combined earth + neutral cutout

[rich spark]

hi everyone, hope you can help. im currently installing a small submain to supply a DB which is then supplying a cctv power supply. there is a new lucy 25amp cutout in an external cabinet which has recently been installed prior to my work being carried out, when i have carried out work which involves a lucy cutout there has always been an earth block already fixed onto the side of the neutral block. The one i am working from just has concentric cable to Live and to the CEN block.
So i am asking if i require an earth rod to a new earth block, or bring an earth cable from the neutral block to an earth block? I would put a rod in myself but i just want to be 100% sure.

thanks

 

[Guest55]

your neutral and earth are connected to the same terminal block within a pme cutout.
the smaller 25a lucy units dont have a seperate earth block.

 

[rich spark]

so my 4mm 3core submain would be connected live on the outgoing of fuse, and the neutral and earth inside both on the CEN block?

 

[Guest55]

yep.
done it myself a 1000 times with my stint in the highways electrical sector.

 

[rich spark]

thanks for the reply,its helped. i was ready to buy rods and cable tomorrow .

 

[Engineer54]

What sort of overall installation are you working on?? Some sort of Highways installation??

Generally, If we are talking about a ''Submain'' from a PME/TNC-S supplied main distribution board, then you can't go making further N-E connections as you go. A PME connection is made ONCE at origin, the main distribution board should then be distributing sub-mains as TN-S, where the earth requires a separate earthing block (EMT).

 

[GLENNSPARK]

What sort of overall installation are you working on?? Some sort of Highways installation??

Generally, If we are talking about a ''Submain'' from a PME/TNC-S supplied main distribution board, then you can't go making further N-E connections as you go. A PME connection is made ONCE at origin, the main distribution board should then be distributing sub-mains as TN-S, or TN which will require a TT earth at the load end of the distributed sub-main.

well...i thought it was clear about creating TN-C....

 

[Engineer54]

well...i thought it was clear about creating TN-C....

lol!! i didn't take notice that he has a 3 core sub-main, so corrected my original post!!

 

[GLENNSPARK]

i mean has it been verified that PME is available here?

or is the O/P just goin `off the cuff`?

 

[GLENNSPARK]

sorry...just re-read #1...
been working 14 hours today so...

 

[Engineer54]

I'm just as confused now!! lol!! The OP starts of by saying he has a concentric sub-main cable, then changes to saying he has a 3 core sub-main cable?? Either way if this is an overall PME supplied installation you can't go making numerous PME N-E connections. So i'm not quite understanding why these so-called sub-main lucy heads, are generally provided with CEN blocks, which to my mind, would make them unsuitable for sub-main installations (unless the N-E connection is via a removable sliding link to enable, either or TN-S / TNC-S supply), they are designed for being placed at the origin of a DNO supply.

 

[Guest55]

I'm just as confused now!! lol!! The OP starts of by saying he has a concentric sub-main cable, then changes to saying he has a 3 core sub-main cable?? Either way if this is an overall PME supplied installation you can't go making numerous PME N-E connections. So i'm not quite understanding why these so-called sub-main lucy heads, are generally provided with CEN blocks, which to my mind, would make them unsuitable for sub-main installations (unless the N-E connection is via a removable sliding link to enable, either or TN-S / TNC-S supply), they are designed for being placed at the origin of a DNO supply.

nope , i understand the post as this ;

a feeder pillar with 25a pme dno cut-out with combined N & E terminal , supplied by pvc concentric cable

then a 3 core submains is ran from this to the cctv switchgear.

at no point is the N & E combined beyond the dno cut-out which is perfectly acceptable.
there is no removable earth link as the cut-out is too physically small for such a feature
as per the picture in this link..........

http://www.lucyswitchgear.com/media/25982/tds slf double pole cne.pdf

as for glenns comments regarding verifying its actually pme , i can absolutely guarantee that the dno will not install a TT supply within a metal enclosure in a public location , for reasons that are blatantly obvious.
;-)

 

[Engineer54]

nope , i understand the post as this ;

a feeder pillar with 25a pme dno cut-out with combined N & E terminal , supplied by pvc concentric cable

then a 3 core submains is ran from this to the cctv switchgear.

at no point is the N & E combined beyond the dno cut-out which is perfectly acceptable.
there is no removable earth link as the cut-out is too physically small for such a feature
as per the picture in this link..........

http://www.lucyswitchgear.com/media/25982/tds slf double pole cne.pdf

as for glenns comments regarding verifying its actually pme , i can absolutely guarantee that the dno will not install a TT supply within a metal enclosure in a public location , for reasons that are blatantly obvious.
;-)

Okay, that makes far more sense than what i made of it, before my second morning cup of coffee!! ...lol!!

I think the confusion here is the term ''sub-main distribution''. If these DNO Lucy cut-out's are direct from the DNO's supply, then they aren't classed as sub-mains as such. I take it that these DNO feeder pillars, as they are being called, don't have a main supply in and then subdivided off via these lucy cut-outs??

 

[Guest55]

the mis understanding is probably from the OP's discription , but any wiring after the cut-out ( eg tails or a swa submain ) will be on the consumers side of the installation.

the feeder pillar itself remains the property of the local authority , only the cutout is owned by the dno.
i've looked for a picture to help describe the set-up but found nowt , i'll break into 1 later and take a photo ( i still have a set of master keys ) ;-)

 

[Engineer54]

the mis understanding is probably from the OP's discription , but any wiring after the cut-out ( eg tails or a swa submain ) will be on the consumers side of the installation.

the feeder pillar itself remains the property of the local authority , only the cutout is owned by the dno.
i've looked for a picture to help describe the set-up but found nowt , i'll break into 1 later and take a photo ( i still have a set of master keys ) ;-)

Now that would be interesting, i'll look forward seeing those feeder pillar pic's!!

I don't think you'd be able to directly terminate a SWA into those Lucy cut-outs, the gland plates are in two halves, one half being integral with the cover plate!!