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SYSTEM DESIGN RECOMMENDATIONS
Discharge line
Oil charge and oil separator
Filter driers
Operating limits
High Pressure
The suction rotolock valves that can be
ordered from Danfoss as accessories
are designed for average pipe sizes, and
selected for systems running at nominal
conditions.
The pipe sizes selected for specific sys-
tems may differ from these recommen-
ded sizes.
It is recommended that the suction
lines be insulated to limit suction gas
superheat.
When the condenser is mounted abo-
ve the compressor, a loop above the
condenser and a U-trap close to the
compressor are required to prevent li-
quid draining from the condenser into
the discharge line during standstill.
In most installations the initial compres-
sor oil charge will be sufficient. In instal-
lations with line runs exceeding 20 m, or
with many oil traps, or an oil separator,
additional oil may be required. In instal-
lations with risk of slow oil return, such
as in multiple evaporator or multiple
condenser installations, an oil separator
is recommended. Also refer to page 29.
For new installations with MTZ com-
pressors, Danfoss recommends using
the Danfoss DML 100%-molecular sieve
solid core filter drier. Molecular sieve
filter driers with loose beads from third
party suppliers should be avoided.
For servicing of existing installations
where acid formation is present, Dan-
foss DCL solid core filter driers contai-
ning activated alumina are recommen-
ded.
The drier should be oversized rather
than undersized. When selecting a drier,
always take into account its capacity
(water content capacity), the system
refrigerating capacity and the system
refrigerant charge.
A high pressure safety switch is requi-
red to stop the compressor should the
discharge pressure exceed the values
shown in the table below. The high
pressure switch can be set to lower
values depending on the application
and ambient conditions. The HP switch
must either be in a lockout circuit, or be
a manual reset device to prevent com-
pressor cycling around the high pressu-
re limit. When a discharge valve is used,
the HP switch must be connected to the
service valve gauge port, which cannot
be isolated.