Controlling The Crii Capacity Controller With The System Controller; Control Via Analogue Signal - Bitzer KT-230-2 Technical Information

8.4 Controlling the CRII capacity controller with
the system controller
The CRII capacity controller can be controlled via Mod-
bus or via an analog signal. Operation of the com-
pressor at reduced capacity is only permitted within the
part-load application limits for the selected refrigerant.
The minimum possible residual capacity depends on
the respective compressor configuration. Program the
system controller accordingly. For application limits see
BITZER SOFTWARE or Technical Information KT-101
for standard compressors and KT-102 for transcritical
CO applications.
2
8.4.1

Control via analogue signal

The compressor capacity is controlled by a DC voltage
signal. This type of control is particularly suitable for
systems with simple controllers equipped with an out-
put for 0 to 10 V and a relay and when the CN14 ter-
minal strip is used for the BEST SOFTWARE.
• Connection on terminal strip CN13, terminals 1 and
2.
• Control signal: 0 to 10 V DC voltage of an analog
output of the superior controller
• Alternatively, a control signal between 4 and 20 mA
can be connected to terminals 1 and 2. To do this,
connect 500 Ω resistor to CN13, terminals 1 and 2 in
parallel to the control signal.
• Control performance: ±0.5% at 100%
• Linear control characteristics
• Starting with firmware version 2.5.248.00, you can
choose between two characteristics, see the follow-
ing illustrations.
• Control range depending on compressor equipment:
– 100% .. 10% residual capacity: Each compressor
in which each cylinder bank is equipped with a
CRII capacity controller. See the solid line below.
– 100% .. 50% residual capacity: For example, a 4-
cylinder compressor equipped with a CRII capa-
city controller. See the dashed line below.
24
CRII
0 .. 10 V
100%
80%
60%
*
CR
min
40%
20%
CR
min
0%
0 2 4
Fig. 10: Standard control characteristics ( M
version 2.5.248.00
CRII
0 .. 10 V
100%
80%
60%
*
CR
min
40%
20%
CR
min
0%
0 2 4
0,1
Fig. 11: Alternative control characteristic ( 0 .. M
version 2.5.248.00 and standard control characteristic in all previous
firmware versions.
Control characteristic M
as soon as the start command is given by the higher-
level system controller (B1). The signal controls the
power control linearly between the maximum and min-
imum possible residual power.
Control characteristic 0 .. M
when the start command is given by the higher-level
system controller (B1) and when a voltage is present at
the DC input. The DC voltage signal is directly conver-
ted proportionally into power requirements. Below the
mechanically possible residual capacity due to the
equipment, the compressor runs with minimum residual
capacity.
• Select control characteristics in the BEST
SOFTWARE: Select M
6 8 10
.. M ) from firmware
IN AX
6 8 10
) from firmware
AX
.. M : The compressor starts
IN AX
: The compressor starts
AX
.. M or 0 .. M in the
IN AX AX
KT-230-2
12
U [V]
12
U [V]