Question regarding signing off 32a ring circuit with broken CPC ring continuity

[ZEDEZ]

I installed a kitchen ring recently. Went back to test after the builders had finished and found that the CPC is broken somewhere inaccessible, everything else tests normal. I’ve got continuity on live conductors, and even with the broken CPC, each socket is connected to the CPC and tests with an acceptable Zs value.

What are my options to be able to sign this off without any destructive investigation / remedial work?

My first thought was to split the ring into two 20a radial circuits. But it would be preferable to leave it connected as a ring for increased capacity.

As far as I understand it the fact that the CPC doesn’t have ring continuity isn’t affecting safety or disconnection times, so is there a reason I couldn’t sign this off and simply note this fact?

 

[Jim_e_Jib]

Builders....!

Even if disconnection times are met, I don't think you can sign it off as the current carrying capacity of the CPC is reduced. 20amp radials sounds like the way to go!

 

[Pete999]

I installed a kitchen ring recently. Went back to test after the builders had finished and found that the CPC is broken somewhere inaccessible, everything else tests normal. I’ve got continuity on live conductors, and even with the broken CPC, each socket is connected to the CPC and tests with an acceptable Zs value.

What are my options to be able to sign this off without any destructive investigation / remedial work?

My first thought was to split the ring into two 20a radial circuits. But it would be preferable to leave it connected as a ring for increased capacity.

As far as I understand it the fact that the CPC doesn’t have ring continuity isn’t affecting safety or disconnection times, so is there a reason I couldn’t sign this off and simply note this fact?

If it's a Kitchen RFC it shouldn't be that difficult to find out where the break in the cpc is, so if you aren't feeling competent to do that route, turn the RFC into 2 by 20Amp Radials. Leaving the RFC as it is, would be unacceptable in my book, I certainly wouldn't leave it in that condition, as it is now it's not a RFC is it?

 

[Deleted account]

How is it broken where its inaccessible?

And no it cannot be signed off as is.

You have effectively halved the cross sectional area of the cpc.
Maybe, just maybe if you can work out the minimum cross sectional area of cpc via adiabatic is acceptable at less than 1.5mm in either direction, but not good practice and I wouldn't.

 

[Silly Sausage]

My first thought was to split the ring into two 20a radial circuits. But it would be preferable to leave it connected as a ring for increased capacity.

I would've thought 2 20A ccts would have more capacity than a single 32A cct?

You need to remove/isolate the damaged section of cable whatever you end up doing.

 

[Risteard]

In addition to the cpc being broken you know that the cable has been damaged. How can you possibly be certain that other parts aren't damaged? Remember that testing does not trump inspection so just because the rest tests out fine doesn't mean that it is fine.

 

[telectrix]

In addition to the cpc being broken you know that the cable has been damaged. How can you possibly be certain that other parts aren't damaged? Remember that testing does not trump inspection so just because the rest tests out fine doesn't mean that it is fine.

funny you should say that. just been to a lighting fauly, wylex board from c 1970's, 3036's replaced with 60898 plug-in MCBs. MCB for upstairs lights won't hold. cabled dissed from board, all readings show no faults. down to visual.... JB in attic. LN in, 3 T&E out. switching for attic light. so out with all the loop cables. ID the incoming (not wet finger), into 5 port wagos. connect loop out #1, MCB holds, loopout 2 MCB holds, loop 3 in MCB trips. good old bang test. fault traced so far to a 20A D/P switcth apparently feeds a bulkhead that's not worked for years. cable buried in render. so... faulty bit left out. down pub for a pint.

 

[Deleted account]

Splitting the ring into 2 radials should not be the first option or even the last.
If the break splits the sockets and there loads equally maybe it's a solution, but if it splits between one socket only and several or worse it's on one of the legs before any sockets then it's not an option at all.

Agree with ristard. It's adamaged cable. It needs sorting.

If it's a damaged cable not sure how the cpc is cut and not at least one of the live conductors. Unless it's a loose connection in an inaccessible j/b?

 

[Pete999]

Splitting the ring into 2 radials should not be the first option or even the last.
If the break splits the sockets and there loads equally maybe it's a solution, but if it splits between one socket only and several or worse it's on one of the legs before any sockets then it's not an option at all.

Agree with ristard. It's adamaged cable. It needs sorting.

If it's a damaged cable not sure how the cpc is cut and not at least one of the live conductors. Unless it's a loose connection in an inaccessible j/b?

I take it Pete you are having a go at my reply about turning the RFC into 2 Radials, and of course you are right the damaged section should be removed, it was my assumption that the OP would do this, but assumption is the route of all evil, should have been more explicit in my first response, the OP seems to have a few Quals and should be aware of this step, message to oneself never assume anything, good point though.

 

[Baddegg]

If it was fine on first fix and broken when you went back tell the customer it needs sorting and the builder is paying.....

 

[gazdkw82]

It can't be that hard to find which leg has open circuit on CPC.

Narrow it down between the sockets. Once you know the leg, repair or disconnect and make 2 radials

 

[Pete999]

If it was fine on first fix and broken when you went back tell the customer it needs sorting and the builder is paying.....

True, but the builder could, and probably will deny any involvement, or any responsibility, so to say the builder will pay, is being a trifle preemptive.

 

[DPG]

Let us know what the fault was when you find it. Kitchen cupboard screw maybe?

 

[Pete999]

Let us know what the fault was when you find it. Kitchen cupboard screw maybe?

Yep a Good idea.

 

[Deleted account]

Pete999

Definately not having a go at anyone giving this option.

I actually put an agree on your post and others posts who made this suggestion prior to me making mine.

Splitting the ring is a viable option, I just wanted to highlight its not the first.

 

[Pete999]

Pete999

Definately not having a go at anyone giving this option.

I actually put an agree on your post and others posts who made this suggestion prior to me making mine.

Splitting the ring is a viable option, I just wanted to highlight its not the first.

I know, I jumped the gun I think Pete, I should have been more explicit, sorry if it caused any disharmony in the discussion it was never meant to, appreciate your reply. Live long and Prosper.

 

[FatAlan]

Have you double checked the terminations at each socket? Not wanting to teach sucking eggs and all that and am only a novice, but I recently installed a RFC, checked continuity prior to second fix and all was good. Second fix resulted in a break in continuity on the line. I automatically assumed the worse re builders / plumbers. I then tested along on one side of the ring until I found the area where the break was. Double checked the socket terminations and bobs your uncle! Could just be a bit of CPC sleeving caught in the termination.
As above if there is damage to a cable somewhere I’d want to find and repair it.

 

[Wilko]

Hi - if the CPC is not continuous then it can't be an RFC - reg 543.2.9 applies. I had to be reminded of this myself a while back .

 

[Deleted account]

Jumped the gun I think Pete, I should have been more explicit, sorry if it caused any disharmony in the dicussion it was never meant to.

It didn't. Like all social media it's hard to put into words intent meaning and feeling which is why a lot of people cannot interpret messages properly.
I put myself in this catagory.
Millions of years to learn to communicate with speech face to face. 25 years of social media. We don't stand a chance.

 

[littlespark]

Don’t sign it off.

Builder has made a boo boo. Rawlplug hole drilled through a cable would be my bet.
Assuming it was all ok when you tested, and now it’s not.... must be something the builder has done.

You can work out which leg is down. Look for drill holes in the path of where you think the cable is.
You might be able to find it visually, and fit a joint box in the back of a cupboard maybe?

I wouldn’t split it into 2 radials unless there’s very little load. Kitchens will have kettles toasters etc without washing machines, dryers etc which could be in a utility room on a different circuit.