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In the UK, what type of flexible conduit should I use for electrics in shed that run underground and emerge through the concrete base? I see various standards quoted such as IP66. Would this be suitable- http://www.screwfix.com/p/adaptaflex-standard-weight-nylon-conduit-28mm-x-10m-black/89238

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If you're just looking to get a power supply to the shed, you probably don't need to use conduit at all. Steel Wire Armoured (SWA -- roughly equivalent to jacketed/direct bury rated MC) cable is suited to being run underground and doesn't need to be in a conduit. Additional benefits are that it's more resistant to a stray spade trying to dig through it (though if you aim to bury deep enough, that shouldn't be a problem - general guidance is at least 450mm deep, but minimum 2 spades deep should be sufficient) and you don't need to mess about pulling cable through the conduit.

If you want to make it easy to replace the cable entering the shed (should you ever need to), you could use a piece of pipe / conduit / trunking to pass through the concrete base to allow the cable to be pulled easily through.

  • For folks in the rest of the world -- are you referring to something akin to the NEC type AC (with a bonded-armor grounding conductor) or the NEC type MC (with a full-gauge internal grounding conductor that may be bonded to the armor as well) when you say "armored cable"? I ask because NEC type AC is forbidden in damp or wet conditions (such as direct bury!), where as NEC type MC needs to be identified for direct burial service in order to be used in a direct bury application. – ThreePhaseEel Nov 18 '15 at 2:50
  • I'm not familiar with either of those, but a quick look at Google Images suggests they aren't a direct equivalent. When I say "armoured cable", I mean what is properly referred to as Steel Wire Armoured (SWA) cable, such as shown here tlc-direct.co.uk/Main_Index/Cable_Index/Armoured_SWA (though I note that the photos are of the old colour core insulation, no longer used in the UK). – John Nov 18 '15 at 14:11
  • It seems like the two-core SWA is used in a similar fashion to AC (with the armor providing the sole grounding conductor) and the three-core SWA is closer to MC (with the ability to have internal grounding). Either way -- the main technical issue with burying AC is that AC is not jacketed, while direct bury MC is, as well as both types of SWA. – ThreePhaseEel Nov 18 '15 at 23:22

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