel
ZXDE
Not approved for pump-down
* Limited to -20°C (1.35 bar rel) for ZXME020
Table 21: Minimum cut-out value for pump-down
NOTE: ZXLE units have an additional 5-second switch-off delay which must be taken into
account for the pump-down function.
NOTE: The values in the table show the lowest suction temperatures / pressures in the
envelopes. Depending on the condensing temperature in the real system it might be required
to adjust / increase the cut-out value according to the approved envelope published in Select.
2.14.3 Pump-down with room thermostat (not available on ZXDE units)
Configure parameter
C05
"Compressor regulation probe selection" to "3" (Suction pressure switch /
Room thermostat input). In addition, change setting for
G56
from "0" to "1". This is information to the
controller that a solenoid valve is present.
Change the functionality of Digital Input 3 (
DI3
) (Parameter
R07
) to setting 1 (Suction pressure switch
/ Room thermostat input) and adjust the relay output configuration
S07
to 7 (Liquid line solenoid).
Parameter Factory settings
Pump-down settings
C02
2 bar relative
Cut-out value for pump-down, eg, 0.2 bar rel
C05
1 = Suction pressure probe =
SuP
3 = Suction pressure switch / Room thermostat
=
diS
G11
3 minutes
Maximum pump-down time
G56
0 = No
1 = Yes
R07
0 = Not used =
nu
1 = Suction pressure switch / Room thermostat
=
SuS
S07
0 = Not used =
nu
7 = Liquid line solenoid =
LLS
Table 22: Pump-down 1
Room thermostat switch status
Liquid line solenoid valve status
Closed
Switch on / Energized
Open
Switch off / De-energized
Table 23: Pump-down 2
For example, if the room thermostat switch is closed, the liquid line solenoid valve is activated, and
the compressor will run when the suction pressure value is higher than the compressor cut-in value
C01
.
The liquid line solenoid valve will be switched off if the room thermostat switch is open and pump-
down will start. The compressor will stop once the suction pressure value is lower than the
compressor cut-out value
C02
or when the pump-down duration is longer than the maximum pump-
down time
G11
setting.
