Honeywell Krom Schroder BCU 580 - 5.2 Proof of closure function

BCU 580 · Edition 11.15l 36
Valve proving system
5.2 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 95 (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
4
75
8
4
8
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 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 received 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.