Danfoss VLT FC 103 Programming Manual page 152

Parameter Description
3.19.2 25-0* System Settings
Parameters related to control principles and configuration
of the system.
25-00 Cascade Controller
Option: Function:
For operation of multiple devices (compressor)
systems where capacity is adapted to actual load
by means of speed control combined with on/off
control of the devices. For simplicity only
compressor systems are described.
[0] Disabled The Cascade Controller is not active. All built-in
*
relays assigned to compressor motors in the
cascade function will be de-energized. If a
variable speed compressor is connected to the
frequency converter directly (not controlled by a
built-in relay), this compressor will be controlled
as a single compressor system.
[1] Enabled The Cascade Controller is active and will stage/
destage compressors according to load on the
system.
NOTE
This parameter can only be [1] Enabled, if 22-75 Short Cycle
Protection is set to [0] Disabled.
25-04 Compressor Cycling
Option: Function:
To provide equal hours of operation with fixed
speed compressors, the compressor use can be
cycled. The selection of compressor cycling is
either "first in – last out" or equal running hours
for each compressor.
[0] Disabled The fixed speed compressors will be connected in
*
the order 1 – 2 – 3 and disconnected in the
order 3 – 2 – 1. (First in – last out)
[1] Enabled The fixed speed compressors will be connected/
disconnected to have equal running hours for
each compressor.
25-06 Number of Compressors
The number of compressors connected to the Cascade Controller
including the variable speed compressor. If the variable speed
compressor is connected directly to the frequency converter and
the other fixed speed compressors (lag compressors) are
controlled by the two built in relays, three compressors can be
controlled. If both the variable speed and fixed speed
compressors are to be controlled by built-in relays, only two
compressors can be connected.
Range:
2 [ 2 - 9 ]
*
®
VLT Refrigeration Drive Programming Guide
Function:
If 25-06 Number of Compressors is
set to 2 compressors: 1 variable
speed compressor and 1 fixed
speed compressor, both
controlled by built -in relay.
®
MG16H102 - VLT is a registered Danfoss trademark
25-06 Number of Compressors
The number of compressors connected to the Cascade Controller
including the variable speed compressor. If the variable speed
compressor is connected directly to the frequency converter and
the other fixed speed compressors (lag compressors) are
controlled by the two built in relays, three compressors can be
controlled. If both the variable speed and fixed speed
compressors are to be controlled by built-in relays, only two
compressors can be connected.
Range:
3.19.3 25-2* Zone Settings
Parameters for setting the zones within which the pressure
will be allowed to operate before staging/destaging fixed
speed compressors. Also includes various timers to stabilize
control.
Illustration 3.63 The fixed speed compressor(s) is staged/
destaged if the actual feedback enters one of the zones outside
the neutral zone for more than the delay time set for this zone.
If the actual feedback enters the ++zone or - -zone the
compressor(s) is staged/destaged at the time the first delay
timer runs out. The ++zone delay should therefore always be set
shorter than the + zone delay to make it active.
25-20 Neutral Zone [unit]
Range: Function:
4.00 [0-9999.99] Set the neutral zone (NZ) to accommodate
*
normal system pressure fluctuations. In pack
control systems, to avoid frequent switching
Function:
If 25-06 Number of Compressors is
set to 3 compressors: 1 variable
speed compressor and 2 fixed
speed compressor, all controlled
by built -in relay
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