SWA support - Regulation 522.8.5

Discussion in 'Electricians' Talk' started by John Williamson, Nov 17, 2021.

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  1. Hopefully a yes or no answer. I'm going to run some SWA cable (without connecting it up to anything, a spark will be doing this), under some floorboards and through a trench outside while it's open for some work on other utilities.

    In terms of supporting the SWA (likely a 16mm or 25mm so pretty chunky) I read the following:

    "Regulation 522.8.5 requires every cable to be installed to avoid any undue mechanical strain and to make sure that there is no strain on the conductors and connections."

    Would the actual ground (i.e soil) under the ground floor void count as adequate support or is there some crazy exception to this? In short can I lay it on the earth under the floorboards?

    In terms of the vertical up towards the CU I understand there will be a requirement for cleats but just wondering about this horizontal run which would be about 6 meters.
     
  2. Hans_25

    Hans_25 Screwfix Select

    Don't see a problem there. Cables are routinely laid on the ground and my SWA outside is on the ground, spark who signed it off said it was fine as its not in an area where its likely to be tripped over.
     
    John Williamson likes this.
  3. Bazza-spark

    Bazza-spark Screwfix Select

    You need to consider the requirement here:

    522.8.10 Except where installed in a conduit or duct which provides equivalent protection against mechanical damage, a cable buried in the ground shall incorporate an earthed armour or metal sheath or both, suitable for use as a protective conductor. The location of buried cables shall be marked by cable covers or a suitable marker tape. Buried conduits and ducts shall be suitably identified. Buried cables, conduits and ducts shall be at a sufficient depth to avoid being damaged by any reasonably foreseeable disturbance of the ground.

    The bottom of the trench is often covered with a layer of sand, then sand above the cable to potect against damage from stones before the warning tape.
     
    John Williamson likes this.
  4. Bob Rathbone

    Bob Rathbone Screwfix Select

    Regulation 522.8.5 refers to the need for a cable gland or similar device to prevent a pulling force being exerted on the cable conductors or connections. It does not refer to cable supports such as clipping.
    If the soil into which the cable is to be laid contains stones or other sharp objects that may damage the cable sheath, the cable should be laid on a bed of material that will not damage the sheath and is thick enough to prevent damage by the objects in the soil below. A similar layer should be put on top of the cable to keep any sharp objects in the soil away from the cable. Warning tape above at a depth that will be found before excavation damages the cable. Sorry it's in bold, the formatting carried over from copying the reg number.
     
  5. Thanks Bob. Key word here is "IF the soil into which the cable is to be laid contains stones" which to me says after lifting a few boards IF it's soil with no sharp stones, then just lay the cable and put back the floorboards.
     
  6. Bazza-spark

    Bazza-spark Screwfix Select

    The sand and tape is for the trench, not under the boards as the cable is only under it own weight there, whereas once the trench is filled in there is a lot of weight on it.
     
    John Williamson likes this.

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