TN-S or TNC-S

[ACDC]

Hello folks.
Need a bit of direction on this one. I went on a survey job the other week, and i need some opinions if the photo shows a TN-S or a TNC-S system? I took a measurment of the Ze, which was 0.54ohms, which suggests a TN-S, but looking at the earth block next to the cut out, there is a solid bar which goes into the neutral connection of the cut out, so could it be TNC-S?

Another thing is the way the flying earth lead connects onto the lead sheath of the incoming supply, this cant be normal practice can it? jubilee clipped, and undersized?

Any thoughts welcome

 

[SPARTYKUS]

Looks TNS to me, it originates from the sheath below, as for the connection I've seen worse!

Bit of a weird one though. Where is it (as in geography?)

Best way is to phone up supplier, if you can get through to anyone with an ounce of sense.

 

[malcolmsanford]

Looks like what you have there is a TN-S and some time in it's history a TNC-S head fitted to the installation.

I would imagine inside the head there is no neutral to earth link and for some reason someone as used the earth terminal on the head as a sort of MET. Best way to tell is do a PSSC and PEFC test, if it is a TNC-S then they would be virtually identical, if it;s a TN-S then the PSCC will be higher

 

[ACDC]

Thanks for the replies guys, much appreciated! Iwont bother phoning the DNO (Been there too many times before being passed piller to post) The site is near Newport S Wales.

Thanks for that info Malcolm, its true when they say you learn something new everyday, will remember that.

Am i right in saying the the lead sheath connection should be soldered? (no clamp used)

 

[Engineer54]

Thanks for the replies guys, much appreciated! Iwont bother phoning the DNO (Been there too many times before being passed piller to post) The site is near Newport S Wales.

Thanks for that info Malcolm, its true when they say you learn something new everyday, will remember that.

Am i right in saying the the lead sheath connection should be soldered? (no clamp used)

Originally it was, you can just make out what looks like the original sweated bare tinned copper earth lead. As this is a 3 phase cable i would remove that DIY jubilee clip and replace it with ''constant pressure spring clamp'' using a braid tail to connect to the installations MET.

If after testing TN-S is confirmed then remove those connections from the cut-out N-E point...

 

[Knobhead]

Constant Force Springs : 3M UK & Ireland

There are two springs and enough braid in a kit for two cables.

Or you could use a Hepworth clamp which the DNO uses, but you need a special tool to apply them.
http://www.sicame.co.uk/Section8/8.05-8.06.pdf

 

[netblindpaul]

Going totally against whet E54 has said & I don't care!
Oh and also Tony the same.

DON'T TOUCH the "jubilee clip" on the cable.
WPD may well know it's there and have left it.
If they do it will be recorded in their system.

They have a policy of NOT removing these live as they have had a few cable blow outs when doing this.
Their current policy is to leave them alone unless they need attention.
Then they do an underground live cut external to the premises, remove the clamp, test & inspect the cable, then re-energise.
Having nearly lost a guy to this they now no longer take risks, so neither should you.
Apart from that you are not "allowed" to work on the DNO kit in the UK "officially" it would be a criminal offence.

I don't know why you have problems contacting engineers at WPD they are very helpful and approachable in my experience as well as easy to contact.


WPD have a statute law responsibility to tell you what the supply is, end of story, under ESQCR.
They may have to attend site to do so though.
This should not be a problem.

 

[Engineer54]

Well thank god i don't live/work in the UK anymore, where as a qualified electrician/engineer your frightened to correct a simple cock-up made by an unqualified/incompedent DIY'er!!!

I don't believe for a New York second that the DNO would even THINK about cutting a cable to replace a TN-S clamp, even less actually do it!!! You don't even need to remove the non-compliant jubilee clip, to perform a good TN-S earth connection, just roll the constant force spring clamps above or below the existing JC. Chopping the cable off and using the new braided cord.... It's a bit different, if it meant taking a blow tourch to the cable, to sweat a new TN-S connection, i'd certainly leave that to the DNO!! Not so sure Tony would though. ..lol!!!

Going by what i've seen of DNO work at service cut-out positions, often performed by un-trained meter fitters, i wouldn't think twice about installing a constant force spring clamp, your not even using a tool of any kind to fit it.

