Carel PRK300D0E0, User Manual, Page: 33 / 104

33
ENG
pRack +0300025EN rel. 1.3 - 17.12.2015
6. FUNCTIONS
Note : Certain special conditions or functions in the pRack software
cause the unit to shutdown:
•
Confi guration of some parameters: e.g. inputs/outputs, confi guration
of compressors, inverter parameters.
•
Installation of default parameters
•
Manual management
6.2 Control
pRack pR300 can manage two types of control:
•
Proportional band (P, P+I);
•
Neutral zone (fi xed times, variable times).
Both types of control can be applied to both compressors and
condensers, according to the settings defi ned during start-up or in main
menu branches C.a.b/C.b.b and D.a.b/D.b.b.
The type of control chosen is independent for each line present, either
suction or condenser.
In addition, pRack pR300 can use as the reference for control either the
pressure or the converted temperature, or the temperature read by probe
if there is no pressure probe, even if reference is only made to pressure
below.
The control set point can be compensated by an off set linked to digital
inputs, probes, supervisor or time bands, for details see paragraph 6.5
relating to compressor and fan energy saving.
Both types of control are described below, and are valid for both control
of suction pressure and condensing pressure, and operation with backup
probes and/or probes not working.
pRack pR300 can manage up to 2 suction lines and 2 condenser lines.
Many of the functions described in this chapter apply in the same way
to all the lines (e.g.: control, rotation), while others apply in the same way
to the suction lines (e.g.: oil management). The exception involves the
generic functions that apply, irrespective of line, suction or condenser, to
pRack boards with pLAN addresses from 1 to 4.
Where not expressly indicated or where it is clear that the description
refers to one specifi c line rather than another (e.g.: compressor or fan
management), the descriptions are considered as being common to all
lines; any specifi c Situations are described on a case-by-case basis.
Below is a chart of the main functions described and their fi eld of
application:
Function L1 suction L2 suction L1 condens. L2 condens.
Unit On-Off √ √ √ √
Control P+I control √ √ √ √
Control in Neutral zone √ √ √ √
Modulation in Neutral zone √ √ √ √
Control with backup probes √ √ √ √
Rotation √ √ √ √
Modulation device √ √ √ √
Compressors Screw compressors √ - - -
Reciprocating and scroll compressors √ √ - -
Digital Scroll™ compressors √ √ - -
Bitzer CRII compressors √ √ - -
Fan management - - √ √
Energy saving Set point compensation √ √ √ √
Floating set point √ √ √ √
Accessory functions Oil management √ √ - -
Subcooling √ √ - -
Economizer √ √ - -
Liquid injection √ √ - -
Heat recovery - - √ √
Generic functions (*) (*) (*) (*) (*)
ChillBooster - - √ √
DSS √ √ - -
Tab. 6.a
(*) not linked to lines, but rather the pLAN address of the boards
The functions are described in detail in the following paragraphs.
6.1 Unit On-Off
The unit can be switched on and off from:
•
User terminal
•
Supervisor
•
Digital input
On-off from the user terminal and the confi guration parameters are
available under the main menu, branch A.c, and are diff erentiated based
on the access level; the User password allows display only.
On-off from the supervisor and from the digital input and start-up after
a blackout (with specifi c delay, to avoid continuous starts and stops in
the event of instability in the power supply) must be enabled using the
parameters visible only with the Manufacturer password.
On-off from the digital input is equivalent to an enabling Signal, that is, if
the digital input is Off the unit cannot be switched on in any other way,
while if is On, the unit can be switched on or off in any other way, with
the same priority (the most recent control has precedence, whatever the
origin), as shown in the fi gure:
User interface
Supervisor
Digital Input
Unit On/Off
Fig. 6.a
When there are two suction and condenser lines, on-off is independent for
each line, while when there are two suction lines and one condenser line,
it is independent for the suction lines, while the condenser line stops when
both suction lines are off , and starts when at least one suction line is on.