■ Expected steam volume, taking account of the static head of the
system
■ Pre-charge pressure
V
dev
= (V
col
+ V
dpipe
+ V
e
+ V
fv
)·Df
V
dev
Nominal volume of the expansion vessel in l
V
col
Liquid content of the collectors in l
In systems with Vitosol-FM/300-TM this value = 0
V
dpipe
Content of the pipework subject to steam loads in l
(Calculated from the steam spread and the pipework
content per m pipe length)
In systems with Vitosol-FM/300-TM this value = 0
V
e
Increase in the volume of the heat transfer medium in
its liquid state in l
V
e
= V
a
· β
V
a
System volume (content of the collectors, the
heat exchanger and the pipework)
β
Expansion factor
β = 0.1 to 0.13 for Viessmann heat transfer medi-
um
V
fv
Liquid seal in the expansion vessel in l
(4 % of the system volume, min. 3 l)
Df
Pressure factor
(p
e
+ 1) : (p
e
− p
o
)
p
e
Max. system pressure at the safety valve in bar
(90 % of the safety valve response pressure)
p
o
System pre-charge pressure
– Vitosol 200-TM/Vitosol F:
p
o
= 1 bar + 0.1 bar/m static head
– Vitosol-FM/Vitosol 300-TM:
p
o
= 3 bar + 0.1 bar/m static head
To determine the system and steam volume in the pipework, the content per m of pipe must be taken into consideration.
Vitotrans 200, type WTT
Part no.
3003 453
3003 454
3003 455
3003 456
3003 457
3003 458
3003 459
Capacity
l
4
9
13
16
34
43
61
Copper pipe
Dim.
12 x 1
15 x 1
18 x 1
22 x 1
28 x 1.5
35 x 1.5
42 x 1.5
DN10
DN13
DN16
DN20
DN25
DN32
DN40
Capacity
l/m pipe
0.079
0.133
0.201
0.314
0.491
0.804
1.195
Corrugated
stainless
steel pipe
Dim.
DN 16
Capacity
l/m pipe
0.25
For the liquid content of the following components see the relevant
"Specification" chapter:
■ Collectors
■ Solar-Divicon and solar pump assembly
■ DHW cylinder and heating water buffer cylinder
Note
Check the size of the expansion vessel on site.
Calculation with "Solsec" design program
The "Solsec" program is available at www.viessmann.com for calcu-
lating the residual cooling capacity and sizing the expansion vessels.
Safety valve
The heat transfer medium is drained from the solar thermal system
via the safety valve if the max. permissible system pressure is
exceeded. According to DIN 3320, the response pressure of the
safety valve is the max. system pr10 %.
The safety valve must comply with EN 12975 and EN 12977, be
matched to the heating output of the collectors and be able to handle
their maximum output of 900 W/m
2
.
Absorber area in m
2
Valve size (size of the inlet cross-section)
DN
40
15
80
20
160
25
Discharge and drain lines must terminate in an open container,
capable of collecting the total content of the collectors.
Viessmann Solar-Divicons are equipped with 6 bar safety valves at
the factory. In solar thermal systems equipped with switching collec-
tors, the 6 bar safety valves fitted at the factory can be replaced with
8 bar valves. See accessories, page 86.
High limit safety cut-out
The solar control units Vitosolic 100 and 200 are equipped with an
electronic temperature limiter.
A high limit safety cut-out in the cylinder is required when less than
40 l cylinder capacity is available per m
2
absorber area. This reliably
prevents temperatures above 95 °C in the cylinder.
Example:
■ 3 Vitosol-F flat-plate collectors, 7 m
2
absorber area
■ DHW cylinder with 300 l capacity
■ 300 : 7 = 42.8 l/m
2
A high limit safety cut-out is
not
required.
Information regarding design and operation
(cont.)
136
VIESMANN
VITOSOL
13
5822 440 GB