Carel easy small wide, User Manual, Page: 30 / 56

30
ENG
ir0300028EN rel. 1.1 - 05.05.2017
r3=0,1
ON
OFF
CMP
rr rn/2 rn/2
AUX
rd
St
Fig. 6.d
r3=0,1
ON
OFF
CMP
rr rn/2
AUX
rd/2 rd/2
AUX2
St
Fig. 6.e
Reverse operation (r3 =2), with 1 compressor output (CMP) and 2
compressor outputs (CMP and AUX2).
r3=2
ON
OFF
CMP
rn/2
rd
AUX
rn/2 rr
Sv
St
Fig. 6.f
r3=2
ON
OFF
CMP
rn/2
rd/2
AUX
rn/2
rr
Sv
AUX2
rd/2
St
Fig. 6.g
Key
St Set point rd Diff erential
rn Neutral zone rr Reverse diff erential
6.4 Pump down
The pump down function has the purpose completely emptying the
evaporator of refrigerant on reaching the set point. The controller fi rst
deactivates the pump down valve and then, after a certain time, the
compressor. The application diagram shows the pump down valve and
the low pressure switch. When the controller restarts the compressor,
if protection times c1 and c2 have elapsed, the pump down valve is
opened, and after the time c8 the compressor is activated. The parameters
involved are listed below.
Par. Description Def Min Max UOM
c7 Maximum pump down time (PD)
0 = pump down disabled 0 0 900 s
c8 Compress. start delay after opening PD valve 5 0 60 s
c9 Autostart in pump down 0 0 1 -
0 = Disabled
1 = Pump down whenever closing pump down
valve & following low pressure switch activation
with no cooling demand
c10 Pump down by time or pressure
0/1 = pressure/time
0 0 1 -
Tab. 6.d
Note: c8 is a masked parameter, and can be made visible using the
VPM tool.
C
L
PDV
M
CMP
E
T V2
P
ir33+
S
F
Fig. 6.h
Key
CMP Compressor P Low pressure switch
C Condenser F Filter-drier
L Liquid receiver E Evaporator
V2 Thermostatic expansion valve S Liquid gauge
PDV Pump down valve
Pump down can be selected:
•
by pressure (pressure switch required): when the pump down valve
closes, the compressor continues operating until the pressure switch
measures the defi ned low pressure value. The compressor is then
stopped. If the pressure switch does not measure the defi ned value
before c7 elapses, the “Pd” alarm - pump down ended by timeout - is
activated;
•
by time (pressure switch optional): when the valve closes, the
compressor continues operating for the time c7 or until reaching the
low pressure value. The “Pd” alarm - pump down ended by timeout - is
not activated.
c10 = 0: Pump down by pressure
Pressure switch activated before c7 Pressure switch activated after c7
ON
OFF
ON
OFF
t
CMP,
FAN
VPD
c7
PRESSURE
SWITCH
St
ON
OFF
ALARM
Pd
ON
OFF
Sv
c7
Fig. 6.i
Key
CMP, FAN Compressor, fan c7 Maximum pump down time
VPD Pump down valve Pd Pump down alarm
Pressure switch Pressure switch t Time
Sv Virtual probe