Water Connection; H Vitolig - Viessmann Vitolig
200 Technical Manual

3 Vitolig 300

3.5 Water connection

Safety equipment acc. to DIN 4751 2
DIN 4751 2 requires the following safety
equipment to be installed:
General design notes
This boiler is only suitable for heating
systems with pumped hot water.
H The minimum boiler water inlet
temperature is 60 ºC.
Only regulated heating circuits with
mixers may be installed.
We recommend the installation of a
check valve into the heating flow, acting
as gravity brake. This prevents
uncontrolled heat entering the heating
system through gravity, when DHW
heating is given priority, or the system
is in summer mode.
For underfloor heating circuits, a high
limit thermostat should be installed.
20
H A sealed expansion vessel.
H A safety valve at the highest point of
the boiler or a pipe connected with the
boiler.
The pipework between the boiler and
the safety valve must not be able to be
shut off. Pumps, fittings or restrictions
must not be present in this pipework.
The blow−off line should be constructed
so as to prevent the possibility of
increases in pressure.
Any expelled heating water must be
able to be drained off safely. Arrange
the outlet of the blow−off line so that
any water expelled from the safety
valve can be safely observed and
drained off.
H A low water indicator (water limiter
available as accessory).
H A thermometer and a pressure gauge.
H An automatic device for heat disposal,
which prevents the maximum
permissible operating temperature to
be exceeded. To affect this, connect a
thermostatic drain valve (available as
accessory) to the integral heat
exchanger.
H Vitolig 300 can be operated with a
return temperature as low as 20 ºC
when operated with an internal return
temperature raising facility. This makes
an external return temperature raising
facility unnecessary.
Systems with a combination or heating
water buffer storage unit loaded directly
by Vitolig 300 are an exception to this
rule. The large volume of cold water
returning from the cylinder in such
cases necessitates the installation of an
external return temperature raising
facility.
H In many cases, the heat demand of a
building does not remain constant
(extensions or thermal insulation
measures). Therefore, the rated output
is matched to the maximum heat
demand foreseeable in the long term. A
heating water buffer storage unit
should be installed, if the heat demand
of 8 kW (for Vitolig 300, 5 to 15 kW) or
12 kW (for Vitolig 300, 8 to 26 kW) will
not be reached within a given period.