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Unit Start-up
Figure 68. Stopped to Starting
Limit Conditions
Symbio800 will automatically limit certain operating parameters during startup and run modes to
maintain optimum chiller performance and prevent nuisance diagnostic trips. These limit condi-
tions are noted in
Table 33. Limit Conditions
Running - Limited
Condenser Pressure
Limit
Low Evaporator Re-
frigerant Temperature
Inhibit
Capacity Limited by
Low
Liquid Level
Current Limit
Phase Unbalance
Limit
Low Discharge Super-
heat Limit
Oil Loss Avoidance
High Motor Winding
Temp Limit
Max CFM Limit
Low Water Temp Dif-
ference Limit
110
AdaptiR™ with AFD option Sequence of Operation
Stopped to Starting
Table
33.
The chiller, circuit, and compressor are currently running, but the operation of the
chiller/compressor is being actively limited by the controls. Further information is pro-
vided by the sub-mode.
The circuit is experiencing condenser pressures at or near the condenser limit setting.
The compressor will be unloaded to prevent exceeding the limits.
The circuit is experiencing saturated evaporator temperatures at or near the Low Refrig-
erant Temperature Cutout setting. The compressors will be unloaded to prevent trip-
ping.
The circuit is experiencing low refrigerant liquid levels and the EXV is at or near full
open. The compressor will be unloaded to prevent tripping.
The compressor is running and its capacity is being limited by motor power. For RTHD
with VSD, this limit do not work on the motor current directly, the motor current still
can go to 100% RLA.
The compressor is running and its capacity is being limited by excessive phase current
unbalance.
This is limit control that acts to prevent chiller shutdown when the discharge superheat
approaches the limit setpoint by increasing VFD frequency.
This limit control that acts to prevent chiller shutdown when measured refrigerant flow
too low by increasing compressor capacity including increasing slide valve capacity and/
or VFD frequency.
This is limit control that acts to prevent chiller shutdown when the measured motor
temp approaches limit setpoint by increasing compressor capacity.
This is limit control that acts to prevent chiller shutdown when the estimated evaporator
refrigerant flow approaches the calculated maximum flow by limiting maximum com-
pressor capacity.
This is limit control that acts to prevent too much refrigerant flow bypass from condens-
er to compressor that will cause very low efficiency.
RTHD-SVX04K-EN
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