New service head/cut out. Which earth should i go for?

[omega015]

I called the DNO for my area yesterday afternoon to enquire about what earth arrangements my area might have. The lady just said your electrician will know as we don't. The reason for me asking them is it doesn't appear I have any main earth. It looks like I have some supplementary bonding but I still need to investigate those connections to confirm. While on the phone not getting any information she just offered to sell me a PME, but I mentioned that my service head is the old cast iron type with possible asbestos, fused neutral, ceramic holders etc... and are these being replaced as a matter of course (hoping they would in which case I would get my earth). I mentioned flickering lights too in which case she says ooo that would be an emergency and engineer will be out in next 3 hours. oh S*** I thought best finish work early as I have some work to do (as the CU, meter, cutout is all at the back of a corner cupboard in the kitchen and pretty inaccessible for most.

so off I rushed home and cleared the cupboard out, had to remove the built-in fridge and some other panels my poor kitchen...

the guy arrived, declined the offer for a cuppa and went straight to it. opened main cut out, gave all cables a good wiggle and tightened everything up (as it was the lighting flicker fault he was here for) and even tightened up all connections in my CU. did some readings between L - N on their side and said all seems well. but said I had never had an earth and he would put in for the cut out to be replaced in which point I should get an earth from the sheath. so I am guessing I will then have an TN-S system. he did say he suggests thinking about PME (TN-C-S) and paying for this would speed up the cutout replacement.

my question is......(finally I hear you all say)..... should I stick to the TN-S or go for the TN-C-S? or wait until the cutout has been done, and have a spark check the Z's on the TN-S and go from there? does going down the TN-C-S router afterwards mean they will disconnect the earth from the Sheath or will I have best of both then?

all this comes about as I am having some work done and pretty much getting the whole house rewired (slowly mind you) and will be getting the CU replaced and moved after I get the supplier to move my meter and fit an isolator. they did offer to upgrade the tails too but the guy last night said they were 25's already. And he also told us that there was a recent death of a guy changing a cutout so its now mandatory for them to cut the service outside before changing them so he said they will have to dig up some of my drive. which is ugly concrete anyway, but I am also wondering is this a job to be completed in one day (including filling the drive back in with concrete) or will this be a couple? as I ask this because I was contemplating running some MDPE pipe for water and some SWA cable to the garage which is about 1.5meters from the house anyway and if they're digging up between the two then seems like it could be an ideal time to do that?

and as you all love some pics here we go.....

Untitled

• omega015
• 4 Dec 2013
• 1

Untitled

• omega015
• 4 Dec 2013
• 1

 

[PrenticeBoyofDerry]

I would personal prefer a TN-S but an TN-C-S would be fine, the main concern is getting it sorted immediately!

They do require to isolate the supply to work on it and normally the DNO are quite quick in doing the digging, jointing and back filling, providing the weather is fair.
But there has been occasions where they have left the hole for weeks on jobs that I have worked on.

 

[omega015]

Sorry I thought of another question.... on the PME application form it mentions...

The providing of a PME connection is not just the fitting of an earth connection; your own electrical
contractor has a requirement to ensure that the wiring of the property complies with BS7671
(IEE wiring regulations) Once tested your contractor will provide you with a certificate which you should
retain.

I assume the sparky wont be providing anything until all the work has finally completed, and moved the CU to its new location and tested and energized. But what does BS7671 state/require?

Currently there is an RCD (but lights and garage and boiler are not on that side) and a good chance of supplementary bonding but would the DNO require something now in terms of paperwork or testing before the replace the cutout? or would this only be needed if I applied for PME? the ultimate goal is the new CU will be 17th ed. high integrity in its new location. But this wont be till after Christmas.

npower just rang and they wont move the meter to the other side of that internal wall so looks like my cutout, meter and new isolator which is confirmed for Friday the 13th (hope that's not an omen) will all stay in that cupboard for now. But.... this does lead to a further question. I have heard about maximum of 3meters for tails (or something to that affect) but as the isolator will now be in that cupboard and I want the CU moving to the other side of that wall I think the distance will be around 3-5meters from the isolator to CU. will that be an issue? or because its after the isolator it doesn't matter (and it will not be plastered over or anything.

 

[PrenticeBoyofDerry]

I assume the sparky wont be providing anything until all the work has finally completed, and moved the CU to its new location and tested and energized.

The electrician cannot complete the documents and issue certificates, until they have done inspection and testing, the final stages of testing involves energising the installation and includes function tests.

But what does BS7671 state/require?

Many things, there are many requirements within in it, that will all be dealt with by your competent electrician.

Currently there is an RCD (but lights and garage and boiler are not on that side) and a good chance of supplementary bonding but would the DNO require something now in terms of paperwork or testing before the replace the cutout?

They are not concerned about the consumer side, I have not been on a job where they have asked the client for any documents regarding the customers installation.

I have heard about maximum of 3meters for tails (or something to that affect) but as the isolator will now be in that cupboard and I want the CU moving to the other side of that wall I think the distance will be around 3-5meters from the isolator to CU. will that be an issue? or because its after the isolator it doesn't matter (and it will not be plastered over or anything.

If in an isolator is to be installed you should be fine.

 

[omega015]

thanks for all you help and replies. I think I will let them change the cutout in their own timescale instead of paying for it and see/hope they put an earth there for me. and thank you for your response

next update will be when the next stage happens

 

[PrenticeBoyofDerry]

I think you should sort out your earthing arrangement immediately regardless of any cost incurred, you need it to be safe!

 

[omega015]

I think you should sort out your earthing arrangement immediately regardless of any cost incurred, you need it to be safe!

yeah good point, ill give them a call to see where things stand.

 

[Taylortwocities]

DNO are quite quick in doing the digging, jointing and back filling, providing the weather is fair.
But there has been occasions where they have left the hole for weeks on jobs that I have worked on.

Usually its a different gang that fill in the holes, it all depends on their scheduled coffee break load.

 

[skenk]

Last time I reported a 'no earth' (there was one under some tar connected to the steel tape sheath but the sheath had apparently failed upstream) the DNO came that day and fitted an upfront 30ma RCD them left it without an earth for 2 months before digging up the garden and replacing the cable.