BCU 580 · Edition 11.15
84
10 .6 .9 Capacity control (bus)
Parameter 75
Controlling the burner capacity using the fieldbus is only pos-
sible with bus module BCM 500 connected and enabled (P80 =
1 or 2).
The output at terminal 56 has a different function.
Parameter 75 = 0: Off. No capacity control possible using
the fieldbus.
Parameter 75 = 1: MIN. to MAX. capacity; standby in position
for MIN. capacity. The control range while the burner is oper-
ating is between the positions for minimum capacity (S4) and
maximum capacity (S3). The burner is ignited in the position
for ignition capacity (S1). 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,
RBW or alternatively with a comparable three-point step ac-
tuator.
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.
IC 20
Switching cam setting for ignition capacity, minimum and
maximum capacity as well as pre-purge and standby:
S1: for ignition capacity of the burner.
S3: for maximum capacity of the burner and pre-purge.
S4: for minimum capacity of the burner and standby.
0°
90°
S4
S1
S3
Burner control range
Butterfly valve setting range
Control range
Move to ignition position
Ignition pos.
Min.
pos.
Closed
pos.
Max. pos.
MIN
MIN
MIN
MAX
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
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
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