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CHAPTER 5: CONTROL AND SAFETY DEVICES
5.1 CONTROL DEVICES
All the control devices are tested on factory before the unit is delivered.
Their operating mode is described in the following paragraphs.
5.1.1 HUMIDITY CONTROL SWITCH
Humidity control switch (Humidistst) enables or disables unit operation depending on the humidity value
desired.
To verify its correct operation, rotate the control knob clock wise (or set the desired value through the
instrument keyboard if a keyboard instrument should be present) and set the humidity desired value close to
lower limit. At this point verify that fan and compressor (after a time delay) will be started in sequence. Verify
as well that the unit is stopped when humidity set is reached.
5.2 SAFETY DEVICES
All the safety devices are set and tested on factory before they are delivered.
Their operating mode is described in the following paragraphs.
All service operations on control and safety devices must be done by TRAINED PEOPLE ONLY:
wrong setting values of the mentioned devices could cause serious damage to the unit and
injuries to the people.
5.2.1 HIGH PRESSURE SWITCH
High pressure switch stops the unit when the discharge pressure exceeds its pre-set limit value.
The reset is manual (by pressing the push-button at the top of the pressure switch located in the electric panel)
and can be done only when pressure is decreased below the device reset value (see table below).
5.2.2 LOW PRESSURE SWITCH
Low pressure switch stops the unit when the suction pressure decreases below its limit pre-set value.
The reset is automatic and it occurs only when pressure is higher than the device differential resetting value
(see table below).
5.2.3 DEFROST THERMOSTAT
This device signals to electronic control that defrost procedure is needed (see paragraph 4.5).
When defrost cycle is activated, defrost thermostat will control its conclusion.
CONTROL DEVICES
ACTIVATION
DIFFERENTIAL
REINSERTION
High pressure switch (bar)
29
7.7
Manual
Low pressure switch (bar)
0.7
2.2
Automatic
Defrost temperature switch (°C)
1
3
Automatic