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neutralising cable???

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  • 18-05-2010 12:13pm
    #1
    Southern Dandy
    Registered Users Posts: 2,006 ✭✭✭


    Hi lads,

    A buddy got a new esb digital meter installed in his house, the esb electrician said that he needed to get a neutralising cable installed going from the meter to the board, what does he mean by that?
    Feel a bit retarded asking that as i am a sparks but got frack experience all when it comes to domestic and sadly not enough experience outa my apprenticeship.

    Cheers


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    #2
    antomagoo
    Registered Users Posts: 730 ✭✭✭antomagoo


    Can only think it could be for neutralising static, but thought that only applied to high voltage systems, so not sure really :confused:


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    #3
    Randyleprechaun
    Registered Users Posts: 876 ✭✭✭Randyleprechaun


    The neutralising cable from the meter to the board is the other core in your three core cable after you've connected the live 7 neutral to the meter.

    I'm not calling it the "erarth" core to avoid confusion.

    Basically, it connects the all the earths and earthed items in the installation to the ESB's neutral which is at the same potential as earth(or should be anyway). All earths and neutrals have to be seperate in the installation but they are then joined by the ESB hence TN-C-S earthing system

    Without this link you will notice that a fault loop impedance test from L-E will show very poor results as the test current has no way to complete a circuit through the transformer. You may get good results if your earth rod is driven in good ground which will allow the fault current back to the transformer.


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    #4
    bassey
    Registered Users Posts: 936 ✭✭✭bassey


    Yeah the neutralising cable is the cable that conects you're Earth system to the general mass of earth via the ESB neutral that's earthed at the transformer, it'll be in you're meter cabinet I imagine.

    Here's a picture using old colour codes.
    meter_pos_TNCS.gif


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    #5
    Southern Dandy
    Registered Users Posts: 2,006 ✭✭✭Southern Dandy


    So basically its an earth core coming from the esb meter to the consumer unit, connecting the main earth terminal to the meter!!!


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    #6
    Davy
    Registered Users Posts: 19,340 CMod ✭✭✭✭Davy


    I think they say this now if it isnt up to regs. Any older houses, that would have had a neutralising link maybe 2.5 or something would be in the same boat to get it upgraded to new standard


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    #7
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Randyleprechaun wrote: »
    The neutralising cable from the meter to the board is the other core in your three core cable after you've connected the live 7 neutral to the meter.

    I'm not calling it the "erarth" core to avoid confusion.

    Basically, it connects the all the earths and earthed items in the installation to the ESB's neutral which is at the same potential as earth(or should be anyway). All earths and neutrals have to be seperate in the installation but they are then joined by the ESB hence TN-C-S earthing system

    Without this link you will notice that a fault loop impedance test from L-E will show very poor results as the test current has no way to complete a circuit through the transformer. You may get good results if your earth rod is driven in good ground which will allow the fault current back to the transformer.

    I remember talking about this last year on this boards, saying more or less the same thing as you did here, my point was the earth rod rarely if ever has a good enough connection to earth to carry any fault current capabable of tripping breakers. I was told i was wrong (no names mentioned), but its certainly not wrong. The neutral will be the same potential as earth because it has multiple earth rods along its length from the ESB traffo to the house ESB meter. If the neutral breaks before it enters the ESB meter connecting point, the earth rod is now the only return path for the neutral current. If the earth rod was as good a path back to the ESB supply neutral as the now broken neutral was before it broke, then we would not even notice the neutral broken, after all, the path down the intact neutral, and the path down the earth rod and through the general mass of earth and back to the traffo neutral point are both in parallel, but the reality is the neutral breaks and the house experiences almost no power, lights usually light very dimly, but will go off if a heavy load comes on (cooker etc), simply because the earth rod is not a great connection to earth on its own.
    But the earth rod at a house that is neutralied is part of the collective of earth rods at each house and along the ESB neutrals which all act to maintain the neutral at earth potential. Between them all there is a low impedence connection between neutral and earth mass. But when a neutral breaks before the house connection, that house earth rod is now on its own. Thats why a TT house has a main RCD.

    Also even if the earth rod did provide a good earth loop reading in a non neutralised setup, the earth loop impedence test current is very low compared to what a real fault current might be. Another example- A main earth wire just touching the earth bar in an otherwise good installation would pass the loop impedence test, but would`t be a good connection.


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    #8
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Southern Dandy wrote: »
    So basically its an earth core coming from the esb meter to the consumer unit, connecting the main earth terminal to the meter!!!


    It is an earth core connecting the main earth bar of the consumer unit to the ESB neutral, so as to provide a very low resistance for any earth fault which will operate protective trip switches very quickly. It has disadvantages as well though. But thats the reason its used.


