mains earth feed

[kallen100]

Just fitted a new Consumer unit on a TN-C-S arrangement to replace very old fuse board, all went very smooth except for terminating the mains PE to the CU, it needs to be about 10cm longer as I don’t want to over stretch the cable. My question is; can I use a terminal block to extend the PE? If so what type of terminal block do I use? I need everything to be within Regs so when I call the Sparkie to test and certify to Part P, I won’t have to pay him to make any changes.
Just to add; the above install is in a property I’m refurbishing and is isolated at the meter. I don’t want anyone worrying that the CU is live without earth to the meter

Thanks in advance of any help.

 

[holmslaw]

..

 

[kallen100]

Sorry, Protective earth

 

[holmslaw]

..

 

[ajrobb]

The IEE On-site Guide has only one picture showing the general layout of a "TN-C-S system (PME supply) meter position arrangement" and that has a 'main earthing terminal' on the the distribution board with 16mm² going to the CU and separate 10mm² going directly to the gas and water. It indicates that a metal label "SAFETY ELECTRICAL CONNECTION DO NOT REMOVE" should be attached to the MET and each of the gas and water connections.

The TN-S diagram is almost identical except of course the MET is connected to a separate conductor before the fuse.

It only shows the bonding conductors coming from the CU 'installation earthing terminal' for a TT system.

In my case, the conductor from the TN-C-S fuse was only 6mm², but that is not your responsibility. It is probably best to make this conductor quite short. It might be worth notifying the DNO that you have installed a new CU and invite them to upgrade their conductors too. If all your circuits are protected by RCD, you are not asking the earth conductor to take a significant fault current.

 

[kallen100]

Thanks for your help guys, I think I will look to replace the earth. I’m assuming I use a 16mm2 cable as a replacement from the earth block to the CU. I’ve not done this before but I assume there is a duct running from the meter cupboard to the CU and I just push and pull the cable through?

 

[yorkspark]

unlikly to be a duct so will be a struggle.

It depends on tails size for earth size.

If service fuse is 80/100 amp then 25mm tails 16mm earth required, if 60 amp fuse then 16mm tails 10mm earth will suffice however 25mm tails is the norm nowadays.
you may need to replace tails as old installations used 10mm tails if memory serves correctly so not accceptable for modern installations

 

[Chri5]

I need everything to be within Regs so when I call the Sparkie to test and certify to Part P, I won’t have to pay him to make any changes.

All scheme electricians can only test and cert work they have carried out.

I know some will allow a DIY job, but in the strictest sense that is illegal, potentially dangerous and once he completes the notification and test cert, illegal.
It also means the electrician has accepted full ownership of the works so he is liable if anything happens that becomes a safety issue.

Have you at least had the good sense to have him visit of the course of your work. Sight of all 1st fix ?

See open runs, confirms safe routes, seeing terminations at fittings, checking for cable entry in to boxes etc ?

 

[kallen100]

Thanks yorkspark, hopefully I can use the existing earth to pull through the new one.

 

[RF Lighting]

Did you not see Chri5's post?

 

[ajrobb]

Sorry, I assumed that he had already notified LABC and they had assigned an electrician to do first fix and final inspections (PIR).