Ferroli RXA, Техническое руководство

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18
CONNECTIONS
Expansion tank setting
All the storage version units (VA) come complete with expansion tank and safety valve. The expansion tank prefilling pressure
must be adequate for the total volume of the plumbing system to which the unit is connected.
The factory setting (p
VE
= 2 bar g) corresponds to the minimum value necessary for avoiding negative pressure zones inside the
water circuit and the risk of pump cavitation, in the event no users are located above the level on which the unit is installed. In
this case the prefilling pressure must be increased according to the level of the highest user according to the following
relationship :
p
VE
: expansion tank prefilling pressure [bar g]
H
max
: height difference between the highest user and the unit installation level [m]
When the prefilling pressure increases the maximum volume of the system supported by the expansion tank supplied standard
decreases. If the actual volume of the system is greater than that maximum value, an additional expansion tank of adequate
capacity must be installed.
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For units operating with water and glycols calculate the maximum value, applying the correction factors given in the following
table to values obtained from the graph.
The maximum expansion tank prefilling pressure corresponds to the safety valve setting value (6 bar g).
After the water circuit is filled, the pressure at the expansion tank must not be higher than the prefilling pressure.
In case of users located at levels below that on which the unit is installed, make sure the user can take the maximum pressure
generated.
glycol %
Ethylene glycols Propylene glycols
10% 20% 30% 40% 10% 20% 30% 40%
IR (10-40°C) 0.738 0.693 0.652 0.615 0.700 0.608 0.543 0.494
IP (10-60°C) 0.855 0.811 0.769 0.731 0.814 0.718 0.647 0.593