DNO UK power networks changed incoming overhead and now have PME TN-C-S but ccu connection to TT

[Mattrain1390]

Hi all.
I'm currently training as an electrician so would like your views on this for clarity and if I need to get someone in?
I have just moved in to a new (very old) house and on inspection of the CCU I noticed the incoming service cable from the overhead was chard at the top of the dno head.
UK power have been out ( literally within hours?) whilst I was at work and replaced the cable and installed a new fuse and DNO cut out with a PME TN-C-S. The house is on TT earth currently and at the bottom of the new cut out is a short run of earth with a clamp. Would I be right in assuming I can get someone to connect this up to the MET within the CCU making the earth stake redundant? I have posted a picture of the new installation.

 

[davesparks]

You need to confirm that the bonding requirements for a PME supply are met before connecting to it.
TT can, and often will, have smaller main bonding conductors than are required for PME.

Also a general inspection will be required to confirm a basic level of safety before anyone does any work to the installation.

 

[Taylortwocities]

Indeed, also a chenge to the earthing arrangement will completely change the Ze of the installation. Although it will improve the EFLI, Zs for each circuit, it needs checking and documenting.

PS Would like to see a bigger view of all of the cabling, I'm interested in where the pair of (only 10mm?) L&N tails go to.

 

[pc1966]

Would like to see a bigger view of all of the cabling, I'm interested in where the pair of (only 10mm?) L&N tails go to.

I wondered just the same, assumed it was a time-switch for heating or something but they are rather thin!

 

[snowhead]

PS Would like to see a bigger view of all of the cabling, I'm interested in where the pair of (only 10mm?) L&N tails go to.

They look smaller than 10mm, but I'd expect they are an unmetered supply to the control circuit for Off Peak, feeding a Timeswitch or Radio Teleswitch and/or Contactor.

 

[pc1966]

Also a lot of heavy cables. The stuff on the top-left looks bigger than the tails from the cutout, wonder if it is 16 at cut out and 25 on the top-left, or 25 / 35 for some odd reason?

 

[littlespark]

If this was fairly recent, there might be a letter coming in the post to say it’s complete and safe.

The DNO won’t touch anything to do with the house installation, as we don’t do anything to their head and fuses.

Get someone in, although at the moment there’s nothing unsafe with using the old TT

 

[pc1966]

Get someone in, although at the moment there’s nothing unsafe with using the old TT

Do check the main RCD trips on test OK though!

 

[Mattrain1390]

Hi guys. Thanks for replying.

Yes as Snowhead said, the small tails supply the control /meter for the economy 7.

I'll grab another picture.

Also, as per some of your views I was surprised that the DNO put on a 100 A. Im not sure the meter tails are 25mm, I would assume that the DNO would have some liability to check before uprating the fuse?? I'm not aware what the old one was but, as far as I am aware its got to be 20+ years old, it's an oldish 2 rate digital meter........and an old clock style switch for the econ 7 storage heating. ...... My next job is to get on to the supplier to get them to come and check out to the CCU.
[automerge]1590668808[/automerge]

Do check the main RCD trips on test OK though!

Oh yes it works!

 

[ipf]

Before doing anything else, the first thing I'd be doing would be a Ze test on that supply earth.....just to be sure.
As dave said earlier, checking the bonding is very important....second thing on the list.