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Discuss 315a cut out, what size tails in the Electrical Wiring, Theories and Regulations area at ElectrciansForums.co.uk.

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  1. RJP1
    Offline

    RJP1 EF Member

    Location:
    Lincolnshire
    I'm looking at a job for a friend and wpd is upgrading his cut out and wants us to upgrade his whole install. my question is from the new 315a fuses wpd is putting in what size cable would i require to the panel board literally decide it.
    I've has a look on like and uk power networks suggest 240mm cable. am i right in thinking 95mm tried rated would be fine as it can carry upto 321a therefore being protected by the incoming fuses. any help on this would be appreciated.
     
  2. Andy-1960
    Online

    Andy-1960 Electrician's Arms

    Location:
    Wolverhampton
    You need to consider the derating factors for running the number of cores you are installing and also the temperature you need the cables to run at.
    The current rating quoted is for one cable in free air with a core temp of 90 degrees.
    Also, trirated cable is not double insulated
     
  3. anthonybragg
    Online

    anthonybragg Electrician's Arms

    Location:
    NORTHAMPTON
    Business Name:
    CHARLTEC ELECTRICAL LTD
    The DNO or meter operator will not/may not accept Tri rated into their terminal connections.
     
  4. RJP1
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    RJP1 EF Member

    Location:
    Lincolnshire
    It will be in trunking and completely mechanically protected Into the panel board and about 6m is required. I have also been assured that been sssured by wpds SAP that tri rates will be acceptable to be terminated into the cutout.
     
  5. westward10
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    westward10 In echoed steps I walk across an empty dream. Electrician's Arms

    Location:
    Northamptonshire
    As above you must apply grouping factors to tri rated and 95.0 would be way undersized.
     
  6. Wilko
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    Wilko Electrician's Arms

    Location:
    Berkshire
    Business Name:
    Wilko Electrics
    Hi - agree 95mm undersized, sorry RJ.
    Using Table 4D1A, ref method B, 3p+n the first one over 315A is 240mm, as per UKPN.
     
  7. spinlondon
    Offline

    spinlondon Trusted Advisor

    Location:
    Harlow Essex
    Tri rated can be double insulated, the second layer is often some kind of foam which doubles the diameter of the cable.
    As for sizing the cable, don’t size it to the cut out fuse rating, but to the expected load.
    Unless WPD are saying their cut out fuse can be used to protect the installation, you will need to provide your own.
     
  8. Strima
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    Strima Electrician's Arms

    Location:
    St Neots
    As Spinlondon has said, Tri-rated is available as double insulated, we use it a lot for DC systems.
     
  9. Sparkingmad
    Offline

    Sparkingmad Regular EF Member

    Location:
    Dorset
    You will have to apply the correction factors for the installation I’m afraid. Are the tails going into your own sw fuse unit before going into the new board or are you relying on the DNO cut out?
     
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