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Thread: 7.12 Alternative supplies

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    7.12 Alternative supplies

    Time to sit down put plug in the airpods with background sounds and review section 7.12

    What are the requirements .. .the way I read it.

    Labels labels labels and as many more labels and notices on each DB.

    Indicator - A din mount light next to the main switch is my preference.

    Change over switch as per requirements.

    As per requirements - earth leakage protection for plugs ... I am still trying to understand why people insist on installing earth leakage on the supply to the inverter ... I can understand samll plug in UPS ... but not a 5 kva inverter connected directly to a DB.

    V-O-V type generators not to be connected to the "fixed" electrical installation.
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Earthing requirements...

    Where there is no earth spike already installed ... a suitable one must be installed and bonded to the consumer earth terminal with a wire at least half the thickness of the phase conductor ... but not less than 6 mm.

    But this note is rather interesting ... deosnt his mean that if you install a spike you dont need an SPD ... or if you install an SPD you dont need the spike.

    NOTE 2 Protection of photovoltaics can be by means of or surge protective device
    (SPD).

    This section is one that seems to be a little confusing for many.

    7.12.3.1.2 In an installation that is supplied from a combination of
    transformers and alternative supplies located near to each other, the neutral
    points of each of these items shall be connected to a single earthed neutral
    bar (see P.1). This earthed neutral bar shall be the only point at which the
    neutral of the installation is earthed. Any earth leakage device shall be
    positioned in such a way as to avoid incorrect operation due to the existence
    of any parallel neutral/earth path.
    7.12.3.1.3 Where alternative supplies are installed remotely from the
    installation, or from one another, and where it is not possible to make use of
    a single neutral bar or neutral conductor which is earthed, the neutral of each
    unit shall be earthed at the unit and these points shall be bonded to the
    consumer's earth terminal (see 6.12.4). The supply from each unit which
    supplies the installation or part of the installation, shall be switched by means
    of a switch that breaks all live conductors operating substantially together (see
    figures P.2 and P.4), to disconnect the earthed neutral point from the
    installation neutral when the alternative supply is not connected (see also
    6.1.6).
    NOTE Where four pole switching is implemented, consideration should be given to use
    overlapping neutral switching devices.
    7.12.3.1.4 Where only part of an installation is switched to the alternative
    supply in the same distribution board, the neutral bar shall be split (see
    figures P.2 and P.3).
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Gold Member Derlyn's Avatar
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    Quote Originally Posted by ians View Post
    Time to sit down put plug in the airpods with background sounds and review section 7.12

    What are the requirements .. .the way I read it.

    Labels labels labels and as many more labels and notices on each DB.

    Indicator - A din mount light next to the main switch is my preference.

    Change over switch as per requirements.

    As per requirements - earth leakage protection for plugs ... I am still trying to understand why people insist on installing earth leakage on the supply to the inverter ... I can understand samll plug in UPS ... but not a 5 kva inverter connected directly to a DB.

    V-O-V type generators not to be connected to the "fixed" electrical installation.
    Another question.

    Why is it not a requirement that a generator have a built in earth leakage ?
    I mean, after all there are socket outlets on a genny where all sorts of appliances are plugged in.

    Derek

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    The last bit is where I get muddled up. It may be a case of someone sitting me down and explaining and then answering all my questions I have to then understand.

    The whole neutral earth bar bit is tricky. I have seen inverters that output need an "earthing box" so as when it kicks in the alt supply the N and E are bonded but when grid is back then it dissconects and the N is now floating... why can it all not be joined to incoming E and then joined to the N to all be the same.??

    I may be missing something very simple but it seems very complex for no reason..

    They say the N and E shall (i think its a shall)be joined on the supplier side only so if that's the case for not perm joining the inveter output N to E I think they must rethink or at least I must be taught why it must be so.



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    I am trying to figue out why you would feed a changeover over switch from an earth leakage unit ... then fit an earth leakage unit from the alternate supply ... why not just fit the earth leakage P.2/P.3/P.4 on the essential side ... its like saying you can have an earth leakage and you can have and earth leakage while we giving away earth leakage units just add one to the UPS ... it not the show where every one gets something just because they have lots of them
    Comments are based on opinion...not always facts....that's why people use an alias.

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    Hahahah I see what you saying.
    My only guess is to have additional protection if it is a long cable run or likely to be damaged But then discrimination needs to happen. Otherwise its an ELU ping pong match



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    Gold Member Derlyn's Avatar
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    Quote Originally Posted by ians View Post
    I am trying to figue out why you would feed a changeover over switch from an earth leakage unit ... then fit an earth leakage unit from the alternate supply ... why not just fit the earth leakage P.2/P.3/P.4 on the essential side ... its like saying you can have an earth leakage and you can have and earth leakage while we giving away earth leakage units just add one to the UPS ... it not the show where every one gets something just because they have lots of them
    @ Ians

    I am talking about a portable generator, not a standby one that's connected to the installation.

    I'm thinking now, how many people have been shocked while using an appliance plugged into a portable genny ?

    Derek.

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    Quote Originally Posted by Derlyn View Post
    @ Ians

    I am talking about a portable generator, not a standby one that's connected to the installation.

    I'm thinking now, how many people have been shocked while using an appliance plugged into a portable genny ?

    Derek.
    I would assume (never heard of one myself) there have been cases because if you look at the UK for example they use 110 VAC generators for site work ... I used a 5 kva generator for about 10 years ... and boy did that thing get abused and the cables would be in the rain ... hammering away with a jackhammer ... cant say I ever recall a shocking experience ... the only shocking experiences where when we put a pickhead through a 11 kv or HT cables ... the smaller power just made a puff of smoke ... the 11 kv cables would melt the pick head with a pretty spray.

    It became a ghost story about the devil rising ... one of the stronger guys in our team pegged an HT cable the thing blew up ... melted the pick head ... he shat himself ... but the reason he never came back to work ... when system closed again ... that spray made him think the devil was coming out the ground ... he was one of my best strongest team members ... hasnt seen his since that day
    Comments are based on opinion...not always facts....that's why people use an alias.

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    back to the regs.

    brain is too cluttered with crap by 9 pm ... so I decided to get up early this morning and continue with the revision ... which reminded me that I have the latest draft (wish I had 2 big screens in my office ... looks like I ma going shopping today).

    Reading through the draft ... what I was looking for in the ed 3 is there in the draft ... the actual labels required and a lot of info with regards to alternate suppliers ... its looks like my weekend is going to be spent reading SANS regs ... havent done that in a few years (maybe 15 years) I might learn something new (and shopping for 2 big screens ... cant work without the "right" equipment )
    Comments are based on opinion...not always facts....that's why people use an alias.

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    The new draft refers to SSEG's which should be used in with other specifications like the NRS specs.

    I see a lot more information with regards to labels (a good thing) ... I have noticed some of the installers are already using these labels referenced in the draft.
    Comments are based on opinion...not always facts....that's why people use an alias.

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