FCU 500, FCU 505 · Edition 02.17
35
Valve proving system
7 .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 a furnace system, see page 108
(Valve proving system).
The gas line is always safeguarded by a gas solenoid
valve during this check.
Before furnace start-up
P1
HO
00
H7 H8
ϑ
TC Test
1
2
1
13
14
57
42
t
t
PV
t
RF
V1 leaking
V2 leaking
The FCU starts testing the tightness of the gas solenoid
valves and pipework between the valves parallel to the
pre-purge time. The gas line is always safeguarded by a
gas solenoid valve during this check. When pre-purge
is finished and the tightness has been checked suc-
cessfully, the safety valves for operating the system are
opened after the safety interlocks have been enabled.
After furnace shut-down
08
00
ϑ
TC Test
1
2
1
13
14
57
42
t
t
PN
After the furnace has been shut down, the FCU starts
testing the tightness of the gas solenoid valves and
pipework between the valves. After the tightness has
been checked successfully, the next furnace start is
enabled as regards the tightness criteria.
Each time the FCU is reset or connected to mains volt-
age, a tightness test is performed immediately. The
testing time can be reduced for large volumes, see
page 111 (Large test volumes).
