8
REFRIGERANT LUBRICATION CYCLE
Summary —
The 19DV Series chiller uses refrigerant to
lubricate the bearings. The lubrication control is automatical-
ly controlled by the chiller controls. In normal RUN mode re-
frigerant is pumped by means of a refrigerant pump from the
high side condenser float chamber to the bearings. Prior to
start-up liquid level in the high side condenser float chamber
is maintained by pumping refrigerant liquid from the evapo-
rator to the high side float chamber until level sensor is satis-
fied. If liquid high side float level is not satisfied the pump
will move refrigerant from the evaporator to the condenser.
Figures 4 and 5 identify the refrigerant lubrication as-
sembly. Supply refrigerant is pulled through a filter drier by
the refrigerant pump and is pumped to the bearings through
two protective filters and then returned to the evaporator.
There are two pressure sensors located across the refrigerant
pump. During RUN mode a minimum of 12 psid is required
for the refrigerant pump delta difference. An alert will trigger if
this value is less than 13 psid while the machine is in normal
operating mode. Consult the Controls Operation and Trouble-
shooting Manual for details.
Bearings — The 19DV motor-compressor assembly in-
clude two sets of purely refrigerant lubricated bearings. The
motor shaft is supported by a combination set of journal
bearing and roller element bearings on each end of com-
pressor. The refrigerant lubrication pressure difference is
defined as the bearing input pressure minus the bearing out-
put pressure plus the Refrigerant Delta P Offset.
Fig. 4 — Refrigerant Lubrication Cycle
CAUTION
To avoid adverse effects on chiller operation, consider-
ations must be made to condenser water temperature con-
trol. For steady state operation, the minimum operating
refrigerant pressure differential between cooler and con-
denser is approximately 7 psid (48 kPa) with a maximum
evaporator refrigerant temperature of 65°F (18°C). Consult
Chiller Builder for required steady state operational limits
and low lift options. Inverted start conditions are accept-
able for short durations of time, but for periods exceeding 5
minutes, a special control solution strategy should be used
to allow the chiller to establish a minimum refrigerant pres-
sure differential (and thereby adequate equipment cooling).
PURGE SYSTEM
CONDENSER
HIGH SIDE FLOAT
CHAMBER
REFRIGERANT
LUBRICATION
SYSTEM
VENT LINE
COOLER
ECONOMIZER
LOW SIDE
FLOAT CHAMBER
COMPRESSOR
EDUCTOR
= PURGE
= LUBE SYSTEM
= MAIN REFRIGERANT SYSTEM
LEGEND
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