Questions regarding TN-S system and RCD

[Penance]

Hi all,

Please excuse an amount of ignorance in this, only 15th ed trained and been out the game for a while.

I am currently rewiring my house, with advice from 17th ed but not completed the course yet.

We have a TN-s system which at a guess is 40+ years old.

Recently our supplyer installed a new meter and the chap made a comment about TN-s possibly being poor on older installations due to sheath corrosion, which i remember from my apprentice days.
I have yet to measure Ze, mainly due to not having the equipment yet. If Ze is too high what are my options, I can pay to have a PME conversion but can i put an earth rod in and see if that brings Ze to an acceptable reading?

He also passed comment on the CU i am using, it is a MK split load, 100A DP isolator, RCD on each rail and then MCB's. He said this would not pass as the RCD needs to be at source IE will cut power to the whole board under fault condition.
I have not heard of this before and somehow doubt it is correct, can anyone give me the correct answer.

 

[High Tower]

Hes a meter fitter= hes probably a muppet

If the Ze is too high then yea you will have to TT it, the Cu with dual 30mA RCD's more than comply so that will not be a problem.

thing to do is to beg borrow or steal a ELI meter and find out for sure, if it comes in under 0.8 ohm then happy days !!

 

[ukpablo]

Your split load MK board is fine.
If you were to protect the consumer unit with an rcd at source, the whole installation would trip if any fault occured. This makes fitting a split load board pointless!
SO the split load board is most certainly ok, and as long as you seperate the ccts correctly,, will def comply with current regulation.
If u have a fault on one rcd, the whole installation will not trip out, so upstairs skts and downstairs lights on one rcd and vice versa on the other, if u know what i mean!
That guy sound like he needs some up to date training me thinks??!

 

[High Tower]

Penance, if you pm me i will pm you my number in return, or my email, if you need any advice of guidence

 

[Penance]

Thanks guy, bit rusty here but didnt think i was that bad. You have confirmed what i thought.

I think i will need to borrow/steal a meter at some point. Dont really want to buy one until i will have more permanent use for it.

High Tower, many thanks for the offer, pm on way.

 

[mechelec]

If it turns out you have a high Ze then get the DNO in to sort it out FOC. If they supply a property with an earth then they are obliged to maintain it. If the do not supply an earth (TT) then if it is available in your area you can apply for a pme but it will cost.

 

[Engineer54]

Your listening to, at best a semi ,semi skilled meter installer and at worst a guy that's had a day or two of training in meter installations, who's been listening to things he doesn't understand!!
Now your worrying about a supply cable's earthing system? The chances of your TN-S earth being shot, is going to be pretty slim, so forget everything he said or told you, and wait until you do your rewire and find out for your self with an ELI test....

Carry on like this and you'll end up giving yourself an ulcer....lol!!!

 

[tonys]

Carry on like this and you'll end up giving yourself an ulcer....lol!!!

Like it lol, best post yourve made so far lol

Surprised no-ones asked you, if your aware of part p and if your not part of a scheme are you going to notify building control lol now that should start the ulcer off nicely lol

 

[Penance]

Yes I am aware of part p and under guidance the work is is done to that.

Currently I have only replaced the lighting feed as the original was perished rubber sheathed. All switch drops are already in t&e and have not been changed yet.

The new CU is not yet installed.

Afaik this means the work was not notifiable. When I am ready to completely rewire then bc will be notified. Thanks for your concern tho

 

[High Tower]

If it turns out you have a high Ze then get the DNO in to sort it out FOC. If they supply a property with an earth then they are obliged to maintain it. If the do not supply an earth (TT) then if it is available in your area you can apply for a pme but it will cost.

Id be interested how often you have managed to get the DNO to take responsability for anything mate?? let alone for their aging equipment and cables!!

Hello and welcome to central neworks, howcan i help???

Well i seem to experiencing Ze values in excess of the permitted range for a TNS system

long pause

....................EH?

 

[mechelec]

Afaik this means the work was not notifiable. When I am ready to completely rewire then bc will be notified. Thanks for your concern tho [/QUOTE]

If you didnt notify who would ever know???????
I know someone who had a kitchen fitted, loads of sockets new CU etc no cert issued. i advised them to chase up the builder(spark) for the cert as it would be a problem when selling the flat. They have just sold it and it was never mentioned. Made me look a bit of idiot.
Sorry if this stirs the ----

 

[mechelec]

Id be interested how often you have managed to get the DNO to take responsability for anything mate?? let alone for their aging equipment and cables!!

Hello and welcome to central neworks, howcan i help???

Well i seem to experiencing Ze values in excess of the permitted range for a TNS system

long pause

....................EH?

Never been a problem yet. Call their emergency number tell them you have a high ELI and they will be out in 4 hours guaranteed.

 

[High Tower]

You must be the chosen one!! lol

I know lots of the lads on here have had massive problems getting them to do anything, me included!

 

[telectrix]

Hi all,

Please excuse an amount of ignorance in this, only 15th ed trained and been out the game for a while.

I am currently rewiring my house, with advice from 17th ed but not completed the course yet.

We have a TN-s system which at a guess is 40+ years old.

Recently our supplyer installed a new meter and the chap made a comment about TN-s possibly being poor on older installations due to sheath corrosion, which i remember from my apprentice days.
I have yet to measure Ze, mainly due to not having the equipment yet. If Ze is too high what are my options, I can pay to have a PME conversion but can i put an earth rod in and see if that brings Ze to an acceptable reading?

He also passed comment on the CU i am using, it is a MK split load, 100A DP isolator, RCD on each rail and then MCB's. He said this would not pass as the RCD needs to be at source IE will cut power to the whole board under fault condition.
I have not heard of this before and somehow doubt it is correct, can anyone give me the correct answer.

never, ever seen lead sheath corroded. before converting to TT, somehow measure the Ze. tyhen you know where you stand. fitting a RCD at sourcenegates the benefit of the split load board. wonder where the meter reader got his knowledge from, rogue traders or jackanory. either way he's talking bull poo

 

[Deleted member 9648]

You must be the chosen one!! lol

I know lots of the lads on here have had massive problems getting them to do anything, me included!

And me........."computer says no"........

 

[Penance]

I have seen corrosion in the cast iron boxes used for jointing.
Anyway currently trying to scrounge a meter to check for sure.

 

[High Tower]

And me........."computer says no"........

Hello, this is central networks, me no speakie english!!!! Electricity whats that then we only deal in unicorns and fairy dust!

Its nice that my 1000th post would be one of complete dribble and nonsense!!

 

[Penance]

Ah, that what the meter guy was talking about!