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Explanations:
The immediate supply of hot water to the draw off points of a
potable water network is realised by the distribution of the hot
water from the potable water heater to one or several circula-
tion risers. Each circulation riser feeds the hot water to the
draw off points via a supply pipe which is connected to the
main riser and the water is fed back to the potable water
heater via a return pipe.
The contractor is responsible for the design of such potable
water networks. He has to observe the hydronic conditions
within these pipe networks in order to ensure that a sufficient
temperature is maintained in all circulation risers. The
pipework conditions must guarantee that a noxious concen-
tration of pathogenic agents (especially legionella) is avoided.
On the one hand, the hydronic conditions are determined by
the flow losses in the pipework of the circulation risers and on
the other hand by the heat losses of hot water when flowing
through the circulation pipes. These heat losses depend on
different parameters (pipe length and dimension, insulation,
ambient and pipe temperature) and have to be considered
individually for each system.
To compensate the heat losses and to keep the temperature
high enough, a certain volume of flow or, strictly speaking, a
certain heat flow has to pass through the circulation pipe. For
this reason, a larger water quantity has to flow through the
circulation risers which are located far away from the potable
water heater than through the risers at a nearer location. This
is achieved by a limitation of the volume of flow in the nearer
circulation pipes by establishing a corresponding differential
pressure with the help of regulating valves.
Taking given temperature limits into consideration, these dif-
ferential pressures can be determined by the contractor with
the help of the calculation procedure of the DVGW work sheet
W 553. The calculation of a circulation pipe within a domestic
water installation can only be made approximately for station-
ary operation (without draining hot water). As the drawn quan-
tities vary at the different locations (bathroom, kitchen, etc.)
during normal operation, the water quantity required to main-
tain the circulation pipe is also varying continuously. An opti-
mum adaptation to these changing hydronic conditions is
guaranteed by the automatic thermostatic regulating valve
"Aquastrom T plus".
System illustration: Circulation pipe
Potable water cold
8 8 8 8
The following model of the valve "Aquastrom T plus" is also
available:
With isolation facility, but without drain valve for hose con-
nection, without thermometer and without insulation.
both ports male thread, flat sealing, according to DIN ISO 228
both ports female thread according to EN 10226
Draining orifice G
with a plug.
Dimensions as item nos. 42055/65.
Notes:
To guarantee the hydronic balancing required in a circulation
system according to DVGW-W553 – with due consideration
of the residual flow rates requires as per VP 554 – not more
than 12 branches should be installed per main circulation
pipe.
In case of more than 12 branches per main circulation pipe,
pumps with a high output would have to be used to produce
the prescribed residual flow rate even in the furthest branch-
es. In the nearer branches, the pumps would, however, pro-
duce excessive differential pressures at the balancing valves
which would lead to noise problems and a possible damage
of the components.
In the event of more than 12 branches (see system illustration
below), additional main circulation pipes installed in parallel
are therefore recommended. Each main pipe should be
equipped with its own pump and a hydronic balance of the in-
dividual pipes should be carried out. In this installation, the
circulation pumps can be designed smaller.
Before putting the circulation installation into operation,
all components/press connection have to be leak tested
to avoid any possible damage caused by water.
max. of 12 risers
Potable
water
circulation pipe
DN 15
G
1
3
⁄
x G
3
⁄
4
4
DN 20
G 1
x G 1
1
1
DN 25
G 1
⁄
x G 1
⁄
4
4
1
1
DN 15
Rp
⁄
x Rp
⁄
2
2
3
3
DN 20
Rp
⁄
x Rp
⁄
4
4
DN 25
Rp 1 x Rp 1
1
⁄
in front of the thermal control unit closed
4
max. of 12 risers
4206604
4206606
4206608
4205604
4205606
4205608
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