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Thread: oosterzee box usage

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    Junior Member markthespark's Avatar
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    Exclamation oosterzee box usage

    Please give me some of your input on using an oosterzee box for supplying two different distribution boards on the same premises and of the same building. It is a three phase supply and the Oosterzee box has three separate 50 amp circuit breakers feeding 1 distribution board and a second single phase cable feeding a second smaller distribution board. The second supply is protected by a 45 amp circuit breaker in the oostersee box and is clearly marked as feeding secondary board. The distribution board also has indication that it is fed from the oosterzee box.
    The supply feeding the main distribution board is a 10 mm whilst the second supply is a 6 mm. Although it is a commercial unit the smaller dist board only supplies a kitchen. Both cables are supplied after the council meter. Is there any reason why I should fail this installation?
    To supply the secondary dist board from the main dist board is virtually impossible!
    I cannot see any indication in the code (SANS 10142) to disqualify the installation

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    Diamond Member AndyD's Avatar
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    So you've got a 50A 3-phase main DB and a 45a single phase subDB fed from the oostersee box which in turn is supplied from the meter. What size cable between the meter and the oostersee box? What is the rating of the OCPD at the meter?

    I guess in theory the oostersee box is basically the main DB even though there are no final circuits fed from it. The other 2 boards it supplies are actually sub DB's. If it conforms to all the regs governing a main DB I wouldn't see any reason to disqualify it.
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    Junior Member markthespark's Avatar
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    Thanks Andy I've just never come accross this situation before and although a little concerned, I was more concerned about council regs than sans regs. cable sizing and OCPD rating good to go so I'm happy! just needed extra reassurance!! :-)

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    Gold Member Sparks's Avatar
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    I agree although I would say a 3ph isolator must be present as "Main Switch" and the existing breakers labelled "Sub DB1" and Sub DB2" and then the sub DBs also labelled accordingly.

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    Site Caretaker Dave A's Avatar
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    I'm with Sparks - with just one concern remaining -
    Quote Originally Posted by markthespark View Post
    the Oosterzee box has three separate 50 amp circuit breakers feeding 1 distribution board...
    That's the bit that has been worrying me. Is that one breaker per phase?
    If yes, shouldn't this be a 3 phase circuit breaker?
    The trouble with opportunity is it normally comes dressed up as work.

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    Gold Member Sparks's Avatar
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    Yes I missed that, I thought the boards were supplied with single phase. That specific board would need a 3ph CB after the 3ph isolator.

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