72
5.6. Refrigerant Lubrication Control
For the 19DV system, refrigerant is used to lubricate and cool the compressor bearings. The refrigerant
lubrication system mainly includes refrigerant pumptwo control valves, evaporator and condenser filter,
moisture removal desiccant, bearing filter, liquid level switch and additive reclaim system.
Once chiller startup, the system will go into prestart check process. After prestart check ok, control will
check whether bearing pressure difference is less than 5psi before turn on refrigrant pump. This is to
prevent pressure tranduser abnormal reading. Then, refrigrant pump willl be turned on and control will
check whether Liquid Level switch is closed. If the Liquid Level switch is open which means low liquuied
level, then pump refrigerant from evaporator to condenser until Liquid Level is satisfied. Then, control will
continue to pump refrigerant from evaporator to condenser, after bearing pressure difference reaches
8psi, keep lasting for 20s unitil compressor is on.
During pre-lubrication, if the bearing pressure difference is less than 8 psi for continuously 8 seconds
more than 4 retry times, the chiller will shutdown.
The compressor will run after the pre-lubrication process. Refrigerant will be pumped to bearing and
drain to evaporator from condenser float chamber.
When chiller shutdown, the condenser control valve will be closed and the refrigerant will be pumped
from evaporator to bearing and drain to condenser.
5.7. Control Point
5.7.1. Set Point
Set point can be configured at menu “Setpoint” at “USER” access level.
The SETPOINT is determined by the HEAT/COOL MODE, EWT OPTION, and ICE BUILD OPTION in
the below table.
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