Carel Hecu CO2, User Manual

Page: 31 / 64

31
ENG
Hecu
C O
2
+0300085EN rel. 2.2 - 07.05.2019
The following diagram explains operation and control of the electronic
expansion valve and the superheat set point:
t
t
t
t
t
t
Cmp speed
EEV position
EEV Max opening
Cabinet SH
Cabinet SH
setpoint OK
ON
C1 Washing
C2 Washing
C3 Washing
OFF
ON
OFF
ON
OFF
t1
t1 = time ON td = Fixing time function
td td td
t1 t1
Legende:
Fig. 6.t
Washing of individual cabinets can be confi gured exclusively in sequential
mode.
tON is the duration of each single washing cycle. “N. of washing per day in
each evap.” is the number of washing cycles per day for each evaporator.
Fixing time is the transition time at the end of each single washing cycle
to keep the system in stable conditions.
If using evaporators managed by non-Carel controllers (third party
devices), a digital output can be used, as described in the following
paragraph.
Digital output for cabinet washing
The purpose of this function is to exploit the "Hecu wash" function to
enable a digital output that can be used to "wash" evaporators with third-
party controllers.
To activate this function, the evaporators with MP
X
/Ultra
C
ella
controllers must not be enabled, then on screen Fab
1
5 enable the
washing cycles as shown below:
Then select the digital output on screen Faa68.
The DO will be used by third-party controllers (evaporators) to activate
cabinet set point compensation: for example, from 5°C to -50°C. This
action will open the expansion valve and at the same time the superheat
control will remain active to avoid the return of liquid on the unit’s suction
line. The number of wash cycles is selected on the following screen.
Note : this function will be less eff ective than the one Carel provides
via serial connection of the evaporators managed by MPXPRO and
UltraCella controllers.
C
ompressor “ready” digital output
On screen Baccm, a digital output can be selected that is activated when
the compressor is "ready". This means that it is able to deliver its cooling
capacity.
On stand-alone units, this can be used as a "control" digital input on the
cabinets to improve control/synchronization between the condensing
unit and the evaporators.
The function is NOT active when:
•
The compressor is off due to timers (minimum Off time or timer
between starts)
•
The compressor is off due to cut-off
•
On LT units, if the compressor is off due to the DSS function
•
The compressor is off due to an alarm, with the following exceptions
(to prevent the unit from shutting down):
–
Low suction pressure alarm
–
Low SH