How would you recommend carrying power between 2 buildings in a regional location? Should we install waterproof conduit or are there other options – and how deep would you recommend trenching?
A: How you support the cable depends on trench depth. If you go down 60 centimetres, then you can use UF cable without bothering with conduit – it goes without saying that you need to balance the effort required in an install like this. How heavy is traffic over the ground? How hard is the ground to trench? How likely is it there will be digging on the site?
We’d suggest using conduit at 45cm and this will allow you to use less expensive cable, though it will still need to nylon coated. GFCI protected direct burial feeder cable supported by PVC conduit at ground entry and exit points works at 30cm. Shallower than this you need to be thinking about metal conduit. You also need to be paying attention to regulations around safety signage and safety switching.
Unless the ground is very soft you are going to want to use a walk-behind trencher (rent one) rather than a mattock and shovel. Feeding cable into underground conduit can be tricky – make sure the cable feed is successful before backfilling. Most cored cables will feed well by hand from the supply entry point but if there are complex changes of direct or tight corners, you may have issues with friction and/or folding of the cable.
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