Engineering information and sizing the heat source
6 720 645 817
(2010/09)
39
5.3
Important hydraulic system components
5.3.1
Hydraulics for maximum utilisation of the
condensing effect
For systems where the heating circuits are connected via
a low loss header, we recommend that the pump is
controlled subject to boiler output. This operating
principle enables the system to operate with maximum
utilisation of the condensing effect.
5.3.2
Underfloor heating system
Due to their low design temperatures, underfloor
heating systems are ideal for combination with a
Suprapur gas condensing boiler. Due to the inertia
during heat-up, we recommend weather-compensated
operation combined with a separate flow
rate-dependent room temperature controller. In
conjunction with the boiler control unit, the FW ...
controllers are suitable for this purpose.
A temperature limiter is required to protect the
underfloor heating system. It should be connected to the
IPM ... For the temperature limiter, contact thermostat
TB 1 can be used, for example.
Automatic system-controlled
screed drying
is
not
possible here, and should therefore be allowed for on
site. Automatic screed drying with the FW ... controller is
only possible via an underfloor heating circuit with
mixer.
5.3.3
Diaphragm expansion vessel
In accordance with DIN EN 12828, water heating
systems must be equipped with a diaphragm expansion
vessel (MAG).
Rough guide to selecting a diaphragm expansion vessel
1. MAG pre-charge pressure
Form. 3 Formula for the MAG pre-charge pressure
(minimum 0.5 bar)
p
0
Pre-charge pressure of the MAG in bar
p
st
Static pressure of the heating system in bar (subject to
building height)
2. System fill pressure
Form. 4 Formula for the system fill pressure
(minimum 1.0 bar)
p
a
System fill pressure in bar
p
0
Pre-charge pressure of the MAG in bar
3. System volume
Subject to various heating system parameters, the
system volume can be checked on the graph in Fig. 25.
4. Maximum permissible system volume
Subject to a maximum flow temperature to be set
ϑ
V
and
the pre-charge pressure determined according to
formula 3 p
0
of the MAG, the permissible maximum
system volume for various MAG can be checked in
table 19.
The system volume checked acc. to point 3 in Fig. 25
must be smaller than the maximum permissible system
volume. Select a larger diaphragm expansion vessel if
that is not the case.
Example 1
Given
n
System output Q
K
= 200 kW
o
Underfloor heating/radiators
Actual
p
Total system water content = 4000 l
(
Æ
Fig. 25, curve
a
)
Fig. 25 Standard values for average water content of
heating systems
a
Underfloor heating system and steel/cast iron radiators
with pipes sized for gravity circulation (20 l/kW)
b
Panel radiators (10 l/kW)
c
Convectors (6 l/kW)
V
A
Average total water content
Q
K
Rated output
Always use the Suprapur gas condensing
boilers with a low loss header.
p
0
p
st
=
p
a
p
0
0.5 bar
+
=
.
0
1
2
3
4
5
6
7
8
9
10
11
12
0
100
200
300
400
500
600
a
b
c
V
A
/ m
3
Q
K
/ kW
.
6 720 643 417-29.1O
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