System Design Recommendations; Piping Design - Danfoss Maneurop NTZ048 Selection And Application Manuallines

SYSTEM DESIGN RECOMMENDATIONS

Piping design

Suction line
12
Maneurop® NTZ compressors have
been designed and qualified for sta-
tionary equipment using standard al-
ternating power supply. Danfoss does
not warrant the compressors for use
on mobile applications such as trucks,
railways, subways, ships etc.
Oil in a refrigeration circuit is requi-
red to lubricate moving parts in the
compressor. During normal system
operation small oil quantities will
continuously leave the compressor,
with the discharge gas. Therefore, the
system piping shall be designed in a
way which allows a good oil circula-
tion, avoiding oil being trapped in the
system and ensuring a constant oil
return to the compressor. As long as
the amount of oil circulating through
the system is small it will contribute to
Horizontal suction line sections shall
have a slope of 0.5% in the direction
of refrigerant flow (5 mm per meter).
The cross-section of horizontal suction
lines shall be such that the resulting
gas velocity is at least 4 m/s. In vertical
risers, a gas velocity of 8 to 12 m/s is
required to ensure proper oil return. A
max. 4 m
max. 4 m
RECIPROCATING COMPRESSORS
These selection and application gui-
delines concern single compressors
only. For guidelines on manifolding
Maneurop® NTZ compressors, please
refer to literature called "Parallel Appli-
cation Guidelines".
good system operation and improved
heat transfer efficiency.
Lubricant getting trapped in the
evaporator or suction lines will affect
system performance and will ultima-
tely lead to compressor lubrication
failures. Where a poor oil return situa-
tion exists, adding lubricant will not
help safeguard the compressor. Only
a correct piping design can ensure
adequate oil circulation maintaining
safe oil level in the compressor.
U-trap is required at the foot of each
vertical riser. If the riser is higher than
4 m, additional U-traps are required for
each additional 4 meters.The length of
each U-trap must be as short as pos-
sible to avoid the accumulation of
excessive quantities of oil (see figure
below).
To condenser
0.5 % slope,
4 m/s or more
U-trap
U-trap, as short as possible
8 to 12 m/s
0.5 % slope,
Evaporator
4 m/s or more
U-trap, as short as possible