93-530-70 Issue 0 Page 12 of 44 © Protec Fire Detection PLC 2007
8.0 Alarm Circuit Connections
The 3300 has four alarm circuit outputs, all are rated for continuous use at 150mA and protected from
over-load by an auto resetting thermal ‘fuse’. The ‘fuse’ will reset when the cause of overload has
been removed and the alarm output has been de-activated.
Figure 8.0 shows typical connections for a 3300 alarm circuit.
Figure 8.0 Typical 3300 Alarm Circuit Connection.
• Ensure the length of the alarm circuit wiring is no more than 500 metres.
• Ensure the capacitance of the alarm circuit wiring is no more than 0.27µF (micro-Farads).
• The 10kΩ end of line resistor must be connected at the very end of the alarm circuit wiring,
ensuring the whole line is monitored for open circuit faults.
• Spurs should not be connected from the alarm wiring as the spur will not be monitored for open
circuit faults.
• Only polarised and suppressed sounders should be used on the 3300 alarm circuits. Failure to
use polarised sounders will result in an alarm circuit fault. All Protec S3000 sounders are polarised
and suppressed as standard.
• Efforts should be made to evenly spread the sounder load across the 4 alarm circuits, to avoid
overloading any one of the alarm outputs.
• It is acceptable to connect alarm circuits 1 and 2 or alarm circuits 3 and 4 in parallel (to obtain a
drive rating of 300mA continuous), however the end of line resistor value must be changed to
4k7Ω 1/2W 5%. This is detailed in figure 8.1
Figure 8.1 Enhanced Alarm Circuit Drive Details
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