Selection Of Rated Output; System Design; Safety Equipment; Low Water Indicator - Viessmann VITODENS 300 Datasheet

Design information

Selection of rated output

Select the boiler according to the required
heat demand, including DHW demand.
The rated output of condensing boilers
may be higher than the calculated heat
demand of the building in question.
The standard efficiency of condensing
boilers remains constant over a wide
range of boiler loads. It remains almost
unchanged even if the heat output is
twice as high as the heat demand.

System design

H The boiler water temperature is limited
to 74 ºC.
To minimise distribution losses, we
recommend that you size the heat
distribution system and the DHW
heating system for a max. flow
temperature of 70 ºC.
H Depending on local regulations, the
installation of a condensing boiler may
need to be notified or authorised.
H If possible, install no mixing devices in
heating circuits, because the utilisation
of condensing technology demands low
return temperatures.
Use only three−way mixers where
mixers are required, e.g. for
multi−circuit or underfloor heating
systems.

Safety equipment

Boilers for hot water heating systems and
with a safety temperature of max. 110 ºC
are equipped with a type−tested safety
valve in accordance with EN 12828 and in
accordance with their type approval.
38
Underfloor heating
For underfloor heating, we recommend
the use of impermeable pipes to prevent
the infusion of oxygen through the pipe
walls. Provide system separation in
underfloor heating systems for plastic
pipes (DIN 4726) which are
non−impermeable. We supply separate
heat exchangers for this purpose.
Connect underfloor heating systems and
heating circuits with very large water
content (> 15 litres/kW) to the boiler via a
three−way mixer, even when using
condensing boilers. See Technical Guide
on control of underfloor heating systems
or Vitodens Technical Guide.
Install a temperature limiter into the
underfloor heating circuit to limit the
maximum temperature.
Observe DIN 18560 2.
Plastic pipe systems for radiators
We also recommend the installation of a
temperature limiter to limit the maximum
temperature for plastic heating pipework
in heating circuits with radiators.

Low water indicator

According to EN 12828, special low water
level protection can be omitted for boilers
up to 300 kW, as long as heating can be
reliably prevented when the water level is
too low.
Viessmann Vitodens 300 are equipped
with a low water indicator (boil−dry
protection). Tests have verified that the
burner will be automatically switched OFF
in the event of water shortage due to a
leak in the heating system, before the
boiler or flue gas systems reach
unacceptably high temperatures.
Notification
Within four weeks of the initial
commissioning, the operator may need to
notify the local chimney sweep
accordingly (check local regulations).
Condensate and neutralisation
See Vitodens Technical Guide.
Additional requirements when
installing boilers with liquid gas
operation in rooms below
ground level
According to TRF 1996 volume 2 valid
since 1 September 1997 an external
safety solenoid valve is no longer
required when installing Vitodens 300
boilers below ground level.
However, the high safety standard
derived from the use of an external safety
solenoid valve has proved to be valuable.
We therefore recommend the installation
of an external safety solenoid valve plus
the internal extension H 1, when installing
Vitodens 300 in rooms below ground
level.
Technical guide
For further details regarding the design
and sizing, see Vitodens Technical Guide.
VITODENS 300