11 Electrical checks of 
main parts
463
SMGB0087 rev.0 - 12/2013
11
11.4  High pressure protection device
If the discharge pressure is excessively high the compressor and the component parts of the refrigeration cycle can be 
damaged. 
•  High Pressure Switch (PSH):
If the discharge pressure is excessively high the compressor and the component parts of the refrigeration cycle can be da-
maged. Therefore, in case that the discharge pressure is higher than 4.15 MPa (R410A) the protection control is activated 
and the compressor is stopped.
•  Pressure Switch for Control (PSC):
In case that the discharge pressure is higher than 3.6 MPa (R410A) 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 ow adjustment control the 
high pressure not to increase excessively by leading the high pressure gas to the low pressure side.
1. Gas by-pass circuit.
2. Capillary tube.
3. Solenoid valve.
1
2
3
RAS-(2-2.5)HVNP1 / RAS-3HVNC1
High pressure 
switch
Pressure switch 
for control
Brazing
RAS-3HVNP1E RAS-(4-6)H(V)NP1E
Upper Cover
Discharge Pipe
Brazing
Part
Brazing Part
Low Pressure Switch
(PSL)
Suction Pipe
High Pressure Switch
(PSH)
Pressure Sensor
for PD Control
Electrical Box
Discharge pipe
Electrical Box
Upper 
cover
High pressure switch
Pressure sensor for 
PD control
Brazing 
part
Low pressure 
switch
Suction 
pipe
Brazing part
Discharge Pipe
Brazing Part
Brazing Part
Brazing Part
Low Pressure Switch (PSL)
Suction Pipe
High Pressure Switch (PSH)
Pressure Sensor for PD Control
to DRM1 and SC terminals.
or transmission wiring
Do not connect power supply
17E26270A
CAUTION
SCAS4755 DRM1
PCN1
TR1
IC1