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    #9
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    bassey wrote: »
    Yeah the neutralising cable is the cable that conects you're Earth system to the general mass of earth via the ESB neutral that's earthed at the transformer, it'll be in you're meter cabinet I imagine.

    It is connected to general mass of earth in this way alright, but the general mass of earth actually does`t really play much part in any fault current from a house in the neutralised system. The neutral is also earthed at any point the ESB cables enter connection points, for example in mini pillars in housing estates.


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    #10
    Randyleprechaun
    Registered Users Posts: 876 ✭✭✭Randyleprechaun


    This thread is gone of on a tangent.(like one I started before eh robbie!!!! LOL)

    It's as simple as this, the neutralising conductor(which in most houses is the earth core of the 3 core cable going from meter to consumer unit) brings all the earthed equipment in the house or any installation to the same potential(voltage) as the ESB neutral which is 0 volts or "earth" potential.

    It provides a circuit for fault current which will(or should) ensure a large enough amount of current will flow to trip the protective device. This is why we check loop impedance from L-N and L-E after powering up any new installation.

    The earth rod in most installations never carries any current. it is in effect, a back up to the ESB neutral. it provides a circuit for current in the event of a fault. This current could actually go down to the earth through your earth rod, go up your neighbours earth rod, through his earth bar and back to the traffo through his neutralising conductor(provided his ESB neutral is OK). Most earth rods are driven into stoney, or sandy ground and never tested so they probably aren't even up to the task.


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    #11
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Randyleprechaun wrote: »
    The earth rod in most installations never carries any current. it is in effect, a back up to the ESB neutral. it provides a circuit for current in the event of a fault. This current could actually go down to the earth through your earth rod, go up your neighbours earth rod, through his earth bar and back to the traffo through his neutralising conductor(provided his ESB neutral is OK). Most earth rods are driven into stoney, or sandy ground and never tested so they probably aren't even up to the task.

    Yes but the earth rod is not really a back up to broken neutrals, its in reality another earthing point for the neutral conductor. No real fault current will go down an earth rod, If a 220v main supply is connected to the earth rod, it would be unlikely to trip a 20 amp mcb, let alone have fault currets up the neighbours earth rod. This is not a random theory, nothing compares to actual tests, which i did, and seen done on earth rods. They did`t trip 20 amp breakers directly connected to the rod.
    Why would any major fault current go up neighbours earth rod and onto neutral that way, when the much lower impedence path is to the minipillar earthed neutral bar with multiple earth rods to it.
    And to add to that, if a house neutral breaks at the mini pillar, the power in the house in effect goes,,, now consider that, power gone, now if the earth rod was capapable of carrying any decent fault current, or was a nice low impedence path, then the earth rod path would in effect act like a neutral, but no point goin on about it i suppose.


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    #12
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Randyleprechaun wrote: »
    This thread is gone of on a tangent.

    Yes your right, im goin mad


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    #13
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Randyleprechaun wrote: »
    Ah I wasn't blaming you, but it's funny how these things go way of the boil.....says me and I talking about tangents eh!!!!!!!!!

    Yes but i probably am the worst for getting carried away, usually i blame the bottle of wine but none today,


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    #14
    Randyleprechaun
    Registered Users Posts: 876 ✭✭✭Randyleprechaun


    robbie7730 wrote: »
    Yes your right, im goin mad
    Ah I wasn't blaming you, but it's funny how these things go way of the boil.....says me and I talking about tangents eh!!!!!!!!!


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    #15
    Randyleprechaun
    Registered Users Posts: 876 ✭✭✭Randyleprechaun


    robbie7730 wrote: »
    Yes but the earth rod is not really a back up to broken neutrals, its in reality another earthing point for the neutral conductor. No real fault current will go down an earth rod, If a 220v main supply is connected to the earth rod, it would be unlikely to trip a 20 amp mcb, let alone have fault currets up the neighbours earth rod. This is not a random theory, nothing compares to actual tests, which i did, and seen done on earth rods. They did`t trip 20 amp breakers directly connected to the rod.
    Why would any major fault current go up neighbours earth rod and onto neutral that way, when the much lower impedence path is to the minipillar earthed neutral bar with multiple earth rods to it.
    And to add to that, if a house neutral breaks at the mini pillar, the power in the house in effect goes,,, now consider that, power gone, now if the earth rod was capapable of carrying any decent fault current, or was a nice low impedence path, then the earth rod path would in effect act like a neutral, but no point goin on about it.


    I see your point, but it's amazing what you can encounter when out and about checking these faults. They can be hard to explain at times.

    I once saw all the bonded metal work in a number of houses(all on the one traffo)coming live due to a fault a spark made in a shed of one of the houses. Never found out what the fault was as the ESb found it and rectified it or got him to rectify it


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    #16
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    Randyleprechaun wrote: »
    I see your point, but it's amazing what you can encounter when out and about checking these faults. They can be hard to explain at times.

