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Posted By Topic: Main earth and Main neutral on same busbar

Jul 04 2018 07:57

Hey guys,

Trying to find any answers into whether i can use this setup or not for my submain earth and neutral.
The main earth and neutral are on the same solid bar with no removable MEN connection.

I was planning to have the submain neutral and PEC on this bar, each being secured to the bar seperately and with two nuts each and labelled to identify the circuits associated with them.

I have been through 2.9.4 and section 5 to ensure that i can legally do this or not. There is nothing prohibiting, although there is no removable MEN link. Technically, the board is providing and earth and neutral bar, they just both are connected to it.

A bit about the board; commercial, three phase main switchboard for the site. Use to be an old hospital, and now has a few additional buildings on it and is now a place of residence. It has the mains connections with 4 bars in total, 1 for each phase and 1 with the main earth and main neutral connected.

Although others have feed other DBs from this earth/neutral bar, is it still ok to do so or would i need to install seperate earth and neutral busbars with a removable MEN connection? (Now high risk, would need inspection etc)


Jul 04 2018 15:03

you are looking in the wrong place, like you said nothing (i can see) in 3000, but the the ESR\'s, the definitions, of a main earthing system (b) comprises of an earth electrode, an earthing conductor that is connected between the earth electrode and a MEM switchboard, and a removable link between the neutral and earth conductors within that MEM switchboard\"

so must have a removable MEM link

Jul 04 2018 17:29

The key to this question is “Did it comply when it was installed”.
Most likely it did.
Is it electrically unsafe?

Just being old and different does not make it electrically unsafe.

If it is not electrically unsafe it can remain in service.

The modern definition of an earthing system was not applicable back when this was likely installed so is also irrelevant.

There will be hundreds if not thousands of sheds out there with NZI splitter boxes with N&E on the same stud. As long as the link is in place completely safe and compliant.

Jul 04 2018 18:34

@ Codaxx, just so we are clear , are all the final sub-circuit earths attached to the same Common bar ? along with the Neutrals.

Jul 04 2018 18:37

Electrically safe,
in terms of the main neutral running too it, a correctly sized main earth running too it, correctly sized copper bar to connect the neutrals and earths, tested with seperate earth rod to ensure a connection to earth, just no removable link.

Since it was OK at time of install, would it be OK to use the same bar now?

Jul 04 2018 18:42

There is another board attached to the main board, which has a seperate earth and neutral bar with MEN link, but it has all its own lupus protection and final subcircuits.

The main Earth/Neutral bar has the main neutral, main earth and PEC and neutrals to other subboard

Jul 04 2018 18:58

AH so no we have a different picture of what you actually have , its sounds to me that you do have an MEN link it is just located in the \"attached\" panel .If I am correct the Neutral bar you have been referring to is actually the Main Neutral Stud for what of a better description. As per Sarmajors comments it was a requirement to have the main earth on the same Stud as the main Neutral. So if you assume that was all that was on that bar originally then perfectly fine.If other have attached additionally Sub earths to that same stud Stud ( Bar) then that is wrong it would not have been compliant. The clue here is that all your final Subcircuits conductors are on the main earth and Neutral Bars with a MEN Link , it just so happens that for what ever reason the Neutral bar has that extension to the Bar your talking about.
Anyway thats what I would guess from Your new description .
Hope that helps .

Jul 04 2018 19:20

Ah ok. So my submains neutral and earth will need to be attached to that bar with the MEN link and NO other connection eg earth or neutral should be connected to the main stud/bar apart from the main neutral and main earth?
Will have to change what i have done tomorrow so it is compliant...made a connection to to the main bar/stud

Jul 04 2018 19:33

Your on the right track now , Your sub-main Neutral can be on that bar you talked about if it is easier to attach there,as you can consider it an extension of the Neutral Bar, but yes your sub-main earth should be on the Earth bar.


Jul 04 2018 19:39

Some older boards with the set up your describing had a larger bar which provided provision for larger studs ( double nutted ) or threaded bolts to the bar for connection of larger conductors such as sub-mains etc , but no provision for the earth for the sub-main was needed as it was common to do it like our outbuilding provisions and run seperate earths to a seperate earth stake and all boards had an MEN link

Jul 05 2018 10:39

Yes an existing set-up that complied when installed is allowed to continue in service.
BUT that doesn\'t mean you can add another circuit / submain to that old single-bar set-up. Adding stuff is making a change, and EVERY aspect of the new work must comply with current requirements. For example; you MUST connect your new N & E to separate bars.And you MUST have a separate N terminal for the new outgoing circuit. So if you haven\'t got separate bars, or a spare N terminal; you\'ll have to upgrade.

In this case; seems there\'s a sub-board next to the MSB, and it has separate bars & link. That\'s OK; ESR 113 applies to that set-up too. Because it has separate bars you can maybe connect to the DB instead of the MSB Assuming there\'s a spare N terminal, and the submain is up to the extra load, and you don\'t want to use the \"outbuilding\" provisions for your new submain, etc)

There\'s also the fact that when you issue your CoC (before connection your new stuff) and then move on to the pre-connection checks [ESR 73A?] one of these checks is tghat there is in fact a \"main earthing system\" (as defined); so you\'d need to upgrade the MSB bars to comply, including if necessary installing an electrode.


Jul 05 2018 13:39

AlecK , you may well be correct but it has hard to tell exactly from the description what the set up really is, I\'m inclined to think from what has been said that we are looking at One Main switchboard here, he says there is another board \"attached\" which has an MEN link and Neutral and earth bars . The clue here is that there is no Earth bar or bars in the section of the board with The Main Neutral connection and earth conductors associated with the panel connect to the earth Bar in the adjacent Chamber where there is also an MEN LINK.I\'m guessing there is a link between the Neutral Stud Bar he is talking about and the Neutral bar in the panel adjacent.
But Like you I can only guess without seeing a pic or something.
Sounds like it could be a totally legit set up and all he needs to do is make sure his PEC is on the Earth bar and Neutral is on the Neutral bar .

Jul 05 2018 14:44

Thanks for the responses team. Ill get a photo up tomorrow of the setup.
As TheDon has said, there is an attached board (a few actually) and it seems that most of the other board neutrals and earth run to this other bar, containing an MEN link that is in one of the attached boards.

The confusion for me was when i saw other submains neutrals + earths attached to the earth/neutral main stud/bar, knowing, that we now need a removable MEN link which this stud bar did not have which may be due to the standards back then allowing this type of setup.

Ill get a photo tommorow to explain better what i am trying to say