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Buried depth of SWA cable when passing through obstruction in route

Jason McKenzie

Good afternoon,

I have an installation of a 6mm SWA cable, for a supply to a domestic EV charger. The route is obstructed by front of house, brick built access steps, with a concrete slab top, and the preferred route is to pass under/through the steps, which are 900mm wide, this would require drilling a hole in either side of the bricks which form the steps. The regs state no specific depth, just sufficient to avoid damage. As there is almost zero chance of any mechanical damage, and the rest of the cable run will be above ground, should the route through the steps, just be at a convenient position?

Many thanks for any advice.

  • +1

    should the route through the steps, just be at a convenient position

    I don't see why not. I'd probably even consider the route through the steps to be more concealed within a building rather than buried in the ground (not that it makes much difference, with SWA).

       - Andy.

  • +1

    There is guidance for buried cables on what is considered "sufficient depth to avoid damage". There are also firm requirements for specific cases.  In the general case, the guidance can be found in Guidance Note 1.

    However, because not all of this information is readily available in one place, and the question is often asked of technical helplines, it's been summarised in Table K.1 of Appendix K to the 5th Edition of the IET Code of Practice for EV Charging Equipment Installation. The Appendix also contains a summary of the NJUG guidance for depth under highways, and the minimum height of overhead cables is summarised in Table K.3.

    However, regards steps, I would say that the SWA passing through them is not "buried" but "encased in building fabric" just like being in a wall and a lesser depth might be acceptable

    One thing to consider, though, is whether there is sufficient air around the cable as it passes through the steps, to avoid de-rating as per a buried cable.

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