Planning the Installation
Page 18
Table 5: Voltage drop along cable
Cable Length (Standard 7/0.2 alarm cable)
You can reduce voltage drop using either or both of these methods:
Double-up the supply connections (12V and 0V). This will halve the resistance on
each core and therefore halve the voltage drop.
Supply power to the detection devices from the control unit's Aux output using two
additional cores in the cable (that is, use 6-core cable). This reduces the current
drawn by the bus devices and is the preferred method of reducing voltage drop,
since detectors generally operate at lower voltages (9.5V).
If you cannot reduce voltage drop sufficiently, install one or more remote power supplies,
as described next.
Using remote power supplies
When voltage drop along the bus cable exceeds requirements, or the demand on the
control unit's power supply exceeds its capacity, you should install one or more EXP-PSU
remote power supplies. Figure 5 shows the recommended method of connecting a remote
power supply. It should be fitted close to the equipment it is powering.
Figure
Connecting a Remote Power Supply
Device 1
0V
Bus
Device 2
Remote PSU
Device 4
Device 3
12V
B
A
0V
12VAB
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