Product Overview

Application examples
The diagrams shown here are principles only, without installation-specific details.
For accurate control of evaporators from 0…100 % refrigeration capacity.
3-port hot-gas bypass
control application
•
Suitable for test rooms, laboratory systems, small chilled water units and DX
evaporators with a refrigeration capacity of up to approx. 40 kW.
Recommended differential pressure Δpv100 across the fully opened valve
(control path AB → A) 0.5 < Δp
v100 < 1 bar (see selection chart)
4721Z04
+
–
AB
A
B
Refrigeration capacity Q
0
Refrigerant
Condensation temperature t
c
Evaporation temperature t
0
Liquid temperature t
fl
Selected valve
Differential pressure Δp
v100
across valve
24 kW
R22
40 °C
+ 5 °C
35 °C
M3FB15LX/A
0.7 bar
The control valve throttles the capacity of a compressor stage. The hot gas is
injected directly into the evaporator allowing capacity control from 100 % to
approximately 0 %.
Indir
ect hot-gas
bypass
•
Suitable for use in large refrigeration systems in air conditioning applications, to
prevent unacceptable fluctuations in temperature between compressor stages.
The differential pressure Δp
v100
across the fully opened valve is determined by the
condensation pressure at low load minus the pressure upstream of the evaporator.
If no details are provided, the differential pressure Δp
v100 can be assumed to
be 4 bar.
4721Z05
+
–
A
AB
Refrigeration capacity Q
0
,one compressor stage
Refrigerant
Condensation temperature full/low load t
c
Evaporation temperature full load/low load t
0
Liquid temperature t
fl
Differential pressure Δp
v100
(from R22 vapor table)
Selected valve
Actual capacity,
approx.
30 kW
R22
45 / 35 °C
5 / 15 °C
40 / 30 °C
5.6 bar
M3FB15LX/A
40 kW
The control valve throttles the capacity of a compressor stage. The gas is fed to
the suction side of the compressor and cooled by a re-injection valve. Capacity
control ranges from 100 % to approx. 10 %.
Direct hot-ga
s
bypass
•
Suitable for large refrigeration systems for air conditioning, with several compressors
or compressor stages, and where the evaporator and compressor are some distance
apart (attention must be paid to oil return).
The differential pressure Δp
v100
across the fully opened valve is determined by the
condensation pressure at low load minus the suction pressure.
If no details are provided, the differential pressure Δp
v100
can be assumed to
be 6 bar.
4721Z06
+
–
A
AB
Refrigeration capacity Q
0
of one compressor stage
Refrigerant
Condensation temperature full/low load t
c
Evaporation temperature full load/low load t
0
Liquid temperature t
fl
Differential pressure Δp
v100
(from R22 vapor table)
Selected valve
40 kW
R22
45 / 35 °C
2 / 10 °C
40 / 30 °C
6.5 bar
M3FB15LX/A
5 / 10
Siemens Modulating refrigerant valves with magnetic actuator‚ PS43 CE2N4721en
Building Technologies 03.05..2011