    I once saw all the bonded metal work in a number of houses(all on the one traffo)coming live due to a fault a spark made in a shed of one of the houses. Never found out what the fault was as the ESb found it and rectified it or got him to rectify it

    Thats usually an ESB broken neutral feeding a mini pillar neutral bar and so 3 or 4 houses are in effect connected in star with no neutral and because the loads are not balanced, the neutrals and earths in the houses can go up toward 230v, i seen that exact thing last year on parents road, one house had 320 volts L-N and everything in the house ruined, and as i said, if earth rods were nice low resistance paths then this broken neutral would go un-noticed
    But strange things do happen alright. I had an RCD tripping in a house before with the main switch off at MCB board. It was actually caused by something similar to what you said about fault current up neighbours earth rod. Lots of mysteries in the electrical world


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    #17
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    robbie7730 wrote: »
    Yes but the earth rod is not really a back up to broken neutrals, its in reality another earthing point for the neutral conductor. No real fault current will go down an earth rod, If a 220v main supply is connected to the earth rod, it would be unlikely to trip a 20 amp mcb, let alone have fault currets up the neighbours earth rod. This is not a random theory, nothing compares to actual tests, which i did, and seen done on earth rods. They did`t trip 20 amp breakers directly connected to the rod.
    Why would any major fault current go up neighbours earth rod and onto neutral that way, when the much lower impedence path is to the minipillar earthed neutral bar with multiple earth rods to it.
    And to add to that, if a house neutral breaks at the mini pillar, the power in the house in effect goes,,, now consider that, power gone, now if the earth rod was capapable of carrying any decent fault current, or was a nice low impedence path, then the earth rod path would in effect act like a neutral, but no point goin on about it i suppose.

    they look for Ze under 200 ohm for TT systems in the Uk.
    enough to operate the 'main rcd'

    you could check it by testing loop-impedance at the mains with the 'earthing conductor' going to the rod


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    #18
    Southern Dandy
    Registered Users Posts: 2,006 ✭✭✭Southern Dandy


    Jebus that got a bit hairy for a bit, cheers for all those many many many bits of information there, it was like being back in FAS. appreciate it though am putting it in tomorrrow.


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    #19
    Merch
    Closed Accounts Posts: 3,327 ✭✭✭Merch


    Hmmm, my reply off thread? wonder if I can get some replies, just curious, I have an earthing point as does my neighbour (semi d) between me and neighbour on path beside meter, I have no main rcd, instead an rcd off the sockets only.
    I always assumed I had a TT layout, does this mean I could have an earth rod as a backup, house in Dub suburbs, mid-late nineties build.


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    #20
    bassey
    Registered Users Posts: 936 ✭✭✭bassey


    I don't know of any houses in Dublin that don't have T-N CS earthing systems..


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    #21
    Merch
    Closed Accounts Posts: 3,327 ✭✭✭Merch


    Hmm, from what I know (not sparks) that sounds like it might make more sense if I only have an RCD on the sockets then?
    I feel like there might be more protection there if I have TN-C-S, but I'm just wondering what the earth rod is for now? a backup?


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    #22
    bassey
    Registered Users Posts: 936 ✭✭✭bassey


    Most houses only have an RCD for their sockets and immersion. None on the lights or cooker


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    #23
    Merch
    Closed Accounts Posts: 3,327 ✭✭✭Merch


    okay, that I'd be aware of, but not why? and why the earth rod if I have TN-C-S?


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    #24
    bassey
    Registered Users Posts: 936 ✭✭✭bassey


    Well a cooker would cause nuisance tripping, and there's just no real need for lights. The earth rod is there to provide a back up in case of the ESB neutral is broken (Some eejit in a digger etc.)


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    #25
    M cebee
    Closed Accounts Posts: 4,431 ✭✭✭M cebee


    Merch wrote: »
    Hmmm, my reply off thread? wonder if I can get some replies, just curious, I have an earthing point as does my neighbour (semi d) between me and neighbour on path beside meter, I have no main rcd, instead an rcd off the sockets only.
    I always assumed I had a TT layout, does this mean I could have an earth rod as a backup, house in Dub suburbs, mid-late nineties build.

    you've tn-c-s: a low impedance earth fault loop-'ads' via mcbs

    for 'tt' the fault loop impedance is higher -'ads' via rcd/mcbs


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    #26
    Bruthal
    Closed Accounts Posts: 13,422 ✭✭✭✭Bruthal


    bassey wrote: »
    Well a cooker would cause nuisance tripping, and there's just no real need for lights. The earth rod is there to provide a back up in case of the ESB neutral is broken (Some eejit in a digger etc.)

