Observe the standards and also follow the recommendations below:
❒ Max. cumulative value for alkaline earth: 1.0 mmol/l or 100 mg/l (corresponds to
5.6 dH)
❒ Use softened water as the make-up water
❒ Avoid leaks and use a closed heating system to maintain water quality during op‐
eration
2.4.5 Notes for using pressure maintenance systems
Pressure maintenance systems in hot-water heating systems keep the required pres‐
sure within predefined limits and balance out volume variations caused by changes in
the hot-water temperature. Two main systems are used:
Compressor-controlled pressure maintenance
In compressor-controlled pressure maintenance units, a variable air cushion in the ex‐
pansion tank is responsible for volume compensation and pressure maintenance. If
the pressure is too low, the compressor pumps air into the tank. If the pressure is too
high, air is released by means of a solenoid valve. The systems are built solely with
closed-diaphragm expansion tanks to prevent the damaging introduction of oxygen in‐
to the heating water.
Pump-controlled pressure maintenance
A pump-controlled pressure maintenance unit essentially consists of a pressure-main‐
tenance 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 expan‐
sion 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.
Safety
2
Design Information
Installation Instructions Turbomat TM 400-500 | M0690213_en
9
