User Manual
Use of the MVF661…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 %.
70179
+
–
MVF661...N
Suitable for use in large refrigeration
systems in air conditioning plant, to prevent
unacceptable temperature fluctuations
between the compressor stages.
Indirect hot-gas
bypass application
Application example
With low loads, the evaporating and condensing pressures can fluctuate depending on
the type of pressure control. In such cases, evaporating pressure increases and
condensing 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
0
= 4 °C; t
c
= 40 °C
Part load Q
0
per stage = 28 kW; t
0
= 4 °C; t
c
= 23 °C
KH-R507 t
0
= 0 °C t
0
= 10 °C Interpolation at t
c
= 23 °C
t
c
= 2 °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
0
= 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 MVF661.25-2.5N is suitable, since: 2.03 m
3
/h / 2.5 m
3
/h x 100 % = 81 % (> 50 %)
Direct hot-gas bypass
application
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. Capacity
control ranges from 100 % down to approximately 10 %.
70180
+
–
MVF661...N
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).
12/16
Building Technologies Refrigerant Valves PN 40 CE2N4716en
HVAC Products 08.06.2005