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Thread: Inverter Install Compliance

  1. #31
    Full Member Tonye's Avatar
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    Quote Originally Posted by hartdev@hotmail.com View Post
    I have almost completed the electrical installation in a nice new home in Cape Town. The company which installed the solar and battery backup inverter etc were very quick, in and out on a day I was not on site. They have requested that i rewire the D.B to isolate backup circuits from the non backup circuits. By doing this i would have to disconnect the backup circuits from the earth leakage device. The solar installers don't seem to have an earth leakage device at all in their though so I am trying to find out if the backup inverter has some sort of built in earth leakage protection, I downloaded a manual and saw nothing mentioned. (Victron 24/3000/70).
    I will try and answer your questions to the best of my ability & also with reference to SANS 10142 regulations.

    If alternate power is to be fed into a DB board together with Grid power, you need to have a split neutral bar. One for Grid power & one for the alternate power.
    Both power sources earth terminals need to be earthed to the main earth terminal.
    You also need to have a seperate main switch to disconnect the alternate power to the main DB.
    Also a power on indicator (visible or audible) shall be provided together with a notice indicating that the alternate power main switch shall also be switched off in an emergency.

    With regards to the earth leakage, to my knowledge no inverters have built in earth leakage protection. This is because inverters have a floating neutral with no reference to earth. By measuiring voltage on the inverter output, one usually finds Live-Neutral = 220v, Live- Earth = 110v & neutral- Earth = 110v.
    To resolve this problem & ensure correct operation of an earth leakage unit, you need to bridge the neutral to earth on the inverter output.
    Some inverters have an auto neutral to earth connection when the inverter is running in inverter mode.
    Bear in mind, if the inverter does not have an auto neutral to earth connection and you bridge the neutral to earth on the inverter, the supply to the inverter charger (if it has a built in charger) cannot be fed from a circuit breaker connected to the grid fed earth leakage unit.
    The earth leakage would trip, as it sees the bridged neutral to earth as a fault.

    The regulations also state that if alternate power feeds plug circuits, they have to have earth leakage protection.

    If not all plugs are being fed from the alternate power source, you would have two earth leakage units. One for grid fed plugs & one for alternate power fed plugs.

    I have just completed an inverter installation on a three phase board feeding single phase loads with split neutrals. The same would apply on a single phase supply.

    I have attached a basic wiring diagram showing essential wiring

    wiring diagram new.pdf

    Hope this helps
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  3. #32
    Diamond Member AndyD's Avatar
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    Quote Originally Posted by Tonye View Post
    To resolve this problem & ensure correct operation of an earth leakage unit, you need to bridge the neutral to earth on the inverter output.
    Some inverters have an auto neutral to earth connection when the inverter is running in inverter mode.
    Bear in mind, if the inverter does not have an auto neutral to earth connection and you bridge the neutral to earth on the inverter, the supply to the inverter charger (if it has a built in charger) cannot be fed from a circuit breaker connected to the grid fed earth leakage unit.
    The earth leakage would trip, as it sees the bridged neutral to earth as a fault.
    I think it's against the regs to have a neutral-earth connection within the installation itself, there's implications for fault current alternative paths etc. I'd need to comb the regs when I've got time in the office to find the relevant paragraph.
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  5. #33
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    @Tonye
    Just to add

    In regards to plug circuits being under earth leakage. All plug circuits shall have earth leakage protection wheter or not from mains or alternative supply.

    It's only dedicated circuits which can be taken off earth leakage protection.

    *take note of conditions to be adhered*

    Cutting a normal plug top off and putting on a dedicated plug top so to fit the half earth plug socket does not make the appliance acceptable for use on non-earth leakage protected plug sockets

    Also, where visual (light indication)/audible indication is required for alternative supply is where the alternative supply has automatic change over. Where manual change over is used, notice of alternative supply is sufficient. Also rember that all DB boards fed from alternative supply should have this indication, including sub DB boards.

    @Andy
    You are very much correct in saying that. The earth neutral bridge is only allowed on the supplier side (thus a little box between the alternative supply and DB board with earth neutral bridge plus indication of such is sufficient)

    Can't remember the page in SANS10142, but it basically says that the earth neutral bridge is not allowed to be made on the consumer side, thus on the DB board.

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  7. #34
    Full Member Tonye's Avatar
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    @Andy, I agree. Regulation 6.1.6 stipulates " The neutral conductor shall not be connected direct to earth or to the earth continuity conductor on the load side of the point of control.
    However the neutrals of each supply shall be earthed at the supply (Regulation 7.12.3.1.3) and then Regulation 7.12.3.1.4
    covers the split neutral scenario.

    @Dieter, I agree with no earth leakage required for dedicated circuits.
    I was referring to std plug circuits.

    With regards the audible or visual indication for alternate supply, the regulations do not differentiate between manual or automatic switching.
    Regulation 7.12.2.1a simply specifies that if part of a DB is fed from an alternate supply, then such indication is required together with a notice.

