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3.6 - Pressure sensors
Two types of electronic sensors (high and low pressure) are used
to measure various pressures in each circuit.
These electronic sensors deliver 0 to 5 VDC. The sensors are
connected to the SIOB board.
Discharge pressure sensors (high pressure type)
These sensors measure the discharge pressure in each circuit.
They are used to control head pressure or high pressure load
shedding. Discharge pressure sensors are mounted on the
discharge line piping of each circuit.
Suction pressure sensors (low pressure type)
These sensors measure the suction pressure in each circuit.
They are used for EXV control. Suction pressure sensors are
located on the suction piping of each circuit.
Oil pressure sensors (high pressure type)
These sensors measure the oil pressure of each compressor.
Oil pressure sensors are located at the oil port of the
compressor. The economizer pressure is subtracted from this
value to arrive at the differential oil pressure.
Economizer pressure sensors (high pressure type)
These sensors measure the intermediate pressure between
high and low pressure. They are used to control the economizer
performance.
Heat reclaim condenser outlet pressure sensors (optional)
These sensors (for air-cooled units with heat reclaim option)
permit control of the load in the heat reclaim mode (see also
section 7.16).
3.7 - Temperature sensors
Temperature sensors constantly measure the temperature of
various components of the unit, ensuring the correct operation
of the system.
Evaporator entering and leaving water temperature sensors
The evaporator entering and leaving water temperature sensors
are installed in the entering and leaving side water box. They are
used for capacity control and safety purposes.
Condenser entering and leaving water temperature sensors
These sensors measure the entering and leaving water
temperatures in water-cooled units or air-cooled units with the
heat reclaim option.
Suction gas temperature sensor
This sensor is used to control the suction gas temperature. It is
located at the suction line of each compressor.
Discharge gas temperature sensor
This sensor is used to control the discharge gas temperature, and
permits control of the discharge superheat temperature. It is
located at the discharge line of the compressor.
Motor temperature sensor
This sensor is used to control the motor temperature of each
compressor.
Oil temperature sensor
This sensor is used to control the oil temperature of each
compressor.
Temperature setpoint reset sensor
This 4-20 mA sensor can be installed remotely from the unit. It
is used to reset the setpoint on the unit.
Outdoor temperature sensor
This sensor is mounted on the control box of air-cooled units.
Outdoor temperature sensor is used for start-up, setpoint
temperature reset and frost protection control.
Master/slave water sensor (optional)
The water temperature sensor is used for master/slave assembly
control.
3.8 - Actuators
Evaporator pumps
The controller can regulate one or two evaporator pumps
and takes care of the automatic changeover between these
pumps (see also section 7.3).
Condenser pump
In water-cooled units the controller can regulate one condenser
pump.
Electronic expansion valve
The electronic expansion valve (EXV) is used to adjust the
up or down to vary the cross-section of the refrigerant path. This
piston is driven by an electronically controlled linear stepper motor.
The high degree of accuracy with which the piston is positioned
Water ow switch
condition shuts off the unit.
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