RECIPROCATING COMPRESSORS
Evaporator
To condenser
Loop, as high as top
of condenser
max. 4 m
max. 4 m
U-trap, as short as possible
U-trap
8 to 12 m/s
0.5 % slope,
4 m/s or more
U-trap, as short as possible
U-trap
0.5 % slope,
4 m/s or more
Condenser
13
Discharge line
SYSTEM DESIGN RECOMMENDATIONS
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 com-
pressor oil charge will be sufficient. In
installations with line runs exceeding
20 m, or with many oil traps or an oil
separator, additional oil may be requi-
red. In installations with the risk of slow
oil return such as in multiple evapora-
tor or multiple condenser installations,
an oil separator is recommended. Also
refer to the section "Oil charge and oil
level".
Gas velocities higher than 12 m/s will
not contribute to significantly better
oil return. However they will cause hi-
gher noise levels and result in higher
suction line pressure drops which will
have a negative effect on the system
capacity. Note that the suction roto-
lock valves, which can be ordered from
Danfoss as accessories, are designed
for average pipe sizes, selected for sys-
tems running at nominal conditions.
The pipe sizes selected for specific
systems may differ from these average
sizes.
The suction line must always be insu-
lated to limit suction gas superheat.
Oil charge and oil separator
Filter driers
For new installations with NTZ 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 shall be avoided.
For servicing of existing installations
where acid formation is present the
Danfoss DCL solid core filter driers
An MOP-type expansion valve or suc-
tion pressure regulator (i.e. Danfoss
KVL) must be used to limit suction
pressure at a maximum of 4 bar effec-
tive (-5°C). Do not apply both of these
devices in combination with one ano-
ther.
A suction line heat exchanger is not re-
commended for low temperature ap-
plications as this may cause high suc-
Suction line heat exchanger
containing activated alumina are
recommended.
The drier is to 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.
Suction pressure control
When compressors are mounted onto
a rack for a multi-evaporator system
(i.e. supermarket) or when evapora-
tors operate at different temperatures,
use pressure regulators (Danfoss KVP)
without an MOP expansion valve.
tion gas superheat which can result in
too high discharge temperature.
Содержание Maneurop NTZ048
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