Is a borrowed earth allowed?

[a-z electrics]

Done an EICR yday on an old house and all ok apart from 2 issues..
1) 32A cooker circuit had high resistance pec continuity (over2kohms) ALTHO it did buzz out on my voltage probes. Hence not able to get a Zs reading and no rcd tripping. The dual rcd consumer unit was fitted 10 yrs ago and those test readings all available and fine. Kitchen was refitted 3 yrs ago and no docs available so they extended original cooker cable prob from the switch which is now tiled over somewhere.
.. I've put in an earth wire link from an immediately adjacent rfc socket into the cooker switch and this solves this problem.
Question .. is this ok as a permanent solution if i label up what ive done?
2) lowish IR readings 1.75M L-E and N-E on light circuits and one rfc but possibly in hindsight due to some bulbs, fan and appliances still plugged in. Could this account for it?

 

[Midwest]

Not like you . Promotion has mellowed you.

He is coming over a bit mellow at the moment. How long before his moustache slips?

 

[ruston]

When Elsparko comes back.

 

[buzzlightyear]

He is coming over a bit mellow at the moment. How long before his moustache slips?

YEAP .

 

[westward10]

I meant Midwest... sorry Westy!

He needs to change his name. Something more befitting a Moderator.

Open to suggestions providing it doesn't contain the word head and other body parts.

 

[DieselShunter]

I agree with Westy, the circuits cannot now be independently isolated, anyone working on the RFC in the future could potentially get a shock from the cooker circuit in the event of a fault on the cooker.
It is as BL says like borrowing a neutral, as soon as that link is disconnected there could be a potential difference between the two earth conductors.
Big problem with temporary repairs is that they have a nasty habit of become permanent repairs!
Also, what has now been done must surely screw the test results for the RFC, so how do you document that in the EICR?
Correct thing to do would be to isolate the cooker circuit and label it saying it is not to be used until remedial action has been carried out and document that to the client.

Borrowing a CPC is not the same as borrowing a Neutral. The Neutral is a live conductor whereas the CPC is not.

 

[Deleted member 9648]

Personally I would be reluctant to do it, but as far as I can see it complies. More of a concern is that the OP suggests the cooker circuit was extended during the kitchen refit and the joint appears hidden, if they didn't bother with the earth makes you wonder what the other connections are like.

 

[westward10]

Essentially the best course of action is to further investigate and if necessary rewire it.

 

[Wilko]

Hi - to me that circuit is proven to have a fault and the cause of the fault has not been found. There may be other faults or sections of the cable without CPC. CPC for 6mm is typically 2.5mm and the circuit has been returned to service with 1.5mm CPC from another circuit if I've understood correctly (?). I'm afraid this does not pass my sniff test for a fault free circuit, but I'm happy to learn .

 

[a-z electrics]

I'd just isolated the circuit, with clients permission of course.

You've not really done a permanent repair, and now your liable, should anything go wrong. If it was young family or someone frail, then as a temporary fix ok.

So you would have just left an unearthed cooker and microwave (also on the circuit) unearthed would you? Or say to the tenants you can't cook for 2 weeks? I have left it in a safer condition than it was. It is now effectively earthed.

 

[a-z electrics]

bang.

Better go bang than electrocuted..

 

[The Ghost]

I would not do it. For one thing as already mentioned how will you record your R1/R2 or Zs and how will you do IR what will your schedule of results look like? Anyway what I would do is find the fault on the circuit (if ordered to, F.I. in the meantime) rather than this "ad hoc" (to put it charitably) arrangement is it good workmanship (134)? and I would be asking myself does this acheive separation of circuits. And yes as said I would be worried about cross circuit faults increasing risk of shock to livestock or persons. And even if it was acceptable there is a fault identified that should not have been fixed but the person ordering the work informed and possibly (as said) isolated until remedial measures have been taken. As it is the way I read it you have left a fault (F.I.) and it needs to be investigated and fixed.

 

[a-z electrics]

Hi - to me that circuit is proven to have a fault and the cause of the fault has not been found. There may be other faults or sections of the cable without CPC. CPC for 6mm is typically 2.5mm and the circuit has been returned to service with 1.5mm CPC from another circuit if I've understood correctly (?). I'm afraid this does not pass my sniff test for a fault free circuit, but I'm happy to learn .

Not sure I understand where you're coming from.. I've done all the applicable tests, no other faults found.
32 A cooker circuit same as 32A ring circuit. There are TWO 1.5mm earth wires in a ring circuit in these parts, although I grant you in the unlikely event both circuits have a simultaneous earth fault that may stretch things a little but are you saying it wouldn't trip?

 

[a-z electrics]

Thanks for all replies.. I get the gist and will take it up with the client. Just wondered how my temp fix sat with you guys. The cooker switch isn't too far from the fuse box so a new cable is probably best bet.. cheers

 

[buzzlightyear]

I've done all the applicable tests, no other faults found.
32 A cooker circuit same as 32A ring circuit. There are TWO 1.5mm earth wires in a ring circuit in these parts,

I you Have done a Eicr ,then it would be unsatisfactory in my humble option,

 

[a-z electrics]

Not sure I understand where you're coming from.. I've done all the applicable tests, no other faults found.
32 A cooker circuit same as 32A ring circuit. There are TWO 1.5mm earth wires in a ring circuit in these parts, although I grant you in the unlikely event both circuits have a simultaneous earth fault that may stretch things a little but are you saying it wouldn't trip?

Ok I give up, I'm orrffh to cook a curry is my excuse.

My thoughts were that the cpc must remain effective throughout the life of the install. Therefore, if the RFC is altered or removed subsequently, the installer altering/removing may not know the other circuit is reliant on its cpc.

As stated, I put warning labels on the fusebox and at the socket concerned which is right next to cooker switch. Also noted in the eicr..

Trouble is the diffence in size of cpc. 1.5mm on a 2.5mm ring (essentially 3mm) the cooker if in a 10mm t&e.. With a 4mm cpc... 6mm t&e is fine at 2.5mm cpc

Yes cooker wires 6mm and 2.5mm. the link I put in was 2.5mm also..

 

[a-z electrics]

If you got those readings of the same lighting circuit, then I would say there is a fault on that circuit. Did you disconnect the earth and neutral for that circuit out of the board before testing?

Yes..

 

[a-z electrics]

Yes..

Sorry, line and neutrals disconnected, not earths..

 

[Wilko]

Not sure I understand where you're coming from.. I've done all the applicable tests, no other faults found.
32 A cooker circuit same as 32A ring circuit. There are TWO 1.5mm earth wires in a ring circuit in these parts, although I grant you in the unlikely event both circuits have a simultaneous earth fault that may stretch things a little but are you saying it wouldn't trip?

Hi - I agree you've left it in a better state than when you arrived, no question. It should trip if there is an appliance fault. But as it's not been possible so far to find why there is a 2K Ohm CPC then we can't say what has happened to that cable with certainty. So we can't say it won't get worse, whether other conductors have been affected and have reduced ccc, for example. Also, I think there is likelihood that additional protection for cables in walls is now kaput for that cooker circuit, for example.

 

[The Ghost]

Hmmpff bad spelling, that's all I get

 

[Midwest]

So you would have just left an unearthed cooker and microwave (also on the circuit) unearthed would you? Or say to the tenants you can't cook for 2 weeks? I have left it in a safer condition than it was. It is now effectively earthed.

Regardless of whether it contravenes a regulation or not, you have some reservations in your own mind, otherwise you would have not posted about it in the first place. As others have stated, you've done nothing wrong. So leave it as is.

Or you could rectify it, as you feel it should be.