BCU 580 · Edition 11.15
33
5 .2 Proof of closure function
The proof of closure function monitors the function of the gas
solenoid valve V1. The proof of closure function can be activated
using parameter 51 = 4, see page 89 (Valve proving system).
A limit switch on gas solenoid valve V1 signals the closed
position of the valve to the BCU (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 closure
function, the BCU complies with the requirements of NFPA 85
(Boiler and Combustion Systems Hazards Code) and NFPA 86
(Standard for Ovens and Furnaces).
5 .2 .1 Program sequence
When the start-up signal
ϑ1
is received at terminal 1, the BCU
checks that valve V1 is in its closed position using the POC
switch. After a timeout time of 10 s, a signal from the POC switch
(valve V1 is closed) must be received at terminal 45. Otherwise,
the BCU performs a fault lock-out with fault message c1.
As soon as the BCU has opened valve V1, it queries the open
position of the valve via the POC switch. If a signal is still re-
ceived at terminal 45 from the POC switch after a timeout time
of 10 s, the BCU performs a fault lock-out with fault message c8.
Valve proving system
