Table of Contents
Advertisement
6.3
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
R407C / R134a 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 16). 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 be 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 16: 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. 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 indicates. This is due to the high
hygroscopicity of POE oil. To determine the actual moisture content of the lubricant, samples have
to be taken from the system and analysed.
NOTE: ZRH* and ZBH* horizontal scroll compressors are fitted with an internal oil pump.
NOTE: Rotalock valves should be periodically re-torqued to ensure that leak tightness is
maintained.
6.4
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.
6.5
Unbrazing system components
WARNING
Explosive flame! Burning! Oil-refrigerant mixtures are highly flammable.
Remove all refrigerant before opening the system. Avoid working with an
unshielded flame in a refrigerant charged system.
Before opening up a system it is important to remove all refrigerant from both the high and low sides
of the system. If the refrigerant charge is removed from a scroll-equipped unit from the high side only,
22
C6.2.7/1007-0619/E
Advertisement
Table of Contents
