Data Sheet for Product

Technical Instructions M3FB…LX… Series Modulating Control Valve
Document Number CA2N4721E-P25 for Hot Gas Control
December 4, 2019
Page 8 Siemens Industry, Inc.
Application Examples,
Continued
Direct Hot-gas Bypass
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 approximately 10%.
• 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 pressure differential pv100 across the fully-open valve is determined by the
condensation pressure at low load minus the suction pressure.
• If no details are provided, the pressure differential pv100 can be assumed to be 87
psi (6 bar).
Example:
Refrigerant capacity of one
compressor stage
Refrigerant
Condensation temperature full
load/low load
Evaporation temperature full
load/low load
Liquid temperature t
fl
Pressure differential pv100
(from R22 vapor table)
Selected valve
11.4 tons
R22
113°F/95°F
(45°C/35°C)
36°F/-50°F
(2°C/10°C)
104°F/86°F
(40°C/30°C)
94 psi (6.5 bar)
M3FB15LX/A
Figure 7. Direct Hot-gas Bypass Application.
Heat recovery
The hot-gas diverting valve may be used for modulating recovery of the heat from the
condenser, even in the event of high pressure differentials.
Recommended pressure drop pv100 across the fully-open valve
(control path AB → A): between 0.5 and 1 bar.
Example:
Refrigeration capacity Q
Refrigerant
Condensation temperature tc
Evaporation temperature to
Liquid temperature tfl
Selected valve
Actual pressure drop
19.1 tons
R134a
122°F (50°C)
36°F (2°C)
113 (45°C)
M3FB32LX
10 psi (0.7 bar)
Figure 8. Heat Recovery Application.