Carel PRK300D0E0, User Manual, Page: 36 / 104

36
ENG
pRack +0300025EN rel. 1.3 - 17.12.2015
6.3 Compressors
pRack pR300 can manage up to 2 suction lines with diff erent types of
compressors and capacity modulation devices, applying common types
of device rotation and controlling both the start mode and the safety
times for each type of compressor, as well as a number of accessory
functions.
The compressor functions and related parameter settings are enabled
from main menu branch C.a/C.b.
These features and functions are described in detail in the following
paragraphs.
6.3.1 Possible compressor confi gurations
pRack pR300 can manage diff erent types of compressors:
•
Reciprocating
•
Scroll
•
Screw
Moreover, a capacity modulation device is allowed for each suction line,
which may be one of the following, according to the type of compressor:
Compressors and modulation devices
Compressors modulation devices
Reciprocating Inverter
Scroll
Inverter
Digital Scroll™
Screw
Inverter
Continuous capacity control
Bitzer CRII Modulating capacity control
Tab. 6.b
Note : The same modulation device is used on each line.
The maximum number of compressors and load stages per line varied
according to the type of compressor:
Compressors and modulation devices
Compressors Maximum No. Load stages
Reciprocating 12 24 total
Scroll 12 24 total
Screw 2 4
Bitzer CRII 2 3
Tab. 6.c
Note : Screw compressors can only be confi gured on line 1 and the
board must be dedicated only to line 1. One Bitzer CRII compressor
can be confi gured for each line.
The compressor size refers to its capacity and number of load stages or
to the inverter presence, therefore diff erent sizes need to be defi ned
for compressors with the same capacity yet a diff erent number of load
stages. The inverter is always associated to size 1.
Tutorial : below is one example of some possible confi gurations:
•
One line, 4 reciprocating compressors with the same capacity, the fi rst
with inverter (2 sizes).
•
One line, 4 scroll compressors with the same capacity, the fi rst Digital
Scroll™ (1 sizes).
•
One line, 4 reciprocating compressors with the same capacity, the fi rst
two with 4 load stages, the other two not capacity-controlled (2 sizes).
•
One line, 4 reciprocating compressors with the same capacity and 4
load stages each (1 size).
•
Two lines, line 1 with 2 screw compressors with the same capacity,
the fi rst with continuous modulation, line 2 with 4 reciprocating
compressors with two diff erent capacities, the fi rst two with 4 load
stages, the other two with 2 load stages (1 size on line 1, 2 sizes on
line 2).
•
Two lines, line 1 with 4 scroll compressors, the fi rst Digital Scroll™, line
2 with 4 reciprocating compressors, the fi rst with inverter (1 size line 1,
2 sizes line 2).
6.3.2 Rotation
pRack pR300 can manage 4 diff erent types of device rotation:
•
FIFO (First In First Out): the fi rst device to start is also the fi rst to stop
•
LIFO (Last In First Out): the last device to start is the fi rst to stop
•
By time: the device with the least number of operating hours starts and
the device with highest number of operating hours stops
•
Custom: the on/off sequences are defi ned by the user
Note : Diff erent Sizes of compressors can only be managed with
Custom rotation.
The type of rotation is selected and the corresponding parameters set
during the start-up procedure or in main menu branch C.a.f/C.b.f.
The activation thresholds are calculated diff erently depending on
whether FIFO, LIFO, time or Custom rotation is used:
Device activation threshold calculation
Rotation Threshold calculation
FIFO
LIFO
By time Static: the range of variation of the control request is divided equally
between the number of stages available
Custom Dynamic: the thresholds are calculated depending on the
capacity eff ectively available
Tab. 6.d
Example 1: FIFO rotation, 4 compressors of the same capacity
without load stages.
The activation thresholds are 25, 50, 75 and 100 %.
C1
25% 50% 75% 100% Regulation request
C2 C3 C4
Fig. 6.h
Example 2: Custom rotation, 4 compressors with capacities of 10,
20, 30 and 40 kW. The activation thresholds with all the compressors
available are 10, 30, 60, 100 %.
C 1
10% 3 0% 6 0% 100%
Regu l ation re q uest
C 2 C 3 C 4
Fig. 6.i
If an alarm is active on compressor 3, the recalculated activation
thresholds are 10, 30, 70 %.
10% 3 0% 7 0%
Regu l ation re q uest
C 2 C 4
Fig. 6.j
Activation of the compressors and load stages may be:
•
Grouped (CpppCppp): fi rst all the load stages are activated on one
compressor before starting the next one
•
Balanced (CCpppppp): fi rst all the compressors are started at minimum
capacity and then the corresponding load stages are activated, one for
each compressor, in sequence.