Worcester benchmark ZWB 7-25 R 25 HE Design, Installation And Servicing Instructions page 59

Check the central heating system pressure
B The pointer on the pressure gauge (8.1) should be about
1 bar.
B If the pointer is below 1 bar (when the system is cold), top up
the system with water until the pointer is 1 bar. Your installer
will have shown you how to do this.
B The maximum operating pressure of 2.5 bar at maximum
central heating flow temperature must not be exceeded. If the
pressure increases to 3 bar then the relief valve (15) opens.
6 720 610 577 GB (03.11)
Operating the Appliance
2
3
1
4
0
bar
CH
C
8.1
15
6 720 610 600-03.1O
11