price to convert TT electric supply to TNCS supply

gamston

hi there
i need to ring the electric company next week to get them in to check if its possible to convert my TT pole supply to TNCS
just wondering if any one has had it done recently & how much did it cost

Risteard

gamston said:

hi there
i need to ring the electric company next week to get them in to check if its possible to convert my TT pole supply to TNCS
just wondering if any one has had it done recently & how much did it cost

You will also need to consider whether the Earthing conductor and main protective bonding conductors etc. are adequately sized. You should get an electrical contractor on board too. What is the reason for seeking to change from TT (Direct Earthing)? 

Only the DNO can answer for their side as TN-C-S is generally PME which requires multiple Earthing connections of the PEN conductor. Only they know what work is required on their network. 

gamston

Looking to move, so want to get the place into shape
this place has never had an earth, I've lived here 40yrs and been ok, but want to sort before i put on market

dj1471

gamston said:

this place has never had an earth, I've lived here 40yrs and been ok, but want to sort before i put on market

Come again? If it’s TT then you have an earth rod, this is a perfectly acceptable form of earthing.

Money would be better spent on upgrading the CU to add RCD protection, if not already present.

Risteard

dj1471 said:

gamston said:

this place has never had an earth, I've lived here 40yrs and been ok, but want to sort before i put on market

Come again? If it’s TT then you have an earth rod, this is a perfectly acceptable form of earthing.

Money would be better spent on upgrading the CU to add RCD protection, if not already present.

TT will have RCD protection, otherwise there won't be any fault protection (previously referred to as protection against indirect contact) unless there is an extremely low impedance Earth path through the electrode and general mass of Earth (which there almost certainly won't be)!

There may not be 30mA RCD additional protection (previously supplementary protection), however. It could be a time-delayed device which a much greater rated residual operating current.

gamston

there is a RCD but no earth, never has been as far as i know
yes could have earth rods but the cable run is not simple/easy, i don't want it just pegged to outside wall, want it run via loft/garage
so i was thinking get the DNO out (thats free ?) to look and tell me if I can get PME, and cost, then i need a electrical contractor to fit earth from CU to DNO PME point and sign off

Section62

gamston said:

there is a RCD but no earth, never has been as far as i know

Are you sure it is an RCD?  With older installations there's a chance of finding voltage-operated ELCBs, which can look very similar, but function differently.  You'd still expect to find some system earthing, but it wasn't unknown in the past for the earthing to be achieved via the incoming water pipe or something similarly unsuitable.

It would be very odd for an electrician to install an RCD in an everyday situation without first making sure the earthing arrangements were appropriate.  If there has been DIY work done in the past there could be other hurdles to overcome before you can get sign-off.

gamston said:

so i was thinking get the DNO out (thats free ?) to look and tell me if I can get PME, and cost, then i need a electrical contractor to fit earth from CU to DNO PME point and sign off

Are you in a town or village, or somewhere more isolated?  Any neighbours with a PME system?

If they can provide one easily, various DNOs will provide a PME terminal for a fixed rate of around £150 to £200.  If the local supply arrangements aren't suitable for PME then the DNO can refuse to provide one (on safety grounds) but might be agreeable to upgrading the local supply on a costs basis.  In that case, the ease/practicality of obtaining sufficient multiple earthing points for the PEN conductor is usually the main driver of cost.

gamston

I live in the sticks, feed via a pole route single phase, but neighbour has 3 phase as when built they put in electric underfloor heating both built in mid 60's
think it must have used water pipe as earth 

fenwick458

so the answer to the question, unfortunately nobody on here can tell you how much it will cost. I've seen the price ranging from £0, to £1500, to a flat out refusal to do it, depending on the location. only way to find out is to ring the DNO
more often for the houses I have worked at it's been free for the homeowner, as these were just houses that had been forgotten about when the rest of the village was upgraded to PME years ago.
actually, from what you've said "in the sticks, overhead supply" I'm going to guess upgrading it is going to be expensive. and it'd probably be cheaper getting an electrician to put some rods in

Risteard

gamston said:

there is a RCD but no earth, never has been as far as i know
yes could have earth rods but the cable run is not simple/easy, i don't want it just pegged to outside wall, want it run via loft/garage
so i was thinking get the DNO out (thats free ?) to look and tell me if I can get PME, and cost, then i need a electrical contractor to fit earth from CU to DNO PME point and sign off

There are also likely to be issues with the size of the main protective bonding conductors etc. It's not simply a case of make it TN-C-S now - there are particular safety requirements for a TN-C-S installation.

Ectophile

Many years ago, it was acceptable to use the cold water pipe as a substitute for an earth rod.  But it's not so clever as old iron/steel/lead pipes get replaced with plastic ones.