Suction Line Accumulator - Emerson Copeland YB56K1G Application Manuallines

test. Systems with multiple compressors (two, three, or more) require additional oil balancing
qualification between the parallel compressors.
A sample compressor equipped with an external oil sight tube can be ordered from Copeland for lab
testing.
Records of the evaporating temperature and the bottom shell temperature shall be taken with a high
sampling rate during the entire oil return or oil balance testing and under all tested conditions. The
liquid level in the sight tube has to be observed and recorded too. Testing conditions shall include
the different operation modes and varying loads. If the system is reversible, the tests should be
conducted in cooling, heating and defrost modes.
System engineers should review the system design and operation to identify the critical conditions
and to check oil return, oil balancing, liquid floodback and oil dilution. For discussion of individual test
results and system behaviour, eg, with regard to oil dilution, please contact the Application
Engineering department. Typically, the following situations should be considered:
▪ In single compressor systems: to check oil return, testing conditions shall be at minimum mass
flow and minimum density of suction gas in continuous and frequent start/stop cycling.
▪ In multiple compressor systems: to check oil return and oil balancing in the tandem or trio,
testing conditions shall be at the corner points of the system application envelope in continuous
and frequent start/stop cycling.
▪ In all systems: to test liquid floodback and oil dilution, all possible transient operation conditions
in the system should be checked, eg, compressor frequent start/stop, compressor start after long
off time with migration, defrost, switching between the operation modes in reversible systems,
load changes, fans or pumps cycling at low load and more. To evaluate the risk of liquid floodback
and oil dilution, please refer to the chart in
inlet have to be checked.
The bottom shell temperature together with the evaporating temperature gives an indication whether
liquid refrigerant is returning or diluted in the compressor oil sump. The compressor sump
temperature must remain in the (green) safe area, as shown in the chart in Figure 13. In case of
operation in the (red) unsafe area, adjustments are required in order to modify the system design,
refrigerant charge or superheat setting of the expansion device(s). The bottom shell temperature
should be measured accurately. The thermo-probe must be properly insulated and positioned on the
opposite side of the sight glass or at an angle of 90° clockwise from the suction inlet with view on the
top.
Figure 13: Oil dilution chart (tb = bottom shell temperature; te = evaporating temperature) and position of oil
temperature sensor

3.16 Suction line accumulator

Due to Copeland scroll's inherent ability to handle liquid refrigerant, for example in flooded start and
defrost cycle operation, an accumulator is not required in most systems.
To determine if a suction line accumulator is required, the system designer must check this with an
appropriate test scenario. See section 3.15 "Compressor oil return, oil balancing, refrigerant
floodback and oil dilution tests".
AGL_Ref_ST_YBK1G_EN_Rev01
Figure 13. Liquid level and superheat at compressor
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