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Hitachi SAMURAI Series Service Manual page 124

Air cooled water chillers and air to water heat pump
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4. Troubleshooting
Protection control function
4.5 Protection control function
This Chiller unit is provided with protection control functions to release abnormal statuses before reaching alarm because
of abnormality occurrence.
Name of
protection control
Conditions for
(Compressor
frequency control)
 I1 > Setting value×0.97
Overcurrent
protection
 I1 > Setting value
(Unit current)
* I1: Unit current
 Pd-Ps ≤ 0.3MPa
 Pd-Ps ≤ 0.25MPa
Differential
Pressure Protection
* Pd: High pressure
Ps: Low pressure
 Twp ≤ 2ºC
Outlet Water
Temperature
 Twp ≤ 1.5ºC
Decrease
* Twp: Outlet water
Prevention
temperature (Protection)
 Pd ≥ 1.84MPa
Discharge Pressure
Over-increase
 Pd ≥ 1.86MPa
Prevention
*Pd: High pressure
Air-cooled systems
(Cooling only)
Suction Pressure
 Ps < 0.17MPa
Decrease
Prevention
 Ps < 0.13MPa
* Ps: Low pressure
Cooler inlet
refrigerant
Tr < -4ºC
temperature
* Tr: Cooler inlet
decrease
refrigerant temperature
prevention (at
Cooling operation)
 Ps ≤ 0.05MPa AND
100% pressure switch for
detection ON
Frost formation
limitation
 Ps ≤ 0.05MPa AND
100% pressure switch for
detection OFF
116
SMGB0082 rev.1 - 07/2015
Description of Control
Operation
 Load up prohibition
 Forced load down
 Load down
prohibition
 Forced load up
 Load up prohibition
 Forced load down
 Load up prohibition
 Forced load down
 Load up prohibition
 Forced load down
Load up prohibition
 Forced load down
 Load up prohibition
Release conditions
 I1 < Setting value×0.95
 I1 < Setting value×0.98
 60 seconds passed and
Pd-Ps > 0.3MPa
 Ps > 0.3MPa
 30 seconds passed and
Twp > 2ºC
 Twp > 2ºC
 10 minutes have passed
or
Pd ≤ 1.76MPa
over-increase
 Pd ≤ 1.84MPa → To
Control 
Air-cooled systems (Cooling
only)
Low pressure
 Ps < 0.19MPa
 Ps < 0.15MPa
60 seconds passed
5 minutes passed OR Ps ≥
0.1MPa
Display
LCD
Segment
Current
limited
Differential
pressure
limited
Outlet water
temperature
limited
High
pressure
limited
decrease
limited
Cooler
refrigerant
temperature
limited
-
-
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