shared neutral in lighting circuits

[plebeian]

I need some help in deconstructing the following ( please see photos of upstairs downstairs switches ) as I don't know what the circuit diagram would look like in this case?
It works perfectly well
Is seems to be a shared neutral circuit but does not follow the normal convention as shown in the diagram.
As the cabling is inaccessable I cannot trace the route.
Is this a known standard 1960's circuit

 

[Grant webber]

That's a shared neutral. If theres an up stairs and down stairs lighting circuit. Commonly how it used to be done. And can be dangerous if you dont know it's there.

 

[Electric Magic]

Why don't you think it is the same as the diagram? Without testing can't say for certain but the downstairs switch appears to have one cable providing a permanent line for (presumably) the hall light and the other switch, which is providing 2 way switching (via the grey twin cable and the upstairs light switch) to the landing? light. It appears from the photos as if there are no circuit protective conductors, which would put the install before 1966. If the upstairs and downstairs are on separate lighting circuits the landing light probably does "borrow" a neutral from the upstairs circuit. I see a lot of houses in my area with the same thing. I wouldn't call it a standard circuit as that might denote that it was once acceptable (as far as I know it's never been in line with the regs to borrow a neutral, even if it was fairly common practice in some parts of the country).

 

[snowhead]

Given the 2 photos it's impossible to say whether there is a shared / borrowed neutral involved.
Both the 2 way, presumably stairs light and the one way share the same Live.

1960's and even later, convention would have been all lights, both upstairs and down on the same circuit, therefore a shared / borrowed neutral could not exist they would just all be on the same circuit.

 

[HappyHippyDad]

There are no neutrals there. They are all permanent lives and switch lives.
I'm guessing you're looking at the red link conductor going between switches, that's a permanent live not a neutral.

 

[Lucien Nunes]

I think the point of the pics is to show the situation that is suspected of giving rise to the borrowed neutral at the far end. Namely that the line of the 1w is also used to feed the 2w, and sent via the 2c strapper and the other 2w to a light on a different floor, where it borrows that floor's neutral. There's no certainty that's what has been done, but it's highly likely, given the age and nature of the installation.

 

[phil 01]

I think the point of the pics is to show the situation that is suspected of giving rise to the borrowed neutral at the far end. Namely that the line of the 1w is also used to feed the 2w, and sent via the 2c strapper and the other 2w to a light on a different floor, where it borrows that floor's neutral. There's no certainty that's what has been done, but it's highly likely, given the age and nature of the installation.

I guess your trying to establish whether there’s a borrowed neutral on the the circuit, first are there 2 lighting circuits, if yes does the 2 gang switch control hall light and landing 2 way, if yes, if you isolate the downstairs lighting circuit does the landing 2 way on the 2 gang not work, if yes borrowed neutral on 2 way

 

[plebeian]

I guess your trying to establish whether there’s a borrowed neutral on the the circuit, first are there 2 lighting circuits, if yes does the 2 gang switch control hall light and landing 2 way, if yes, if you isolate the downstairs lighting circuit does the landing 2 way on the 2 gang not work, if yes borrowed neutral on 2 way

Thanks - I will try that

 

[plebeian]

Question: If it is a shared neutral is there any reason why the two circuits should not be combined to form one circuit obviating any problems arising from this dubious installation?

 

[7029 dave]

2way landing switching ? very common in the 60's set up. Bridged live of downstairs I bet.

 

[phil 01]

2way landing switching ? very common in the 60's set up. Bridged live of downstairs I bet.

You can make it one circuit but it’s poor practice, most houses have 2 lighting circuits, if the decoration is not a concern cure the problem with a length of 3 core and Earth

 

[sinewove]

Or run a brown single and earth from the upstairs lighting circuit in the consumer unit to the 2 gang switch, disconnect the link and connect to common terminal of the 2 way switch.The circuit should be rcd,d.
Regards,S

 

[plebeian]

You can make it one circuit but it’s poor practice, most houses have 2 lighting circuits, if the decoration is not a concern cure the problem with a length of 3 core and Earth

There are five lighting circuits: two in the old house, two in the two later extensions and one in the garage.
There is another wall light opposite the 60's upstairs/ downstairs light which can illuminate the landing and hall it is connected to the extensions cu