Broken cpc ring on 30A ring!

[Octopus]

Hi all, I'm new here and looking for some pointers as to how to approach a "problem" I encountered on Friday.

My work entailed adding 2 new fused spurs for outside lights on a house. All was going really well until I got high readings on the earth loop test.

After some more tests I established that the R1 and Rn on the ring are good but the R2/cpc has no continuity.

More head scratching and I've established that a spur was added to connect a cooker hood (many years ago) and the "broken" connection is in this "leg" of the ring circuit.

The problem is that the the "connection" which is believed to be faulty is not accessable, and the home owner doesn't want me to pull up the new hardwood flooring they've put down.

I've established that would be possible to "add" a cpc link between the two "known" ends of the circuit so that the CPC continuity is restored - in this solution the R1 and Rn would use the "old" cable.

Is this an acceptable fix?
Or do I need to upset them by ripping up their flooring to gain access the the junction box?
Or can I leave the house "as is" with the fault and complete my MWC with high values on the earth looop?

Thanks for your help.

 

[ukpablo]

how many sockets on the ring?

can u split into two radials? change breakers etc?

Or really emphasize that the current state of the existing problem is dangerous and would highly reccomend that it is dealt with immediatly.

If not, you could issue a danger notice and leave disconnected? The trouble is that your name is on the cert.

I would reccomend u change the complete leg. Im sure running a single in would not compromise the situation, but make it better, however what is to say that the line and neutral are not damaged? What was the ir test like on the cct?

your call, what would u do in your own house?

If your professional opinion is not appreciated by the customer, than what can u do?!

hope u get the conclusion u are after.

 

[nickblake]

Hi all, I'm new here and looking for some pointers as to how to approach a "problem" I encountered on Friday.

My work entailed adding 2 new fused spurs for outside lights on a house. All was going really well until I got high readings on the earth loop test.

After some more tests I established that the R1 and Rn on the ring are good but the R2/cpc has no continuity.

More head scratching and I've established that a spur was added to connect a cooker hood (many years ago) and the "broken" connection is in this "leg" of the ring circuit.

The problem is that the the "connection" which is believed to be faulty is not accessable, and the home owner doesn't want me to pull up the new hardwood flooring they've put down.

I've established that would be possible to "add" a cpc link between the two "known" ends of the circuit so that the CPC continuity is restored - in this solution the R1 and Rn would use the "old" cable.

Is this an acceptable fix?
Or do I need to upset them by ripping up their flooring to gain access the the junction box?
Or can I leave the house "as is" with the fault and complete my MWC with high values on the earth looop?

Thanks for your help.

yes it is an acceptable fix as the earth will not be protected the minimum size is 4 mm (i think) when it is done lable the CDU and make a note whats been done on the certificate

 

[jeremy]

I've split a ring into 2 radials before, after completely cutting back the offending leg at both sockets. Goes to show the importance of screw down terminals being available for inspection( and repair). I use Hellerman Tyton or Wago push fit connectors now. Bit more expensive but fit and forget. I use heat shrink to mech protect the cables and would welcome advice or comments on its suitability?

 

[Octopus]

Hum - the idea of splitting the ring into 2 radials doesn't really work because they don't have spare capacity in their consumer unit nor the fact that the offending junction box, which connects to their cooker hood is the one that's inaccessable - hence the thought of linking the two "known" earths together.

The r1 and rn readings are exactly the same hence the confidence that the issue is a "non" connection of the earth.

I'll going to review the use of 4mm cpc in place to secure a good reliable earth on the ring circuit and as the link would be outdoors i'll need to factor in some trunking too.

Thanks to all for their suggestions so far.

 

[blackiel]

If its your name on the cert...make sure alls right when you leave,otherwise dont cert,if they want a cert,trace it all,rip the floor up and make sure youre certain,.....run a new CPC??..how do you know youre not adding to an existing problem...???

Wish you well...
Be lucky!!

 

[ukpablo]

how many sockets on the ring?


If not, you could issue a danger notice and leave disconnected? The trouble is that your name is on the cert.

I would reccomend u change the complete leg. Im sure running a single in would not compromise the situation, but make it better, however what is to say that the line and neutral are not damaged? What was the ir test like on the cct?

your call, what would u do in your own house?

If your professional opinion is not appreciated by the customer, than what can u do?!

hope u get the conclusion u are after.

thats what i mean too.
if the cpc is damaged, what are the line cables like?
i would def investigate and replace leg completely!

 

[Octopus]

Hum. Thanks for more comments.

In my investigation I did continuity tests on R1, Rn and R2 - both for the ring and then on the "offending" section of the circuit - hence identifying the "issue"

I then did IR on the cables (from both ends) to further confirm my findings. All was good.

Ideally I would want the customer to lift the fllor and allow access to the offending junction box but its their pride and joy.

The junction box allows a spur to the cooker hood.

There isn't a "pretty" way of replacing the section of the ring - hence the idea of connecting the cpc's of the 2 sockets either side of the section where the cpc is known not to be continuous.

 

[ukpablo]

fair comment!
im stumped too??!
im sure u will resolve with the right solution!

best of luck

 

[AIM]

Murdoch,
1st priority is CPC continuity. You have confirmed via IR that conductors are OK. However are you 100% sure of the location of the CPC failure? if not you will need to work back to known good point of CPC to verify IR readings. Hope I'm not telling you how to suck eggs!!

Can you reinstate CPC continuity from either side? If so you should be able to confirm all is in order without ripping the floor up.

Good luck with this one.

AIM

 

[Octopus]

Aim,

The CPC has perfect continuity to the CU from the "both sides" of the known issue so that's good.

Thanks

 

[jeremy]

Just had a bit of a random thought; if you can run a new 4mm cpc , can you run a new 2.5 T&e to replace the unknown bit beneath the floor or would de-rating the breaker to 16/20A depending on length, insulation etc allow radial split?

 

[Octopus]

On reflection, and bearing in mind the input of other contributors, it would be possible to run new 2.5 t&e from socket 1 to the cooker hood spur to socket 2. This part of the ring would need to run in trunking along the outside of the kitchen wall.

This solution would take the "old" leg out of the ring completely.

A good idea? An acceptable solution?