Prevention Control For High Pressure Increase During Cooling Operation - Hitachi RAS-2-HVNP Service Manual

5. Control System
5.5.2 Prevention Control for High Pressure Increase during Cooling Operation
This function is performed to prevent the abnormal condition (Alarm Code: 02) when the air flow volume is decreased
by a seasonal wind against air outlet of the outdoor unit. When the following conditions are met, the forced Thermo-OFF
operation will be performed.
The cause of stoppage will be 13 during Thermo-OFF.
RAS-(2-2.5)HVNP / RAS-3HVNC
1 Y52C is turned "ON" during the cooling operation, or RY1 is turned "ON" (during the compressor operation).
2 Pressure switch for control is turned "ON".
3 Outdoor liquid pipe temperature ≥ 55ºC
RAS-(4-12)H(V)NC(E)
1 Y52C is turned "ON" during the cooling operation, or RY1 is turned "ON" (during the compressor operation).
2 Pressure switch for control is turned "ON".
3 Condensation temperature ≥ 62ºC
RAS-(3-12)H(V)NP(E)
1 Y52C is turned "ON" during the cooling operation, or RY1 is turned "ON" (during the compressor operation).
2 High Pressure ≥ 3.8MPa
139
SMGB0079 rev.0 - 01/2013
ON 3.6MPa
OFF 2.85MPa
ON 3.6MPa
OFF 2.85MPa
5