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

 

[Octopus]

And the problem is?

You can take the relevant tests

 

[davesparks]

I’m lost, what’s wrong here and why does it need recording on an EIC?

 

[Taylortwocities]

Parallel earth paths are common in existing installations. It's not even worth time looking for it.

 

[Gavin John Hyde]

It hasnt stopped me taking the tests I was merely checking whether to record it or not, given it was such a new installation i was a bit surprised to find one. Come across plenty in older homes not many in new. my only real concern was the possibility of joined circuits on line and neutral but i had ruled that out already. so just peace of mind really.

 

[static zap]

(Had a thought if it was a " helping hand " by design ,
may be near furthest point in lighting circuit ! )

 

[kingeri]

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.

 

[Toneyz]

Could be supplementary bonding or both the metal boxes touching metal stud. Take it the insulation resistance testing was ok? I would do a R1 +R2 test on both circuits removing C.P.C. from earth bar.

 

[Deleted member 26818]

Not only is it common, in some circumstances it’s required by BS7671.

 

[Dave OCD]

Most houses will have it on upstairs & downstairs lighting circuits if a multigang switch is used at the foot of the stairs.

 

[Deleted member 26818]

I think the most common interconnection is between upstairs lighting and boiler circuits.

 

[Dave OCD]

Why so ? Sorry if I'm being dim, ready for a break !

 

[Deleted member 26818]

Bathroom supplementary bonding.

 

[Dave OCD]

Ah of course !

 

[Gavin John Hyde]

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