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Thread: 3 phase changeover

  1. #11
    Full Member Tonye's Avatar
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    Hi SeanM, you are correct with regards neutral being switched.

  2. #12
    Full Member Tonye's Avatar
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    7.12.2.4 Where the alternative supply is intended to provide a supply to an
    installation that is not connected to the main supply, or to provide a supply
    as a switched alternative to the main supply, the capacity and operating
    characteristics of the alternative supply shall be such that danger or damage
    to equipment does not arise after the connection or disconnection of any
    intended load
    as a result of the deviation of the voltage or frequency from the
    standard range. Means shall be provided to automatically disconnect such
    parts of the installation,
    as may be necessary if the capacity of the
    alternative supply is exceeded

    In one part they refer to any intended load & in the other they refer to the installation


    I think what is confusing here is the reference to parts of the installation

    It should read, where an alternate supply feeds an installation or part of an installation, Means shall be provided to automatically disconnect the installation or such part of the installation, as may be necessary if the capacity of the alternative supply is exceeded.

    This is how I interpret it

    Another thing is that Eskom ask people to manually turn off their geyser to avert Load shedding (exceeding their capacity)
    but supposedly this is not allowed when feeding from an alternate power supply

  3. #13
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    Quote Originally Posted by SeanM View Post
    Morning All

    I have a comment about automatic changeovers.

    The regulations clearly state that in a three phase installation all phases and neutral shall be switched with regards to alternative supplies I have yet to see any automatic changeovers do this.

    Referring specifically to generators , the 4 pole change over has been in the majority of Municipal bylaws for years and an Eskom bylaw .I found my 1991 application to register with Eskom as a contractor which stated 4 pole change over on all installations.
    The 4 Pole change over was written into SANS 10142-1 in 2003 and has also been there in the form of "you may not earth the neutral after the point of control". Sans 10142-1 clause 6.1.6

    Inverters/UPS do not need a change over switch but they do show a bypass switch - Nowhere do I find that a bypass switch shall be used - Seems like an optional

    But yet the supplies of change over switch inform me that here are more 3 pole switches sold then 4 pole. Shows you how many contractors/ consultants do not keep up to date .

  4. #14
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    Hi Tonye

    Would be interesting to hear other opinions on the clause 7.12.2.4

    The protection of the inverter output as a whole is covered under 7.12.5.1 - I see 7.12.2.4 as a requirement to prevent unnecessary tripping of the inverter and frustration prevention for the client.Same way that they suggest no more than 5KW per socket outlet circuit , but you can install 1 circuit for the complete installation.

    But lets forget regulations for a while and concentrate on logic.

    I go to the trouble of having a contractor install an inverter to make my life comfortable around load shedding.The last thing I want while I am at work,out of town, or enjoying a beer in the pub with mates is a call from my wife complaining that loadshedding is on and she is in darkness because the inverter has tripped .I will now have to spend time trying to talk her through switching circuits off. or - If I buy a house which has an inverter installed I may be that person that has absolutely no idea what a DB even looks like , will now sit through load shedding only to find part of my house come back on afterwards.

    The client today may not be the user tomorrow and as contractors we should be taking that into account.

    We have found the majority of Domestic clients want the same sort of set up usage mainly TV a light to be able to move around without falling over something, or a light for the kids to continue with home work.

    Where we have for some reason done domestic installations of inverters we have install a separate DB , with a circuit to the TV ,DSTV ,Hifi and router on a 10 amp or 5 amp CB , depending on equipment.
    We have also then installed a 5 amp or 10 amp CB to one light circuit , or rewire one circuit and installed LED.
    No change over and a seamless operation during load shedding , that the clients do not even realize that load shedding has begun while watching his favorite TV show.

    We have had some awkward clients that always refer to their mates that have complete house running on 2 batteries etc etc. After 2 or 3 months those mates have contacted us as the frustration levels have increased with loadshedding , battery failure , inverter failure etc. and they now also want to just sit back and watch tv without getting up to switch things off especially when they have been out and the kids/wife have forgotten to switch items off and overloaded the system constantly .

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