Installation
The system must be monitored after initial 
start-up for a minimum of 60 minutes to ensure 
proper operating characteristics such as:
• Proper metering device operation and desired 
super heat readings,
• Suction and discharge pressure are within 
acceptable levels,
• Correct oil level in compressor sump indicating 
proper oil return,
• Low foaming in sight glass and compressor 
sump temperature 18°F above saturation 
temperature to show that there is no refrigerant 
migration taking place,
• Acceptable cycling rate of compressors, 
including duration of run times,
• Current draw of individual compressors within 
acceptable values (max. operating current),
• No abnormal vibrations and noise.
Commissioning
Oil level checking and 
top-up
In installations with good oil return and line 
runs up to 66 ft, no additional oil is required. 
If installation lines exceed 66 ft, additional oil 
may be needed. 1 or 2% of the total system 
refrigerant charge (in weight) can be used to 
roughly dene the required oil top-up quantity 
but in any case the oil charge has to be adjusted 
based on the oil level in the compressor sight 
glass. 
When the compressor is running under stabilized 
conditions the oil level must be visible in the 
sight glass.
The presence of foam lling in the sight glass 
indicates large concentration of refrigerant in the 
oil and / or presence of liquid returning to the 
compressor.
The oil level can also be checked a few minutes 
after the compressor stops.
When the compressor is o, the level in the 
sight glass can be inuenced by the presence of 
refrigerant in the oil.
Always use original Danfoss oil from new cans.
Compressor series Oil
SM Mineral oil 160P
SY P.O.E. 320 SZ
SZ P.O.E. 160 SZ
Top-up the oil while the compressor is idle. Use 
the schrader connector or any other accessible 
connector on the compressor suction line and 
a suitable pump. See News bulletin «Lubricants 
lling in instructions for Danfoss Commercial 
Compressors».
47
FRCC.PC.003.A5.22
Application guidelines