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New earting regulations?


Beat

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I just finished installing a Voltronic Mecer 3kW inverter configured as UPS at a friends house. Built a separate DB for essentials with change over switch. Works fine so far.

Now my friend tells me that somebody has informed him that the inverter earth cannot be connected to the main DB earth bar, but must be wired to a separate earth spike. That doesn't make any sense to me. Note that the inverter has automatic neutral to earth bonding when running in battery mode. I would like to hear from the experts in SA regulations here in the forum what they know about this. Thank you in advance.

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Earthing Sans10142-1-2 Draft
General
a) Requirements of SANS 10142-1, Section 6.12 applies for AC installations.
b) In the event of a new EGI, the requirements of SANS 10142-1 shall be followed to determine
the appropriate earthing system on the AC side of the installation.
Inverter-Based Generation Earthing
a) Earthing is the practice of providing a low impedance path to earth for safety purposes. This 
requires an earth rod at the installation or at the supply.
b) The most common method of system earthing on the DC side of the installation is floating, i.e.,
neither the positive nor the negative terminal of the DC source is earthed. However, a 
Protective Earth connection shall be implemented for exposed metallic parts in all installations.
c) Earthing of one (1) of the live (current-carrying) conductors on the DC side of the installation is 
permitted, if there is at least Simple Separation between the AC side and the DC side of the 
installation. This is referred to as Functional Earthing.
d) Alternative (functional) DC earthing systems are provided in Annexure F: Earthing.
NOTE 1: The main reason that Functional Earthing is not recommended, is that when one (1) of the 
current-carrying conductors are earthed, a single earth fault will enable a fault current to flow, 
whereas a floating DC system requires two (2) earth faults before the fault current will flow.
NOTE 2: Alternative earthing systems may require"

Above regulation Sans 10142-1-2 still in draft.

As far as i know the inverter needs to be earthed to the incoming main earth wire connected to the earth bar(PE) in the original db board. 

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On 2023/04/14 at 3:29 PM, TaliaB said:

As far as i know the inverter needs to be earthed to the incoming main earth wire connected to the earth bar(PE) in the original db board. 

Thank you, TaliaB, for your reply. It's very much what what I have thought.

Earthing regulations are somewhat different in different countries. In Switzerland for instance, where I come from, each DB must be earthed at the place where it is installed. The power companies do not provide earth wire. To my times we used the incoming water pipe for that while they were metallic. For security reasons the water meter hat to be electrically jumped to allow the water people to safely exchange it.

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On 2023/04/14 at 3:29 PM, TaliaB said:

Protective Earth connection shall be implemented for exposed metallic parts in all installations.

95% of Lithium batteries are in metal enclosures.  So that would mean batteries would also need to be earthed.  I just checked on my Hubble AM4 and there is absolutely no provision made for that.

Why is it that these regulations always sound as if they have been written by lawyers, rather than engineers?  I wish they would include some more diagrams.  I suppose that is left to some "author" that will interpret the words, make some diagrams and sell his book for R 2500.    I do a lot of my own plumbing, including changing the underground pipes for new toilets, etc.  So I brought this SA Plumbers Guide.  It was a few years back and was about R2000.  What a WASTE.  I learned NOTHING from that book.  Much about geyser installations but nothing on designing proper grey/black water drainage systems.

Best to just follow common sense and logic and ignore the rest.  This new world has anyway turned into a bunch of liars and cheats.   It is easier to ask for forgiveness than for permission.

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56 minutes ago, Modina said:

Why is it that these regulations always sound as if they have been written by lawyers, rather than engineers?

I think this quite common now. Read the current regulations of any sport that you follow. They will always have that style of writing that you refer to. IMO it's to try and remove any ambiguities from the regulations. Everything must be just so, and so is measured like this and so on. They're aiming for zero grey areas.

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2 hours ago, Modina said:

95% of Lithium batteries are in metal enclosures.  So that would mean batteries would also need to be earthed.  I just checked on my Hubble AM4 and there is absolutely no provision made for that.

Well, batteries fall in general in the category below 50V that has very little regulation. Otherwise even cars would have to be earthed. They contain even a high voltage part, the ignition.

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1 hour ago, Beat said:

Well, batteries fall in general in the category below 50V that has very little regulation. Otherwise even cars would have to be earthed. They contain even a high voltage part, the ignition.

I think you will find that it is only below 30V DC where the regs relax significantly.  Otherwise, for an ELV source which is not isolated from an LV installation, pretty much all the rules apply.

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