Immergas VICTRIX EXTRA 12 PLUS Instructions And Recommendations page 48

In the C and C installations, the appliance flue exhaust must be fitted with a Ø 80 flue gas non-return valve kit, consisting of the valve
(10) (12)
itself with instructions, specification and relative sticker with additional safety information (Fig.34).
48
A
S
C
≤
Key (Fig. 39):
C
12
A - Intake
C - Minimum slope 5%
S - Exhaust
39
C
10
38
40