Installing Very Long Alarm Sensor Zone Loops
What’s the best way to handle very long zone loops? Would you recommend using a large AWG cable, or other there other techniques that would be more effective?
If you’re installing long cable runs in zone loops there are going to be issues of voltage loss. Given most security cables have a resistance of 16.4 ohms per 100m across a 2-wire circuit, and a PIR taking 20mA will have a voltage drop of 0.33V per 100m, you’ve got plenty of scope in domestic and SME situations.
On big installs with enormous cable runs you’ll run into trouble, especially if instead of using star configuration you add multiple sensors to some of your loops. There’s a degree of customisation in the field required to uncover what works best on your site. Larger diameter cables will assist and, in some cases, they may double your reach. In other installations you should consider BUS-based systems and/or remote controllers to support far-flung sensors.
Long range wireless is another option and, depending on the environment, you may get reliable performance of 300 metres or more, though this will require on-site testing and will need to be managed to ensure range is not attenuated over time. Manufacturers are reluctant to make claims about wireless sensor range because conditions will impact on performance, but these devices can have more reach than you’d expect, especially if installed line of sight. If we needed very long range wireless we’d talk to BGWT about DSC PowerG, which has a full range of sensors offering 2000 metres line of sight – that’s very strong performance.
It may also be worth considering Wi-Fi sensors that leverage existing networks to deal with extreme long ranges. If you choose this path physical security, including tamper, cyber security and power redundancy considerations apply to blue cable and any network devices involved.
Something you need to remember with V DC runs from the controller to the sensor, is that the signal needs to go both ways and the maximum length of the cable run is for the round trip.