STIEBEL ELTRON HM Trend - Filling and venting the system

8 | HM (S)| HM(S) Trend www.stiebel-eltron.com
INSTALLATION
Installation
9.6 Filling the system
9.6.1 General information
!
Material losses
Never switch on the power before filling the system.
!
Material losses
High flow rates or water hammer can damage the ap-
pliance.
 Fill the appliance at a low flow rate.
In the delivered condition, the diverter valve of the MFG is posi-
tioned at the centre, enabling the heating and DHW circuits to be
filled evenly. If power is switched on, the diverter valve automat-
ically moves into the central heating position.
If you intend filling or draining the system later, first place the
diverter valve into its centre position.
For this, enable controller parameter DRAIN HYD in the DIAGNO-
SIS/ RELAY TEST SYSTEM menu.
9.6.2 Determine the fill pressure
The diaphragm expansion vessel installed in the appliance has a
volume of 24 litres. The pre-charge pressure P0 is 1.5 bar.
If the height difference ∆h between the highest point of the heat-
ing system and the diaphragm expansion vessel is no more than
13 m, the diaphragm expansion vessel can be used without any
changes being required.
 Fill the heating system at a pressure of at least 1.8 bar (P0
+ 0.3 bar). Observe the safety valve’s response pressure of 3
bar.
If the height difference between the highest point of the heating
system and the diaphragm expansion vessel is more than 13 m,
the pre-charge pressure needs to be adapted.
 Calculate the pre-charge pressure:
P0 =
∆h
10
+ 0,2 bar
D0000081230
 Note that the heating system fill pressure increases
accordingly.
 Check whether a further external diaphragm expansion ves-
sel needs to be installed.
 Fill the heating system at the appropriate pressure (P0 + 0.3
bar). Observe the safety valve’s response pressure of 3 bar.
9.7 Venting the appliance
Multifunction assembly (MFG)
D0000041463
1
1 Air vent valve
 Vent the pipework by pulling up the red cap on the air vent
valve.
 Close the air vent valve after the venting process.
9.7.1 HM(S) | HM(S) Trend with ASL-HM
Heating circuit
D0000041462
1
1 Air vent valve
 Vent the heating circuit at the ASL-HM connector block.