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4.10.2. Sensor assembly
The temperature sensor must be placed as close as possible to the collector field delivery line (a specific holder is provided with the
optional connection kit).
To ensure an accurate reading of the temperature, fill-in the holder with a heat transfer paste with suitable features before positioning
the sensor in the holder.
To fit the sensor use only high operating temperature materials (up to 250 °C for the sensor, the heat transfer paste, the wires, the
materials for seals and insulation).
4.10.3. Operating pressure
The collectors maximum pressure is of 10 bars.
We recommend keeping the system operating pressure within a range of 3.5 and 4.5 bars.
4.10.4. Deareation
To deareate the system use only manual valves that, under system normal operation, must always be kept
closed.
!
If using the deareation automatic valves they must be intercepted with a cock that, under the system normal
operating conditions, must always be closed.
During system deareation, considering the high temperature the heat transfer fluid can reach, there is the risk of
scalding due to steam or heat transfer fluid.
!
Activate the deareation valves only if the heat transfer fluid temperature is lower than 60 °C.
When emptying the system the collectors must be cold!
Cover the collectors and empty the system possibly during the first hours in the morning.
The system must be deareated:
- upon system start-up (after filling-in operation);
- 4 weeks after start-up;
- if necessary for example in case of faults.
4.10.5. Heat transfer fluid check
Periodically check the pressure, the anti-freeze features and the pH value of the heat transfer fluid.
Nominal value of the anti-freeze feature approximately from - 20 °C to - 25 °C, or according to the weather conditions.
Check the pH value with a suitable measurement instrument (pH nominal value ca. 7.5). If the pH falls below the limit value of 7, replace
the heat transfer fluid.
When topping-up the heat transfer fluid, use the same fluid type used for the filling-in operation.
!
Do not mix different types of solar fluids.
4.10.6. Expansion tank
The solar circuit shall have an expansion tank ensuring the correct and safe operation under all conditions.
The expansion tank shall be chosen among those designed for power solar systems, which are able to stand high temperatures and
operating pressures that the solar circuit can reach.
Do not use standard expansion tanks for heating circuits that reach maximum operating temperatures lower than those of the
expansion tanks specifically designed for power solar systems.
To protect the expansion tank membrane we recommend installing the expansion tank on the solar circuit return pipes, with connection
pipe downwards.
To prevent the expansion tank from accumulating heat, we suggest not to carry out the heat insulation.
The expansion tank dimensioning must be performed according to the circuit features. It will be necessary to consider:
- the fluid total quantity inside the power solar system (collectors + pipes + water heater coil +... );
- minimum and maximum pressures that can be reached inside the power solar system;
- minimum and maximum temperatures that can be reached by the fluid upon system operation.
The expansion tank useful volume (V
V
= (V
+ V
+ V
) * k * (P
+ 1) / (P
U
D
L
V
MAX
where
V
stands for the expansion tank;
U
V
stands for the expansion volume of the heat transfer fluid, calculated as V
D
V
stands for the power solar system total volume (equal to the sum of collectors, pipes, heat exchanger and any other system
T
components);
n
expansion coefficient (it depends on the heat transfer fluid composition; see instructions about heat transfer fluid);
V
heat transfer fluid volume in the expansion tank;
L
V
evaporation volume in case of stagnation (if foreseen, it can be considered equal to the fluid content in the collectors);
V
31
) can be calculated with the formula below:
U
- P
)
MAX
MIN
* n;
T
EN
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