earth loop help!

[the_flash]

Hi guys just looking for some advice
I moved into my new flat in feb
about a month ago I signed up for british gas's electrical cover and one of their engineers came out and look at my fusebox ect and it turns out that the there is a high impedence value for the earthing loop. the guy from british gas gave me EDF's number to call to get it sorted as they are the main supplier, the problem is that because my place is a flat it means the whole block will need to be shut down to sort it and because of that the maintainence firm who look after the flats(SHAWS) need to be involed. the thing is I'm getting a lot of conflicting messages first EDF said that SHAWS will need to let everyone in the flats know that the electrics will be off then contact EDF with a date when they can do the work. Then EDF told me that they will contact all the flats and sort the work out totally from their end, after waiting a week I phoned EDF for a progress report and they appologised and told me that SHAWS would need to arrange everything and of course SHAWS are dragging their heels and fobbing me off with the usual "we're dealing with it" stuff.
my main questions are: is this a serious problem? who's responsability is it to get it sorted? is there anything I can do to hurry things along?

thanks in adance

 

[JohnD]

start up a Residents Association for your flats and raise it there.

you could possibly also cut out the agent and save them ripping you off.

 

[holmslaw]

..

 

[sparkybird]

EDF, as I'm sure you know by now are a nightmare to deal with. A few of my customers have had more luck (and free earth upgrades, originally quoted at 2K!) by going to customer relations - the number is 0800 0284587.

 

[the_flash]

right thanks for that number sparky, I phoned them and it seems i've got to get the mantenence company out to check if its just my flat that has the problem or if its the supply from EDF so its another call to hml shaw to make sure they are doing their part. just as a point the impedance is 1.08 ohms (ze) how bad is this?

 

[holmslaw]

..

 

[oharaf]

If you have a TT earthing system it's very good!!!

(but I'm sure you haven't)

TNC-S must be less than 0.35 ohms and TN-S needs to be less than 0.8 ohms.

So your Ze is clearly to high and this requires investigation.

By the way did you read Ze by disconnecting the MAIN earth at the CU or did you leave it in place?

Unless you disconnect it from the CU to test you will get parallel paths which will effect your reading!

 

[the_flash]

all I saw was the guy from british gas homecare put a probe onto the cable that was coming in from the fuse box under the stairs in the communal hall and when i spoke to EDF just now they said it should be .8 so that must be TN-S i suppose

 

[oharaf]

Take what EDF say with a pinch of salt.

I have made enquiries on Ze on a number of occasions they always give you the maximum permitted i.e. 0.8 or 0.35 depending on your supply. So yes now at least you know it is TN-S

But who actually knows the exact reading, you'll have to do it

 

[GElec1]

Hi

As a matter of interest could the maintenance company install an rcd on your consumer unit as this would at least add extra protection to your flat.

Arguably, the improvement of the Ze would not be required.

 

[Taylortwocities]

Hi

As a matter of interest could the maintenance company install an rcd on your consumer unit as this would at least add extra protection to your flat.

Arguably, the improvement of the Ze would not be required.

No. The use of an RCD is ONE method where the required Zs (not Ze)cannot be achieved.

It is up to the DNO to deliver a supply that has a Ze of less than 0.35 ohms for TNC-S and less than 0.8 ohms for TN-S.

 

[the_flash]

So can I just ask how dangerous is having an impedence of 1.8? as my wife is now bouncing off the walls as she is sure the flat is going to burst into flames at any moment

 

[pompeygit]

As the internal expedance(ze) is so high basically it means that in the event of an electrical fault the mcb or fuse will take longer to diconnect than is allowed. Say you have a healthy ring circuit (0.5ohms)with a faulty toaster in. The mcb should disconnect almost instantaneously because it will generate a fault current in excess of 160amps.

however, in your case a ze of 1.08 + 0.5 = an impedance of 1.58 ohms. This will only generate 145Amps of fault current which take slightly longer than the required 160Amps to clear the fault instantaneously.

As you can read from other posters your ze is above the accepted norms and you should have had a more concerned reaction from your supplier. Incidentally you mentioned a 1.8 ohms in your last post and 1.08 earlier....which is it. If it is 1.8 then this fault could take 30 secs to clear....much too long for a toaster to carry a potentially lethal shock.

 

[pompeygit]

Correction to 1st senrence.....should read external expedance

 

[ban-all-sheds]

Try again - 3rd time lucky