Advice please re Earthing

[nickbrom]

Hi all
would appreciate your advice.. I believe this to be a TN-S system It is in fact at mother-in law's house , planning to fit a new consumer unit.

The main earth bonding obviously does not look like anything i came across in my training. What is the procedure required here?
Secondly there is only one bonding conductor going from here to the gas and water, which are next to each other in the larder. the conductor goes to the water pipe and then a tail goes from there to the gas. The continuity reading for the cable is 0.28 ohms.

have attached a pic .. hope this makes sense

cheers

nick

 

[tony mc]

That does not look good at all a few more pictures would be helpful.

It looks like a DIY TNS job but you really need that looking at.

If this is your first attempt at replacing a CU I would strongly recommend you get someone experianced to go over thing with you before you start IMO!

As far as the gas and the water is concerned re bonding they can be on the same unbroken cable but 0.28 ohms is a very high reading what is the CSA of the cable and how far is the run?

 

[nickblake]

You dont need seperate bonding conductors for water and gas as long as the cable is continuose , you are right when you say its a TNS system a dodgy one mind not quite sure about the earth connection it looks like a piece of builders band which is not very clever, the cut out is very old could be a good idea to get the DNO out and give it the once over , the continuity reading for a bond appears very high, i would expect it to be less than 0.10 ohms , but that depends obviously on the length of the cable run and the size of the cable , what was the Ze reading TNS it should be no more than 0.8 ohms this will be with the CDU earth and the Earth bonds disconnected

 

[Des 56]

The suppliers fuse was probably once in a metal enclosure with the strap that you see, bolted to the housing of the enclosure
The strap then left floating when changes were made,probably by the supplier
The connection itself may very well be a good one
If so your earthing conductor can be lugged and bolted onto the strap if readings permit

 

[topquark]

There is a sticky thread on CU changes. You should have a read of that. As a minimum you should check Ze, check for borrowed neutrals, IR test the installation (as a whole, not necessarily down to each individual circuit (unless you find a problem when checking the whole installation)). You should do this before changing the CU (and fix (or get the DNO to fix) anything you find wrong).

Edit: sticky thread is here: http://www.electriciansforums.net/e...ctrical-regulations/12971-cu-changes-you.html

 

[nickbrom]

thanks guys am going back tomorrow, so will confirm the CSA of the cable and the test the continuity again. At a guess 5 metres max.

 

[nickblake]

5 meters and 0.28 ohms i'd be suprised if the continuity reading was any more than 0.03 ohms on that length, did you zero the leads before testing

 

[topquark]

5 meters and 0.28 ohms i'd be suprised if the continuity reading was any more than 0.03 ohms on that length, did you zero the leads before testing

I thought that was the CSA of the cable

 

[Engineer54]

You wouldn't happen to be in the WPD area would you?? I'm reliably told that is the sort of earthing arrangment that some of there employee's provide at service cutouts??? lol!!!

 

[nickblake]

I thought that was the CSA of the cable

there's a thought on a CSA of 5 meters what length would the cable have to be to get a reading of 0.28 ohms

na im off for a beer

 

[Knobhead]

That looks like perforated copper tape to me. It used to be used a lot up to about the 70’s. Just terminate it to a MET block and work from there.