D-EIMWC00804-14EN
Centrifugal Chillers
43
Surge and Stall
Stall and surge are a characteristic of all centrifugal compressors. These conditions
occur when low load combines with high compressor lift. In a stall, discharge gas has
insufficient velocity leaving the impeller to reach the volute and just “sits” or stalls in the
diffuser section. The compressor sound level goes way down due to no flow and the
impeller starts to heat up. In surge, the heated discharge gas alternately flows back
through the impeller and then reverses to the volute about every two seconds. Extreme
noise and vibration occur. The compressor is equipped with a temperature sensor that
shuts it off if these conditions occur.
Lubrication System
The lubrication system provides lubrication and heat removal for compressor bearings
and internal parts. In addition, the system provides lubricant under pressure to
hydraulically operate the unloading piston for positioning the inlet guide vanes for
capacity control. DWDC, dual compressor chillers, have completely independent
lubrication systems for each compressor.
Only the recommended lubricant, as shown in Table 13, can be used for proper operation
of the hydraulic system and bearing lubrication system. Each unit is factory-charged
with the correct amount of the recommended lubricant. Under normal operation, no
additional lubricant is needed. Lubricant must be visible in the sump sight glass at all
times.
The lubricant system for the CE0050 compressor is completely self-contained within the
compressor housing. The assembly includes the pump, pump motor, and lubricant
heater. The oil is pumped to the internal oil filter in the compressor casting and then to
the internal refrigerant-cooled oil cooler.
The other compressor sizes, CE063, through CE126, utilize a separate lubricant pump
located in the sump. The sump includes the pump, motor, heater and lubricant/vapor
separator system. The lubricant is pumped through the external oil cooler and then to the
oil filter located inside the compressor housing. DWSC/DWDC/DWCC 063-126 units,
single or dual compressor, all utilize a water-cooled oil cooler for each compressor.
The oil coolers maintain the proper oil temperature under normal operating conditions.
The coolant flow control valve maintains 95°F to 105°F (35°C to 41°C). Lubrication
protection for coast down in the event of a power failure is accomplished by a spring-
loaded piston in models CE050 through 100. When the oil pump is started, the piston is
forced back against the spring by the oil pressure, compressing the spring, and filling the
piston cavity with oil. When the pump stops, the spring pressure on the piston forces the
oil back out to the bearings.
In model CE126 the compressor coast down lubrication is supplied from a gravity feed
oil reservoir.
A typical flow diagram is shown in Figure 24.
Table 13, Approved Polyolester Oils For R-134a Units
Compressor Models
CE050 - 126
Lubricant Designation
Mobil Artic EAL 46;
ICI Emkarate RL32H
(2)
Daikin Part Number
55 Gal. Drum
5 Gal. Drum
1 Gal. Can
735030432, Rev 47
735030433, Rev 47
735030435, Rev 47
Compressor Oil Label
070200106, Rev OB
NOTES:
1. Approved oil from two suppliers can be mixed, although they have slightly different viscosity.
2. Lubricant from either supplier can be furnished when ordering by Daikin part number.