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  9. #35
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    Quote Originally Posted by Tonye View Post
    With regards the audible or visual indication for alternate supply, the regulations do not differentiate between manual or automatic switching.
    Regulation 7.12.2.1a simply specifies that if part of a DB is fed from an alternate supply, then such indication is required together with a notice.
    Thnx for pointing that out. I was referencing from municipality's requirements documentation, but in effect the SANS10142 over rules any of their requirements.

    I see "The wiring of premises: Part 3: Low Voltage Embedded Generators" target date is 2016-03-31. This is going to be very interesting....

    https://www.sabs.co.za/Business_Unit...Work/PW067.PDF

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  11. #36
    Site Caretaker Dave A's Avatar
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    Quote Originally Posted by AndyD View Post
    I think it's against the regs to have a neutral-earth connection within the installation itself, there's implications for fault current alternative paths etc.
    Bear in mind any given portion of the installation is only going to be powered by one supply at a time. The trick is to configure everything in such away that the neutral-earth connections are only on the (various) supply sides. (i.e. on the supply side of the crossover switch).

    That said -
    This is normally easily achieved where the alternative supply is a generator (excluding V-0-V generators with a centre tap to earth). The situation where the alternative supply is an inverter and the crossover switch is essentially incorporated in the inverter supply device does look like it might pose some special challenges.

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  13. #37
    Full Member Tonye's Avatar
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    @Dave, hence the split neutrals

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    hartdev@hotmail.com (02-Jan-16)

  15. #38
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    Thanks so much for the information guys, this really is not something you can ask most electricians working around the neighbourhood.
    I have not yet looked at your diagram Tonye but I will as soon as I can get on my PC.
    The solar installer has apparently applied for the grid feed energy dispenser so that is being taken care of.
    He has gone quiet since I mentioned an earth leakage device I'm betting he has plenty of installations in Cape Town with no such protection.
    I will have to sort that out. I plan to power his inverter charger from a non earth leakage protected circuit. From his inverter output I will have to connect the neutral to earth before his mains/off/inverter change over switch, I will then wire this through an earth leakage device into our main D.B where the dedicated circuits will have their own neutral bar. I will add an indicator light to be on whenever the dedicated circuits are on with a notice indicating that the solar installers change over switch needs to be in the off position to completely isolate the installation.
    Although I don't like connecting the earth to the neutral on the output side of the inverter, I feel it is safer than doing without an earth leakage device.
    As long as there is no connections between earth's or neutrals of the dedicated circuits and the standard circuits there shouldn't be any problems.
    It's a constant argument I have with an electrician friend I have that each circuit is to have it's own earth wire and its own neutral wire etc, this is one of those times when it becomes so important. Some guys like to connect every earth together in the house, although it ensures a good earth when there is a problem with a circuit it can complicate everything.
    Thanks again guys, I will try to find the specific paragraphs in the sans book so I can motivate to the project manager why these changes need to be made. I won't sign off if it is not done...

  16. #39
    Full Member Tonye's Avatar
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    @hartdev, I do not think the changeover switch would be considered a main switch to disconnect the alternate power.
    As the changeover switch changes from grid power to zero power & then Inverter power, it would be possible that power can still be
    fed to the essential loads if the changeover switch is not in the correct position.
    It would probably be safer to install a d/pole circuit breaker with low threshold value.(check Regulation 7.12.4) This way you will also be protecting the Inverter & cabling.
    Also ensure that the power supplying the inverter charger is fed from the input side of changeover switch (grid input) & not the output side feeding the essential loads, or your inverter will go into a frenzy when running on inverter battery mode.
    Also, although the neutrals must be split, the Earths should all be connected to the main Earth.
    Check with your Solar inverter guys if the inverter has a auto neutral to earth connection on inverter mode.
    If so, you would not need to manually bridge the neutral to earth.
    Once installation is complete & while running in inverter battery mode, simply test the earth leakage unit feeding the essential loads. If the circuits are healthy & tripping the earth leakage, you are sorted.

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  18. #40
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    Thanks very much guys
    Sorry for the delayed reply. The solar installer has been really slack in answering any questions, eg. whether there is an auto neutral to earth connection etc.
    In emails where the client and project manager were CCd , he kept writing things like " I will try my best to make the changes to conform to Devereux's standards" (Devereux being my first name).
    I made it quite clear that they were in fact sabs standards and not my own.
    I disconnected his system and issued my COC for the home installation without his system included and informed him that he would need to hire a registered electrician to sign off his installation with a supplementary certificate to mine .I will be returning in a week or two to make sure it has been done safely and the neccessary indicators,signage and earth leakage protection installed, but if not, I won't simply wash my hands of it. Safety is number 1 and I will ensure it is done properly.
    Thanks so much for your input on this matter, wishing you all a very happy new year.

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