Defrost - Carel MPXPRO User Manual

ON
CMP
OFF
c3
Key:
t time

6.7 Defrost

The advanced parameters for defrost management include general
parameters on the time base, activation delays, synchronization between
Master and Slaves, the stages of the defrost such as pump down and
dripping, and the advanced defrost functions, such as:
• Skip defrost;
• Running time;
• Sequential stops;
• Power defrost.
End defrost synchronized by Master (parameter d2)
Par. Description
d2 End defrost synchronized by Master
0 = not synchronized;1 = synchronized
The parameter determines whether or not, in a local network, MPXPRO
awaits an end defrost signal from the Master at the end of the defrost.
End defrost signal by timeout (parameter r3)
Par. Description
r3 End defrost signal by timeout
0 = disabled, 1 = enabled
For defrosts that end by temperature (d0=0, 1, 5) , this enables the end
defrost by timeout signals Ed1 and Ed2.
Defrost on power-up (parameter d4)
Par. Description
d4 Defrost on power-up
0= disabled ; 1 = enabled
(Master = network defrost;
Slave = local defrost)
The defrost call on power-up has priority over the control request and the
activation of the continuous cycle. For Master controllers, the defrost on
power-up will be a network defrost; for Slave controllers it will be local.
Defrost delay on power-up (parameter d5)
Par. Description
d5 Defrost delay on power-up (if d4=1)
0 = delay disabled
Also active when d4=0. If the digital input is set to enable or start a defrost
from an external contact, parameter d5 represents the delay between
when the defrost is enabled or called, and when it eff ectively starts.
For Mater/Slave networks where the defrost needs to be activated from
a digital input on the Master, use parameter d5 to delay the various
defrosts, thus avoiding current overloads.
t
c2
c1
Fig. 6.i
CMP compressor
Def Min Max
1 0 1
Tab. 6.g.a
Def Min Max UoM
0 0 1
Tab. 6.g.b
Def Min Max UoM
0 0 1
Tab. 6.g.c
Def Min Max UoM
0 0 240
Tab. 6.g.d
Note: to avoid unwanted defrosts controlled by the controller
timer, set parameter dI=0 (defrosts from keypad, RTC, compressor
running time or digital input only).
Time base for defrost (parameter dC)
Par. Description
dC Time base for defrost
0=dI in hours, dP1, dP2 and ddP in minutes;
1= dI in minutes, dP1, dP2 and ddP in
seconds
This defi nes the unit of measure used to count the times for parameters
dI (defrost interval), dP1, dP2 and ddP (defrost duration):
• dC=0 =>dI expressed in hours, dP1, dP2 and ddP in minutes;
• dC=1 =>dI expressed in minutes, dP1, dP2 and ddP in seconds.
Note: parameter dC=1 can be useful for quickly testing the defrost
operation with reduced times. It is also useful for controlling the
operation of air dryers. The defrost cycle thus becomes the condensate
discharge cycle, which needs to be started at short intervals (minutes)
and for very brief periods (seconds).
Dripping time after defrost (parameter dd)
Par. Description
dd Dripping time after defrost (fans off )
UoM
0 = no dripping
-
This parameter is used to stop the compressor and the evaporator fans
following a defrost so as to allow the evaporator to drip. The value of the
parameter indicates the off time in minutes. If dd=0 no dripping time
is enabled, and at the end of the defrost control resumes immediately,
without stopping the compressor and the fan, if active.
-
Pump down phase duration
Par. Description
dH1 Pump down phase duration
0 = pump down disabled
The pump down phase is the period in which the evaporator is emptied
of liquid refrigerant. Parameter dH1 defi nes the duration of the pump
down phase during all types of defrost, heater or hot gas. Setting dH1=0
disables the pump down phase.
-
Important : the controller does not have two separate outputs to
manage the compressor and solenoid valve.
Type of multiplexed hot gas defrost
Par. Description
dHG Type of hot gas defrost
0 = equalizing valve normally closed
1 = equalizing valve normally open
min
See paragraph 5.6 for an installation diagram with equalizing valve.
Located in parallel with the suction valve, it can be open only in the
dripping phase or also during the normal refrigeration cycle, the pump
down and post-dripping phases.
47
ENG
Def Min Max UoM
0 0 1
Tab. 6.g.e
Def Min Max UoM
2 0 15 min
Tab. 6.g.f
Def Min Max UoM
0 0 999
Tab. 6.g.g
Def Min Max UoM
0 0 1
Tab. 6.g.h
MPXPRO - + 0300055EN rel. 1.1 30/08/10
-
s
-