TNS / TNCS supply balls up can someone shed some light????

[lloyd1980]

Hi all

Had a bit of an unusual one today and would like some advice please.

Did some work in a property, tested it and the system on first inspection looks like a TNCS
with the earth combined with the neutral at the cut out.

now here comes the unusual bit, at the bottom of the drive (big house) where the supply comes down off the pole there is a BS1361 cut out in a make shift brick housing with no door open to the elements, the cable feeding the house is just supplied from the top of the 'garden' cut out.

NICEIC inspection today and that was one of the houses I took him to, The ZE when i tested it at the board for certification was 0.34 so just under.
Tested it today with NIC man there and it came back at 0.45.
He then starts jumping up and down, take him to 'garden' cut out and he nearly has a heart attack.
Scot power manweb happen to be out in st. He collars them and TBH they were less than interested and told him to call head office.

NIC guys seems to think orig builder has been given the manweb quote to run cable through garden 100m to house, it would have been a lot of money and has told them to drop supply at edge of premesis, then got his spark to run the cable to feed the house and dabbed it into the 'garden' cut out.

At the moment the earth is shared with the neutral all the way back to the transformer and is showing at o.45 ohms

manweb have supplied a cable to garden cut out which is TNS with a clamp around the armour

manweb would allow 0.8 as TNS, where do I stand?????????
NICEIC guy is talking about earth rods if theres no earth at the pole and then none of the MCB's tripping due to high impedance so therefore needing RCBO's and complete change of dis -boards

I told the homeowner of all this today and he basically kicked off at me saying its been fine up to now , then asking me to tell him exactly what difference it makes to him if his daughter puts her finger in a socket, he knows he has an earth as its reading 0.45
if it was connected to armoured you would be allowed 0.8
I was on spot and couldnt give him a def answer as surley the RCBO/MCBS would still trip

What is the exact threat this poses to him????

If anyone can give me the answer id be gratefull , spent hours trawling through 7671 with no joy, the cust obviously thinks im trying to stretch the job and would just like to give him a definative answer.

very frustrating day all in all

 

[nickblake]

well what a situation one good thing comes out of it scottish power dont give a monkeys even to an NIC inspector ,welcome to our world
well where are the meters in the house or at the pole , if its TNS like you have said then you are correct in the 0.8 max readings , now if your test resaults fall within the permited maximuim as set out in BS7671 for the protective device used then i think you will find that the protective device will disconnect in the required times think what you need to do also is ring scottish power and ask a representitive to visit the site with you to give you more advice etc and always keep the NIC informed of what you are doing IE send the correspondance its a difficult situation you are in but im sure with some proffesionalisum you can get through it good luck mate and keep us up dated

 

[Chr!s]

Did some work in a property, tested it and the system on first inspection looks like a TNCS
with the earth combined with the neutral at the cut out.

What type of cut out is within the property?

with the earth combined with the neutral at the cut out

That would mean you have a pen conductor Reg 543.4.2

now here comes the unusual bit, at the bottom of the drive (big house) where the supply comes down off the pole there is a BS1361 cut out in a make shift brick housing with no door open to the elements, the cable feeding the house is just supplied from the top of the 'garden' cut out.

What size 1361?

NICEIC inspection today and that was one of the houses I took him to, The ZE when i tested it at the board for certification was 0.34 so just under.
Tested it today with NIC man there and it came back at 0.45.
He then starts jumping up and down, take him to 'garden' cut out and he nearly has a heart attack.
Scot power manweb happen to be out in st. He collars them and TBH they were less than interested and told him to call head office.

It wouldn't be the dnos responsibility to protect the distribution circuit.If your testing at the property that wont be your Ze, your ZE will be at the cut out in the garden.

manweb would allow 0.8 as TNS, where do I stand?????????
NICEIC guy is talking about earth rods if theres no earth at the pole and then none of the MCB's tripping due to high impedance so therefore needing RCBO's and complete change of dis -boards

The distribution circuit needs sorting for starters

 

[lloyd1980]

What type of cut out is within the property?



That would mean you have a pen conductor Reg 543.4.2



What size 1361?



It wouldn't be the dnos responsibility to protect the distribution circuit.If your testing at the property that wont be your Ze, your ZE will be at the cut out in the garden.



The distribution circuit needs sorting for starters

I kniow what your saying about the Ze being at the garden cut out, but then that would mean the cable from there to the house cut out would need a ZS taking
where would I clarify that on the terst sheet? what would be its circuit description prtective device , surley not the garden cut out?

what danger does it pose to him? I obviously see the NICEIC guys point, I see scot powers point in that they have just suppied a cable to the end of the garden (assuming this at min) and I see the homeowners point of why does it make a difference to me??

the Cut out in the house is 100A and has a cartrige fuse in the live and neutral. its double the width of a 1361, I called it a 1361 as not sure BS number. the cut out in garden is same as one in house, , not opened up garden one to check rating.

where do I stand its a nightmare, the cust is a regular customer and unless I can win him on side he is blatently thinking im screwing him and Ill lose his custom.

rock and a hard place!!!

oh and I dont even want to go near the old metal 3 phase wylex dis board(single phase supply with phases linked out)
I did alterations on lighting cct, installed mini CU fed lights from this and the faults were horrendous.
It frankly scares me at the amount of possible work he is potentially going to pay for and whether I can really be that bothered with the hassle of a snotty customer combined with a potential fight to be paid

 

[lloyd1980]

well what a situation one good thing comes out of it scottish power dont give a monkeys even to an NIC inspector ,welcome to our world
well where are the meters in the house or at the pole , if its TNS like you have said then you are correct in the 0.8 max readings , now if your test resaults fall within the permited maximuim as set out in BS7671 for the protective device used then i think you will find that the protective device will disconnect in the required times think what you need to do also is ring scottish power and ask a representitive to visit the site with you to give you more advice etc and always keep the NIC informed of what you are doing IE send the correspondance its a difficult situation you are in but im sure with some proffesionalisum you can get through it good luck mate and keep us up dated

the meter is at the house and when I was installing a new mini CU I had a look and the spark or whoever had done it had taken the neutral tail on consumers side of meter and connected it into the supply neutral at the side of the cut out dodgy)
I reinstated it into the meter.

its connected at the house as a TNCS so the earth is WITH the neutral, at the garden its just live and neutral out top of cut out with no earth connection made so earth is with neutral all way to transformer.
scot power have provided cable from pole to cut out which is TNS with a clamp to be earthed to

so the earth provided isnt attached to anything the house just happend to have an earth as theyve stuffed the earth in with the neutral

its reading at 0.45 where do I stand and how do i explain potential risks to the homeowner

 

[IQ Electrical]

You have a fused neutral too?

This is interesting, are you 100% sure that the cable to the house is not a DNO cable?

Is there a meter in the garden incomer cabinet?