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Chapter 4
Whenever the generators lack a device, those missing can be installed on the generator fl ow pipe, within
a distance no greater than 1m from the machine.
Domestic type heating appliances with manual or manual-automatic feed inserted in closed vessel heating
plant, must be equipped with an internal cooling circuit prepared by the appliance manufacturer, activated
by a thermal safety valve which does not require auxiliary energy and such to guarantee that the limit
temperature set by the Standard is not exceeded. The connection between the power supply unit and the
valve must be free from interceptions; interception is allowed if the valve is activated by a specifi c tool.
Cooling circuit upstream pressure must be at least 1.5 bar.
SAFETY VALVE
The load capacity of the safety valve must allow the discharge of a quantity of vapour, not lower than:
Q/0.58 [kg/h]
where:
Q
is the useful outlet power to the generator water expressed in kilowatt.
The diameter of the minimum net transversal section of the valve inlet must not be lower than 15 mm. The
valve load pressure, equal to the calibration pressure, increased by the overpressure, cannot exceed the
maximum exercise pressure of the heat generator.
The designer must check that the maximum pressure existing in every point of the plant, does not exceed
the maximum exercise pressure of its every component .
The safety valve must be connected to the highest part of the heat generator or outlet pipes, immediately
near the generator. The length of the pipes route included between the attachment to the generator and
the safety valve must not be higher than 1 m.
The connection piping of the safety valve to the heat generator must not be traceable and must not
present, in any point, section lower to the inlet of the safety valve or the sum of the inlet sections in case of
more valves under the individual pipe.
The discharge piping of the safety valve must be realised in order not to alter the regular functioning of the
valves and not to cause damages to persons; the discharge must fl ow immediately near the safety valve
and be accessible and visible.
The diameter of the discharge piping must not however be lower than that of the outlet connection of the
safety valve. For diameter of outlet connection it is intended the minimum internal diameter on the valve
outlet upstream of the eventual internal threading.
CLOSED EXPANSION VESSEL
GENERALITY
The vessel maximum exercise pressure must not be lower than the calibration pressure of the safety valve,
increased by overpressure, characteristic of the same valve, bearing in mind the eventual level diff erence
between vessel and valve and the pressure generated by the functioning of the pump.
The capacity of the expansion vessel/s is valued depending on the total plant capacity as results from the
project. The closed expansion vessels must comply with the legislation in force regarding the planning,
manufacturing, evaluation of conformity and use for pressure appliances.
19
HYDRAULIC PLANT CONNECTION
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