Carrier 19DV Series Installation, Operation And Maintenance Instructions page 21

Fig 9 – VFD cabinet lifting lugs
2.5.5.6 Purge system
The purge system is located under the condenser. See Fig. 10. It has two gas inlets coming from condenser and
compressor. When chiller is running, the condenser line is active/open and non-condensable gas will pulled out
from condenser and when chiller is idle the compressor line is active and non-condensable are pulled out from
compressor volute. This is implemented due to non-condensable gas density being less than refrigerant and
therefore it will accumulate at the highest point when chiller is not running.
In the purge tank the purge gas is cooled by a separate integral R-134a cooling system. The cooling system
consists of an compressor, an air cooled condenser coil, an expansion valve, and a cooling coil in purge tank.
Cooling the purge gas results in condensation of R-1233zd(E) vapor as it touches the coil resulting in a vacuum
which the result that more refrigerant is pushed to the coil. As the purge tank fills up with refrigerant it will be
drained through the purge drain to the refrigerant pump assembly. See Fig. 11.
Non-condensable that comes into contact with the cold coil in the purge tank will not condense and will
accumulate at the top of the purge tank. When the controls sense that there is sufficient non-condensable gas in
the purge tank, the control will open the pumpout valve, activate the purge evacuation pump, and force the gas
through the active carbon filters. To capture any remaining refrigerant the gas is routed through two active carbon
filters that will absorb any remaining refrigerant. As the carbon filters becomes saturated the system will
regenerate the filters by applying heat to the filters while under vacuum and then disperse the regenerated
refrigerant back to the cooler while releasing the non-condensable to atmosphere.
The 19DV purge control is automatic. Purge control should be active when purge inlet temperature (evaporator
refrigerant liquid temp when chiller compressor OFF or condenser saturated temperature when chiller compressor
ON) is greater than purge active temperature set point default 18.3°C. If chiller compressor is running, condenser
solenoid valve should be opened to purge refrigerant from condenser.
If chiller compressor is not running, open the compressor solenoid valve to purge refrigerant from compressor. If
Purge Comp Suction Temp is less than purge compressor off temp (default to -15.5°C) and the refrigerant level
flag is ON, close compressor solenoid valve, condenser solenoid valve, and open pump out solenoid valve. Purge
vent valve and purge vacuum pump shall be kept ON for about 10s. After 10s discharge, pump out solenoid valve,
purge vent valve, and purge vacuum pump shall be kept OFF. Condenser solenoid valve shall be opened if chiller
compressor is running or compressor solenoid valve shall be opened if chiller compressor is not running.
After 10s discharge, it will start 20s delay. Then, check purge compressor suction temperature again; if it is less
than -14°C, it will continue cycle as before.
If refrigerant level in the purge tank is high (both PGLE_HI and PGLE_LO are ON), or purge compressor suction
temperature is less than -11°C and PGLE_LO is ON, then drainage solenoid valve should be opened to drain
refrigerant from purge tank to evaporator (open SV04, SV01, SV02 when chiller is off, open SV04, SV01 when
chiller is on). After PGLE_LO is OFF, keep drain process for another 1s, then set the refrigerant level flag to ON. If
purge level in the purge tank is low (both PGLE_HI and PGLE_LO are OFF), drainage solenoid valve should be
closed.
If pump out solenoid valve is accumulated ON for 100 minutes, purge system should do regeneration process for
reg_tim minutes (default = 120 minutes - 19DV Configuration Menu), regardless whether purge is active. When
regeneration process active, the Purge Regeneration Valve and Purge Heater should be on for reg_tim minutes,
purge vacuum pump should be on for 3 minutes and then 10 minutes off, alternating during reg_tim minutes. Upon
regeneration completion, purge system will wait for another 4 hours to let carbon filter cool down before it will
operate normally.
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