TN-S & TT on same installation what should I class it as?

[wildgoose]

You think that was close !!!
One of our lads had a wee mishap this morning while installing a stake on a local farm .
It was a 3ph 35mm incomer before he literally blew it clean apart on all 3 phases , the supply side was still live when they got to us !
I knew it was going to be painful when the first two vans turned up but my arse near on gave out when the other three turned up !!!!!!!!!!!!


View attachment 18005View attachment 18006View attachment 18007View attachment 18008View attachment 18009

That was bad luck!

Now the question we are all wanting to ask - who pays??

 

[GLENNSPARK]

My advice is not to make any judgement call on this one. Call in your local supply authority to address this HORROR show
or u could get egg on your face, they can confirm TNS max 0.8 ohms or TNCS max 0.35 ohms for your Ze's
They are normally very helpful and it should be free of charge
Let us all know the outcome

so you would just go with this would you....rather than get a measured value eh?
LOL....

 

[Knobhead]

Could you smell any gas there?
That looks distinctly like a meter union seal lying next to the rod, seen a few of those before! :wink_smile: :smilielol5:

You running the gas meter backwards at the weekends then Archy?

 

[JD6400]

That was bad luck!

Now the question we are all wanting to ask - who pays??

I have already assumed the position and await delivery of the bill while firmly gripping my ankles , with out even a hint of any Vaseline in sight !!!!:blush2:

What do you reckon it will be then ?

A builder we work with hit two only a few months apart last year on a local estate we work for , i think the first was £7000+vat and second was £5500+vat !:dunce2: But in fairness they were both HV underground and not LV like this one .

 

[Miketwinny]

Re: TN-S & TT on same installation what should I class it as?

is the main switch an RCD? cant be a TT if its not.

No RCD protection on the installation.

 

[Miketwinny]

got a 16mm earthing conductor from main supply sheath goin in to the MET + an earth electrode(rod) next to the supply with a 10mm earthing conductor comin off it to the MET
Should I class it as a TT system for test results and mark the EIC as TN-S & TT :nonod: View attachment 17960[/QUOTE

**** me...If this is the way he creates a earth then I think it would be safer without... Close or What

been like that from new 43 years no problems guna do a Ze test soon.

 

[JD6400]

Surely you had a wee peak at that Tx between the shed and the pole? Would yer man not have figured that the cable didn't dissipate through the atmosphere and that it was most likely underground? lol.

It was actually some form of voltage suppressor and not a Tx apparently but that is besides the point , just thought i would throw that in as even the jointer's had not seen one before !

 

[sparkymalarky]

ballpark figure? £750 - £1500? assume to replace cable & labour etc.

 

[JD6400]

I am hoping for something under £2500 , the more under the better !

 

[wildgoose]

I have already assumed the position and await delivery of the bill while firmly gripping my ankles , with out even a hint of any Vaseline in sight !!!!:blush2:

What do you reckon it will be then ?

A builder we work with hit two only a few months apart last year on a local estate we work for , i think the first was £7000+vat and second was £5500+vat !:dunce2: But in fairness they were both HV underground and not LV like this one .

I'm afraid you just can't call it until the bill arrives. On an optimistic note there have been a couple of instances recently where my DNO have charged nothing ?? One was a serious moving of the incoming power so that the client could have the incoming service moved. Cable excavated with mini digger, cut, jointed and extended. All FOC - was Very impressed.

Fingers crossed then

 

[tigi]

Hi Miketwinny

Your original question was how you would class this supply.
Well moving on, that supply cable looks very much like a jute covered, steel and lead covered cable
which would indicate it was intended as a TNS supply. It would be the largest TNCS supply cable i have ever
seen and also the 1st where the N/E was not taken from the service head. This very much looks
like the earth is a sweated joint onto the steel/ lead. As I said on my original post all your asking is for
the supply authority to confirm type of supply.
Just trying to put in some helpful info mate.

 

[baldsparkies]

Jeysuz I can't hardly believe what I'm seeing. - someones driven an earth rod in but an inch from the service mains and the gas mains......

thats more of a worry!

Don't think there is any concern.

If you look closely there is a fresh concrete pour where the services are coming up.
I think you will find the rod was placed in the vertical service trench prior to the concrete being poured.
You would have quite a job driving a copper rod through solid concrete.


TN-S (once proven) and leave it at that.

 

[Engineer54]

Did you test the Ze? What was the TNS Ze?

im just wondering now why on earth that rod is there

This was common practice in the 50's on council estates. Absolutely nothing wrong in it either. Though from the photo, this looks like one of those thin twigs, and if it is, it hasn't been in for 43 years!! They didn't make thin twigs in those day's, they were all 10 foot X 5/8''-3/4'' proper rods in them days!! lol!!

 

[Rampantchilli]

Re: TN-S & TT on same installation what should I class it as?

ballpark figure? £750 - £1500? assume to replace cable & labour etc.

I'd figure much more, my local DNO charge 750 just for cutting a service and terminating in new meter box, and we did the digging, fitted the box and supplied the hockey stick.
7 vans = 7 men times 2 hours and I bet they are close to 750 before the add on any call out or digger or materials

- - - Updated - - -

ballpark figure? £750 - £1500? assume to replace cable & labour etc.

I'd figure much more, my local DNO charge 750 just for cutting a service and terminating in new meter box, and we did the digging, fitted the box and supplied the hockey stick.
7 vans = 7 men times 2 hours and I bet they are close to 750 before the add on any call out or digger or materials

 

[Stroppy]

View attachment 18007
Of all the square inches in all the field, he had to stake into that one. Horrendous bad luck to stake at that exact point and not an inch either side!

 

[SPARTYKUS]

Don't think there is any concern.

If you look closely there is a fresh concrete pour where the services are coming up.
I think you will find the rod was placed in the vertical service trench prior to the concrete being poured.
You would have quite a job driving a copper rod through solid concrete.


TN-S (once proven) and leave it at that.

Who knows!

And yes you are right, driving a rod through concrete would be difficult.

 

[Miketwinny]

Maybe at some point in the past (or from new) the Ze simply wasn't good enough so to lower it or there was a 'long time to fix' fault they knocked a rod in. If it's been concreted/screeded in like that from new suggests to me it got put in when you could see what was going on underneath.

Done a Ze test today 0.16ohm well below the max 0.8ohm for a TN-S system so disconnected the earth rod from the MET and will leave rod alone as now redundent and class as TN-S on EIC.:smiley2:

 

[Engineer54]

Done a Ze test today 0.16ohm well below the max 0.8ohm for a TN-S system so disconnected the earth rod from the MET and will leave rod alone as now redundent and class as TN-S on EIC.:smiley2:

Why disconnect the rod, what harm do you think it's doing?? It was always a TN-S, even before you disconnected the rod!!

The fact is, you now have an extraneous earth, in close proximity to both gas and electrical supply that isn't now connected to the MET!! A bit foolish don't you think?? lol!!

 

[Miketwinny]

Why disconnect the rod, what harm do you think it's doing?? It was always a TN-S, even before you disconnected the rod!!

The fact is, you now have an extraneous earth, in close proximity to both gas and electrical supply that isn't now connected to the MET!! A bit foolish don't you think?? lol!!

True, live and learn.What would you recommend grind rod down and fill hole or just connect to MET with new clamp and 10mm cable.

 

[Engineer54]

Just connect this rod up as it was before, (maybe cut a bit off the top if you want) with as you say a new clamp and 10mm cable. A bit too close to the gas pipe to be playing around with a grinder in my opinion.... lol!!