BCU 580 · Edition 11.15
87
Parameter 75 = 4: MIN. to MAX. capacity; standby in position
for MIN. capacity; burner quick start.
The control range while the burner is operating is between
the positions for minimum capacity (S4) and maximum capac-
ity (S3). The burner is ignited in the position for ignition capac-
ity (S1). Switching cam S2 (reverse direction of rotation) ensures
that the position for ignition capacity is approached without
pre-purging first (quick start). When the burner is switched off,
the actuator is moved to the position for minimum capacity (S4).
This operating mode can be achieved with an actuator IC 20
or alternatively with a comparable three-point step actuator.
If the air supply is stopped on a heated furnace with the
burner switched off, the controls may be damaged by the
hot furnace atmosphere as a result of the lowest possible
position of the butterfly valve, limited by S4. If pre-purge is
active, considerably lower air capacity than the maximum
air capacity will be used for purging.
IC 20
Switching cam setting for ignition capacity, minimum and
maximum capacity and reverse direction of rotation to ap-
proach the position for ignition capacity:
S1: for ignition capacity of the burner.
S2: for reversing the direction of rotation to approach the posi-
tion for ignition capacity.
S3: for maximum capacity of the burner and pre-purge.
S4: for the closed position of the butterfly valve and standby.
S4
S2
S3
S1
0°
90°
Move to ignition position
Burner control range
Butterfly valve setting range
Control range
Max. pos.
OPEN
Ignition
pos.
Reversing direction of rotation
for quick start
Min.
pos.
Closed
pos.
MIN
MIN
MIN
MAX
MAX
PE
L1
N
3 2 1
16
6
7
4
8
12 11
15
13
S3
S4
S11
S10
0°
90°
M
IC 20
PE
S1
S2
90°
➔
0°
0°
➔
90°
S1
Min
Max
S2
Y-
Y+
53
54
55
56
52
1
2
3
46
45
65
66
67
68
49
50
51
17
18
37
38
13
14
15
BCU 580..F1
3,15AT
µC
88
c
c
41
42
24V
DC
5 6
9
11 12
10
7
62 61
Parameters > Air control > Capacity control (bus)
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