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Discuss Oven & Hob - Again! in the Electrical Forum area at ElectrciansForums.co.uk.

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  1. MikeBa
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    MikeBa New EF Member

    First post on forum, so go easy on me please!.

    I am looking to add a hob to an existing installation –details as follows:-
    Existing oven – 3 kW – adding 7 kW hob
    1998 build
    32A MCB type B feeding 6.0mm2 t&e radial circuit about10m length clipped to wall, behind plasterboard connecting to 45A DP isolator with13A plug – above work top – closed to oven/ hob area.
    From DP isolator 2 x 4.5mm2 t&e to under worktop – one to13A unswitched socket supplying the (present) gas hob ignition – the other to45A cooker connection unit.
    From the CCU a 2.5mm2 t&e to oven.

    With diversity the proposed addition works – (3000W + 7000W)/240V – 41.7A
    First 10A + 30% remaining + 5A for socket = (41.7A-10A) x .3+ 10A + 5 A = 24.5A < 32 A

    My concern is that the 2 x 4.5mm2 from DP isolator and 2.5mm2from CCU are being protected by a 32A MCB – not to regs and one of the 4.5mm2.t&ewould not be sufficient to supply the 7 kW hob.

    To correct this I propose linking the 2 x 4.5mm t&e intoa twin CCU (discussed on this forum) and connecting the oven and hob into this.Probably replacing the 2.5mm2 t&e to the oven with 6.0mm2. This will placeat least 6.0mm2 to the complete circuit and allow the diversity calc to bevalid all the way to the CCU.

    The hob requires a flexible high temp (90 deg) cable that I amtrying to source (various threads on this forum relating to the rarity).

    Thanks in advance for the help!.

     
  2. Amp David
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    Amp David Trusted Advisor

    Location:
    Glossop
    A 4.5mm cable how that done?

    Should also be using 230 volt in your calcs.
     
  3. MikeBa
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    MikeBa New EF Member

    2 x 4.5mm cables out of the DP isolator at present - not up to capacity as 2 x single - OK when linked in parallel?
     
  4. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

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    cheshire/staffordshire
    Business Name:
    Telectrix
    do you mean 4.0mm?
     
  5. MikeBa
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    MikeBa New EF Member

    Sorry - you are correct - i have checked them with a vernnier gauge and the table off the forum - i mean 4.0mm!!.
     
  6. telectrix
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    telectrix Scouser and Proud of It Trusted Advisor

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    4'0mm will happily take 32A if not in insulating wall.
     
  7. MikeBa
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    MikeBa New EF Member

    Thanks for that Telectrix!.
    Is there a benefit to linking the existing 2 x 4.0mm between the DP isolator and (Dual) CCU - my reasoning being that this give better flexability in sharing power between the two appliances - or is this just unnecessary?
     
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