Models 14.4 - 26.4, controller pCO
2
Blue Box - Page 73
8.2 OPERATING DESCRIPTION
8.2.1 Introduction
The microprocessor control regulates the water temperature of the evaporator maintaining it at the set-point
value acting on the compressors management.
The control manages all the components of the chiller, the alarms and “ancillary” functions.
Almost all the parameters referred to below (set-points, differentials, calibration, delays...) can be programmed
by means of the various menus. Refer to the specific manual for the pCO
2
controller.
8.2.2 Unit in stand-by mode
The unit is in stand-by mode when it is correctly supplied with power but not actually enabled to operate.
In this condition the display shows the values of the various machine parameters, but the operation of the
compressor is not inhibited.
Power-on is obtained by pressing the “ON-OFF” button of the microprocessor control or via an external interlock.
8.2.3 Enabling the unit
Start-up of the unit from stand-by mode can be achieved after closing the external enabling contact, by pressing
the "ON/OFF" button, or by means of a signal on the serial line.
Activation of the controller outputs that manage the various sections of the chiller is executed in strict compliance
with the operating times. If the "ON" button is pressed before the external interlocks are closed, the display
indicates which of the external interlocks is not yet enabled.
Operation of the pump has priority to the compressors, which can start only after the evaporator and condenser
pumps are running.
8.2.4 Pumps management
The microprocessor controller does not manage the operation of chilled water and condenser pumps.
When the unit is switched from normal operation to stand-by, due to the opening of an external interlock, the
active pump must be stopped with a delay following the stopping of the last active compressor, to benefit from
the thermal inertia of the system.
8.2.5 Compressor start-up
The controller allows the compressors to be started if the flow switch input is closed within the compressor start-
up delay time interval. If the flow switch input opens, after the compressor has started, the trip is retarded if it
occurs within the time programmed for the compressor stop.
If the unit trips due to the opening of the flow switch input, the relative alarm is displayed.
Starting and stopping of the compressors and capacity step control is managed by the controller in accordance
with the building cooling demands.
8.2.6 Chiller mode operation
In chiller operation, the controller lowers the water temperature value, maintaining it as close as possible to the
programmed set-point.
In the standard version, in which the control acts on the evaporator entering water, the management of compressor
operation and capacity steps is linked to the difference between the entering water temperature and the programmed
set-point.
Summary of Contents for SIGMA 2002
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Page 99: ...Blue Box 93 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 SIGMA 2002 DC MODELS 3 2 13 2...
Page 100: ...Blue Box 94 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 SIGMA 2002 DC MODELS 14 4 26 4...
Page 101: ...Blue Box 95 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 HP MODELS 3 2 8 2 14 4 16 4...
Page 102: ...Blue Box 96 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 HP MODELS 9 2 13 2 18 4 26 4...
Page 103: ...Blue Box 97 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 LE SIGMA 2002 LE DC MODELS 3 2 26 4...
Page 104: ...Blue Box 98 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 LE HP MODELS 3 2 26 4...
Page 105: ...Blue Box 99 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 LC MODELS 3 2 13 2...
Page 106: ...Blue Box 100 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 LC MODELS 14 4 26 4...
Page 107: ...Blue Box 101 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 LC HP MODELS 3 2 13 2...
Page 108: ...Blue Box 102 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 LC HP MODELS 14 4 26 4...
Page 109: ...Blue Box 103 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 LC DC MODELS 3 2 13 2...
Page 110: ...Blue Box 104 REFRIGERANT CIRCUIT DIAGRAM SIGMA 2002 LC DC MODELS 14 4 26 4...
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