Protection Control Function - Hitachi SAMURAI Series Service Manual

4. Troubleshooting

Protection control function

4.4 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 Operation
(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)
Cooling
 Pd ≥ 1.41MPa
 Pd ≥ 1.44MPa
*Pd: High pressure
Discharge Pressure
Over-increase
Prevention
Cooling
 Pd ≥ 1.84MPa
 Pd ≥ 1.87MPa
*Pd: High pressure
Water-cooled systems
(Cooling only)
Suction Pressure
 Ps < 0.18MPa
Decrease
Prevention
 Ps < 0.14MPa
* Ps: Low pressure
Cooler inlet
refrigerant
Tr < -4ºC
temperature
* Tr: Cooler inlet refrigerant
decrease
temperature
prevention (at
Cooling operation)
92
SMGB0097 rev.0 - 07/2015
Description of Control
 I1 < Setting
value×0.95
 Load up prohibition
 I1 < Setting
 Forced load down
value×0.98
 60 seconds passed
 Load down prohibition
and Pd-Ps > 0.3MPa
 Forced load up
 Ps > 0.3MPa
 30 seconds passed
 Load up prohibition
and Twp > 2ºC
 Forced load down
 Twp > 2ºC
Cooling
 10 minutes have
 Load up prohibition
passed or
Pd ≤ 1.39MPa
 Forced load down
 Pd ≤ 1.41MPa →
To Control 
Cooling
 10 minutes have
 Load up prohibition
passed or
Pd ≤ 1.82MPa
 Forced load down
 Pd ≤ 1.84MPa →
To Control 
Water-cooled systems
(Cooling only)
 Load up prohibition
 Ps < 0.20MPa
 Forced load down
 Ps < 0.16MPa
Load up prohibition 60 seconds passed
Release conditions
LCD
Current
limited
Differential
pressure
limited
Outlet water
temperature
limited
High
pressure
over-increase
limited
High
pressure
over-increase
limited
Low pressure
decrease
limited
Cooler
refrigerant
temperature
limited
Display
Segment