Why neutral at other switch?

[ericmark]

Which I marked as 'JOINT'

Sorry yes.

 

[sparkwright]

It's the joint with the connector block within the switch which prompted Sunray's diagram, as the connector in the switch photo may have been confusing, because as you say, it's not included in Eric's diagram.

Alternative 2 way switch wiring methods have been going on at least 70 years, if not considerably longer.

 

[sparkwright]

Sorry yes.

Eric, how is the other switch wired, and are there neutrals in it?

 

[ericmark]

I may have worked it out without re-opening bottom switch which is hard to get to at the moment. There are three lighting circuits, one for flat under the main house, one bottom floor of main house and one upper floor of main house. Before the CU was changed, the flat had its own CU and the house had a fuse box.

I had assumed the 4 gang switch was powered from the house fuse box before the change, however maybe it was powered from the flat CU and house fuse box, so the one switch would have three line supplies, one from each RCBO I had assumed two line supplies.

In day light should be easy enough to test by switching off the RCBO's.

So I am now thinking the 4 gang switch has 3 lines and 2 neutrals.

 

[SUNRAY]

There's ALWAYS been more than one method of two way switching...

The so-called old school method relates to that very common wiring diagram with the main feed in the first common, and the live to the light in the second common. That kind of diagram always ends up in text books and even on this forum - yet in reality it's seldom done like that, especially now.

I reckon (But I'm happy to be corrected anecdotally) that in the 50's this was to only way it was ever done. Even with 3C&E one would expect to see a connecter (often a wire nut) behind the wooden patress.

 

[ericmark]

Personally I would wire this way but nothing wrong with the other method.

 

[SUNRAY]

Personally I would wire this way View attachment 245251 but nothing wrong with the other method.

In my home I have both methods, I'm happy to say; all wired by me.

 

[JohnW2]

Alternative 2 way switch wiring methods have been going on at least 70 years, if not considerably longer.

I don't doubt you. As I said, there are umpteen ways in which it could theoretically be done, so I would be surprised if others had not been used. However, in terms of my personal experience ...

I reckon (But I'm happy to be corrected anecdotally) that in the 50's this was to only way it was ever done.

... and it's the only way I ever saw it done in the 60s and probably most/all of the 70s. I obviously must have missed out on seeing examples of the 'alternative methods'.

Kind Regards, John

 

[plugwash]

I don't doubt you. As I said, there are umpteen ways in which it could theoretically be done

Afaict there are really only 3 ways of achiving two way switching with a pair of SPDT switches. Of course there are umpteen wiring layouts to achive those 3. Two of those 3 ways are still considered acceptable, one of them is considered a very bad idea.

1. Feed to the com of one switch, two strappers between the L1/L2 of the switches and load to the common of the other switch.
2. All 3 terminals on the switches connected together, feed and load to L1/L2.
3. Live and neutral to the L1 and L2 of the switches, load connected between the COM terminals. This is a bad idea because it can leave the load live when off and because it risks pulling an arc between live and neutral.

 

[SUNRAY]

Afaict there are really only 3 ways of achiving two way switching with a pair of SPDT switches. Of course there are umpteen wiring layouts to achive those 3. Two of those 3 ways are still considered acceptable, one of them is considered a very bad idea.

1. Feed to the com of one switch, two strappers between the L1/L2 of the switches and load to the common of the other switch.
2. All 3 terminals on the switches connected together, feed and load to L1/L2.
3. Live and neutral to the L1 and L2 of the switches, load connected between the COM terminals. This is a bad idea because it can leave the load live when off and because it risks pulling an arc between live and neutral.

That just about sums it up, as you say there are a selection of ways of achieving them but the final result is those three.

I came across a number three only a few months ago but it is rare these days.

I also found a reversing system on a machine deliberatly done that way with 2 switches, at opposite ends of the machine, such that the motor was shorted to brake it between changes. Albeit done with individual switch blocks, possibly reducing the arcing effect

 

[JohnW2]

Afaict there are really only 3 ways of achiving two way switching with a pair of SPDT switches. Of course there are umpteen wiring layouts to achive those 3. Two of those 3 ways are still considered acceptable, one of them is considered a very bad idea.

Agreed. I was including the 'wiring layouts' in my 'umpteen' - but, even then, was perhaps a bit of an OTT word to use. Probably the most important of the variants of 'wiring layout' is, with your (1) [what I call the 'old-fashioned' method] the question of whether the neutral travels with the strippers (ideally in the same 3C cable) or whether it is supplied totally separately to the load 'at the other end'.

I have personally never come across your (3) other than in discussions in this forum, but it clearly is 'a bad idea', being even worse than just 'switching (only) the neutral'.

Kind Regards, John

 

[SUNRAY]

Agreed. I was including the 'wiring layouts' in my 'umpteen' - but, even then, was perhaps a bit of an OTT word to use. Probably the most important of the variants of 'wiring layout' is, with your (1) [what I call the 'old-fashioned' method] the question of whether the neutral travels with the strippers (ideally in the same 3C cable) or whether it is supplied totally separately to the load 'at the other end'.

I have personally never come across your (3) other than in discussions in this forum, but it clearly is 'a bad idea', being even worse than just 'switching (only) the neutral'.

Kind Regards, John

I'd like to travel with the strippers please
I believe it's still practiced in USA if one of the YT videos I saw a little while ago is valid.
It used to be popular for outside lighting between buildings, for example farms, where a light mid way between buildings only required one wire from each end. One thing stopping that arrangement was if the 2 buildings are on different phases

 

[SUNRAY]

My most recent example of number 3

https://www.diynot.com/diy/threads/2-way-lights-again-oh-and-why-i-dont-like-domestics.513146/

 

[JohnW2]

I'd like to travel with the strippers please

... I'll be on the lookout for your typos!!

I believe it's still practiced in USA if one of the YT videos I saw a little while ago is valid.

What "it" are you talking about? If you're talking about the situation in which the neutral does not 'travel with the strappers' (i.e. L connected to common on first switch and N connected to the load at the 'other end') (which is not ideal in terms of EMC, and can increase the temptation to 'borrow a neutral'), then that was the arrangement with several of the 2-way switching situations I inherited in my current house. In other circuits, the N diud 'travel with the strappers' in 3C+E cable.

Kind Regards, John

 

[JohnW2]

My most recent example of number 3 https://www.diynot.com/diy/threads/2-way-lights-again-oh-and-why-i-dont-like-domestics.513146/

As I said, I've seen it discussed here, but have never personally met it in real life.

Kind Regards, John