Proof Of Closure Function; Program Sequence - Honeywell Krom Schroder BCU 580 Technical Information

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.
ϑ
1
2
µC
By checking the closed position using the proof of clo-
3
sure function, the BCU complies with the requirements
BCU 560..C1
of NFPA 85 (Boiler and Combustion Systems Hazards
58 47
Code) and NFPA 86 (Standard for Ovens and Furnaces).
M

5 .2 .1 Program sequence

PZL
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.
BCU 580 · Edition 11.15l
V1 V2
GZL
14 13
45
P
>750°
TC
48
PDZ
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.
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