Melted wire at DP Switch

Discussion in 'Electricians' Talk' started by Colin19, Nov 2, 2019.

  1. Colin19

    Colin19 New Member

    Seeking a little advice.

    24kWh Storage heater

    Dedicated feed from CU.

    40A MCB >>>> 40A DP switch >>>> timer box >>>>> 24kWh heater.........all 2.5mm cable.

    Live has melted brown covering and DP box - this is the feed from DP box to timer.

    No smell or damage at timer, heater checked and all OK, no smell or heated cable anywher else on circuit.

    Is the MCB too large B40A ??

    If heat had travelled up from heater - then I would expect smell/damage at timer, but nothing there, melt point is at DP box live to the timer.

    Any advice would be appreciated.
  2. JP.

    JP. Screwfix Select

    Loose connection causing arcing
  3. Philip Hyde

    Philip Hyde Screwfix Select

    40A on 2.5mm is a massive No.
  4. JP.

    JP. Screwfix Select

    Aye concur..possibly a wind up tbqh
  5. Colin19

    Colin19 New Member

    Thanks for at least concuring with others.

    But no wind up..........geniune question.

    Arcing at DP box may well be my problem.

    Philip - thanks for the nudge on 40A MCB..........I will change a 16A or 20A,,,,,,,,,,,what would you suggest.

    Thanks so far
  6. Comlec

    Comlec Screwfix Select

    Your 2.4kW heater with draw about 10amps so a 16A MCB will be fine.

    The 40A MCB is not ideal as does not offer any overload protection for this circuit but will still operate on short circuit. However, a circuit with this single heater can not be overloaded.

    The fault you describe will not produce an overload, as JP suggests, it is arcing in a single conductor.
  7. Philip Hyde

    Philip Hyde Screwfix Select

    16 or 20 will be fine. It will protect the cable from overcurrent damage as per regs!
  8. Woloumbo

    Woloumbo Active Member

    What is the kW rating of the heater? NOT the Kwh rating. You be confusing numbers
  9. Colin19

    Colin19 New Member

    Heater is a Dimplex CXL24N Storage heater. Instruction book only gives 24kWh, nothing shown for heater rating.

    Looked at web.........couldn't see anything there either.

  10. Woloumbo

    Woloumbo Active Member

    its 3.4kW or 15A
  11. Comlec

    Comlec Screwfix Select

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