Parallel earth path between 2 circuits

[Gavin John Hyde]

I have a ring circuit (circuit 1) and a light circuit (circuit2) in a flat im working on and i have somewhere in the walls or ceiling a joined earth path. From what i have seen there is no obvious metal conduit, so it seems its either the ventilation system that is fed by the same ring and goes to each room near the light circuit in question or one of the metal stud parts on internal walls.
I have tested between them and confirmed at light points and sockets that a path exists. I have added in a new shower circuit and extra sockets and some downlights. it was by chance i clipped the wrong earth when i had them out in the cu for the EIC that i discovered the shared earth path.
It is only between these two circuits, The flat is part of a newish building around 3 years old and is made mainly of a wooden frame and structure with stone cladding. There is some metal stud work but most of the building was modular and delivered in sections to be put together. think of it as a giant kit house.. I have put an endoscope in the voids but not seen anything as yet that is 100% the linked path. There is one water pipe around 2 metres in length entering the flat then the water and heating are all plastic pipes. with the boiler outside the flat door in a cupboard.
Given the nature of the building its not wise to start pulling bits apart and making holes into wooden joists etc..
Its clearly been there since it was built.
What would you put on certificate to indicate this... I have put so far ... shared parallel earth path between circuit x and y. location not known due to nature of building.

Any thoughts or advice

 

[Deleted member 26818]

all tests come out okay. its linked somewhere within the structure of the flat, unlikely to ever find out where,

Is there a heated towel rail or heater in the bathroom spurred off the ring?

 

[Taylortwocities]

Bathroom supplementary bonding.

A 3 year old installation would have RCDs and wouldn’t need supplementary bonding in the bathroom.
It would only need a 2+1 box with a light switch and a socket in it to create a shared earth. There’s all sorts of possibilities.

 

[lurch]

It's common for CPCs to be interconnected for whatever reason, be it by design or by accident, think supplementary bonding. Seen CPCs joined at the end of circuits to bring down Zs of both as well.

really?

 

[Octopus]

I don't understand the problem .....................

 

[7029 dave]

They are all common at the CU.

 

[Risteard]

A 3 year old installation would have RCDs and wouldn’t need supplementary bonding in the bathroom.

May not need...

 

[Risteard]

There's also no requirement for a CPC to be specific to one circuit.

 

[lurch]

There's also no requirement for a CPC to be specific to one circuit.

good practice?

 

[Risteard]

good practice?

Not necessarily. Containment (as an example) will have a common cpc.

 

[Gavin John Hyde]

I found the cause of the link. There is electrics in the bathroom walls and ceiling ready for a hoist for disabled people to be installed. Its pre wired in case of need and just needs the plaster board or blank plates taking back to expose. The light circuit is bonded to the metal support in the ceiling and the same frame goes down the side wall to a metal thing that will have the hoist attached. This is linked to the ring cpc. Through the socket on adjoining wall. Hence the link. The owner had found the drawings for it. Full of some garb about part m and disabled access... But mystery solved

 

[DPG]

That's different! At least it's put your mind at rest. Nice one.

 

[static zap]

THE .. electrics in the bathroom walls....Through the socket on adjoining wall.

Are they aligned with "safe zone" of a joining wall socket ?
..or a present for someone fitting a bathroom cabinet !

 

[123]

@Gavin John Hyde Have you charged the customer for the time spent looking at this?

 

[Gavin John Hyde]

@Gavin John Hyde Have you charged the customer for the time spent looking at this?

Yes, charged them as its part of a batch of jobs i did for the customer and also useful as i am fitting a heated mirror in said bathroom soon - so needed to be sure of what im connecting onto. Only thought of it when i saw the papers he had and was checking in wall for stud work as prep for the heated mirror cable routes.