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3062165_201508
If the system operating pressure is set too low or if it drops a little due to leaks
or ventilation, this may result in partial boiling of the solar fluid during system
operation. This is particularly harmful to parts with high temperatures, where
there is a pressure drop upstream of the collector array, or at the highest point
of the solar circuit. A steam bubble at this point will reduce or completely halt
the flow. In addition, the formation of steam due to stagnation occurs much
more frequently where system operating pressure is low.
System operating pressure
1 Positive system pressure
at highest point
1.5 - 2.0 bar
2 Addition per metre
static head
+0.1 bar / m
3
System operating pressure
(pressure gauge)
_______bar
System operating pressure
_______bar
Fill reserve for venting
+ 0.1 bar
Charge pressure
_______bar
System operating pressure
_______bar
Deduction for hydraulic seal
-0.3 bar
4 Addition per metre height
difference, pressure gauge -
DEV
+0.1 bar / m
5
DEV pre-charge pressure
_______bar
An indication of the correct system operating pressure is an overpressure
of 1.5 - 2.0 bar at the highest point of the system when cold. The system
operating pressure at the solar module is therefore 1.5 - 2.0 bar plus 0.1 bar
per metre of static head between the pressure gauge in the solar module and
the highest point of the system.
Since some air continues to form after commissioning, the charge pressure
should be a little higher (suggestion: +0.1 bar) than the system operating
pressure.
The pre-charge pressure in the DEV for the required hydraulic seal is set
at least 0.3 bar lower than the system operating pressure. Any difference in
height between the pressure gauge and the DEV should be taken into account
here. If for example the DEV is installed one metre lower than the pressure
gauge, the pre-charge pressure in the DEV must be matched to the system
operating pressure effective here (+0.1 bar), thus the pre-charge pressure
should be only 0.2 bar lower than what the pressure gauge displays.
This matched pressure ratio between the charge pressure, system operating
pressure and pre-charge pressure in the DEV is a requirement for the reliable
long-term operation of a solar thermal system.
System operating pressure
Summary of Contents for TopSon F3-1
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