64
ENG
µchiller +0300053EN rel. 2.2 - 14.12.2021
Functions
High compression ratio prevention (zone 2)
A high compression ratio is a thermal limit of compressor operation: normally control is activated at the limit of the envelope,
reducing capacity when the limit is exceeded; if a probe is fi tted to measure discharge temperature (HP version only) and if the
temperature approaches the limits, compressor capacity will be modulated so as to managed the critical condition. A specifi c
algorithm initially slows down the increase in capacity, until stopping it completely when at the set point (5°C below the ma-
ximum limit); if the temperature increases further, the algorithm gradually and slowly reduces capacity, taking into account
compressor thermal inertia.
AL
Z3
Z2
Z1
Td
HT
5.0°C
CT
DT
(5.0°C)
t
300053_LMNxy_R01
Key
Td Discharge temperature
HT Low discharge temperature alarm threshold
CT High discharge temperature control threshold
DT Control action deviation
AL High discharge temperature alarm zone
Z3 Capacity reduction zone
Z2 Acceleration control zone
Z1 Normal operating zone
Fig. 5.o
Device Description
BLDC compressor 1. Decrease the rate of capacity increase.
2. Limit capacity
Tandem on-off compressors -
ExV valve -
Fan -
High condensing pressure prevention (zone 3)
Device Description
BLDC compressor 1. Decrease the rate of capacity increase.
2. Limit capacity
Tandem on-off compressors 1. -
2. Shutdown a compressor
ExV valve -
Fan -
High motor current prevention (zone 4)
Device Description
BLDC compressor 1. Decrease the rate of capacity increase.
2. Limit capacity
Tandem on-off compressors 1. -
2. Shutdown a compressor
ExV valve MOP with specifi c algorithm
Fan -
High evaporation pressure prevention (zone 5)
Device Description
BLDC compressor 1. Decrease the rate of capacity reduction.
2.
Tandem on-off compressors -
ExV valve MOP
Fan -
Low compression ratio prevention (zone 6)
Device Description
BLDC compressor 1. Decrease the rate of capacity reduction.
2. Increase capacity
Tandem on-off compressors -
ExV valve Variable MOP
Fan Increase condensing pressure set point/decrease evaporation pressure setpoint
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