Installation
Refrigerant charging
It is recommended that system charging be
done using the weighed charge method, adding
refrigerant to the high side of the system.
Charging the high and low sides of a system
with gas simultaneously at a controlled rate is
also an acceptable method. Do not exceed the
recommended unit charge, and never charge
liquid to the low side.
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
regarding refrigerant reclamation and storage.
Insulation resistance and
dielectric strength
Insulation resistance must be higher than 1
megohm when measured with a 500 volt direct
current 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 duration. Leakage current is less than 5
mA.
MLZ/MLM scroll compressors are configured
with the pump assembly at the top of the shell,
and the motor below. As a result, the motor
can be partially immersed in refrigerant and
oil. The presence of refrigerant around the
motor windings will result in lower resistance
values to ground and higher leakage current
readings. Such readings do not indicate a faulty
compressor, and should not be cause for concern.
In testing insulation resistance, Danfoss
recommends that the system be first operated
briefly to distribute refrigerant throughout the
system. Following this brief operation, retest the
compressor for insulation resistance or current
leakage.
Never reset a breaker or replace a fuse without
first checking for a ground fault (a short circuit to
ground). Be alert for sounds of arcing inside the
compressor.
In installations with good oil return and line
runs up to 10 m, no additional oil is required. If
installation lines exceed 10 m, additional oil may
be needed. 3 or 4% of the total system refrigerant
charge (in weight) can be used to roughly define
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 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 influenced by the presence of
refrigerant in the oil.
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
filling in instructions for Danfoss Commercial
Compressors".
MLZ116 is factory charged with PVE32, when
topping up the compressor, customer could also
use PVE68 lubricant. Danfoss supply PVE68 as
accessory.
There will be no reliability risks even MLZ116 is
with 100% PVE68.
Oil level checking and
top-up
34
FRCC.PC.035.A5.02
Application Guidelines
Single compressors
