Viessmann Vitocrossal 200 Service Instructions Manual page 47

Gas burner control unit flow chart
Phase
01 Test for heat demand
02 Checking the idle state of the air pressure switch and
the fan
03 Fan ramps up to speed (a fault shutdown will be in-
itiated if the air pressure switch does not signal within
this time scale, that the air pressure has reached a
defined range or if the fan does not reach its set
speed)
04 Pre purge I
05 Pre purge II
06 Pre purge III
07 Ignition setting (the burner control unit will enter a
fault state if the fan does not achieve its set speed)
08 Pre ignition
09 Start up safety time (safety time A) (safety valves en-
abled at the beginning of safety time A, safety time <
1 s); (no gas pressure switch monitoring)
10 Stabilising the flame in the ignition position
11 Changing to the control mode (ramps to the set
speed selected at the control unit)
12 Operation (the system will be restarted after expiry of
this time)
13 Afterburn time
17 Post purge
18 Restart blocking time
19 Gas shortage position
20 Standby
(a restart follows a heat demand and the system re-
starts after expiry of this time)
in case of fault shutdown from phase 09:
21 Fan run on before lockout
Gas burner control unit flow chart
(cont.)
Duration
1 s
1 to 30 s
1 to 30 s
5 s
1 s
30 s
1 to 30 s
2 s
2 to 10 s
20 to 60 s
1 to 30 s
max. 23:59 h
max. 30 s
1 to 60 s
0 s
max. 30 min
max. 23:59 h
5 s
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