Connecting the DHW cylinder on the water side
System schematics with all recommended valves ( Fig. 9, page 46).
Air vent valve
Shut-off valve with drain valve
Pressure Relief Valve
DHW circulation pump
Pressure reducer valve (if required)
Pressure gauge connector
Cold water inlet
Table 7 System schematics ( Fig. 9, page 46)
▶ Use installation material that is heat-resistant to 160 °C (320 °F).
▶ Never use open, vented expansion vessels.
▶ Use metal connection fittings in potable water heating systems with
▶ Size the drain line in accordance with the connection.
▶ To facilitate debris removal, never install elbows in the drain line.
▶ If using a non-return valve in the cold water supply: Install a pressure
relief valve between the non-return valve and cold water inlet.
▶ Install a pressure reducer if the static system pressure is in excess of
Installing a pressure relief valve (on site)
▶ Install a type-tested pressure relief valve on site that is approved for
potable water (DN 20) in the cold water supply ( Fig. 9,
▶ Observe the pressure relief valve installation instructions.
▶ Terminate the discharge pipe of the pressure relief valve where it will
be easily visible in the frost-proof area via a dewatering point.
– The discharge pipe must be at least equal to the outlet cross-
section of the pressure relief valve.
– The discharge pipe must be able to discharge at least the flow rate
that is feasible at the cold water inlet ( Tab. 4, page 25).
▶ Attach a notice with the following text to the pressure relief valve:
"Never close the discharge pipe. During heating, water may be
discharged for operational reasons."
If the static system pressure exceeds 80 % of the pressure relief valve
▶ Install a pressure reducer upstream ( Fig. 9, page 46).
< 4.8 bar
Table 8 Selection of a suitable pressure reducer
W 120-5 O – 6 720 819 306 (2018/10)
in the EU
outside the EU
max. 4.8 bar
max. 5.0 bar
max. 5.0 bar
Installing the hot water temperature sensor
Install the hot water temperature sensor at the test point  to measure
and monitor the DHW temperature in the DHW cylinder
( Fig. 3 page 45).
▶ Install the hot water temperature sensor ( Fig. 10, page 47).
Ensure that the sensor surface has contact with the sensor pocket
surface over its full length.