What’s the maximum distance we can run an alarm system zone loop in larger industrial applications? We’re tossing up wireless but we don’t have line of sight.

A: The diameter of the wire is important here because if the wire’s small you’ll get greater power loss through resistance. Quite simply, the larger the diameter of the wire, the greater will be its capacity to carry a given current for longer distances with less loss. It’s best practice to use a wire with a larger diameter than you need – that’s much better than having one that’s too small, though there are cost issues.

In terms of their ability to carry power, 18 AWG twisted pair will give adequate 12V performance up to 200m, 16 AWG will give you just under 300m and 14 AWG will handle just under 350m. Bear in mind that 14AWG is relatively heavy and expensive cable.

If you’re using modern 6-core cables from Belden, DCS, X2 and others, these are likely to be good quality but being multi-stranded, their core diameters may be smaller than the AWG measurements mentioned here and will impact on transmission range. If in doubt chat to suppliers about what’s possible.