What gauge is used for direct buried service wire?

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Direct buried service wire uses small-diameter copper conductors inside a burial-rated jacket, sized to carry the required low-level service current while staying compact enough for underground installation. The conductor size is chosen to balance how much current it can safely carry and how much voltage drop you’ll see over the typical burial distance, all within the constraints of the cable’s outer sheath. 19 AWG is the standard size specified for direct-burial service wire in many OSP designs because it provides sufficient ampacity for common low-voltage service needs while keeping the cable thin and flexible enough for burial. Using a much smaller conductor, like 24 AWG, would lead to excessive resistance and voltage drop; larger sizes such as 18 AWG or 21 AWG aren’t the standard offerings for these direct-burial service cables and don’t align with typical catalog specifications for this application. Always follow the manufacturer’s installation instructions and applicable codes when selecting and burying service conductors.