18.13 Connecting the DHW circulation and thermostatic mixing valve
To ensure trouble-free functioning of the solar thermal system, it is
important that, in the DHW cylinder, areas with cold water are available
to receive the solar energy. These areas must not under any circum-
stances be reached by the DHW circulation return. The DHW circula-
tion connection in the DHW cylinder
must
therefore be used (see fol-
lowing diagram).
DHW with
temperatures in excess of 60 °C
can cause scalding. To
limit the temperature to 60 °C, install a mixing device, e.g. a thermo-
static mixing valve (see page 107). If the maximum set temperature is
exceeded, the valve mixes cold water into the DHW as it is drawn
off.
If the thermostatic mixing valve is used in conjunction with a DHW
circulation pipe, a bypass line is required between the DHW circulation
inlet on the DHW cylinder and the cold water inlet on the mixing valve.
To avoid incorrect circulation, a check valve should be installed (see
following diagram).
A
C
C
B
C
D
E
F
A
DHW circulation pump
B
Automatic thermostatic mixing valve
C
Check valve
D
DHW circulation return in summer
Line required to prevent excessive temperatures in summer.
E
DHW circulation return in winter
Flow temperature max 60 °C.
F
Thermostatic mixing valve inlet
Pipe runs as short as possible, as these receive no flow in win-
ter.
Note
Viessmann offers a thermostatic DHW circulation set as an accessory
(see page 107).
18.14 Intended use
The appliance is only intended to be installed and operated in sealed
unvented systems that comply with EN 12828 / DIN 1988, or solar
thermal systems that comply with EN 12977, with due attention paid
to the associated installation, service and operating instructions. DHW
cylinders are only designed to store and heat water of potable water
quality. Heating water buffer cylinders are only designed to hold fill
water of potable water quality. Only operate solar collectors with the
heat transfer medium approved by the manufacturer.
Intended use presupposes that a fixed installation in conjunction with
permissible, system-specific components has been carried out.
Commercial or industrial usage for a purpose other than heating the
building or DHW shall be deemed inappropriate.
Any usage beyond this must be approved by the manufacturer for the
individual case.
Incorrect usage or operation of the appliance (e.g. the appliance being
opened by the system user) is prohibited and results in an exclusion
of liability.
Incorrect usage also occurs if the components in the system are modi-
fied from their intended use (e.g. through direct DHW heating in the
collector).
Adhere to statutory regulations, especially concerning the hygiene of
potable water.
Information regarding design and operation
(cont.)
156
VIESMANN
VITOSOL
18
5822 440 GB
