how to upgrade the earthing conductor?

[theugly]

hi all, just a silly question because i never replaced an earthing conductor before,

just finished an inspection. the earthing conductoris only about 6mm. i am thinking to upgrade it to 16mm. the end of the conductor is taped in the supplier's thick conductor. I think it is a TN-C-S system, the outside metal of the trunk is for neutral and earth. i untaped it and found the end of the earhting is buried in some dark color painting, can i forced the earthing out and replace it straightaway?

thanks a lot,

 

[white armour]

Hi pal, not sure I would not want to be taking it off the incoming supply conductor, (think the term is "sweated on"). Have seen the conductor taken from the incoming supply into an Earth block and then 16mm main earth to board/10mm bonding to services etc.

Regards WA

 

[Sav]

I think you are talking about a TN-S system there mate.

Your probably looking at the swa from the incoming supply which is normally used as an earth for a TN-S system.
Did you say you have just done an inspection ?

Sav

 

[brucelee]

Hi mate
What size are the tails
If its TN-C-S then the earthing conductor has to be 16mm if carrying out alterations and additios

but you say the existing earthing conductor is connected to the suppliers conductor

If you are unsure mate what system it is or what to do then my best advice would be to contact the DNO to ask what type of earthing system it is
and if you are thinking of replacing this maybe you could ask the dno to upgrade as you shouldnt be messing with the DNOs cut out fuse or equipment they will fit a isolator and upgrade existing tails from cutout to meter and then to main 100A isolator switch and they will fit a earthing conductor to there equipment either by pme or tns

others more experienced may advise you better

what size are the Main protective bonding conductors to the water and gas

If your only carrying out a PIR then you only are inspecting the existing installation and should record observations and code as appropriate any code 1s need urgent attention or immediatly isolate the defective part code 2s require improvement

 

[Sparky Ninja]

can I ask why you think it's a TNC-S system?
and why an existing 6mm earthing conductor would need to be replaced?

 

[Sparky Ninja]

If its TN-C-S then the earthing conductor has to be 16mm if carrying out alterations and additios

????? where's that from?

 

[theugly]

from all the replies do you all mean that 6mm is ok from supply to earthing block, as long as from earthing block to consumer unit is16mm?

 

[ridemx27]

That will be a tn-s system and is the suppliers earth to met, so providing you have a ze lower than 0.8 ohms and the consumers earth from the met to the consumer unit is of an adequate size its of no concern to your pir. If on the other hand the small wire is coming straight off the sheath into the consumer unit i usually reterminate into an external met and take a 16mm into the cu it will then satisfy the cert as the consumers main earthing conductor is of the right size. you should neva mess with there incoming cable, if you take a ze reading and it doesnt satisfy you contact the supplier to upgrade hope this may help.

 

[theugly]

thanks all, last question, how to distinguish between tn-s and tn-c-s?

 

[ridemx27]

on a tnc-s earth is taken from the neutral conductor at the supply cut out, u may somtimes come across and installation where it has a wire from the sheath and the neutral to the met this would be recorded as a tnc-s and is where the sheath of the cable has broken down over the years and the resistance to earth has become to high so the supplier has upgraded the system to tnc-s and left the sheath earth terminated.

 

[IQ Electrical]

thanks all, last question, how to distinguish between tn-s and tn-c-s?

Are you kidding me here?
You've done a PIR which requires 'an above average knowledge of BS7671' and you can't identify the earthing system?

 

[Mark_Burgess]

thanks all, last question, how to distinguish between tn-s and tn-c-s?

You could see the illustrated pictures in your on site guide or GN3 book.

 

[Sav]

Are you kidding me here?
You've done a PIR which requires 'an above average knowledge of BS7671' and you can't identify the earthing system?

Thats what I thought in my post, hence the " you have just done an inspection" quote !!
Sav

 

[Mark_Burgess]

I am waiting for the, I dont have an on site guide, or whats a GN3 book!!

 

[rocker]

When you say 'inspection', you mean having a look when pricing a job, not a periodic inspection, right?

 

[theugly]

calm down guys, let me explain before you get further, i certainly know the difference between the two systems, but when you are on site, it is difficult to tell the difference between them, i know you guys are very experienced, but from on site guide i dont think it is very obvious and enough to make everyone can identify them immediately, so why not be more patient and more constructive?

 

[IQ Electrical]

calm down guys, let me explain before you get further, i certainly know the difference between the two systems, but when you are on site, it is difficult to tell the difference between them, i know you guys are very experienced, but from on site guide i dont think it is very obvious and enough to make everyone can identify them immediately, so why not be more patient and more constructive?

I like to think I am helpful here but it's one thing asking about the interpretation of a certain regulation and another thing asking worryingly basic questions AFTER an inspection.

 

[rocker]

If you haven't seen many of them then yes it may be a bit tricky, but for somebody who is experienced enough to do a periodic inspection, you should be able to do it in your sleep.

The purpose of a PIR is to determine the safety of an installation.

If you can't identity the earthing system, how can you tell that the Ze is low enough? This is a major safety issue.

I'm sorry mate but if you are indeed doing a PIR you may find yourself on more sticky wickets in the future.

 

[Mark_Burgess]

You could always have a lengthy phone call with the supplier and ask them what the earthing arrangement is, they should be able to give you the information you require, after being passed around about.

Also, never remove the tape or sleeving off the incoming supply unless you want to be prosecuted for tampering with the suppliers equipment!

 

[ridemx27]

Like iq said pir require an above knowledge of Bs7671, i served about 6 years before completing a pir on my own and the amount of people iv seen coding no rcd protection etc as code 1 !!! point is its in in depth test which requires a lot of on-site knowledge and the regs extremley well, sounds like u may of been thrown in the deep end iv had the same with employers in the past.