Borrowed Neutral question/s

[CortinaV8]

My house has borrowed neutrals, found out the hard way a few weeks back while changing a light fitting in the kitchen, tested dead but got a shock.

House is 1930's rewire was done in the 80's at some point.

CU has been replaced with a split RCD board from an old wylex board, I think you can see where I am going with this one.

Hall/Landing

From the double switch in the hall i have a T&E and a single core cable
Upstairs at the single switch I have one T&E, I have seen the other end of the single up in the loft previously.

.......

Kitchen

This room used to have two way lighting but has since been changed, single switch as you enter the room only operates the light closest to me, just a single T&E back to the JB.

The other end of the room by the back door has a double switch, T&E cable plus a single that goes directly back into the light fitting (This I imagine would have gone back to the ther light originally)

Only one of the two switches operates anything.

My questions

Hall/landing - How do I rectify this fault\design flaw

Kitchen - I want both light to come on and off together from a single switch at either end of the room, is this possible?

I ask now as I have a stud wall down and can get to the cables very easily at the moment.

 

[holmslaw]

..

 

[Space cat]

From the double switch in the hall i have a T&E and a single core cable

Do you mean that you have three cores in the same switch? What's in the other switch? Does it control a downstairs light?

Upstairs at the single switch I have one T&E, I have seen the other end of the single up in the loft previously.

Two cores aren't enough for two-way switching with standard (non-electronic) switches. Are you sure there isn't a third wire in there somewhere? The single wire you see in the loft is unlikely to be the one you have downstairs.

Here's how those old two-way switches were usually wired up:

1) Live feed goes to COM on one switch.

2) Twin core cable links L1 and L2 to corresponding terminals at the other switch.

3) Switched live comes from COM at the other switch to the light.

4) The other side of the light goes to neutral.

If you draw this out you'll see that neutral return from an upstairs light goes naturally to neutral on the upstairs circuit but ---

The lazy electrician all too often takes the live feed from the downstairs circuit - because that's where the first switch is!

To make two-way switching work properly you need three wires running between floors. The one you are most likely missing is the live feed from the upstairs circuit to the downstairs switch. One solution is to replace the existing flat T&E with 3-core; red/yellow/blue if you can find some because you'll have the old colours. The other option is to add an extra, single core cable.

The wiring goes like this:

1) Remove the existing live feed from the downstairs switch. This will be easy if it's a short link from another switch. If it's a single core running off somewhere else you could just isolate it but I don't like that. Every wire has two ends and I'm not happy unless I know where both of them are! Find its other end and disconnect that as well. If you're really lucky it'll be long enough to reach the upstairs switch - and so you have your third wire.

2) Rewire the two switches using the modern method, ie all three terminals linked like to like.

3) Connect a live feed from the upstairs circuit to L1 in the upstairs switch.

4) Put the wire to the light in L2.

Since this isn't a trivial operation I strongly recommend that you plan everything before you change anything. Start with a drawing of everything you think you've got. Now test it to see if that's really what you've got. Example: You think you've found the other end of the wire on COM downstairs? Disconnect it and see if the light has stopped working. Has anything else stopped working?

I can't help much with your kitchen lights from the information you've posted. Yes, you can certainly wire them so that both lights work the way you want but we need to know more about that double switch by the door. Do all three cores go into the same switch? Is there anything at all in the other one and, if so, what does it control? An outside light perhaps?

Edited to remove over-enthusiastic smileys and surplus commas.

 

[ban-all-sheds]

Spacey - do you think you could stop peppering your posts with so many smileys?

They are tiresome and pointless....

 

[Space cat]

Spacey - do you think you could stop peppering your posts with so many smileys?

Sorry!

 

[holmslaw]

..

 

[oharaf]

Sorry is this not www.smileyfetish.net

 

[DIYedboy]

Don't forget...................you cannot run a single unless it's in conduit etc (no 'mechanical protection')

 

[ColJack]

Don't forget...................you cannot run a single unless it's in conduit etc (no 'mechanical protection')

lets be clear about this, you can run single cable provided it's sheathed single cable ( the stuff with the grey outer, and it's usually single and earth.. )..

To make two-way switching work properly you need three wires running between floors

also not true, 2 wire 2 way was a popular method..

you have a single from the mains into the downstairs switch, 2 strappers to the upstairs switch, and a single from the upstairs swith to the light..
so a T+E between switches is perfectly acceptable..

 

[Space cat]

also not true, 2 wire 2 way was a popular method..

you have a single from the mains into the downstairs switch, 2 strappers to the upstairs switch, and a single from the upstairs swith to the light..
so a T+E between switches is perfectly acceptable..

Yes, that does work but ---

The single from the mains into the downstairs switch is from the downstairs lighting circuit - and where does the neutral return from the upstairs light go?

I'll rephrase the original statement:

To make two-way switching work properly WITHOUT BORROWING A NEUTRAL, you need three wires running between floors.

 

[holmslaw]

..

 

[ban-all-sheds]

Yes, that does work but ---

The single from the mains into the downstairs switch is from the downstairs lighting circuit - and where does the neutral return from the upstairs light go? <pointless and annoying smileys>

To the upstairs lighting circuit, which is the same as he downstairs one?

To make two-way switching work properly WITHOUT BORROWING A NEUTRAL, you need three wires running between floors. <pointless and annoying smileys>

What if you've only got 1 lighting circuit?:

2 wire 2 way was a popular method..

 

[ban-all-sheds]

Bas, he's doing the smiley thing again, ave a word.

What would be the point of that?