Broken CPC, done all I can but still no luck.

junior-sparky · Sep 30, 2014

I've been let loose today to do a PIR, EICR, E, I,E,I, O what ever they wanna call them these days in an empty flat and have an annoying CPC broken in RFC.

2 bed flat
3 way CU - Cooker (30), Lights (6) and RFC(30)

End to end of r1 and rn fine but r2 is broken.

This is what I did-

connected opposites r1 and r2 in choc and using my kewtech R2 adapter went round testing all sockets and nothing was showing as broken.
removed said sockets and nothing is loose or broken and even tightened all screws to make sure.
connected one leg of r1 and r2 and found that only one socket in the flat was giving me a reading.
connected other leg of r1 and r2 and guess what! everything else but that socket above had a reading.
take the cover off again, everything looks right
do my end to end reading again, r1, rn all fine but r2 still broke.

Flat is empty no spare way make them into 2 radials if i wanted.

everything else in the flat is fine.

what am i missing????

thanks in advance.

Andy78 · Sep 30, 2014

An EICR you are just reporting your findings, not fault finding and fixing.
C2 and further investigation required.

Sounds to me like you have successfully identified the leg of cable that is missing it's CPC though. My money would be on a JB under the floor between the sockets.

driverman · Sep 30, 2014

Not that I'm into testing..........but from what you say using your R2 adapter you are obtaining an earth at each and every socket, am I right? If so break must be between CU and a first socket on a particular leg of the ring.

SJD · Sep 30, 2014

Are you sure you've not missed anything, like a fused connection unit, a socket hidden behind somewhere etc.? I once found the cables for a socket behind the wallpaper, an open drylining box papered over, with an open L and N connection!

When testing just one cable R1+R2 connected, if you measure carefully, you can often place the sockets in the order they are connected round the ring, though bad connections and poor switches can make this a bit hit & miss - unless you open each socket up and test at the terminals behind. Might help determining where to look.

Octopus · Sep 30, 2014

When you do an EICR, its about a report on the installation, nothing more unless you identify C1's, nothing less.

Surely your mentor/boss told you this?

junior-sparky · Sep 30, 2014

Thanks for the help.

I searched that flat top to bottom, only FCU was a combi boiler spurred off the RFC but obviously disconnected it.

There were however an awful amount of nails/screws in the walls, some in the permitted zones. maybe i should of testes a screw or two LOL.

Murdoch - We are more than likely to be replacing the old CU for a new one and thought as i was already in the flat with cover off and wires in hand i might be able to prevent us/me having problems if we do get the CU change. This was my only job for the day as not needed elsewhere and wanted to test it as much as possible to gain better understanding of why and how its doing it.

Andy78 · Sep 30, 2014

Why did you disconnect the boiler spur ?

junior-sparky · Sep 30, 2014

Murdoch said:
When you do an EICR, its about a report on the installation, nothing more unless you identify C1's, nothing less.

Surely your mentor/boss told you this?

would a broken cpc not be a potential C1? I'm not full of experience but could you say your halfing the cpc required?

Richard Burns · Sep 30, 2014

If there is a break in CPC and you have found that the readings change at one socket remember the break could be at the next socket along
like so, either of these breaks would give the same results:

[ElectriciansForums.net] Broken CPC, done all I can but still no luck.

Andy78 · Sep 30, 2014

junior-sparky said:
would a broken cpc not be a potential C1? I'm not full of experience but could you say your halfing the cpc required?

C2 as a fault would need to occur for it to be dangerous.
C1 is immediate danger with no other conditions present

junior-sparky · Sep 30, 2014

Andy78 said:
Why did you disconnect the boiler spur ?

purely just for being over cautious. i only disconnected the boiler appliance itself not the fcu wiring, sorry for confusion.

i know it wouldnt of made a difference but scratching head syndrome kicked in and tried anything.

Plonker 3 · Sep 30, 2014

Right what were your r1,r2 & rnreadings? What was you R1+R2 reading? And was it the same at every socket?

Octopus · Sep 30, 2014

One thing worth trying is doing a Zs at each socket to see if you get a "jump" in the readings at all.

davesparks · Sep 30, 2014

He 'a already identified that the fault is between the first and second socket, so what is there to be gained by doing other tests around the ring?

Testing the cable between those 2 sockets would be a good idea.

SJD · Sep 30, 2014

junior-sparky said:
There were however an awful amount of nails/screws in the walls, some in the permitted zones. maybe i should of tested a screw or two LOL.

It could be a screw in lots of places. As an example, I once had a RFC with a CPC break, which turned out to be caused by a screw through the cable some 20 years prior when an extension had been built, the screw was to hold a moved stud wall to a joist, under a floor board. Actually the screw had shorted CPC to L, been removed (and fuse replaced (and nothing said to the owner)) and the screw inserted somewhere else nearby. The evidence was the flashover marks in the cable when removed. As to finding it - a cable tracing kit, tracing the cable round in the void between floors, with signal injected onto CPC from each end in turn.