ABB i-bus
®
KNX
Planning and application
FCC/S 1.X.X.1 | 2CDC 508 200 D0211 Rev A 361
On a fan with speed switching or changeover switching, the individual speed is controlled as fol-
lows:
The speeds are controlled via the following values for a 3-speed fan:
•
Speed 0: 0 (0 %)
•
Speed 1: 1…85 (1…33 %)
•
Speed 2: 86…170 (34…67 %)
•
Speed 3: 171…255 (68…100 %)
The speeds are controlled via the following values for a 2-speed fan:
•
Speed 0: 0 (0 %)
•
Speed 1: 1…128 (1…50 %)
•
Speed 2: 129…255 (51…100 %)
The speeds are controlled via the following values for a 1-speed fan:
•
Speed 0: 0 (0 %)
•
Speed 1: 1…255 (1…100 %)
With a continuous fan, the desired speed is entered directly and transmitted to the fan.
1-byte value
Percent
Hexadecimal
Binary value bit
76543210
Fan speed
0
0
00
00000000
0 (OFF)
1…85
1 %…33 %
55
00000001 …
01010101
Fan speed 1
86…170
34 %…67 %
AA
01010110 …
10101010
Fan speed 2
171…255
68 %…100 %
FF
10101011 …
11111111
Fan speed 3
Table 38: Fan speed depending on the entered value
12.2.5
Switchover between automatic and direct operation
Switchover between automatic operation and direct operation is possible. The changeover to man-
ual fan control is implemented via a 1 bit value or automatically after a certain time period elapses.
The fan speed is switched in accordance with the 1-byte value received.
Fan control is changed back to automatic operation if a 1 is received on the respective group ob-
ject.
The current status of automatic operation is fed back via a 1 bit value.
12.2.6
Speed switching logic
The control value for changing the speed is calculated as follows:
•
Switching up: control value ≥ thr 1/2 hysteresis
•
Switching down: control value ≥ thr 1/2 hysteresis
The value 0 is an exception. If this is selected as the switchover point between 0 and 1, switching
up (0 > 1) takes place only from a control value greater than 0 and switching down (1 > 0) only
from a control value equal to zero.
The following additionally applies:
•
Switching always takes place to the highest speed with 100 %
•
The fan is always switched off at 0 %.
The following example describes the sequence of speed switchover depending on the control
value and the parametrized thresholds and hysteresis values.