Viessmann VITODENS 242-F Technical Manual page 71

Design information
Expansion vessel
The expansion vessel can be calculated once the steam spread has
been determined and any heat sinks that may be used have been
taken into consideration.
The required volume is determined by the following factors:
■ Expansion of the heat transfer medium in its liquid state
■ Liquid seal
■ Expected steam volume, taking account of the static head of the
system
■ Pre-charge pressure
V = (V + V + V + V )·Df
dev col dpipe e fv
V Nominal volume of the expansion vessel in l
dev
V Liquid content of the solar collectors in l
col
V Content of the pipework subject to steam loads in l
dpipe
(Calculated from the steam spread and the pipework content
per m pipe length)
To determine the steam volume in the pipework, the capacity per m of pipe must be taken into consideration.
Copper pipe Dim.
Capacity l/m pipe
Corrugated stainless Dim.
steel pipe
Capacity l/m pipe
For the liquid content of the solar collectors, see the Vitosol technical
guide.
Quick selection of expansion vessel and heat sink
The details in the following table are standard values. They allow
quick estimates at the design and calculation stage. We recommend
verifying the values with appropriate calculations. The selection
refers to a hydraulic system with a liquid "bag" and use of a 6 bar
safety valve.
Vitosol 100-FM/200-FM, type SV
Absorber area in m 2 Static head in m
2.01 and 2.3
4.02 and 4.6
6.03 and 6.9
Vitosol 100-FM/200-FM, type SH
Static head in m
Absorber area in m 2
2.3
4.6
6.9
VITODENS
(cont.)
12 × 1
DN 10
0.079
System capacity in l
5
10
15
5
10
15
5
10
15
System capacity in l
5
10
15
5
10
15
5
10
15
V Increase in the volume of the heat transfer medium in its liq-
e
uid state in l
V = V · β
e a
V System volume (content of the solar collectors, the heat
a
exchanger and the pipework)
β Expansion factor
β = 0.13 for Viessmann heat transfer medium from −20 to
120 ºC
V Liquid seal in the expansion vessel in l
fv
(4 % of the system volume, min. 3 l)
Df Pressure factor
(p + 1): (p − p
e e o
p Max. system pressure at the safety valve in bar (90 % of
e
the safety valve response pressure)
p System pre-charge pressure
o
p = 1 bar + 0.1 bar/m static head
o
15 × 1 18 × 1 22 × 1
DN 13 DN 16 DN 20
0.133 0.201 0.314
DN 16
0.25
For further information, see the Vitosol technical guide.
Note
Check the size of the expansion vessel on site.
Recom. expansion vessel
capacity in l
22.3
25.7
29.2
24.7
27.6
31.0
28.5
29.6
32.9
Recom. expansion vessel
capacity in l
22.9
26.4
29.8
26.0
28.9
32.3
30.5
31.5
34.8
)
28 × 1.5 35 × 1.5
DN 25 DN 32
0.491 0.804
Recom. heat sink
(see page 70)
18 —
25
25 2 m uninsulated pipe
—
—
40 Type 21
0.6 m uninsulated pipe
—
Recom. heat sink
(see page 70)
18 —
25
40 2 m uninsulated pipe
—
—
40 Type 21
0.6 m uninsulated pipe
50 —
VIESMANN
42 x 1.5
DN 40
1.195
5
71