BCU 460, BCU 465 · Edition 11.19
41
Valve proving system
6 .1 .1 Test instant
Depending on the parameter setting, the tightness
control checks the tightness of the pipework and the
gas solenoid valves before each start-up and/or after
each shut-down of the burner, see page 100 (Valve
proving system).
The gas line is always safeguarded by a gas solenoid
valve during this check.
Before burner start-up
The valve check is started when the start-up signal
ϑ
is present at terminal 1. The BCU checks the tightness
of the gas solenoid valves and the pipework between
the valves. The gas line is always safeguarded by a gas
solenoid valve during this check. The burner is ignited
when pre-purge is ended and the tightness has been
checked successfully.
After burner shut-down
After the burner has been shut down, the BCU checks
the tightness of the gas solenoid valves and the pipe-
work between them. Once the test has been carried out
successfully, the next burner start is enabled. The BCU
immediately conducts a tightness test if mains voltage
is available or if it is reset after a fault lock-out.
PZH
PZL
PDZ
BCU 460..C1F1
µC
VAS
VAS 1
VAG
DG
DG
V1
V2
V3
p
u
/2
61 62
60
38
22
52
65
67
66
56
36 37
ϑ
1
35
3
2
DL
min
V
p1
An additional bypass/relief valve must be installed in
gas sections with an air/gas ratio control. This ensures
that the test volume V
p1
can be vented during the tight-
ness test with the air/gas ratio control closed.