93-509-09 - Issue 2 Rev 2 Page 8 of 20 Copyright Protec Fire Detection PLC
2.4 ALARM CABLING
The main consideration for the alarm cable is the length. This length must include all spurs. For example, an
alarm circuit of 800m with three spurs of 150m must be considered as being 1250m in length.
Notes :- 1. The alarm cabling must be wired in a minimum standard of 2.5mm
2
fire rated cable.
2. If however, the total alarm cabling length is less than 1km, then the alarm circuit may be
wired in a minimum standard of 1.5mm
2
fire rated cable. In countries where local standards
permit, the alarm circuit can be wired in ‘Twin Figure 8’ cable but the cable length and load
will have to be reduced in accordance with the lower conductor size.
3. The maximum permissible alarm circuit length is limited by volt drop.
EACH OF THE ALARM CIRCUITS MUST BE WIRED IN A SEPARATE PAIR. WHEN THE CABLE HAS A
SCREEN THEN THE SCREEN MUST BE EARTHED AND CONTINUOUS OVER THE CABLE RUN.
TABLE 1 - CABLING, NUMBER OF CORES
CABLE Number of Cores
1. Supply 230 volts 50Hz
2. Network Data
Repeat Panel Data
3. Loop Circuit
Alarm Circuit
4. Power Pair For: -
Zone/Alarm Interface Units
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