BCU 580 · Edition 11.15
27
5 .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 89 (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
1 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 pilot 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 tight-
ness of the gas solenoid valves and the pipework between
them. Once the test has been carried out successfully, the
next burner start is enabled.
The BCU always conducts a tightness test if mains voltage is
available or if it is reset after a fault lock-out.
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 tightness test with
the air/gas ratio control closed.
BCU 580..C0F3
µC
VAS
VAS 1
VAG
V1
V2
V4
13 14
57
PZH
p
u
/2
45
V
p1
VAS
VAS 1
VAG
V1
V2
V3
V4
VAS 1
BCU 580..C0F3
µC
13 14 15 57
p
u
/2
45
PZH
V
p1
Valve proving system > Tightness test