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Thread: Changeover switch

  1. #1
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    Changeover switch

    Hello all,

    Could anyone please shed some light!. With regards to a generator, is it necessary to have overcorrect protection before the changeover switch?? Here in Cape town 90% of the guys fit the transfer switch before the Main switch of the installation, thus the first component of the installation is in fact the changeover switch, and not the Main Switch. So in order to work on the transfer switch the breaker in the boundary box where the meter is also located needs to be switched off (which is the councils property?) ... this just doesnt seem right to me.

    My query is for a 200A commercial premises, whereby the generator has its own Breaker of also 200A and feeds the entire installation.

    The reason why I ask this is, in the example on page 355 of the SANS book, they clearly show a point of control for the Council or Eskom supply being BEFORE the changeover. And, Point of Control being defined as "the point at which a consumer can, on or in any premises, switch off the electrical installation from the electricity supplied from the point of supply".. and this Point of Control surely not being in the boundary box! What is the correct way? Have an additional breaker before the changeover and label it "Council Mains", and then obviously the "Main Switch" in your Main DB.. or simply install the changeover before the Main Switch with no breaker before other than in the boundary box. As mentioned the generator already has its own breaker. At R3000 a breaker it matters if an one is needed!

    Plz excuse the long explanation
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  2. #2
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    Correction.. "Overcurrent protection"

    Don't think I'm over correct

  3. #3
    Diamond Member AndyD's Avatar
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    The diagram you've posted from the regs is from the 'informative' section and is cited as an 'example' so you can't use it as proof for any argument.

    I don't have a definitive answer but my immediate thoughts are;
    • The point of control could be elsewhere on the premises to the main DB.
    • The point of control doesn't necessarily need to be an over-current protective device, it could in some circumstances be an on-load isolator.
    • Some changeover switches have an 'OFF' position which means they could also fulfil the requirements of being the point of control for multiple sources of supply depending how the installation is configured.
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    Thanks Andy for your response, I agree with what you've said.. and this particular changeover does have an Off position

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