Viessmann Vitocrossal 300 Service Instructions Manual page 37

Diagnostics
(cont.)
After the controller issues a heat demand, the following program sequence
will run:
Phase
01 Test for heat demand
02 Idle state check of the air pressure switch
and the fan
03 Fan ramp up
(a fault shutdown will be initiated if the air pressure switch
does not signal that the air pressure has reached
a defined range within this time scale, or
the fan does not reach its set speed)
04 Pre−purge I
05 Pre−purge II
06 Pre−purge III
07 Ignition position
(the burner control unit will enter a fault state if
the fan does not reach its set speed)
08 Pre−ignition
09 Start−up safety time (safety time A)
(enable safety valves at the start of safety time A,
safety time operation < 1 s)
10 Flame stabilisation in ignition position
11 Changeover to control operation
(ramp up to the set speed programmed in the controller)
12 Operation
(the system will be restarted after expiry of this time)
13 Burner run−on time
17 Post−purge
18 Restart lockout time
19 Gas shortage position
20 Standby
(a restart follows a heat demand, and the system
will be restarted after expiry of this time)
in case of fault shutdown from phase 09:
21 Fan run−on prior to lockout
Troubleshooting
Duration
1 s
1 to 30 s
1 to 30 s
5 s
1 s
30 s
1 to 30 s
2 s
2.8 s
20 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
37