Data Sheet for Product

Technical Instructions MVS661..N Series Modulating Refrigerant Valves
Document Number 155-404 for Ammonia (R717) and Safety Refrigerants
May 11, 2016
Page 12 Siemens Industry, Inc.
Application
Examples
Use of the MVS661…
as an expansion
valve
Capacity optimization
The application examples below reflect principles only. They do not include installation-
specific details such as safety elements refrigerant collectors, and so on.
 Typical control range is 20 to 100%.
 Increased capacity through better use of the evaporator
 The use of two or more compressors or compressor stages significantly increases
efficiency with low loads.
 Especially suitable for fluctuating condensing and evaporating pressures
 For more information, see Engineering Notes.
Electronic superheat control is achieved by using additional control equipment.
Application example
Refrigerant R717C; Q
0
= 205 kW; t
o
= 25°F (–5°C); t
c
= 95°F (35°C)
The correct C
V
(k
vs
) value for the MVS661..-.. valve must be determined.
The important section of table KE for R717C (see Table 6 or Table 7) is the area around
the working point. The correction factor KE relevant to the working point should be
determined by linear interpolation from the four guide values.
Note on interpolation
In practice, the KE, KH or KS value can be estimated because the theoretical C
V
(k
vs
)-
value ascertained will be rounded off by up to 30% to one of the ten available C
V
(k
vs
)-
values, allowing you to proceed directly at Step 4.
Step 1: For t
c
= 95°F (35°C), calculate the value for t
o
= 14°F (-10°C) between
values 68°F (20°C) and 104°F (40°C)in the table; result: 574.
Step 2: For t
c
= 95°F (35°C), calculate the value for t
o
= 32°F (0°C) between values
68°F (20°C) and 104°F (40°C) in the table; result: 553.
Step 3: For t
0
= 23°F (-5°C), calculate the value for t
c
= 95°F (35°C) between
correction factors 574 and 553; calculated in steps 1 and 2; result: 450.
Step 4: Calculate the theoretical C
V
(k
vs
) value; result: 0.53 (0.46 m
3
/h).
Step 5: Select the valve; the valve closest to the theoretical C
V
(k
vs)
value is the
MVS661.25-0.4N.
Step 6: Check that the theoretical C
V
(k
vs
) value is not less than 50% of the nominal
C
V
(k
vs
) value.
Table 5. Interpolation Table.
KE-R717C
t
0
= 14°F
(–10°C)
t
0
= 32°F
(0°C)
Interpolation at
t
c
= 95°F
(35°C)
t
c
= 68°F (20°C)
481
376
481 + [(605 – 481) × (35- 20)/(40 - 20)]
574
t
c
= 95°F (35°C)
574
553
t
c
= 104°F (40°C)
605
612
376 + [(612 - 376) × (35 - 20)/(40 - 20)]
553
Interpolation at
t
0
= 23°F
(-5°C)
574 +[(553 - 574) × (-5 - 0)/(-10 - 0)]
450