Pump-controlled pressure maintenance
A pump-controlled pressure maintenance unit essentially consists of a pressure-
maintenance pump, relief valve and an unpressurised receiving tank. The valve
releases hot water into the receiving tank if the pressure is too high. If the pressure
drops below a preset value, the pump draws water from the receiving tank and feeds it
back into the heating system. Pump-controlled pressure maintenance systems with
open expansion tanks (e.g. without a diaphragm) introduce ambient oxygen via the
surface of the water, exposing the connected system components to the risk of
corrosion. These systems offer no oxygen removal for the purposes of corrosion
control as required by VDI 2035 and in the interests of corrosion protection should not
be used.
3.6 Return temperature control
If the hot water return is below the minimum return temperature, some of the hot water
outfeed will be mixed in. This is done by the return temperature control, which is
integrated in the hydraulics on the side panel of the boiler.
3.7 Use with storage tank
NOTICE
In principle it is not necessary to use a storage tank for the system to run
smoothly. However, we recommend that you use the system with a storage tank,
as this ensures a continuous supply of fuel in the ideal output range of the boiler.
For the correct dimensions of the storage tank and the line insulation (in accordance
with ÖNORM M 7510 or guideline UZ37) please consult your installer or Froling.
3
Design Information
Return temperature control
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