System Operating Pressure - Wolf TopSon F3-1 Installation, Operating And Maintenance Instructions

System operating pressure

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System operating pressure
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.
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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.
Positive system pressure
at highest point
Addition per metre
static head
System operating pressure
(pressure gauge)
System operating pressure
Fill reserve for venting
Charge pressure
System operating pressure
Deduction for hydraulic seal
Addition per metre height
difference, pressure gauge -
DEV
DEV pre-charge pressure
1.5 - 2.0 bar
+0.1 bar / m
_______bar
_______bar
+ 0.1 bar
_______bar
_______bar
-0.3 bar
+0.1 bar / m
_______bar
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