Strange 2-way wiring

[Judd]

Came across some bizarre wiring for a 2-way recently in a old house. Anyone ever seen this before? Was this ever the done thing many moons ago? (Sorry for the rough sketch)

 

[snowhead]

So the lamp gets,
L - N or
L - L or
L - N or
N - N

Interesting, but I've never seen or heard of it.
Maybe goes back to the days of D.C, especially as you've labelled it + / -

 

[Silly Sausage]

Could be confusing confirming polarity on ES fittings.

 

[Marvo]

There's several ways a 2-way system can be wired and this is one of them. It will work fine but it's unorthodox.

 

[littlespark]

Against regs now?
Switching only on live conductor.... meaning, not on the neutral.

Just curious. What’s the wiring method?

 

[davesparks]

I've never seen that before, and I don't think it was ever common practice and it certainly does not comply with the regulations.

 

[buzzlightyear]

that's the worst drawing I have ever seen .come on man get a grip .

 

[westward10]

I suspect the + and - are denoting red and black.

 

[Marvo]

I've never seen that before, and I don't think it was ever common practice and it certainly does not comply with the regulations.

Just out of interest, assuming the lamps aren't ES fittings, what regs would it violate?

 

[davesparks]

Just out of interest, assuming the lamps aren't ES fittings, what regs would it violate?

I don't know the reg number but they forbid a single pole switch being placed in the neutral.

 

[Shoei]

530.3.2 ..... In single-phase circuits an independently operated single-pole switching or protective device shall not be inserted in the neutral conductor alone.

 

[Marvo]

530.3.2 ..... In single-phase circuits an independently operated single-pole switching or protective device shall not be inserted in the neutral conductor alone.

Hmm, sounds like a grey area to me. By the letter of that reg as it's written the switching arrangement in the OP would be fine. If the reg said 'operate' instead of 'inserted' then it would apply but both live and neutral are 'inserted' so it could be argued it doesn't apply.

 

[FatAlan]

Any pics?

 

[Michael Davis-McCoy]

Was shown this wiring diagram over 30 years ago when an electrician asked how many two switching I could draw. I could draw a couple but not this one. I'm impressed it is out there. It does work. It would confuse today's electricians. So it obviously exists out there.

 

[edexlab]

I've seen this method twice, all wired in single red wires one to each switch insulated and sheathed
don't know if there is a proper name for it both properties wired in sixties I think

I was a new spark when I came across it 18 years ago and it did confuse me a bit as I was supposed to just fit a jb and change to a couple of downlights
And of course didn't see anything like this at college

 

[telectrix]

potentially dangerous as when both switches are with common switched to L, the light is off, so Mr. layman would think it was safe to stick his sausage fingers in there.

 

[Judd]

The yanks call it a 'Carter 3-way'

 

[DjMadness]

Hi

This is a functional montage. Some electricians do it to save wires from common poles between the two SPDT switches. So instead of having two wires between each switch, a live wire to the lamp and a neutral, you need only two wires for the lamp support terminal. Bear in mind that there is a need to have L and N inside each surface mounted electrical box (pvc/...) to feed the switches. When this is not appropriate /possible they use the wiring you have in your head.


Dj

 

[Wilko]

Hmm, sounds like a grey area to me. By the letter of that reg as it's written the switching arrangement in the OP would be fine. If the reg said 'operate' instead of 'inserted' then it would apply but both live and neutral are 'inserted' so it could be argued it doesn't apply.

My thought is the intention of the reg is the N not be disconnected unless its coordinated with the L being disconnected, as per DP switching. Whereas the drawing allows N to be disconnected when L is continuous.

 

[ED17]

Are you sure it's a neutral at the switches and not just red and black used as strappers?

 

[Judd]

Are you sure it's a neutral at the switches and not just red and black used as strappers?

Yes I'm sure, why do you ask?

 

[ED17]

Yes I'm sure, why do you ask?

When I was an apprentice, (many, many moons ago) we used to run a twin red/black between switches, live down to one switch and switchwire to the other switch. Don't think my boss had heard of 3c & earth

 

[Charlie_]

That switching arrangement is very common in control circuits, relay logic, etc..