Fridgewatch 2100 Controller Mk4
Publication 3-58
Section 3
Page 30 of 152
Issue 1.1 : 01/08
5.8.
Capacity Control by Fridgewatch 2100
There are three basic capacity control modes:
•
Auto capacity control - by the Fridgewatch 2100 Controller
PID algorithm.
•
Remote capacity control - by a remote controller.
•
Manual capacity control - by the operator.
5.8.1.
Auto Capacity Control
When auto capacity control is selected, Fridgewatch 2100 uses the
proportional, integral and derivative (PID) algorithm, built into the
software program, to match the measured variable as closely as possible
to the set point.
5.8.2. Manual
Capacity
Control
Manual capacity control is the obvious exception to the automatic control
schemes already described. When the operator selects a manual
capacity control mode, auto capacity control elements are ignored and
the operator uses the
and
navigation buttons on the front panel to
generate load and unload pulses. With the Supervisor Key turned to the
Unlocked position, pressing the
button once will generate a load pulse,
while holding the
button down generates a continuous stream of load
pulses; the
button operates in the same way. The duration of each
load pulse is determined by setting S101 (S103) (S105), each unload
pulse by setting S102 (S104) (S106).
In a multi-compressor application, when the controlled compressor
reaches maximum capacity, a further press of the
button starts the
next compressor in the running order. Conversely, on unloading, when
the controlled compressor reaches minimum capacity, a further press of
the
button stops the compressor and transfers control to the previously
started compressor.
In a master/slave configuration, when all the compressors controlled by
the master Fridgewatch 2100 Controller have reached maximum load, a
further press of the
button starts the first compressor in the slave
compressor running order. Conversely, on unloading, when the last
compressor in the slave compressor running order reaches minimum
load, a further press of the
button stops the slave and transfers control
to the master compressor.
5.8.3. Remote
Capacity
Control
In remote capacity control mode, load and unload pulses from a remote
controller, for example, a Fridgewatch Auto Controller or System
Controller, are read into Fridgewatch 2100 Controller and passed on to
the currently controlled compressor to modulate capacity. In a multi-
compressor application, when the first compressor to start reaches
maximum capacity, Fridgewatch 2100 signals this condition to the remote
controller which can provide another load pulse to start the next
compressor in the running order. The remote controller need not be
aware of the number of compressors present and only needs to send a
request to load or unload because Fridgewatch 2100 deals with the rest.
