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Thread: Electrical Compliance queries

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    Electrical Compliance queries

    I have an issue where a Client is questioning three compliancy issues and would like to firstly know your opinion on what you would install (or not install) and secondly the actual SANS code or section that states these issues.
    1) Must you use separate conduits and/or drawboxes if you are running separate circuits (different breakers in DB)
    2) If i have a DB that has Normal and Generator sections, can I run the cabling for emergency section through the Normal load section. (Use DB as a wireway).
    3) Must a plug in a house have a switch or can it be unswitched.

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    Diamond Member AndyD's Avatar
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    Can't help you with references to the regs I'm afraid, I don't have a copy with me at the moment.

    See comments in red;

    Quote Originally Posted by Shepherdsig View Post
    I have an issue where a Client is questioning three compliancy issues and would like to firstly know your opinion on what you would install (or not install) and secondly the actual SANS code or section that states these issues.
    1) Must you use separate conduits and/or drawboxes if you are running separate circuits (different breakers in DB) Containment such as conduits and trunking can contain more than one circuit. There are however regs on how full the containment can be.
    2) If i have a DB that has Normal and Generator sections, can I run the cabling for emergency section through the Normal load section. (Use DB as a wireway). I don't have a copy of the regs here but there's a note in them somewhere that a wireway can contain multiple internal channels or routes for different services. As long as the circuits are all AC and they're all insulated to a value greater than the highes voltage present I think it's fine.
    3) Must a plug in a house have a switch or can it be unswitched. I assume you mean sockets... In general, no they don't need to be switched. Sockets dont require integral switches if certain criteria is fulfiled.
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    Hi

    Before attempting to answer - SANS 10142 is the minimal standard required and the client/ engineer may insist on a higher standard - If there was a specification for the contract then you would need to comply with the specification that you, or the others pricing , would have allowed for at the time of tendering.The specification may not be less than required by SANS 10142. If the client did not have a specification beforehand and now wants to introduce extra requirements then it is a contractual issue and you should be allowed to adjust the pricing to suit his new specification.

    1 - Must you use separate conduits and/or drawboxes if you are running separate circuits (different breakers in DB) - There is no regulation that does not allow it - The number of wires in a conduit is stipulated in Table 6.22 pg 145 - Conductors in the same wireway must be able to withstand the highest conductor voltage 6.1.7 pg 77

    2) If i have a DB that has Normal and Generator sections, can I run the cabling for emergency section through the Normal load section. (Use DB as a wireway) - Reg 6.6.1.1 d) pg 148 refers to Alternative supplies in a DB and requires you to comply with label requirements indicator lights etc ( 7.12.2.1 pg 245) - The complete section on Alternative supplies will be relevant (7.12 pg 244) with regards to neutral bars etc - Also 5.3.7 pg 67 with regards to Isolator requirements

    3) Must a plug in a house have a switch or can it be unswitched When SANS 10142 started aligning itself with the European standards the switching of sockets stopped , over 10 years ago.As far as I am aware it was in the manufacturers regulations under 164 .
    If you look at 10142, new and old edition, there is no reference anymore to the switching of sockets besides construction sites , stages and generator rooms

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    Hi

    When running cables of any kind there is a limit based on the length and the size of the circuit breaker. where is this length taken from.

    The reason I ask is that if you have a sub DB from which another sub DB is run.

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    Diamond Member AndyD's Avatar
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    I don't really understand the question. Cable length is limited by volt drop, not by the circuit breaker.
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    Cable lenghts.docx

    I have attached the table (D.2a) from SANS 10142-1, it basically gives you the length you can run different size cables based on the circuit breaker protection. I understand how to work out the cable size, my question was if you have a sub DB 1 and then there has been another sub DB 2 added on to that sub DB 1. The size of the cable was calculated from sub DB 1 to sub DB 2. I am saying it should actually be calculated from the main DB.

    When you have sub DB 1 40 meters away from the main DB and then go and add sub DB 2 which is 30 meters from sub DB 1, surely you cant work out the cable sized based on the 30 meters must be 70 meters.

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    The recommended CB size in the table is derived from the volt drop calculation as Andy mentioned .

    The table saves you from doing the calculation - There is also a note above the table about checking the current carrying capacity of the cables etc.

    To answer your question - If Main DB feeds Sub Db 1 with 100Amp - And you now want to Feed sub DB 2 with 40 Amp you only need to go to Sub Db 1 for cable length and calculation assuming that the initial cable has been checked for volt drop

    If it is 100Amp feeding 100Amp , that is a different story - Then I would check my Volt drop from DB Main .

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