Planning the Installation
Page 24
If screened cable is required:
1. Avoid earth loops by connecting the screen on the cable to mains earth at the control
unit but not at the keypad or expander.
2. The continuity of the cable screen is most important and screens MUST be
continuous along the full length of the cable.
3. Where the cable enters any metal enclosure, ensure the screen is isolated from the
case.
Cable segregation
Segregate bus cabling from any other wiring, such as mains cables, telephone cables,
computer network cables and R.F. cables.
Keep bus cables clear of cables supplying sounders, extension loudspeakers or any other
high-current devices.
Mains cable routing
Use separate cable-entry holes in the enclosure for mains and signal cables. Please refer
to the figures in
Chapter 3: Installing i-on Control Units
for details of the holes to use for
each type of cable.
Mains cable must be routed away from any aerials in the enclosure (i-on Compact and i-
on30R+ only). For i-on Compact, please refer to Figure 7 on page 29. For i-on30R+,
please refer to Figure 11 on page 32.
Cable length and configuration (star or daisy chain)
You can connect devices either in daisy chain (serially), or in star (parallel) configuration at
the control unit connector (Figure 4). For star configurations, the cable length from control
unit to the most distant bus device should be kept short, and should not exceed 100m.
There should be no more than four arms in the star.
For a daisy-chain configuration, the total cable length should not exceed 1,000m.
Note that if there are only two arms in a star configuration, this is equivalent to a daisy-
chain configuration.
Bus termination
In some cases, the ends of the bus may need to be terminated to improve performance in
electrically noisy environments or where there are long cable runs. The control unit and
bus devices have a termination link on their PCB. Fitting a jumper to the link adds a
termination to the cable.
In a daisy-chain configuration, fit the termination jumpers in the devices at each end of the
chain. In a star configuration, terminate at the two devices on the ends of the longest
cables (Figure 4).