PME (protective multiple earth) for old rewiring.

NelNo

I'm in the process of getting quotes for my house rewiring (its an old house so its a complete rewire job) and a few electricians have pointed out that I need a PME (protective multiple earth) board fitting and that I should contact my electricity providers to do this. I'm with British Gas anybody know what phone number I need to call for this as I dont want to be passed around various departments

One electrician mentioned that this upgrade to the PME shouldnt cost me anything as its the energy companies responsiblity, and isnt really a big job anyone know if this is the case?

Any advise is appreciated, thanks.

tinkerbelle

What you need to do is to find out who your local electric distrubation company is & find the number for the engineering department. The engineering department will raise a job to see if PME is available. The job is that an engineer will check to see if you have PME available in your cable, if PME is available they will advise you to get an electrician to hook you to it. They will not do it for you, iam afraid.

dunloadin

The way the supply to the house is earthed should be irrelevant to the electricians, unless there's no earth at all!! All they need is a point where they connect the earth from the consumer unit to the earth point of the house. Provided by the incomming supply or a copper rod stuck in the ground (common in older properties).

The company who maintains the National Grid in your area (DNO) are responsible for maintaining the earth of your supply...only if they installed it in the first place. This is not BG, the people who you pay your bill to, but if you give them a call they should tell you who the DNO is for your region.

That said, if you have a really old incoming supply head i.e. a cast iron or metal cutout, you can get it replaced for free as these are obsolete, and most DNO's will fit a PME cutout...expect to wait a few months for the work to be done as it's a pretty low proirity job.

NelNo

dunloadin wrote: »

The way the supply to the house is earthed should be irrelevant to the electricians, unless there's no earth at all!! All they need is a point where they connect the earth from the consumer unit to the earth point of the house. Provided by the incomming supply or a copper rod stuck in the ground (common in older properties).

The company who maintains the National Grid in your area (DNO) are responsible for maintaining the earth of your supply...only if they installed it in the first place. This is not BG, the people who you pay your bill to, but if you give them a call they should tell you who the DNO is for your region.

That said, if you have a really old incoming supply head i.e. a cast iron or metal cutout, you can get it replaced for free as these are obsolete, and most DNO's will fit a PME cutout...expect to wait a few months for the work to be done as it's a pretty low proirity job.

From what I remember theres a earth cable screw-tied to a brown cable (or maybe a pipe I cant remember) I know that from checking light switched, sockets etc they have no earth cable.

The electrician mentioned he wont be able to give us a certificate that its being checked if the PME isnt fitted.

dunloadin

Take a look here:

http://www.diynot.com/wiki/electrics:earthing_supply_types_and_bonding:earthing_arrangements

The TN-C-S diagram is PME.

If the earth you described is connected to the main cable below the cutout you have a TN-S system as per the middle diagram. If its a pipe its connected to your looking at your supplementary bonding, if an earth rod then its a TT system.

I know that from checking light switched, sockets etc they have no earth cable.

That sounds a bit dodgy, can see why it needs to be PME, even PME systems have to have earths on the circuits, the earth from the consumer unit should only be connected to the neutral at the cutout.

There's a very good forum on this site with loads of experts who will give you some good advice, might be a better place to ask your question, hope this helps.

wolvotim

If the property is old your local DNO may not give you PME as there are requirements the property has to meet before PME can be given. I have been to a few jobs for work where a customer has been denied PME. Here what our earthing manual says

Central_Networks_Earthing_Manual wrote:

E2.8.5.1 Provision of LV Earthing Terminal
The provision of a LV earthing terminal has been achieved by various means in the past. The
present company policy with regard to the provision of a LV earth terminal is detailed below :-

PME Terminal (TN-C-S)
All new supplies, or existing customers requesting a load increase, will normally be
offered a PME terminal. However, for reasons of safety some installations are not suitable
for a PME earth terminal in which case a TT supply will be offered (see Section E6.3 for a
detailed list of exceptions). Under the ESQC Regulations, the Company is not obliged to
offer a free PME earth terminal to existing customers that do not already have a PME
earth.

Sheath Earth Terminal (TN-S)
The Company has an ongoing obligation to maintain the integrity of the sheath earth
terminal of customers which already have this type of earthing. If an existing sheath earth
customer requests a service alteration or in the event of a fault repair then the existing
sheath earth must be maintained unless the customer request a PME earth terminal
instead. A sheath earth terminal shall not be made available to new customers (or existing
customers if they do not already have an earth terminal).

PNB Earthing
PNB is a special method of earthing, similar to PME, where the neutral earth is installed at
or adjacent to the customer’s installation instead of at the transformer position. This
method can still be used provided the supply is from a dedicated pole mounted
transformer supplying a single customer..
No Company Earth Terminal (TT)
It is not possible for the Company to provide a PME earthing terminal where :-
i) the customer’s installation does not conform to the statutory regulations
regarding the provision of PME supplies.
ii) the customers property is deemed to be unsuitable for a PME supply.
In these circumstances the PME terminal shall be rendered inaccessible to prevent
unauthorised access by third parties and the customer must be advised that it will be
necessary to provide their own alternative means of earth fault protection (e.g. their own
earth electrode and suitably sized RCD).

NelNo

Thanks everyone for all your help, got on touch with both British Gas and YEDL and was shocked at the quickness of their replies (not so fast when you're complaining but fast as anything when you're spending money!). Both are more than willing to fit the PME. YEDL even quoted a price (£160ish) without even inspecting my property!