House rewire earthing whats TT and TNCS and do I need both

[twokcc]

Refurbishing 1930's semi including a full house rewire and new consumer unit.
Electrician just advised me that the house is not earthed and need TT earthing(a rod into ground) and change for supply to a TNCS supply. He quoting for TT for £100 and Northern Powergrid want £160 for the second.
Don't really understand any of this -do I need both and are prices reasonable?

[Salesy]

If you changed supply to TNCS you wouldn't need an earth rod as this is incorporated in the supply and normally much better.

[Ganglandboss]

There are three main types of earthing arrangement used in dwellings:

TT: This is where the supply authority does not provide an earth facility. This is usually the case in overhead supplies. Because of the greater risk of cables coming down in bad weather (for example), loss of an earth could go undetected and pose a risk for the end user. In this situation, an earth electrode has to be installed by arrangement of the consumer. The disadvantage of this is the external earth loop impedance will be higher, so additional safety precautions are required.

TN-C-S: This is where the supplier provides a supply cable with a live conductor and a combined earth and neutral (usually the metallic outer sheath). Earth and neutral are at the same potential but have to be separated into separate conductors for safety reasons. At the supplier's incoming termination, separate earth and neutral cables are taken off the combined earth and neutral conductor.

TNS: In this case, the supplier's cable will have live and neutral conductors and the earth is taken from the outer sheath.

What type of supply cable is it? If it's not overhead, it makes me wonder whether you really do have a TT, or whether you actually have a TN-C-S or TN-S. I would recommend you contact Northern Powergrid and ask them to advise, and possibly get another electrician's opinion.

[twokcc]

Ganglandboss said:

What type of supply cable is it? If it's not overhead, it makes me wonder whether you really do have a TT, or whether you actually have a TN-C-S or TN-S. I would recommend you contact Northern Powergrid and ask them to advise, and possibly get another electrician's opinion.

Thanks for info

It is from an overhead cable from next door(non attached side) which passes over my drive.

Don't know type of cable (its about 2.5 metres high up wall) but have noticed that it branches down on outside wall and enters house in pantry- but also goes round the back of the house to supply next door (attached side). Future plans may be to extend the property at the rear including removal of the rear wall. What would be the situation with the supply to the attached next door neighbours if I decided to do this.
Spoke to Northern Powergrid didn't offer any advise just wanted address of property and sending forms in post so will see what arrives.

[Alucidnation]

TNCS supplies can also be overhead if you have a single cable coming from the pole.

Some suppliers will also convert to TNCS FOC anyway.

All your electrician has to do is phone the supply company and make a PME enquiry, and they will send a couple of lads round to check if its available, and if so, provide an earth terminal.

Edit:

Fill in the forms and see what the survey says.

Its quite possible it would be converted anyway, especially if you have a shared supply with next door and you are thinking of relocating it.

Edited by Alucidnation on Sunday 21st February 19:33

[Yabu]

twokcc said:

Refurbishing 1930's semi including a full house rewire and new consumer unit.
Electrician just advised me that the house is not earthed and need TT earthing(a rod into ground) and change for supply to a TNCS supply. He quoting for TT for £100 and Northern Powergrid want £160 for the second.
Don't really understand any of this -do I need both and are prices reasonable?

Tncs would be my preference over a tt earthing system as the earth resistance reading will be consistent rather than one that changes and has the greater possibility of not being installed correctly.

Then there's the issue of needing a amendment 3 consumer unit and the problem of tt earthing and metal enclosures.
https://www.youtube.com/watch?v=9JLSTjV4imA

Has the consumer unit been changed yet?

[twokcc]

Yabu said:

Has the consumer unit been changed yet?

Thanks to all for response

Yes the old MK sentry unit has been removed and a metal case consumer unit put in its place but not wired up yet.
Would the earthing issue not have been found when this was installed (guess more than 15 years ago) or when the old clock type meter was replaced by a digital meter?

So if I understand this correctly if I get Northern Powergrid to change the supply to a TNCS I dont need the TT earthing rod. From memory conversation with Northern Powergrid was that installation would be about 8-10 weeks - so what do I do about an electricity supply in meantime? would new system be unsafe to use before TNCS installed?

What are my options with supply cable that is attached to outside rear wall that goes to my attached neighbours house can I do anything about having this removed?

[Salesy]

Your electrician will be able to put an earth rod in place until the new supply has been installed thus not leaving you without power.

He can certify the job with the TT system, but will require recertification when the TNCS supply goes in.