AGL_Ref_ST_ZO_E_Rev00
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3.10 Active oil management
CAUTION
Inadequate lubrication! Bearing and moving parts destruction!
Ensure
adequate oil return from the system into the compressor at any time. No liquid
refrigerant return to the compressor. Liquid refrigerant dilutes the oil, could
wash the oil off the bearings and moving parts and could lead to overheating
and compressor failure.
In applications with multiple compressors an active oil management system is required. Emerson
offers the OM4 TraxOil components for low pressure oil management. Typically, an additional oil
reservoir is needed in this case. If the pressure in the oil separator/reservoir is higher than 60 bar
Emerson recommends using the OM5 TraxOil components. The OM5 is suitable for both high- and
low-pressure oil management systems.
The CO
2
compressors ZO(V)*AG are not released for operation with passive oil management.
For low-pressure oil management systems, Emerson
’s recommended differential pressure is 3.5 bar
in order to achieve sufficient oil flow from the oil reservoir to the compressor. This value will give
satisfactory results, while 1.4 bar can be regarded as a minimum required value.
Figure 20: TraxOil OM4 and OM5
3.11 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.
If an accumulator is used, the oil-return orifice should be from 1 to 1.4 mm in diameter for all
ZO(V)*AG models depending on compressor size and compressor floodback results. To protect this
small orifice from plugging with system debris a large-area protective screen no finer than 30 x 30
mesh (0.6 mm openings) is required. Tests have shown that a small screen with a fine mesh can
easily become plugged causing oil starvation to the compressor bearings. The size of the
accumulator depends upon the operating range of the system and the amount of sub-cooling and
subsequent head pressure allowed by the refrigerant control. For the correct selection and size of
the suction line accumulator, refer to the manufacturer’s specifications.
