User Guide

Application guidelines
48 AB237986441643en-US0701
Filter driers A properly sized & type of drier is required.
Important selection criteria include the driers
water content capacity, the system refrigeration
capacity and the system refrigerant charge.
The drier must be able to reach and maintain
a moisture level of 50 ppm end point dryness
(EPD).
For new installations with SM/SY/SZ compressors
with polyolester oil, Danfoss recommends using
the Danfoss DML (100% molecular sieve) solid
core lter drier. Molecular sieve lter driers with
loose beads from third party suppliers shall be
avoided. For servicing of existing installations
where acid formation is present the Danfoss
DCL (solid core) lter driers containing activated
alumina are recommended.
The drier is to be oversized rather than under
sized. When selecting a drier, always take into
account its capacity (water content capacity),
the system refrigeration capacity and the system
refrigerant charge.
After burn out, remove & replace the liquid
line lter drier and install a Danfoss type DAS
burn-out drier of the appropriate capacity.
Refer to the DAS drier instructions and technical
information for correct use of the burnout drier
on the liquid line. Also for new installations with
SM compressors with mineral oil the Danfoss DCL
drier is recommended.
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
compressor. This initial charging operation must
be done in liquid phase. The best location is on
the liquid line between the condenser outlet
and the 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
compressor is running. The refrigerant charge
quantity 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
regarding refrigerant reclamation and
storage. For more detailed information, see
“Recommended refrigerant system charging
practice” news bulletin FRCC.EN.050.
Refrigerant charging
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 5mA.
SM/SY/SZ scroll compressors are congured
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.
In testing insulation resistance, Danfoss
recommends that the system be rst operated
briey 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
rst checking for a ground fault (a short circuit to
ground). Be alert for sounds of arcing inside the
compressor.
Installation