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Neutral to earth on genny

lyledunn
Can I ask your opinion in relation to neutral /earth on this rather untidy changeover arrangement located just downstream of the main isolator? There are 2no 3-pole contractors with mains in bottom left and generator in bottom right. On the stud adjacent they have connected gen neutral, DNO neutral and installation earth. The arrangement means a self-imposed conversion to an unauthorised TNCS. I can’t be sure if the existing supply is already TNCS.
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    However, it seems to me that any given code should be accompanied by a clear indication of the reasons the call has been made along with a reference to at least the most pertinent regulation that has been breached.

    The first bit's easy - reg 463.1.4 demands the switching of all live conductors - so certainly a non-compliace with BS 7671 (not 'just' unlawful under the ESQCR).

    (I can see that 551.6.2 doesn't make the situation entirely clear though)


    551.6.1 reads to me as if the contactors need to be rated for isolation too (I can't tell from the picture whether those do) - so perhaps something more to check there.


    Certainly undesirable to have N currents flowing in protective conductors - but I guess we've all seen long standing N-PE faults in the pre-RCD days not to fear that the sky will fall as a result. Unless there was a particularly small c.p.c. between the DNO supply and this N-PE link, I'd be tempted by a C3 (but with an additional note about contravening the ESQCR).


    Edit - I've just seen Graham's concern about diverted N currents - that's a good  point and could well justify a higher code.


       - Andy.
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    If I spat out the door of the intake room it would land in the Republic of Ireland. There, it is the contractors responsibility to ensure that the installation is effectively “neutralised”, ie the main protective conductor is connected to the supply neutral. This can be done in the main panel for larger installations. Almost all of Ireland is TNCS so where a supply is made available the neutral is used as earth. I have seen the arrangement several times both north and south of the border all by the same genny specialist who is based in the south.

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    Well it had better have an electrode as well, if the intention is to be able run the genset in a fault when the mains supply may be severed, and therefore not providing any earth at all. (if it was only synchronous operation, then you probably could use suppliers earth.)


    Does the Irish regs have anything like ESCQR to contend with ? If not it seems a bit silly to declare  C2 on one side of the fence and no problem on the other.

    however, the fact remains that if this is a site where UK parliament has jurisdiction, it is illegal (but low risk) to bond N and E on the consumers side of the cut-out.

    M.


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    I have had a look through, albeit, ESQCR(NI), but cannot find anything specific that prohibits the connection of a consumer earth to Distributor neutral other than a consumer cannot combine the function of neutral and earth in a single conductor. 

    If anyone has a reference I would appreciate it.
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    Looking further, something I did not realise


    The Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR). ESQCR 2002 apply only to Great Britain. There is a separate legislative framework in Northern Ireland, the Electricity Safety, Quality and Continuity Regulations (Northern Ireland) 2012, that are enforced by HSENI


    from (here - a parliamentary question)

    Does anyone have a list of differences
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    lyledunn:


    I have had a look through, albeit, ESQCR(NI), but cannot find anything specific that prohibits the connection of a consumer earth to Distributor neutral other than a consumer cannot combine the function of neutral and earth in a single conductor. 

    If anyone has a reference I would appreciate it.


    But doesn't that arrangement make the Neutral a PEN conductor beyond the service head? And hence this consumer is combining the function of neutral and earth in a single conductor downstream of the point at which the distributor split the two?


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    I take your point Graham but I read that more as a stipulation that a consumer cannot use a TNC type approach to the wiring within his installation. So in this particular case the function of neutral and earth beyond the service head will be in parallel conductors not in a single one. 

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    lyledunn:

    I take your point Graham but I read that more as a stipulation that a consumer cannot use a TNC type approach to the wiring within his installation. So in this particular case the function of neutral and earth beyond the service head will be in parallel conductors not in a single one. 

     


    I'm confused - what's the IE requirement? Is it to connect the supplier's N to a local electrode (MEN style), or is it to connect the installation's protective conductors to the installation's neutral conductors and then to the supplier's CNE? Or are you saying the supplier provided separate N and PE but the consumer has to connect them together again?

       - Andy.


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    Andy, in the ROI we use TNCS almost entirely. Each installation will also have an electrode. The conductor that is referred to as the earthing conductor in U.K. is referred to as the main protective conductor or neutralising conductor in ROI. The earthing conductor is the one that goes from the MET to the earth electrode. Normally in domestic premises  the DSO will have the  N/E connection sealed and no further neutralising should be made. Sometimes in larger installs the NE link would be made in the main panel. In any event, it is the registered contractors responsibility to ensure that neutralising has been done. However, the photo in my OP is an installation in NI which is presently in the U.K.! Had it been in ROI, it might have been regarded as Ok providing the genny had an independent electrode. It is most likely  a TNCS system but I can’t be absolutely certain as the PE readings are slightly different to PN. I am in the process of checking this out with NIE.

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