Specifications

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Protection against exceeding the maximum operating pressure;
Each boiler shall be served by at least one safety valve in order to protect the
system against exceeding the maximum operating pressure. The safety valve is not
a standard supply with the boiler, it must be fitted by the installer on the flow line of
the boiler without any isolation valve or similar items and they must confirm prEN
1268-1 with a minimum size of DN 15.They must open at a pressure not exceeding
the maximum design pressure of the system and shall be designed to prevent the
maximum operating pressure from being exceeded by more then 10 %. Safety
valves shall be installed so that the pressure drop on the inlet pipe does not exceed 3
% and the pressure drop of the discharge pipe does not exceed 10 % of the safety
valve set pressure.
Safety valves shall discharge safely and boilers greater then 300 kW nominal
heat output have special requirements, please refer to EN 12828.
Each boiler greater then 300 kW nominal heat output shall be served by a
pressure limiter. This is not a standard supply with the boiler; it must be fitted by
the installer on the flow line of the boiler without any isolation valve or similar items.
If the operating pressure of the heating system exceeds the given pressure limit, the
pressure limiter shall shut-off the heating or fuel supply and interlock it against
automatic restoring. Pressure limiter shall be adjusted so that it responds before the
safety valve(s) operate.
Safeguard against lack of water;
Sealed (closed expansion tank systems) shall be equipped with a water level
limiter or other device, e.g. minimum pressure limiter or flow controller, thus
providing interlock protection against excess temperature rise on the heat emitting
surface of the boiler.
Expansion vessels;
When the heating system’s heat carrying medium water is heated it expands
and it cause pressure rise in sealed systems so expansion vessels shall be designed
to accommodate at least the maximum expansion volume of the heating water of the
system including a minimal water reserve volume. The expansion vessel shall
confirm to prEN 13831. For guidance on dimensioning refer to EN 12828 but the
expansion vessel manufacturer’s installation instructions shall be paramount.
The expansion vessel and the connection pipe to the heating system shall be
dimensioned so that the temperature rise up to the maximum operating temperature
does not cause a pressure rise in the system at which the pressure limiting device
and safety valves respond and shall be installed in frost protected rooms or protected
against freezing. Diaphragm-type expansion vessels shall be positioned to the return
pipe of the boiler and shall be no shut-off device positioned between the expansion
vessel and the boiler. Consideration may be given to an engineer’s lockable isolating
valve for maintenance purposes.
Operational requirements of sealed systems;
In order to maintain a safe and economical operation, open vented heating systems
shall be equipped with:
Temperature measuring device (20 % higher then the operating temperature
and mounted in the flow pipe of the system)
Pressure gauge (50 % higher then the operating pressure and mounted in the
flow pipe of the system