5
Condenser entering/leaving water temperature sensor
These sensors measure the entering and leaving water
temperatures in water-cooled units or air-cooled units with
the heat reclaim option.
Temperature setpoint reset sensor
This is an optional 4-20 mA sensor (energy management
option) which can be installed remotely from the unit. It is
used to reset the setpoint on the unit.
3.5 - The controls
Evaporator pumps
The controller can regulate one or two evaporator pumps
and takes care of the automatic changeover between pumps.
Condenser pumps
The controller can regulate one or two condenser pumps and
takes care of the automatic changeover between pumps.
Electronic expansion valve (EXV)
The EXV is used to adjust the refrigerant flow to changes in
the operating conditions of the machine. To adjust the
refrigerant flow, a piston moves constantly 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 ensures that the flow of refrigerant is precisely
controlled.
The water flow switch configuration
This permits automatic control of the minimum water flow
setpoint of the water flow switch.
3.6 - Frequency variator
The frequency variator is used to control the compressor.
It allows compressor start-up and capacity control by modify-
ing the supply frequency. The variator continually monitors
many compressor parameters in order to ensure its protection.
If a problem occurs, the frequency variator triggers an alarm
and if necessary stops the compressor.
The high-pressure switch is directly connected to the
frequency variator.
3.7 - Connections at the user’s terminal block
3.7.1 - General description
The contacts below are available at the user’s terminal block
on the NRCP2-BASE board (see figure of the control board).
Some of them can only be used if the unit operates in remote
operating type (Remote mode).
The table on the next page summarises the connections at
the user’s terminal block.
3.7.2 - Volt-free contact on/off/cooling/heating
If the unit works in the remote operating mode (Remote),
the operation of on/off contacts and heating/cooling contacts
is as follows:
Without multiplexing
Off
Cooling
Heating
On/off contact
Open
Closed
Closed
Cooling/heating contact
-
Open
Closed
3.7.3 - Volt-free setpoint selection contact
Cooling
Heating
csp1
csp2
hsp1
hsp2
Setpoint selection contact
Open
Closed
Open
Closed
3.7.4 - Volt-free capacity limit selection contact
100%
Limit 1
Limit 2
Capacity limit 1
Open
Closed
Open
Capacity limit 2
Open
Open
Closed