    Well in reality the single earth rod at a house wont ever back up a broken neutral at all, if the ESB neutral breaks before the meter position then the earth rod will have little effect on the result. While the neutral is intact the earth rod at the house is connected to all other earth rods on the neutral system from the transformer and is just another earthing point for the neutral in a neutralising system, there are earthing points all along the neutrals. If the single earth rod was a perfect low impedence connection to the ground then a broken neutral before the meter position would go un-noticed. But in reality a broken neutral before the neutralising point brings all earthed systems in a properly earthed house electrical system up towards 230v. If everything is bonded properly then there should be reduced risk of shock because everything is at equal potential.

    Last year i seen a house that had 320v L-N because the main ESB neutral failed onto a MINI pillar neutral bar in effect leaving 4 houses star connected with no neutral, this neutral bar had multiple earth rods onto it, and still they did not really have much effect at maintaining a 0v between the MINI pillar neutral bar and earth, as in the earth rods would of been an alternative path back for the neutral current to bridge the now failed neutral connection, but they dont really carry any large current as each earth rod can be a relatively high impedence.

    Multiple earth rods are connected along ESB neutrals at each cable connecting point, one of which is at the house meter position, to give a reference between L and the general mass of earth. Maybe there are other ways of looking at it but thats how i see it.


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    #27
    Calahonda52
    Registered Users Posts: 12,471 ✭✭✭✭Calahonda52


    As the picture in post 4 describes my setup, I will post my question here:

    Had a day/night meter fitted yesterday and I have the Installation not Neutralised safety letter.

    I know I have to get a RECI to come, and I also know that I have to pay the ESB €198 for coming again.

    Can someone please describe the sequence of events here and what coordination is required between the RECI and the ESB..

    I also have read here that a RECI may decide not work on the system if the neutering cable is not in place so am a bit perplexed.

    http://www.boards.ie/vbulletin/showthread.php?p=96327245
    Thanks as always

    “I can’t pay my staff or mortgage with instagram likes”.



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    #28
    Risteard81
    Registered Users Posts: 2,567 ✭✭✭Risteard81


    Southern Dandy wrote: »
    Hi lads,

    A buddy got a new esb digital meter installed in his house, the esb electrician said that he needed to get a neutralising cable installed going from the meter to the board, what does he mean by that?
    Feel a bit retarded asking that as i am a sparks but got frack experience all when it comes to domestic and sadly not enough experience outa my apprenticeship.

    Cheers
    The neutralising conductor is what is correctly termed the main protective conductor.


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    #29
    Risteard81
    Registered Users Posts: 2,567 ✭✭✭Risteard81


    Apologies. Just noticed post date!


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    #30
    ptogher14
    Registered Users Posts: 203 ✭✭ptogher14


    Calahonda52 wrote: »
    As the picture in post 4 describes my setup, I will post my question here:

    Had a day/night meter fitted yesterday and I have the Installation not Neutralised safety letter.

    I know I have to get a RECI to come, and I also know that I have to pay the ESB €198 for coming again.

    Can someone please describe the sequence of events here and what coordination is required between the RECI and the ESB..

    I also have read here that a RECI may decide not work on the system if the neutering cable is not in place so am a bit perplexed.

    http://www.boards.ie/vbulletin/showthread.php?p=96327245
    Thanks as always

    Calahonda,
    RECI is the governing body for the electrical industry. You will need to get a REC......a registered electrical contractor. Basically you need a link (cable) from your meter box to your distribution board. Contact a sparks. Get them to do the job. Get the ESB back out.

    He will have to issue you a cert after doing this work which could open a can of worms for you. More than likely it will as, if you have no neutralising link I'd imagine the whole house isn't up to current standards.


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    #31
    Tuco88
    Registered Users Posts: 1,051 ✭✭✭Tuco88


    Randyleprechaun wrote: »
    This thread is gone of on a tangent.(like one I started before eh robbie!!!! LOL)

    It's as simple as this, the neutralising conductor(which in most houses is the earth core of the 3 core cable going from meter to consumer unit) brings all the earthed equipment in the house or any installation to the same potential(voltage) as the ESB neutral which is 0 volts or "earth" potential.

    It provides a circuit for fault current which will(or should) ensure a large enough amount of current will flow to trip the protective device. This is why we check loop impedance from L-N and L-E after powering up any new installation.

    The earth rod in most installations never carries any current. it is in effect, a back up to the ESB neutral. it provides a circuit for current in the event of a fault. This current could actually go down to the earth through your earth rod, go up your neighbours earth rod, through his earth bar and back to the traffo through his neutralising conductor(provided his ESB neutral is OK). Most earth rods are driven into stoney, or sandy ground and never tested so they probably aren't even up to the task.

    Do we check the line impedance sorry record ☺? Ie L-N, I only remember the loop impedance recored ie L-E (resistance of phase + resistance of cpc) on the test record sheets.


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