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The data inside this manual are not binding and they can be modified by the manufacturer without notice.
All rights reserved.
NPC 280 - 400
8 . 4
P r e s s u r e t r a n s d u c e r s
All models have a high pressure transducer in the refrigeration circuit.
Measuring the outlet pressures of the compressors, they control the unit operation, according to the pressure setpoint values adjusted by the
electronic control.
With these measured values it is possible to control the following functions of each circuit separately:
•
high pressure alarm;
•
unloading for high pressure;
•
high pressure values measurement.
For this reason, if the pressure of a circuit rises above the set limit, there may be an alarm signal that locks the machine and the more or less
delayed powering-off of one or more compressors.
8 . 5
F a n r e g u l a t i o n
The fans can be controlled in two different ways:
•
with speed regulator (
speed control
)
•
by steps (
step
)
The selection is fixed according to the unit configuration.
1. Units configured with “STEP” fans
These units are furnished with a pressure transducer positioned on the refrigerant compressor outlet pipeline.
According to the pressure detected by the transducer, the electronic control switches on or off the fans.
2. Units configured with fan speed regulator (NOT present with 460/3/60 Hz supply)
The unit is furnished with a speed regulator of fan rotation, which operates to maintain the condensing pressure within a pre-fixed
value.
These units are furnished with a pressure transducer positioned on the refrigerant compressor outlet pipeline.
For example, if the temperature of the air sent to the condenser decreases, the pressure transducer will measure a decreasing of the
condensing pressure. This pressure decreasing is sent to the speed regulator which will reduce the fan speed and consequently, the
condenser air flow will be reduced.
Analogously, when the air temperature to the condenser and the condensing pressure increase, the regulator will increase
continuously the fan speed to increase the air flow through the condenser.
The following graphic shows the progress of the fan rotation speed according to the condensing pressure changings.
ATTENTION
The pressure and the fan rotation speed values are set by the electronic control and can not be modified by the user.
% of rotation speed
condensing
pressure [bar g]
0%
max
min
P min
P max
