General information
Low water indicator
EN 12828 specifies that boilers must be equipped with a low water
indicator (water level limiter). A low water indicator is not required for
the Vitoplex boilers up to 300 kW (except in attic heating centres).
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 and
simultaneous burner operation, before the boiler or the flue system
reach unacceptably high temperatures.
Maximum pressure limiter
This is required for every boiler in a system if the rated boiler output
exceeds 300 kW.
Minimum pressure limiter
Is required once per system.
Safety valve
Equip the boilers to EN 12828 with a type-tested safety valve. This
must be sized according to EN 4126 marked with "D/G/H" according
to TRD 721:
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.
Flash trap
For boilers above 300 kW, install a flash trap with blow-off and drain
line near the safety valve. The blow-off line must lead outdoors. Any
extracted steam must not endanger anyone.
The blow-off line on the safety valve should be constructed so as to
prevent the possibility of increases in pressure. Arrange the outlet of
the drain line so that any water expelled by the safety valve can be
safely observed and drained off.
Flash trap replacement
A flash trap and blow-off line are not required if a second high limit
safety cut-out and a second maximum pressure limiter are installed.
Safety accessories selection table
The following table lists the control equipment required for sealed unvented heating systems.
System Boilers
≤
300 kW
Boilers
> 300 kW
System Boiler
Safety temperature 110 ºC to EN 12828 120 °C to EN 12953
High limit safety cut-out – 1 1 – 2
Control thermostat
Included in the delivery of the boiler control unit
– 1 1 – 1
Boiler thermometer
In the standard delivery of the boiler control unit
1 1 1 –
1 x flow
1 x return
Pressure gauge assembly
Pressure gauge
1 1 1 – 1
Fill and sampling valve – – 1 – 1
Safety valve – 1 1 – 1
Low water indicator (from boiler output >300 kW)
According to EN 12828, the low water indicator can be
replaced by an additional min. pressure limiter.
1 – – – 1
Maximum pressure limiter – 1 1 – 1
Minimum pressure limiter 1 – – 1 –
Flash trap
or
According to the EN 12828, the flash trap is not required, if
an additional high limit safety cut-out and a safety pressure
limiter (maximum pressure limiter) are installed.
1 – – – –
High limit safety cut-out (1) – – – –
Safety pressure limiter (maximum pressure limiter) (1) – – – –
Note
If a boiler is operated at a safety temperature of 120 ºC, it must be supervised in accordance with the Health & Safety at Work Act [Germany].
Components with a safety function must have fail-safe operation, as well as redundancy, heterogeneity and self-monitoring. An accessory pack
is available for 120 ºC safety temperature. Further information is available in EN 12953.
10.5 Fuel
The Vitoplex and Vitorond are suitable for operation with the following
fuels:
■ Fuel oil EL to DIN 51603
■ Natural gas, town gas and LPG according to DVGW Code of Practice
G 260/I and II [Germany] or local regulations. The Viessmann
Vitoflame 100 pressure-jet gas burners are only suitable for opera-
tion with natural gas E and LL.
■ Biogas and sewer gas:
Operation with biogas/sewer gas is possible. Special operating
conditions apply, as these gases generally contain sulphur com-
pounds (the consistency of which can fluctuate considerably) and
other aggressive gases.
– The gas must be free from halogenated hydrocarbon.
– For all operating conditions, the minimum return temperature
should be above 65 ºC. This requires the installation of an effective
return temperature raising facility.
Design information
(cont.)
OIL/GAS BOILERS
VIESMANN
31
5822 426 GB
10
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