A little assistance please Re: TT System, 0.21 ohms on Earth Rod.

[1shortcircuit]

Good afternoon everyone, I'm just looking for a little friendly advice if I may.

I have been to a property to price up installing an Extractor fan (via lighting circuit in Bathroom) and a FCU for a combi boiler.

Before work was due to commence I noticed that the Main Earth was completely uninsulated, exposed to touch and running across the top of a carpet before disappearing under the floor. I advised the client that this would need to be replaced as under fault conditions this could create the risk of electric shock or even a fire.

Now on further investigation I got a reading of 0.21 ohms, I was very surprised. However, I cannot locate the earth rod. Once the cable goes through the boards it disappears through the wall (beneath the lounge area) which has laminate flooring.

Now I'm going to contact Elecsa about this issue but as I do not encounter many TT Systems I would like to hear other peoples opinions.

There is NO RCD protection at all, whether it be for the circuits OR upfront.

I am of the opinion that regardless of what I do I will not better the reading by positioning a new accessible rod outside of the building.

Who else would advise that the circuits to be worked on are protected by a 30mA device and an upfront time delayed RCD? How would you protect the uninsulated main earth? trunking? Be stuffed if I'm going to try and sleeve it :lol Trunking would eliminate the touch factor but risk of fire???

Client is not wanting to spend anymore than is necessary but is about to rent the property out. What should I be advising as a MINIMUM that is not likely to be contradicted by another spark? (lol)


What are the requirements for a property being rented out with regards to the electrical installation?

Any advice will be VERY VERY much appreciated, like I said I will be contacting Elecsa for their view too.

Kind Regards.

1SC

 

[Richard Burns]

If you have a Ze of 0.21 then you would not need to provide the upfront time delay RCD as you would meet disconnection times with the OCPDs.
Obviously you would need the 30mA RCD protection for your circuits (assuming spur is subsurface cable).
Regs wise the earth rod connection should be accessible, so i would try a bit more searching to find it, might be worth asking if an extension has been built and covered the rod!!. Have a wander in the garden in line with where the cable enters the lounge.
Insulating the main earth or replacing (part of) the cable would be good.

I think you have covered what is required in post 12 "

My first advice was, Replace uninsulated main earth - Then discovered that the rod (?) was not accessible, bonding to gas upgraded and taken to consumer unit main earth, circuits to be worked on protected with 30mA device/s."

For the landlords part I believe if it meets BS7671 it will meet the landlords requirement. There is this document from ESC about landlords requirements that may be useful.​

 

[Marvo]

If it's a TT system and you can't find the rod then you don't know where the 0.21ohm reading is coming from and you don't know if it's a reliable setup. I would definitely install a new rod and leave the existing earth wire connected as well after sleeving it.

That .21 reading isa bit too good to be true so I would be suspicious. I might consider putting 40A through it with a loop impedance tester and see if it's got any integrity as long as it's not connected to a gas pipe

 

[trev]

If there's another room which is not covered by laminate flooring could you not lift a few boards there and get into the crawl space underneath as there is often a way through the brickwork supporting floors which might give you access to the rod. At the very least you might be able to trace the cable a bit more.
Well when I say could YOU, i meant send your apprentice

 

[Spazz]

That really dont sound like a TT system with 0.21 ohms.
Call the DNO up and tell them the situation - it might be a cowboy TN-C-S or TN-C.
They should have a record of what is installed, if not as said above could be using a water pipe - way to tell is do a Ze test using a socket and a water pipe as the earth - if you get a lower reading than 0.21ohms then its using the water pipe - try and get as close to the origin of the water pipe as possible to get the best reading and away from the bonding clamp.

Good Luck

 

[trev]

That really dont sound like a TT system with 0.21 ohms.
Call the DNO up and tell them the situation - it might be a cowboy TN-C-S or TN-C.
They should have a record of what is installed, if not as said above could be using a water pipe - way to tell is do a Ze test using a socket and a water pipe as the earth - if you get a lower reading than 0.21ohms then its using the water pipe - try and get as close to the origin of the water pipe as possible to get the best reading and away from the bonding clamp.

Good Luck

TN-C is severely restricted in this country mate, I've never seen one in 33 years in the game.
If his measured Ze is 0.21 how is he likely to get a reading lower than this and if by some chance he did, how would that prove the installation is using the water pipe as it's method of earthing?

 

[Rockingit]

Ermmm...is it too obvious a question to suggest that this might be an OLD cable running to an OLD rod/pipe/creaking stair/whatever and the property has had a PME upgrade?

 

[Spazz]

I know that TN-C is restricted in this country - but we dont know what type of property it is or what it was used for

With the Ze - you have a resistance on the cable - yes I only know that its a very small resistance but might be enough to detect on the Earth Loop Impedance meter. - it may give an idea - the other option is always disconnect the bonding cable off the water pipe and do one on that - that will show the Ze of the pipe as an earth rod - it will either be the same or different - if its the same its using the water pipe - different there is a rod somewhere or its TN-C-S.

I have never come across a TN-C either - was just a suggestion

 

[1shortcircuit]

Here we go, I've uploaded a few pictures that I took at the time that I was having a little poke around :thumbsup

 

[Guitarist]

How did the Big Country song go??? "Walk away, walk away...."

My favourite photo is the one with the pipe lying on the ground...

 

[Richard Burns]

Interesting, looks like the room/hall with most of the photos is an change/extension to the original building, photo 14 shows that the earth and water(?) bonding are very close. (nice lead piping!). I would say that the earthing was committed under the floor with the lead piping.
Sorry, the earth rod would be just by that wall and rod (if any) is under the floor by the water pipe (or IS the water pipe).

Can you trace the bonding from the water pipe to where it goes up through the floor and see if it is connected to the earthing conductor?

 

[Had8Lives]

Simplest way to find out if the bare main earth connects to the water pipe is to turn off the main switch, disconnect the bare earth from the board and test for continuity to the water pipe :-D With regard to RCDs, suggest to the customer the installation of one 30ma RCD in the main tails (the live one looks like it's perishing at the main switch anyway) on the basis that putting the RCD in will cost less than a compensation claim or the death of a tenant from electricution.