C6.2.44/0219/E
25
6.4 Lubrication and oil removal
CAUTION
Chemical reaction! Compressor destruction!
Do not mix up ester oils with
mineral oil and/or alkyl benzene when used with chlorine-free (HFC)
refrigerants.
The compressor is supplied with an initial oil charge. The standard oil charge for use with
refrigerants R450A and R513A is a polyolester (POE) lubricant Emkarate RL 32 3MAF. In the field
the oil level could be topped up with Mobil EAL Arctic 22 CC if 3MAF is not available. See
nameplate for original oil charge shown in litres. A field recharge is from 0.05 to 0.1 litre less.
One disadvantage of POE is that it is far more hygroscopic than mineral oil (see
Figure 18
). Only
brief exposure to ambient air is needed for POE to absorb sufficient moisture to make it
unacceptable for use in a refrigeration system. Since POE holds moisture more readily than
mineral oil it is more difficult to remove it through the use of vacuum. Compressors supplied by
Emerson contain oil with low moisture content, and it may rise during the system assembling
process. Therefore, it is recommended that a properly sized filter drier is installed in all POE
systems. This will maintain the moisture level in the oil to less than 50 ppm. If oil is charged into a
system, it is recommended to use POE with a moisture content no higher than 50 ppm.
Figure 18: Absorption of moisture in ester oil in comparison to mineral oil in ppm by weight at 25°C and 50%
relative humidity (h=hours)
If the moisture content of the oil in a refrigeration system reaches unacceptably high levels,
corrosion and copper plating may occur. The system should be evacuated down to 0.3 mbar or
lower. If there is uncertainty as to the moisture content in the system, an oil sample should be
taken and tested for moisture. Sight glass/moisture indicators currently available can be used with
the HFC refrigerants and lubricants; however, the moisture indicator will just show the moisture
content of the refrigerant. The actual moisture level of POE would be higher than the sight glass
specifies. This is due to the high hygroscopicity of the POE oil. To determine the actual moisture
content of the lubricant, samples have to be taken from the system and analysed.
6.5
Oil additives
Although Emerson cannot comment on any specific product, from our own testing and past
experience, we do not recommend the use of any additives to reduce compressor bearing losses
or for any other purpose. Furthermore, the long term chemical stability of any additive in the
presence of refrigerant, low and high temperatures, and materials commonly found in refrigeration
systems is complex and difficult to evaluate without rigorously controlled chemical laboratory
testing. The use of additives without adequate testing may result in malfunction or premature
failure of components in the system and, in specific cases, in voiding the warranty on the
component.
