What on Earth !!

[mikep]

Will be fitting a new boiler in a 1934 house in the next street to mine, all other houses TNS, checked CCU, new Wylex pop out Mcb's fitted 15-18 years ago 16mm bonding to services but noticed no main earth conductor connected to the incomer armour, looks like it has never been fitted ( no Marks on DNO SWA)

Whoever wired it has just left a 10" 16mm lead from the MET ready to connect to the SWA

Tested Ze on Met 0.08 ohms, pfc of 3.1KA, @ 248volts

Do I just call in EDF and let them sort it out,

I suppose they'll TNCS it if it has a high resistance on the Armour's Earth.

Many thanks All, Mike

 

[Evans Electric]

There are only two choices , methinks, either request an earth connection from the network or put a rod in and make it a TT system. Your Ze reading is , I presume, from the bonding on the water pipes.

 

[mikep]

Yep, Not allowed to be used as an earth I Know, but it has been like it for over 15 years, I think I will call Electrically Dumb Folk ( EDF ) and let them call the shots,

First Choice: TNS

Second choice: TNCS

Third Coice: TT

Mike

 

[Evans Electric]

Sounds good to me , Mike.

 

[Apache]

Yep, Not allowed to be used as an earth I Know, but it has been like it for over 15 years, I think I will call Electrically Dumb Folk ( EDF ) and let them call the shots,First Choice: TNS

Second choice: TNCS

Third Coice: TT

Mike

Many on here would disagree and suggest TT as first choice!

Are you new? Welcome if you are!

 

[mikep]

Yes new on here,

And the reason I thought of TNS first is that all the other houses are, and that they would do all the work rather than me !

 

[Apache]

Yes new on here,And the reason I thought of TNS first is that all the other houses are, and that they would do all the work rather than me !

lol - can't argue with that as an answer!

(TT you can get on with it - don't need anyone else involved )

 

[M107]

I'd TT it & slapped in a 30mA rcd on the tails as an intrim fix, with an advice notice to the customer about a cu change

 

[electricalvillage]

Will be fitting a new boiler in a 1934 house in the next street to mine, all other houses TNS, checked CCU, new Wylex pop out Mcb's fitted 15-18 years ago 16mm bonding to services but noticed no main earth conductor connected to the incomer armour, looks like it has never been fitted ( no Marks on DNO SWA)Whoever wired it has just left a 10" 16mm lead from the MET ready to connect to the SWA

Tested Ze on Met 0.08 ohms, pfc of 3.1KA, @ 248volts

Do I just call in EDF and let them sort it out,

I suppose they'll TNCS it if it has a high resistance on the Armour's Earth.

Many thanks All, Mike

Mike, You tested Ze at the MET without connection to the providers earth facility? The 10" of 16mm is not connected anywhere? Forgive me if I've misunderstood

 

[mikep]

To clarify, just banged the fluke on the met just to see what the path to earth was through the gas & water pipes, I have explained to the customer that you are not allowed to use the other services for earthing and that they have done so since it was rewired 15 years ago !

Anyway think I will phone EDF in.

See what they want to do

Mike.

 

[green-hornet]

Yep, Not allowed to be used as an earth I Know, but it has been like it for over 15 years, I think I will call Electrically Dumb Folk ( EDF ) and let them call the shots,First Choice: TNS

Second choice: TNCS

Third Coice: TT

Mike

First choice TNS = Broken earth caused by corrosion failure to detect leaves properties without any earth, bad practices in connecting the earth strap to the cable leaves a poor connection, different metal types cause metturlurgic reaction and connections fail.

Second Choice TNCS = End of loop normally outside the 0.35 maximum required, bad installation problems on any neutral reduces earthing arrangements, any main fault on the supply side could raise the earth potential to an effective 240 volts, any cable taken outside could be extremely dangerous as the ground potential differs so greatly with the pme earthing.

Third choice TT = A safe and effective means of earthing, when properly connected and arranged the safest local earthing arrangement you will find.

Offers more flexability in design, and is far easier to maintain because the consumer and not the supplier is in control of maintenance.

So I guess I would prefer TT, but each to their own.

 

[mikep]

Blimey when put like that It is more understandable that TT is the way to go, the thing is I am not involved with it yet so thought best to leave it with the customer & DNO, then I can get involved later if required.

let you know what happens.

Many thanks, Mike

 

[mikep]

Forgot to say will go back there in a couple of weeks to fit the boiler but will have to see what happens first.

Mike

 

[Andy™]

First choice TNS = Broken earth caused by corrosion failure to detect leaves properties without any earth, bad practices in connecting the earth strap to the cable leaves a poor connection, different metal types cause metturlurgic reaction and connections fail.Second Choice TNCS = End of loop normally outside the 0.35 maximum required, bad installation problems on any neutral reduces earthing arrangements, any main fault on the supply side could raise the earth potential to an effective 240 volts, any cable taken outside could be extremely dangerous as the ground potential differs so greatly with the pme earthing.

Third choice TT = A safe and effective means of earthing, when properly connected and arranged the safest local earthing arrangement you will find.

Offers more flexability in design, and is far easier to maintain because the consumer and not the supplier is in control of maintenance.

So I guess I would prefer TT, but each to their own.

but at least with a TNS failure, you usually still get a reading similar to what you would on TT. unlike TNCS...