Decision Making Aids For Dhw Heating - Viessmann Vitodens 300-W Technical Manual

Design information

6.3 Decision making aids for DHW heating

To provide the perfect solution for every situation, the Vitodens is
available in the following versions:
■ Vitodens 200-W
– As a gas boiler in combination with a separate DHW cylinder
– As a gas condensing combi boiler with integral, direct DHW
heating
■ Vitodens 300-W
As a gas boiler in combination with a separate DHW cylinder
■ Vitodens 222-W
With integral DHW loading cylinder
Information on water quality
During DHW heating, settling of lime on the surfaces of the plate
heat exchanger cannot be completely prevented. The tendency
towards limescale build-up depends on various conditions, predomi-
nantly on the substances contained in the water, the amount of water
that is heated (DHW consumption) and the DHW temperature.
Although scale deposits inside the plate heat exchanger are gener-
ally minor enough not to cause any reduction in DHW output, such
impairment cannot be excluded with increased water hardness.
From a water hardness of 20 °dH (3.5 mol/m
fore recommend the use of DHW cylinders with internal indirect coils
or a water treatment system in the cold water supply when heating
DHW.
Selection table
DHW demand, con- DHW demand for an apartment
venience
DHW demand for a detached house
Centralised DHW demand for an apartment building
Decentralised DHW demand for an apartment build-
ing
Use of the various One draw-off point
connected draw-off
Several draw-off points, not used simultaneously
points
Several draw-off points, used simultaneously
Distance of draw-off Up to 7 m (excl. DHW circulation pipe)
point from boiler
With DHW circulation pipe
Modernisation DHW cylinder installed
6
project
Replacement of an existing combi boiler
Space requirement Low space requirement (siting in recesses)
Sufficient space available (installation room)
Solar DHW heating Connection to a dual mode DHW cylinder
can be connected
Connection to the integral DHW cylinder
+ = recommended
0 = recommended under certain conditions
– = not recommended
Separate DHW cylinders
For greater DHW convenience, separate DHW cylinders are also
available in white in the following versions:
■ Below the boiler (120 or 150 l)
■ Adjacent the boiler (160, 200, 300 or 400 l)
Further DHW cylinders with up to 1000 l capacity are available in
Vitosilver and may also be used in accordance with the available
heating output.
Sizing the DHW cylinder
Determine the DHW cylinder size in accordance with the specific
DHW demand.
VIESMANN
80
(cont.)
3 ) and higher, we there-
Various factors should be taken into consideration when designing
heating systems and deciding between a gas condensing combi
boiler or a gas boiler with a separate DHW cylinder or an integral
DHW loading cylinder:
■ DHW demand, convenience
■ Use of the various connected draw-off points
■ Distance of the draw-off points from the boiler
■ System modernisation
■ Space requirement
■ Water quality
Please note that regional water supply utilities frequently specify an
average water hardness. Higher levels of water hardness may there-
fore occur from time to time. This may make the use of a water treat-
ment facility advisable even from 17 °dH (> 3.0 mol/m
Vitodens 200-W Vitodens 200-W
gas condensing and Vitodens 300-
combi boiler with W gas boiler with
instantaneous wa- separate DHW
ter heater cylinder
+ +
0 +
– +
+ +
+ 0
+ +
– +
+ +
– +
– +
+ –
+ 0
+ +
– +
– –
The Vitodens 200-W and 300-W boilers are equipped at the factory
with a separate DHW cylinder for DHW heating. For this purpose,
the Vitodens 200-W and 300-W are provided with an integral diverter
valve.
To connect a separate DHW cylinder, always include the connection
set for the respective DHW cylinder in your order.
For DHW cylinder specifications, see chapter "DHW cylinders".
Various consumer combinations may apply.
3
) upwards.
Vitodens 222-W
with integral DHW
loading cylinder
+
+
–
0
0
+
+
+
–
–
0
0
+
–
–
VITODENS