FCU 500, FCU 505 · Edition 02.17
57
Valve proving system
7 .3 Proof of closure function
The proof of closure function monitors the function of
the gas solenoid valve V1. The proof of closure func-
tion can be activated using parameter 51 = 4, see
page 108 (Valve proving system).
A limit switch on gas solenoid valve V1 signals the
closed position of the valve to the FCU (terminal 45) for
this purpose.
BCU 560..C1
µC
P
13
14
47
58
48
TC
PZL
PDZ
M
>750°
ϑ
1
2
3
V1
V2
45
GZL
By checking the closed position using the proof of clo-
sure function, the FCU complies with the requirements
of NFPA 85 (Boiler and Combustion Systems Hazards
Code) and NFPA 86 (Standard for Ovens and Furnaces).
Program sequence
Parallel to the fan run-up time (see page 19 (Pro-
gram sequence)), the FCU checks that valve V1 is in its
closed position using the POC switch. If a signal is not
received at terminal 45 from the POC switch after a
timeout time of 10 s (valve V1 is closed), the FCU per-
forms a fault lock-out with fault message c1.
As soon as the FCU has opened valve V1, it queries the
open position of the valve via the POC switch. If a signal
is still received at terminal 45 from the POC switch after
a timeout time of 10 s, the FCU performs a fault lock-
out with fault message c8.
