Garden room and PME

[Grif]

Ok I hope there are some electricians on here that may be able to shed some light on this....I've had a garden room built last month and when their electrician came to do the 1st fix he said I needed a PME terminal so I get hold of uk pwer networks who came out yesterday (4 weeks was their 1st available appointment) and their guys were completely baffled, he said I have an SSE supply with a good earth and it's not necessary to change to PME and they would only do that if they were going to cut the incoming mains cable, to move the meter for example.

In the mean time the room has been finished, it has its own consumer unit and a large armoured cable runs to the house and is connected to the consumer unit under the stairs. This was all done by their part p sparks who has left it all hooked up and switched on and says "you've got a good earth, its just the wrong type of earth" but won't issue the certificate until I have a PME terminal.

I'm waiting to hear back from them but would be very grateful if any one can help explain what the heck is going on here!

 

[bernardgreen]

Exporting a PME earth to an outbuilding is not the best option and in some circumstances is NOT permissable.

Exporting an earth means using the "earth" in the house as the earth in the outbuilding.

The outbuilding can have its own earth by using a ground rod. The armour of the cable from the house is connected to the house earth for protection if the cable is damaged. The armour is NOT then connected to the earth in the outbuilding which is connected to the ground rod.

 

[ericmark]

I am baffled as to what a SSE supply is. The supplies are normally either TT (earth rod) or TN (supplied by DNO) the TN is further divided into TN-S, and TN-C-S there are others but not as far as domestic goes.

The TN-C-S is basic new name for PME there are slight differences but not really going to concern you.

When exporting a supply from the house we have to basic do a risk assessment and decide if the earth can be exported or if we can use the house earth. Exterior metal work both house and outbuilding and distance between them we all be considered.

But we can only really work with what we have and asking for the earth to be changed by DNO is not really an option. The DNO have to ensure the earth on one house will not result in danger if different to next door house so often they can't change just one house in a row.

I would say the electrician should not make a system live if he is not prepared to raise paperwork. I have in the past fitted earth rods knowing full well when DNO arrives it will change name form earth electrode to extraneous-conductive-part and will not be required but to provide power in mean time it was required.

I think maybe some thing has been lost in the telling of the tail?

 

[EFLImpudence]

Scottish & Southern Electricity

 

[westie101]

I would suggest that he has a TN-S supply based on the DNO comments, that thee electrician is saying PME is better is a load of rubbish.

I see it time and time again that there seems to be a fixation (even on here at times) that PME is the way to go!

It isn't!

The electrician IMO has no right to withhold a certificate, if the existing earthing is acceptable
(or is it he is hoping that the reduction in the ELI will bring his results for the garden room into limits to cover up a poor design?)

 

[Grif]

I think maybe some thing has been lost in the telling of the tail?

Quite possible. I thought he said SSE but I could be wrong. He did show me the the earth cable coming from the mains cable coming out of the ground and said it was attached to the lead armour. So T-N?

The room is about 20 meters from the house consumer unit and is connected with 10mm swa, no external metal work that I can think of.
When the garden room electrician did the first fix, it was the first thing he said when he looked at my board, "you need a PME terminal", before he had done anything else?

 

[westie101]

"you need a PME terminal", before he had done anything else?

i think you need to ask him to explain clearly why, the DNO staff are quite correct in what they say so get him to talk direct to them to agree the solution.
As said there is no need for one anyway

 

[Grif]

Thanks for the replies so far guys! I'm happy that the DNO (what does that stand for?) guys were completely on the level with me and he even left me his managers number which I've passed on to the electrician and asked him to speak to him direct. I'm much less happy with the electrician as he seems quite happy to leave me completely in the dark (no pun intended).

 

[westie101]

DNO = Distribution Network Operator

I had the same yesterday with a customer saying an electrician had advised him to get PME, took some time to explain why it was a bad idea (apart from the cost)

 

[Grif]

double post

 

[bernardgreen]

I wonder if the "electrician" is a qualified electrician. Might be worth asking if he is a member of any recognised scheme.

 

[westie101]

I wonder if the "electrician" is a qualified electrician.

I was told yesterday the the electrician, who he wouldn't name, was vastly experienced and knew what he was talking about!
I asked then if my 40 years as an electrical engineer counted for nothing? Pointed out that I was prepared to put my opinion in writing and asked did he think the electrician would.

That shut him up!

 

[Grif]

Pretty sure he is part p and an NICEIC member, the garden room company subs out to him, but that does not make me any happier I must admit, although better than not being qualified I suppose.

 

[Adam_151]

Could it be that the electrician measured a high Ze and the DNO bloke either just looked at the service and never took a loop reading, or did so with the bonding in place.

Just to give the flip side.

of course if the electrician explained his reasoning for wanting a PME terminal it would save everyone a lot of guessing!

 

[ban-all-sheds]

Thanks for the replies so far guys! I'm happy that the DNO (what does that stand for?) guys were completely on the level with me and he even left me his managers number which I've passed on to the electrician and asked him to speak to him direct. I'm much less happy with the electrician as he seems quite happy to leave me completely in the dark (no pun intended).

Have you paid him anything yet?