APPLICATION GUIDELINES
44
FRCC.PC.007.B5.02
INSTALLATION
In installations with good oil return and line runs
up to 20 m, no additional oil is required. If instal-
lation lines exceed 20 m, additional oil may be
needed. 1 or 2% of the total system refrigerant
charge (in weight) can be used to roughly defi ne
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 fi lling in the sight glass in-
dicates 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 off , the level in the sight
glass can be infl uenced by the presence of refrig-
erant in the oil.
Always use original Danfoss POE oil 160SZ from
new cans.
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
fi lling in instructions for Danfoss Commercial
Compressors».
Oil level checking and
top-up
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 •
superheat readings
Suction and discharge pressure are within ac-•
ceptable levels
Correct oil level in compressor sump indicating •
proper oil return
Low foaming in sight glass and compressor •
sump temperature 10K above saturation tem-
perature to show that there is no refrigerant mi-
gration taking place
Acceptable cycling rate of compressors, includ-•
ing duration of run times
Current draw of individual compressors within •
acceptable values (max operating current)
No abnormal vibrations and noise.•
Commissioning
Insulation resistance and
dielectric strength
Insulation resistance must be higher than 1 meg-
ohm when measured with a 500 volt direct cur-
rent megohm tester.
Each compressor motor is tested at the factory
with a high potential voltage (hi-pot) that exceeds
the UL requirement both in potential and in dura-
tion. Leakage current is less than 0.5 mA.
SH scroll compressors are confi gured with the
pump assembly at the top of the shell, and the
motor below. As a result, the motor can be par-
tially immersed in refrigerant and oil. The pres-
ence of refrigerant around the motor windings
will result in lower resistance values to ground
and higher leakage current readings. Such read-
ings do not indicate a faulty compressor.
In testing insulation resistance, Danfoss recom-
mends that the system be fi rst operated briefl y
to distribute refrigerant throughout the system.
Following this brief operation, retest the compres-
sor for insulation resistance or current leakage.
Never reset a breaker or replace a fuse without
fi rst checking for a ground fault (a short circuit to
ground). Be alert for sounds of arcing inside the
compressor.
For the initial charge the compressor must not
run and eventual service valves must be closed.
Charge refrigerant as close as possible to the
nominal system charge before starting the com-
pressor. This initial charging operation must be
done in liquid phase. The best location is on the
liquid line between the condenser outlet and the
fi lter drier. Then during commissioning, when
needed, a complement of charge can be done
in liquid phase: slowly throttling liquid in on the
low pressure side as far away as possible from
the compressor suction connection while com-
pressor is running. The refrigerant charge quan-
tity must be suitable for both summer and winter
operations.
Vacuum or charge from one side can seal the scrolls
and result in a non-starting compressor. When
servicing, always ensure that LP/HP pressures are
balanced before starting the compressor.
Be sure to follow all government regulations re-
garding refrigerant reclamation and storage.
For more detailed information see "Recom-
mended refrigerant system charging practice"
news bulletin FRCC.EN.050.
Refrigerant charging
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