1. Visiting from the US? Why not try DIYnot.US instead? Click here to continue to DIYnot.US.
    Dismiss Notice

Safe zone with exposed beams

Discussion in 'Electrics UK' started by very_pointy_ears, 26 Feb 2018.

  1. very_pointy_ears

    very_pointy_ears

    Joined:
    29 Mar 2005
    Messages:
    175
    Thanks Received:
    0
    Country:
    United Kingdom
    Even 1.0mm? It indeed is T+E, but I would have thought that would be 10A max.
     
  2. Sponsored Links
  3. EFLImpudence

    EFLImpudence

    Joined:
    7 Jul 2010
    Messages:
    32,544
    Thanks Received:
    3,530
    Location:
    Retired to:
    Country:
    Portugal
    No - 16A.
     
  4. securespark

    securespark

    Joined:
    11 Jan 2004
    Messages:
    34,587
    Thanks Received:
    1,077
    Country:
    United Kingdom
    What do the regs say about 1 milli and "power" circuits?

    [Duck]
     
    • Like Like x 1
  5. JohnW2

    JohnW2

    Joined:
    28 Jan 2011
    Messages:
    43,313
    Thanks Received:
    2,750
    Location:
    Buckinghamshire
    Country:
    United Kingdom
    But an infamous Table in the regs says? :)

    Kind Regards, John
    Edit: typed too slowly again!
     
  6. EFLImpudence

    EFLImpudence

    Joined:
    7 Jul 2010
    Messages:
    32,544
    Thanks Received:
    3,530
    Location:
    Retired to:
    Country:
    Portugal
    Table 52.3 say 1mm² non-sheathed and sheathed cable must not be used for power circuits.
    1mm² non-sheathed and sheathed flexible cable may be used.

    It is nonsense but that's what it says.
     
  7. securespark

    securespark

    Joined:
    11 Jan 2004
    Messages:
    34,587
    Thanks Received:
    1,077
    Country:
    United Kingdom
    It's madness, I tell you, madness!
     
  8. JohnW2

    JohnW2

    Joined:
    28 Jan 2011
    Messages:
    43,313
    Thanks Received:
    2,750
    Location:
    Buckinghamshire
    Country:
    United Kingdom
    It gets 'worse', of course, since the CCC of 1mm² flexible cable is only 10A, not 16A.

    Kind Regards, John
     
  9. securespark

    securespark

    Joined:
    11 Jan 2004
    Messages:
    34,587
    Thanks Received:
    1,077
    Country:
    United Kingdom
    Has the world gone stark raving bonkers?
     
  10. Sponsored Links
  11. very_pointy_ears

    very_pointy_ears

    Joined:
    29 Mar 2005
    Messages:
    175
    Thanks Received:
    0
    Country:
    United Kingdom
    <amateur speculation>Is the outside diameter of the bunch of strands in 1mm flex the same diameter as the solid core in 1mm T+E? If so, then 1mm flex core would have less cross sectional area of copper than solid core because of the gaps between the strands. Really you'd hope that was a true 1mm cross section of copper whether it be flex or solid core. I've no idea whether that's the case or not.</amateur speculation>

    Regarding current ratings of T+E, I just found this: http://www.lightwiring.co.uk/lighti...-cables/twin-and-earth-cable-current-ratings/ which now makes me wonder what's so different about SWA. I bought some 16mm^2 three core SWA a while back to use as a sub main as I want a consumer unit in the garage/workshop to supply several circuits in the workshop and outbuildings. The cable is rated at 119A which is much more than the rating of 16mm T+E on that page I linked.

    Edit: would the 119A rating be when it's being used to carry 3 phase with 3 live cores, instead of being used instead of T+E on a single phase supply?
     
    Last edited: 26 Feb 2018
  12. JohnW2

    JohnW2

    Joined:
    28 Jan 2011
    Messages:
    43,313
    Thanks Received:
    2,750
    Location:
    Buckinghamshire
    Country:
    United Kingdom
    No, I'm afraid that your speculation is wrong. The 1mm² CSA relates to the total copper CSA, whether the conductor is solid or stranded.

    Kind Regards, John
     
  13. JohnW2

    JohnW2

    Joined:
    28 Jan 2011
    Messages:
    43,313
    Thanks Received:
    2,750
    Location:
    Buckinghamshire
    Country:
    United Kingdom
    I really don't know where your 119A figure came from. For 3/4-core cables, the CCCs for 3-phase are actually a bit lower than for single phase. Per the tables in BS7671 which we generally work with, 70° 3-core 16mm² SWA, Method C, has a CCC of 89A for single-phase and 77A for 3-phase, whilst the corresponding figures for 90° SWA are 107A and 96A. For 70° 16mm² T+E, Method C, the CCC is 85A.

    Kind Regards, John
     
  14. very_pointy_ears

    very_pointy_ears

    Joined:
    29 Mar 2005
    Messages:
    175
    Thanks Received:
    0
    Country:
    United Kingdom
    119A was the rating shown on the site when I bought the cable. They didn't state the conditions that were necessary for that rating, though. It was such a long time ago since I bought it that I can't remember where I got it from.
     
  15. securespark

    securespark

    Joined:
    11 Jan 2004
    Messages:
    34,587
    Thanks Received:
    1,077
    Country:
    United Kingdom
    XLPE SWA is rated higher than PVC. But not as high as 119A. It's 94A.
     
  16. JohnW2

    JohnW2

    Joined:
    28 Jan 2011
    Messages:
    43,313
    Thanks Received:
    2,750
    Location:
    Buckinghamshire
    Country:
    United Kingdom
    As I just wrote, 90° thermosetting 16mm² SWA appears to be 'rated' (Method C) at 107A for single-phase, 96A for 3-phase.

    Kind Regards, John
     
  17. securespark

    securespark

    Joined:
    11 Jan 2004
    Messages:
    34,587
    Thanks Received:
    1,077
    Country:
    United Kingdom
    Apologies
    I was relying on a wholesaler's figures..
     
Sponsored Links
Loading...

Share This Page