Ariston CLAS HE R 12 Installation And Servicing Instructions page 13

Feed and vent pipework
The feed and vent pipework from the boiler to the F
& E (Feed & Expansion) tank should be configured as
shown in the fig. below.
Flow
Cylinder
Return
Flow
Heating Circuit
Return
22mm (Min.) Vent Pipe
15mm (Min.) Cold Feed
Pump
15mm (Min.)
Automatic By-Pass
500mm Minimum
Height
2M
Minimum
150mm
Max.
R F
Boiler
installation
13