Data Sheet for Product

16 / 20
Siemens Modulating refrigerant valves, PN 63 CE2N4717en
Smart Infrastructure 2019-11-25
Use of the MVS661..N as a hot-gas valve
The control valve throttles the capacity of a compressor stage. The hot gas passes
directly to the evaporator, thus permitting capacity control in the range from 100 %
down to approximately 0 %.
Suitable for use in large refrigeration
systems in air conditioning plant, to pre-
vent unacceptable temperature fluctua-
tions between the compressor stages.
With low loads, the evaporating and condensing pressures can fluctuate depending on
the type of pressure control. In such cases, evaporating pressure increases and con-
densing pressure decreases. Due to the reduction in differential pressure across the
fully open valve, the volumetric flow rate will drop – the valve is undersized. This is why
the effective pressures must be taken into account when sizing the valve for low loads.
Refrigerant R507; 3 compressor stages; Q
0
= 75 kW; t
o
= 4 °C; t
c
= 40 °C
Part load Q
0
per stage = 28 kW; t
o
= 4 °C; t
c
= 23 °C
KH R507 t
o
= 0 °C t
o
= 10 °C Interpolation at t
c
= 23 °C
t
c
= 20 °C 14,4 9,0 14,4 + [(22,4 - 14,4) x (23 - 20) / (40 - 20)] 15,6
t
c
= 23 °C 15,6 11,0
t
c
= 40 °C 22,4 22,0 9,0 + [(22,0 - 9,0) x (23 - 20) / (40 - 20)] 11,0
Interpolation at t
o
= 4 °C
15,6 + [(11,0 - 15,6) x (4 - 0) / (10 - 0)] 13.8
k
vs
theoretical = 28 kW / 13,8 = 2,03 m
3
/h
Valve MVS661.25-2.5N is suitable, since: 2.03 m
3
/h / 2.5 m
3
/h x 100 % = 81 % (> 50 %)
The control valve throttles the capacity of one compressor stage. The gas is fed to
the suction side of the compressor and then cooled using a reinjection valve. Ca-
pacity control ranges from 100 % down to approximately 10 %.
Suitable for large refrigeration systems on
air conditioning applications with several
compressors or compressor stages, and
where the evaporator and compressor are
some distance apart (attention must be
paid to the oil return).
Indirect hot-gas
b
y
pass application
Application example
Direct hot-gas bypass
application