All this crap is one of the reasons why UK goods are so expensive on the world market, all this nonsense has become far too expensive to absorb, so now you pay for it, ...in cash and loss of jobs!! I'm all for safety, sensible safety, but OTT is and will always be OTT!!

 

[Knobhead]

NBP slaps Tony’s wrist.

OK the DNO may have a record of it. In which case they know it’s a sub standard installation and as such should be forced to do something about it.


I’ve worked with paper lead cables since the start of my appenticship. Unless you’re totally cag handed they are as robust as any other cable type. There are a lot of myths and legends grown up around them, they don’t explode the moment you sneeze near them.

 

[netblindpaul]

Well TBH I don't care what you E54 or you Tony have to say or think about this.

The LAW in the UK makes it a criminal offence to do any work on the DNO systems and supply cables and for you to even suggest this makes you both a pair of numpties.

When have related this information it has come direct from linesmen, technicians and engineers at WPD, they have had bad experiences with these clamps so they are no longer prepared to put their guys at risk of a cable blow out.
I don't care how much experience you have or have not.
The fact that you are prepared to suggest to an unknown poster that they attempt something illegal that could end their life if things go wrong IMHO makes you both a pair of fools.
You have no idea of the experience of the OP or how he is likely to go about this.

You 2 have flabbergasted me tonight & thought you were competent, you have just proved me completely wrong.
BOTH of you.

 

[Engineer54]

On this Score, i really don't particually care what you have to say either.
You have your head wrapped up in far too many rules and regulations, that you've forgot what being a qualified electrician/engineer actually means.

All this scaremongery about the law, ....how many times have we heard from members here and elsewhere, that when they have rang the DNOs about lack of earth leads, they have turned round and told them to install it themselves!!! If only you knew what the DNO companies themselves get upto, then talk to me about this and that being against the law, on their installations!!

Your correct both Myself and Tony have a great many years of experience in this industry, more than enough to know that a constant force clamp on a lead or any other type of cable is a more than a safe method of taking an earth.

Two things Paul, ...One, ...i am No Bodies Fool, either Professionally or in my private life, so please get that well and truly straight in your mind OK!! Two, .... Who the hell are you to question my own, or Tony's competency?? I very strongly suggest that you just don't go there!!

Nothing more i'm willing to say to you on this matter, if i do i'll get an infraction!!!

 

[Des 56]

There sure is a lot of fear in our trade nowadays :33:

Perhaps the general lack of supervision or experience before embarking on the road of electrics has engendered this greater caution amongst so many in this trade

Live working is listed as forbidden fruit and should be avoided at all costs,so say the "books"

But the "books" could never and would never be able to say differently
Live working though has always been with us,experience of the job hopefully keeps us safe

I will be live working tomorrow,illegally as well,because that was what electricians were expected to do, and blind eyes turned where necessary
Experience of terminating lead sheathed cable also gives you a feel for its robustness and I would expect a competent electrician to safely clamp a sheath without exploding it

Perhaps inexperience is by far the greater danger to an electrician.maybe not so the danger of "what" an electrician is working with


Now this is a personal view not a war of words with anyone​

, feel free to have your own view and leave me to mine

 

[Knobhead]

Well that’s told me then, I’m officially a numpty! (As defined by NetBlindPaul.)

Paul, take off the rose tinted glasses and look at the real world!

The dangers of cutting and then rejoining a live cable are one thousand times the risk of removing a clamp, but that’s OK in your book of regulations is it?

What is your real world by the way? You can quote regulations verbatim but do you do any real work? For Christ’s sake don’t tell me you work for the HSE!

 

[ACDC]

Cor blimey lads, put the boxing gloves away, it is christmas!
As stated in my original post, i was undertaking a electrical survey. From this survey i will write a electrical report. I have enough experiance under my belt (15yrs) to know what i should or should not touch. Be assured that i will not be touching the earthing connection on the incoming cable, and i will be contacting the DNO.

Thanks again for you replies chaps.

 

[Chr!s]

It looks like an old TNS and now its been converted to a TNC-S and they have just left the clamp on, contact the DNO, most of the UK DNO'S only have TNC-S now and its not a TT .

Regards Chris