pg. XVI
The safety valve must be connected to the highest part of the heat generator or the outlet tube, next to the generator. The length of the section
of tube between the generator fitting and the safety valve must not be more than one metre. There must be no cocks that can cut off the tube
connecting the safety valve to the heat generator and the section must not be less than the inlet section of the safety valve or the sum of the inlet
sections if there are several valves that head a single tube, at any point whatsoever along its length. The outlet tube of the safety valve must be
installed in such a way that it does not prevent the normal functioning of the valves and will not cause injury to persons ; the outlet must be located
as close as possible to the safety valve and be accessible and visible. The diameter of the outlet tube must not in any case be less than the
diameter of the safety valve outlet fitting. The outlet fitting diameter is the minimum internal diameter of the valve outlet upstream from any existing
internal threading. The valve discharge pressure, equal to the calibration pressure and increased by the overpressure, must not exceed the
maximum working pressure of the heat generator. The designer must ensure that the maximum pressure existing at every point of the system
does not exceed the maximum working pressure of each of its components. The discharge capacity of the safety valve must be calculated
according to the prescriptions set out in UNI 10412/2. The diameter of the minimum net cross section of the valve inlet must in any case be not
less than 15 mm. The maximum working pressure of the closed expansion tank must not be less than the calibration pressure of the
safety valve, plus the specific overpressure of the valve itself, with any difference in height between the tank and the valve taken into
account,and the pressure generated by the functioning of the pump. The capacity of the expansion tank or tanks is evaluated according to the
overall capacity of the plant as per the design. The closed expansion tanks must comply with current regulations governing pressure appliances
in terms of design, construction, conformity assessment and utilization.
The rated volume of the closed expansion tank must be sized in relation to the expansion volume of the water in the
system .
The heat generator must be connected directly to the plant's expansion tank or group of expansion tanks with a tube having an internal
diameter no less than 18 mm. The connecting tube, which may consist of plant parts, must not be fitted with any shutoff cocks or have reduced
sections. One three-way on-off valve may be installed for connecting the tank to the atmosphere for maintenance operations. This device must
be protected against accidental manoeuvres. The connecting tube must be fitted in such a way that no scaling or deposit points are created. If
several heat generators power a single system or secondary circuit, each heat generator must be connected directly to the system's expansion
tank or group of expansion tanks sized overall for the total volume of water contained in the same plant or independent circuit. When it is
necessary to separate the single heat generator from the expansion tank or group of expansion tanks, then a three-way tap having the same
characteristics as those listed above must be installed on the tube that connects the generator to the expansion tank, in order to ensure that the
generator is in any case connected either with the expansion tank or with the atmosphere in every position. The expansion tanks, connecting
tubes, the vent and smoke exhaust pipes must be protected against freezing in areas where this could occur. The solution adopted for this
purpose must be described in the project. Given that the circulation of the water in the heat generator must be maintained in any system and in
all operating conditions within the limits prescribed by the supplier of the generator, in closed expansion tank heating systems, in which the
circulation of the water is assured by means of an electric pump, the pump stopping must not cause, in any operating condition, the temperature
to rise above the limit prescribed in these instructions.
The previous chapter does not replace UNI 10412/2 to which it makes reference . The qualified installer must in any case be
fully aware of this standard and its amending versions.
4.8 INSTR
4.8 INSTR
4.8 INSTR
4.8 INSTR
4.8 INSTRUCTIONS FOR EXECUTING
UCTIONS FOR EXECUTING
UCTIONS FOR EXECUTING
UCTIONS FOR EXECUTING
UCTIONS FOR EXECUTING THE HYDRA
THE HYDRA
THE HYDRA
THE HYDRA
THE HYDRAULIC SY
ULIC SY
ULIC SY
ULIC SY
ULIC SYSTEM CL
STEM CL
STEM CL
STEM CL
STEM CLOSED EXP
OSED EXP
OSED EXP
OSED EXP
OSED EXPANSION
ANSION
ANSION
ANSION
ANSION T
T
T
T
TANK.
ANK.
ANK.
ANK.
ANK.
Systems with closed expansion tank, must be provided with :
a)safety valve
b) thermal relief valve or thermal safety outlet (positive safety)
c) closed expansion tank
d) circulating pump activation thermostat (included in the panel of the central heating
cooker).
e) acoustic alarm activation thermostat.
f) acoustic alarm
g) pressure gauge thermometer
h) circulation system
These devices must be installed on the generator's delivery tube, within not more than 1 metre from the machine.
4.7.1 CONNECTION OF SENSORS S1
4.7.1 CONNECTION OF SENSORS S1
4.7.1 CONNECTION OF SENSORS S1
4.7.1 CONNECTION OF SENSORS S1
4.7.1 CONNECTION OF SENSORS S1 AND S2
AND S2
AND S2
AND S2
AND S2 T
T
T
T
TO
O
O
O
O THE REAR P
THE REAR P
THE REAR P
THE REAR P
THE REAR PANEL OF
ANEL OF
ANEL OF
ANEL OF
ANEL OF THE HEA
THE HEA
THE HEA
THE HEA
THE HEATER / BOILER.
TER / BOILER.
TER / BOILER.
TER / BOILER.
TER / BOILER.
Sensor S2 and sensor S1 must be connected to the dedicated clamps on the rear panel (see para. 5.2). To activate the detections of
Sensors S1 and S2 set THERMOCONTROL ON (see para. 5.8).
