Pvc and polystyrene

Discussion in 'Electricians' Talk' started by Mancave, Jan 2, 2018.

  1. Mancave

    Mancave New Member

    I know this is a well-covered subject but any thoughts much appreciated on a cabling dilemma

    I'm running cables in a cabin that will be insulated with Jablite EPS70 (celo gone silly on prices) but I'm aware of the plasticiser issue and the advice to use a suitable conduit or leave an air gap. I'll have a 25mm air gap which is too close for comfort and most conduit is PVC - so is this any better than using PVC sheathed cable?

    So the question is which conduit is actually suitable, and would it just be better to use LSOH cable which isn't PVC sheathed?

    Thanks in advance!
  2. spinlondon

    spinlondon Screwfix Select

    If you use modern cables, you shouldn’t have a problem.
  3. unphased

    unphased Screwfix Select

    PVC conduit is unplasticized, so there is no chemical reaction with polystyrene. Just install the cables and stop worrying over nothing.
  4. unphased

    unphased Screwfix Select

    Extract from the official literature:
    15 Incorporation of services
    15.1 De-rating of electrical cables should be considered where the insulation restricts air cooling of cables; the boards must not be used in direct contact with electrical heating cables or hot water pipes.
    15.2 Where possible, electrical conduits, gas and water pipes or other services should be contained within ducts or channels within the concrete slab of ground supported floors. Where this is not possible, the services may be accommodated within the insulation, provided they are securely fixed to the concrete slab. Electrical cables should be enclosed in a suitable conduit. With hot pipes, the insulation must be cut back to maintain an air space. ​

    As above, PVC conduit would be suitable for installing cables as it will protect the cables from contact with the EPS.
  5. Lectrician

    Lectrician Screwfix Select

    Celotex type insulation has gone sky high in price as one of the factories had a large fire and production is now struggling to supply demand. Polystyrene is being used in places instead at the moment. Polystyrene does react with PVC cables, those who think it is a myth have never seen it. Standard PVC conduit or capping is all that is needed, or a clear air gap.
  6. Mancave

    Mancave New Member

    Thanks for replies...and advice notes I'll get on and stop worrying!

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