Earth leakage trips with various appliances

[GaryGarden]

Get the DNO guy to do his bit as you are, if he is happy with all their gear (inc the elcb if they put it in) then you work from there. He will hopefully do some tests see if he is happy to share the results with you, maybe some light can be shed on a few things on here.

 

[EFLImpudence]

It is for personal protection so it must be 30mA.

Not by first intent, surely? We are told that the DNO installed it as a 'temporary' measure when they 'temporarily' (15 years ago) TTd the installation, I presume they therefore installed it primarily to give protection against L-E faults.

Are you saying that they would have paid no heed to personal protection and it should be 100mA?

 

[spinynorman]

The SWALEC engineer just left. He found an imbalance between the N and E resistances and fitted a piece of very thick cable between the incoming box and a junction box with several earth wires connected to the fusebox. Sorry for imprecise terminology! Everything is working now, including the shower, so fingers crossed. I couldn't get a straight answer out of him regarding the temporary nature of the earth spike and ELCB but he said it wasn't an uncommon repair. The ELCB is rated at 63A with a nominal trip of 30mA.

 

[JohnW2]

Are you saying that they would have paid no heed to personal protection and it should be 100mA?

I am saying that, in terms of the temporary repair they were doing, they would have had no need to "pay any head to personal protection" and, for that reason, a 100mA would have been adequate for their purpose. They were simply installing an RCD when they 'temporarily' TT'd the installation because the installation's OPDs would (with the TT rod) no longer afford adequate protection (required disconnection times) in the event of L-E faults.

There either was, or was not, already one or more 30mA RCD(s) downstream of the the one the DNO installed; either way, the DNO would have made the installation no less safe (in terms of personal protection) that it previously had been if they had installed a 100mA RCD. Their job was to restore a safe supply - there is no reason why they would/should have taken steps to improve the personal protection afforded by the OP's installation, is there?

Kind Regards, John

 

[westie101]

Given as well that the DNOs are not under any requirement to provide this protection in the first place as well.

Of more interest is the chance that the DNO pretty obviously forgot about it, as did the customer by the look about it!

 

[EFLImpudence]

Ok.
We don't know when the RCD sockets were installed.

Their job was to restore a safe supply - there is no reason why they would/should have taken steps to improve the personal protection afforded by the OP's installation, is there?

Yet they did.
They must have carried the 30mA device or sought one especially.

It just seemed odd to me that some think it should be 100mA.

 

[EFLImpudence]

From what spinynorman now says -

The SWALEC engineer just left. He found an imbalance between the N and E resistances and fitted a piece of very thick cable between the incoming box and a junction box with several earth wires connected to the fusebox.

Is it thought that they have now converted the installation to TN-C-S.

How can this have resolved an N-E fault?
Unless it was/is a fault to the previous earthing conductor which they have disconnected.

 

[spinynorman]

No alteration was made to the ground spike. The engineer only added that short section of cable. I don't know what failed as nothing has changed in respect of appliances or usage. Until recently I've only ever opened the cabinet to allow access for the meter reader.

 

[JohnW2]

Their job was to restore a safe supply - there is no reason why they would/should have taken steps to improve the personal protection afforded by the OP's installation, is there?

Yet they did. They must have carried the 30mA device or sought one especially.

Indeed they did, but don't ask me why. I suppose they might carry them for use when they use gennys or 'borrow' electricity from a neighbouring property but, I can't really think of any other reason why they should carry, let alone 'seek' 30mA RCDs. maybe westie can illuminate us?

It just seemed odd to me that some think it should be 100mA.

I agree. Of course, if a 30mA one works OK in that position (without 'nuisance trips') then it's even better than a 100mA one, since it affords personal protection (if there aren't any other RCD(s), or other RCD(s) are faulty), as well as doing the job it was put there for. However, there will probably be some cases in which the total installation leakage can, at least sometimes, be >30mA, which I guess is at least one of the reasons why 100mA seems to have become established as more-or-less the 'norm' for up-front whole-installation RCDs in TT installations.

Kind Regards, John

 

[JohnW2]

No alteration was made to the ground spike. The engineer only added that short section of cable. I don't know what failed as nothing has changed in respect of appliances or usage.

Is that new short cable connected to the 'cutout'/'service head' where the supplier'a fuse is?

Kind Regards, John

 

[JohnW2]

From what spinynorman now says -... Is it thought that they have now converted the installation to TN-C-S.

It sounds rather like that. From the OP, it sounds as if the original arrangement (15 years ago, before the 'temporary repair') was TN-S with an overhead earth conductor (which was 'temporarily' used to replace the damaged L one) - which is not something I realised they did. Westie??

How can this have resolved an N-E fault?

Good question. Mind you, maybe it is not resolved - ISTR that the OP said that there had been 'several RCD trips in the last 3 weeks' - so maybe the OP should not count too many chickens a couple of hours after the DNO man has done whatever he's done!

Kind Regards, John

 

[westie101]

Finding a supply without an earth connection is far from unusual.
It is often where the original earthing arrangement was from the metal water or gas supply pipe that have been changed to a plastic pipe.
Back then there was no realisation that the house earth was being provided by these other services so a lot of properties suddenly found themselves to be without an earth.
It was only some time after that these organisations found out about it!!
Interestingly the installing company for the gas and water should have replaced the earth connections - but they never did

So there is a realisation the situations exist and as discovered they are rectified, adjacent properties are also checked and corrected

Indeed they did, but don't ask me why. I suppose they might carry them for use when they use gennys or 'borrow' electricity from a neighbouring property but, I can't really think of any other reason why they should carry, let alone 'seek' 30mA RCDs. maybe westie can illuminate us?

Standard piece of kit, just not for use over this length of time (procedurally)
Usually 40A though we are now using a more advanced version

http://www.kelvatek.com/restore.php

This company has some very interesting gear for fault restoration & locating

 

[JohnW2]

Standard piece of kit, just not for use over this length of time (procedurally)

Thanks. What about the previous 'overhead TN-S', if that's what it was? Is/was that a common arrangement?

Kind Regards, John

 

[Iggifer]

http://www.kelvatek.com/restore.php

This company has some very interesting gear for fault restoration & locating

Bet you/they wouldn't accidentally leave one of those at someones house for 15 years!

 

[westie101]

Bet you/they wouldn't accidentally leave one of those at someones house for 15 years!

Only been approved for use for about 8 or 9 years