Specifications

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Devices for controlling the operation temperature to adapt the heat supply to
the heat demand. The maximum set-point of the temperature controller shall not
exceed the maximum operating temperature of the boiler.
Pressure maintaining control device to ensure the required minimum
operating pressure of the system. This can be achieved for example by an automatic
refill-set or expansion vessel linked to a low pressure limiter.
Heating system shall be equipped with devices to fill the system and provide
adjustment of the water level. Connections to a drinking water supply system shall
comply with prEN 806-2, e.g. back flow prevention.
An adequate supply of combustion air is important for safe and clean
combustion. For open flue heating systems with a total rated output higher than
50 kW, the rule regarding the supply of combustion air is treated as satisfied, if the
cross-section of the aperture leading into the open air is at least 150 cm2 and is 2
cm2 larger for each kW of rated output above 50 kW.
8.1.2 MINIMUM SAFETY EQUIPMENT REQUIRED FOR OPEN VENTED
SYTEMS
Expansion cisterns;
Boilers in an open vented system shall be connected to an expansion cistern,
which, is installed at the highest point of the heating system. They shall be
dimensioned so that changes in water volume due to heating up and cooling down
can be accommodated. Open vented system expansion cisterns shall be provided
with a cistern vent and overflow pipe that cannot be blocked. The overflow pipe shall
be dimensioned so that it can safely drain off the maximum mass flow rate entering
the system, which can be achieved by selecting the overflow pipe to be one DN-size
larger then the filling pipe.
Expansion cisterns, safety pipes, open vent and overflow pipes shall be
designed and arranged to protect against freezing.
Installation example is given in figure ….
Safety pipes, feed and expansion pipes;
Boilers shall be connected to an expansion cistern and served by an open vent pipe.
The expansion cistern shall be vented to the atmosphere. The feed and expansion
pipe shall be connected to the lower part of the expansion cistern. Shutting off the
safety pipe or the feed and expansion pipes shall not be possible.
The minimum internal diameter of the open vent safety pipe and feed and
expansion pipe shall be:
Safety pipe: d
s
= 15 + 1.4 √Ф mm (but not less then 19 mm internal diameter)
Feed and expansion pipe: d
fe
= 15+ 1.0 √Ф mm
Where Ф is the nominal heat output of the boiler in kW.