Determining the required nominal diameter
A
ΔT= 15K
ΔT= 20K
ΔT= 30K
ΔT= 5K
ΔT= 10K
C
B
D
2.5
2.5
Mixer control characteristics
2.0
0.1
0.2
0.5
1.0
1.5
5.0
Flow rate in m³/h
10
20 30 40
5
3
1
0.1
0.2
0.5
1.0
1.5
2.0
5.0
Heating circuit output
in kW
A
Divicon with mixer-3
The operating ranges marked
B
to
D
provide optimum control
characteristics with the Divicon mixer:
B
Divicon with mixer-3 (R ¾)
Operating range: 0 to 1.0 m
3
/h
C
Divicon with mixer-3 (R 1)
Operating range: 0 to 1.5 m
3
/h
D
Divicon with mixer-3 (R 1¼)
Operating range: 0 to 2.5 m
3
/h
Example:
■ Heating circuit for radiators with a heating output of
²
= 11.6 kW
■ Heating system temperature 75/60 °C (ΔT = 15 K)
²
=
µ
·
c · ΔT
c = 1.163
Wh
kg · K
µ
²
c · ΔT
=
kg
h
´
=
11600 W · kg · K
1.163 Wh · (75-60) K
= 665
m³
h
0.665
´
(1 kg
≈
1 dm³)
c Specific thermal capacity
µ
Mass flow rate
²
Heating output
´
Flow rate
Select the smallest possible mixer within the application limit with the
value
´
.
Example result: Divicon with mixer-3 (R ¾)
Circulation pump curves and pressure drop on the heating water side
The residual pump head results from the differential between the
selected pump curve and the pressure drop curve of the respective
heating circuit distributor or further components (pipe assembly, dis-
tributor, etc.).
The following pump graphs show the pressure drop curves of the dif-
ferent Divicon heating circuit distributors.
Maximum flow rate
for Divicon:
■ With R ¾ = 1.0 m
3
/h
■ With R 1 = 1.5 m
3
/h
■ With R 1¼ = 2.5 m
3
/h
Example:
Flow rate
´
= 0.665 m
3
/h
Selected:
■ Divicon with mixer R ¾
■ Wilo Yonos PARA 25/6 circulation pump, variable differential pres-
sure operating mode and set to maximum delivery head
■ Pump rate 0.7 m
3
/h
Head of the relevant pump
curve:
48 kPa
Divicon pressure drop:
3.5 kPa
Residual head:
48 kPa – 3.5 kPa = 44.5 kPa.
Note
For further components (pipe assembly, distributor, etc.) determine
the pressure drop and deduct it from the residual head.
Differential pressure-dependent heating circuit pumps
According to the [German] Energy Saving Ordinance (EnEV), circu-
lation pumps in central heating systems must be sized in accordance
with current technical rules.
Ecodesign Directive 2009/125/EC requires high efficiency circulation
pumps to be used throughout Europe from 1 January 2013, if the
pumps are not installed in the heat generator.
Design information
The use of differential pressure-dependent heating circuit pumps
requires heating circuits with variable flow rates, e.g. single-line and
twin-line heating systems with thermostatic valves and underfloor
heating systems with thermostatic valves or zone valves.
Installation accessories
(cont.)
VITOCAL
VIESMANN
65
5831388
6
