Main earth issue

[Scornio]

Hi all, thanks in advance for any helpful comments.

Ive just completed a fuse board change to a flat above a shop. They both have there individual cut outs.
( I also installed main protective boding as there was none is place)

went to do continuity of main earth which I could see at the board, as the cut out was right next to the board I thought this should be easy, except it was not there. So maybe it's a TT? So I completed all other dead tests, all circuits fine. Put board together.
(I rang the dno they insist there is no PME in the area)
I then carried out a ZE Which gave me 0.13 thinking this is pretty good to be a TT I thought this must come from down stairs it appears to the way it goes through the ceiling.
Any how went down to the shop but the owner will not let me have a look, I thought, unhelpful. I rang the dno again and they are going to come down for an investigation hopefully forcing the owner into letting us in.( well not force but you know what I mean)
So what is the position I can leave this installation in? I have no PME except I have a decent earth and in all sense and purposes is very safe.

Thank you for good comments will answer any questions and the end of the working day.

 

[Scornio]

Just thought while
Writing this that there is no pme in the area. So won't be down stairs.

 

[Andy78]

Your post is very confusing.
You could see the main earth but it wasn't there, so you measured the Ze on it ?
You need to get downstairs to see the cutout but the cutout is next to the DB upstairs ?

Can you explain the situation a bit better ?

 

[Kate]

Did you take out the main earth to take your Ze reading?
You may be getting parrallel path readings from the bonding.

I tested a TT system last week, New build. Ze reading was 0.19. Only thing I could put that down to was that its a 25mm earth conductor and it was a cold wet day.

 

[Kate]

I read as...doing flat above a shop. Flat has its own cut out incoming next to that board that appears to be TT.
Ze reading is so low he assumes main earth has been taken off of the main incoming for the shop below that he assumes is PME. But he cant access shop to check

 

[Badged01]

Following on from the above posts, if Im reading this right ......
1) There are two cut-outs. One in the flat above and one below in the shop which you cant access
2) You know the earthing should be TT as the DNO have not PME'd. (and presumably its an old installation?)
3) You can see an earthing conductor at the board "upstairs" but dont know where it terminates "downstairs".
4) When you do a Ze test using said earthing conductor "upstairs" you get a very 'respectable' 0.13.

First thoughts are that the Ze is too good to be true and I would suspect something "fishy" at the unseen end of the earthing conductor! Could be anything from a DIY TN-C-S (perhaps from the downstairs supply?) to a connection to a water/gas pipe to a combination of everything with a TT rod -- the options abound to potentially give a low reading! However, without visually seeing where the cable goes to with the Mk 1 eyeball you cant be sure of anything just yet!.

For me the installation is 'safe' as you have a Ze but clearly it needs further investigation as you cant confirm/deny the source of the earthing meets regs (parallel paths bells are ringing). Be interesting to see if the DNO can shed any further light onto proceedings .......

 

[Andy78]

That's what doesn't make sense Kate. You just don't get DNO cutouts in upstairs flats. I'm assuming now he is looking at an isolator/switch fuse at his DB.

 

[Kate]

That's what doesn't make sense Kate. You just don't get DNO cutouts in upstairs flats. I'm assuming now he is looking at an isolator/switch fuse at his DB.

Ooooooh. Didnt know that was a set in stone thing. Hmmm thinking back to my jobs now the flat DB was always fed from an isolator by the mains incoming in the shop.
Sorry

 

[Badged01]

You just don't get DNO cutouts in upstairs flats.

Whilst generally rare, not always the case. Ive seen a building converted to flats where the basement flat (With its own seperate off-road entrance) had a seperate DNO cut-out to the upstairs flats!

 

[Andy78]

Ooooooh. Didnt know that was a set in stone thing. Hmmm thinking back to my jobs now the flat DB was always fed from an isolator by the mains incoming in the shop.
Sorry

I don't know whether it is a set in stone thing, but I have never seen one, and I just cannot imagine a DNO running an un-isolatable cable vertically through the fabric of a building to the first floor.

I think I may have created a new word in that last sentence.

 

[Andy78]

Whilst generally rare, not always the case. Ive seen a building converted to flats where the basement flat (With its own seperate off-road entrance) had a seperate DNO cut-out to the upstairs flats!

I stand corrected.

 

[Badged01]

I stand corrected.

Nothing of the sort, you just havent come across one yet!

 

[Scornio]

Thanks for the responses... Badge01 has pretty much explained the situation clearer than myself.

The cut out is indeed upstairs and is not an isolator.
I think too that as there is no pme that the good reading I'm getting is because the other end of my earth which I cannot see is attached to the earthing system in the shop. Maybe it was one installation before then got split up but the neccesary earthing was not put in place as is the case usually when dno come along they don't care about an earth and presume an electrician will appear from thin air and install.

 

[GLENNSPARK]

Following on from the above posts, if Im reading this right ......
1) There are two cut-outs. One in the flat above and one below in the shop which you cant access
2) You know the earthing should be TT as the DNO have not PME'd. (and presumably its an old installation?)
3) You can see an earthing conductor at the board "upstairs" but dont know where it terminates "downstairs".
4) When you do a Ze test using said earthing conductor "upstairs" you get a very 'respectable' 0.13.

First thoughts are that the Ze is too good to be true and I would suspect something "fishy" at the unseen end of the earthing conductor! Could be anything from a DIY TN-C-S (perhaps from the downstairs supply?) to a connection to a water/gas pipe to a combination of everything with a TT rod -- the options abound to potentially give a low reading! However, without visually seeing where the cable goes to with the Mk 1 eyeball you cant be sure of anything just yet!.

For me the installation is 'safe' as you have a Ze but clearly it needs further investigation as you cant confirm/deny the source of the earthing meets regs (parallel paths bells are ringing). Be interesting to see if the DNO can shed any further light onto proceedings .......

and judging from experience as well dealing with evasive tennants/owners i`d say there was some power pinching going on as well.....

why else would he deny the O/P access to gain a visual confirmation...

get this all the time...