2Gang Light Switch (Mind Boggling Fault)

[dave (retired)]

Are you sure you are electrician, connecting a neutral to another circuit could be lethal, if you can't connect a light and switch you shouldn't really be trying.

 

[Doc Hudson]

Are you sure you are electrician, connecting a neutral to another circuit could be lethal, if you can't connect a light and switch you shouldn't really be trying.

As you say Dave, it is indeed very concerning that anyone would contemplate connecting a load between two circuits, Live from one, neutral from another. On the face of it the less experienced may not think it is that dangerous as it is only neutrals. But the actual effect is to have one section of cable energised from two separate protective devices, so anyone doing work at a later date could think they have isolated a circuit that can still be energised from another circuit when a light is switched on. This was a common problem with the old landing & hall light scenario. However anyone tries to justify it, it is a clear breach of regulation 314.4, which states that all final circuits must be electrically separate from all other final circuits. Certainly not the work of a trained competent person. Re the original problem, the symptoms of a light going off when another switch is turned on sounds like the new light and switch is wired in parallel with the old switch, so the old switch creates a by-pass path bringing both sides of the new light and switch to the same potential. Which also relates to the symptom of potential disappearing when switch is in one state. And original switch turns old light on. but new light off.

Doc H.

 

[binky]

sounds like the existing light was 'switch fed' to me

 

[M107]

Call a local electrician to take a look. :innocent