High Pressure Protection Device; Ras-3Hvrc2; Ras-(4-6)H(V)(R/N)(C/P)2E - Hitachi UTOPIA RAS-4HVRP2E Service Manual

8 Electrical checks of main parts

High pressure protection device

8.4 High pressure protection device

8.4.1 RAS-3HVRC2

If the discharge pressure is excessively high the compressor and the component parts of the refrigeration cycle can be
damaged. Therefore, in case that the discharge pressure is higher than 4.15 MPa the protection control is activated and
the compressor is stopped.:
In case that the discharge pressure is higher than 3.6 MPa the protection control might be performed.
Depending on model (check refrigerant cycle):
1 For controlling the high pressure not to increase excessively during heating operation the gas by-pass circuit and the
air volume of the outdoor fan is controlled automatically.
2 The gas by-pass circuit which is composed of the solenoid valve and the capillary tube for flow adjustment control the
high pressure not to increase excessively by leading the high pressure gas to the low pressure side.
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N O T E
All figures only for illustration purpose. The actual product may differ.

8.4.2 RAS-(4-6)H(V)(R/N)(C/P)2E

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High pressure control (Pressure sensor Pd)
The high pressure is detected during the heating mode by means of a high pressure sensor and the compressor
frequencies are controlled by the proportional control method with operating capacity of the indoor units (or PID control
for the compressor frequency); therefore, the high pressure is controlled within an appropriate range. The output of the
high pressure sensor during the heating operation activates the protection control, the gas bypass.
Heating Operation
Proportional Control of
Compressor Frequency with
High
Operating Capacity of Indoor Units
Pressure
Control
Protection Control (Gas Bypass
Control)
170 SMGB0136 rev.0 - 07/2021
High pressure
switch
Brazing
Pressure
switch for
control
Pressure MPa (kgf/cm G)
2
Output Characteristics of High Pressure Sensor