Daikin WCT Series Operating & Maintenance Manual page 67

Iron
Iron in the oil may originate from compressor castings, oil pump components, shells, tube sheets,
tube supports, shaft material and rolling element bearings.
Zinc
The source, if any may be from additives in lubricant.
Silicon
Silicon can originate from residual particles of silicon left from the manufacturing process, filter
drier material, or dirt.
Moisture
Moisture in the form of dissolved water can be present in lubricating oil to varying degrees. Some
polyolester lubricants may contain up to 50 parts per million (ppm) of water from new unopened
containers. Other sources of water may be the refrigerant (new refrigerant may contain up to 10 ppm
water), leaking evaporator or condenser tubes, or moisture introduced by the addition of either
contaminated oil or refrigerant or improperly handled oil.
Liquid R-134a has the ability to retain up to 1400 ppm of water in solution at 100 F. With 225 ppm
of water dissolved in liquid R-134a, free water would not be released until the liquid temperature
reached -22 F. Liquid R-134a can hold approximately 470 ppm at 15F (an evaporator temperature
which could be encountered in ice applications). Since free water is what causes acid production,
moisture levels should not be of a concern until they approach the free water release point.
A better indicator of a condition which should be of concern is the TAN (Total Acid Number). A
TAN below 0.09 requires no immediate action. TANs above 0.09 require certain actions. In the
absence of a high TAN reading and a regular loss of oil (which may indicate a heat transfer surface
leak), a high moisture content in an oil analysis is probably due to handling or contamination of the
oil sample. It should be noted that air (and moisture) can penetrate plastic containers. Metal or glass
containers with gasket in the top will slow moisture entry.
In conclusion, a single element of an oil analysis should not be used as the basis to estimate the
overall internal condition of a Daikin chiller. The characteristics of the oil and refrigerant, and
knowledge of the interaction of wear materials in the chiller must be considered when interpreting a
wear metal analysis. Periodic oil analysis performed by a reputable laboratory and used in
conjunction with compressor vibration analysis and operating log review can be helpful tools in
estimating the internal condition of a Daikin chiller.
Daikin recommends that an oil analysis be performed annually. Professional judgment must be
exercised under unusual circumstances, for example, it might be desirable to sample the oil shortly
after a unit has been placed back into operation after it has been opened for service, as recommended
from previous sample results or after a failure. The presence of residual materials from a failure
should be taken into consideration in subsequent analysis. While the unit is in operation, the sample
should be taken from a stream of oil, not in a low spot or quiet area.
Changing Oil Filters
The oil filter in these compressors can be changed by simply isolating the filter cavities. Close the
oil discharge line service valve and the oil pressure regulator valve. Remove any refrigerant using
EPA approved methods, Remove the filter cover, remove the filter and replace with new element.
Reopen the valve in the pump discharge line and purge air from the lubricant filter cavity. Re-adjust
the oil pressure regulator valve for the right pressure differential setting @ 50psi (50Hz) / 36psi
(60Hz) after starting the oil pump manually and before restarting the chiller.
OMM WCT Centrifugal Chillers D-EOMWC01302-16EN - 67/84