D
Heating water buffer cylinder
E
More than 1 heating water buffer cylinder as low loss header
(5 sensors)
F
Heating water buffer cylinder 2
G
Heating water buffer cylinder 1
H
Low loss header
Possible with large water volume in mains
L
TS131
(2 pce from Vitoflex 300-UF, 720 kW)
M
Additional heat generator controlled with a max. retaining
valve for
- Oil/gas boiler
- Electric heater
P
With additional heat generator, dual mode
- Oil, gas, electric
M20 Boiler circuit pump
Y20 Boiler mixer
KW Cold water supply min. 2.5 bar, max. 3.5 bar
Design recommendation
Trade name
Vitoflex 300-UF
Rated heating output
kW
390
530
720
950
1250
Boiler circuit
DN 80
DN 80
DN 100
DN 125
DN 125
Thermally activated safety valve TS-131
pce
1
1
2
2
2
Required water flow rate at 2.5 bar
l/h
1637
2224
3020
3986
5246
Cylinder capacity
l
3200
4300
5800
7600
10000
Supply line ZLg
R
¾
¾
1
1
1¼
Supply line ZLv
R
¾
¾
¾
¾
¾
Drain line ALv
R
¾
¾
¾
¾
¾
Safety valve type SV 68 M
R
1¼
1½
1½
2x 1½
2x 1½
Safety line SL
DN 50
DN 65
DN 80
2x DN 65
2x DN 80
Sizing the expansion vessel
In accordance with EN 12828, water heating systems must be equip-
ped with a diaphragm expansion vessel. The size of the expansion
vessel to be installed is subject to the heating system specification
and should be checked in each case.
Quick selection table for calculating the vessel size V
n
Safety valve
p
sv
bar
3.0
V
n
Pre-charge
pressure
bar
1.0
1.5
1.8
litre
System vol-
ume V
A
litre
220
—
—
25
340
200
—
35
510
320
200
50
840
440
260
80
1050
540
330
100
1470
760
460
140
2100
1090
660
200
2630
1360
820
250
3150
1630
990
300
4200
2180
1320
400
5250
2720
1650
500
6300
3260
1980
600
8400
4350
2640
800
10500
5440
3300
1000
Selection example
Conditions:
p
sv
= 3 bar (response pressure of the safety valve)
H
= 13 m (static head of the system)
Q
= 18 kW (rated heating output of the heat source)
v
= 8.5 l/kW (specific water capacity)
Panel radiators 90/70°C
V
PH
= 1000 l (volume of buffer cylinder)
The specific water capacity v was determined as follows:
■ Radiators: 13.5 l/kW
■ Panel radiators: 8.5 l/kW
■ Underfloor heating system: 20 l/kW
Calculation:
V
A
= Q x v + 1000
V
A
= 18 kW x 8.5 l/kW + 1000 l
= 1153 l
If possible, when calculating the gas pre-charge pressure, select a
supplement of 0.2 bar:
p
0
≥ H/10 + 0.2 bar
p
0
≥ (13/10 + 0.2 bar) = 1.5 bar
From the table:
With p
sv
= 3 bar, p
0
= 1.5 bar, V
A
= 1153 l
V
n
= 250 l (for V
A
max. 1360 l)
Selected:
1 x diaphragm expansion vessel N 250 (from Vitoset pricelist)
■ All details relate to a flow temperature of
90 °C
.
■ The tables have allowed for a hydraulic seal to DIN 4807-2.
Recommendation:
■ Select a sufficiently high safety valve response pressure:
p
sv
≥ p
0
+ 1.5 bar
■ For circulation pumps, due to the inlet pressure required, select at
least 0.3 bar above the pre-charge pressure even for attic installa-
tions: p
0
≥ 1.5 bar
■ Set the fill or starting pressure on the water side of vented systems
in their cold state at least 0.3 bar above the pre-charge pressure:
p
F
≥ p
0
+ 0.3 bar
Conversion factors for alternative flow temperatures other than 90 °C
Flow temperature °C
50
55
60
65
70
75
80
85
90
95
100
Conversion factor
3.03
2.50
2.13
1.82
1.59
1.39
1.24
1.11
1.00
0.90
0.82
Divide the vessel size found in accordance with the above tables by the conversion factor.
Design information
(cont.)
90
Viesmann
VITOFLEX 300-UF
9
5682428
