Carel PRK300D0E0, User Manual, Page: 90 / 104

90
ENG
pRack +0300025EN rel. 1.3 - 17.12.2015
Fig. A.r
pRack pR300 L1 connections
ac. Description Probe type Notes
Text Outside temperature NTC - HP
PD
L1
Condensing pressure line 1
(medium temperature) 4-20 mA 0-18.2barg
TD
L1
Discharge temperature line 1
(medium temperature) NTC - HF To control discharge
temperature
PS
L1
Suction pressure line 1 (me-
dium temperature) 4-20 mA 0-10barg To control low pressure
alarm
TS
L1
Suction temperature line 1
(medium temperature) NTC - HF To control suction
superheat
P
REC
CO2 receiver pressure 4-20 mA 0-10barg To control medium
temperature com-
pressors
Tab. 11.b
pRack pR300T L2 connections
ac. Description Probe type Notes
TD
L2
Discharge temperature line 2
(low temperature) NTC – HF To control discharge
temperature (opt.)
PS
L2
Suction pressure line 2 (low
temperature) 4-20 mA 0-44.8barg
TS
L2
Suction temperature line 2
(low temperature) NTC - HF To control suction
superheat
Tab. 11.c
EVD EVO connections
ac. Description Probe type
P
REC
Discharge pressure line 2 (low temperature) 4-20 mA 0-44.8barg
P
E
Heat exchanger evaporation pressure Ratiometric -1-9.3barg
T
GS
Heat exchanger superheated gas temperature NTC – HF
Tab. 11.d
Dettagli Wizard della confi gurazione pRack
In this type of system, it is important to coordinate operation of the
medium temperature rack with tube bundle evaporator control, to
prevent low pressure problems. Pressure control inside the receiver is the
main task; given the quantity of refrigerant contained and consequently
its signifi cant inertia, it is essential to activate the compressors based on
the receiver pressure, and medium temperature rack suction pressure will
only be monitored for safety, to prevent low pressure problems.
Medium temperature circuit control
Medium temperature circuit control uses a pressure sensor installed on
the low temperature receiver; in order to exploit this sensor, pRack needs
to use an auxiliary control function available under COMPRESSORS
o
LINE
1
o
CONTROL, in screen Cab20
Fig. 11.t
This screen is used to enable the function, set the required type of control
and the refrigerant in the auxiliary circuit.
An “auxiliary” control probe needs to be confi gured under INPUTS/
OUTPUTS
o
STATUS
o
ANALOG INPUTS in a free position on the controller.
The high and low auxiliary pressure/temperature probe alarms need to
be set under COMPRESSORS
o
LINE 1
o
ALARMS, checking the control
parameters.
EVD EVO and EXV drivers
Management of the tube bundle evaporator is critical in these types
of applications, and the size of the evaporator, inertia of the load and
proximity to the compressors require very fi ne control, which needs to
adapt rapidly when the compressors are started or stopped, respond
gradually to changes of load, not fl ood the compressors, and protect
against low suction pressure alarms.
Functions on the EVD EVO driver, such as low superheat, low suction
temperature, low suction pressure and high CO
2
condensing pressure
protection, therefore need to be correctly calibrated based on system
features (number and type of compressors, size of the evaporator and the
receiver, whether there are receivers on the suction line, system dynamics).
All these settings are found under OTHER FUNCTIONS
o
EVS on the board
that manages suction line 1.
Note: One DRIVER is needed for each valve; if a Twin Driver is used, this
will be managed as a single driver. The connection should be done on the fi rst
valve too (EXV1- J27 if a built-in driver is used).
•
Pumped, 2 suction lines (external driver for managing the heat
exchanger on the fi rst line), 1 condenser line, single board;
I/ O
S2
S1
EVD
evolution
EEV
S3
FBUS
I/ O
I/ O
pR300
Fig. A.s
Board with
pLAN address 1