Help with wiring a Light Switch

[Brettster]

I know we have a few electricians on this forum so I hope you can help?

I ordered a wifi controlled light switch so I can be ultra lazy and ask Alexa to turn on the lights!!
but the switch needs a Neutral, live and switched live inputs

When I opened up the light switch currently in use
this is what I see

with a live wire detector the two wires that are taped up dont make it buzz so is one of those the Neutral I need for the new smart switch?

our wiring is quite old!

 

[big10p]

That is old wiring. Uses the old wiring colour scheme. Before a qualified electrician chimes in, I will just say that I believe red=live, black=neutral and green=earth.

 

[stevebm1]

looks like it may have been part of a ring main changed to a light switch going from that wiring

 

[Rog69]

It looks like there could well have been a double switch there in the
past and the taped up pair are just redundant switch wires to a now
removed wall light or something.

If the black on the taped up pair is a neutral you will be able to measure mains voltage between it and the red connected to the switch (or black, depending on how the sparky connected it in the light fitting or if the switch is closed or not).

I would be cautious though because you don't know for sure what those taped up wires are connected to and if they are still live, even the black (I learned never to trust anyone else's adherence to wiring colours back when I was a sparky) so tread carefully and get a sparky in if there is any doubt.

 

[Brettster]

Thanks for the reply’s
I’ll hook up a meter as suggested and see what I get

 

[Brettster]

Ok so I measured the taped up black and got about 206Vac from the black in the switch
I put the taped up black into the N and the black from the switch into the L in and the red into the L out
but I didn't see anything happen with the new switch so im now at a loss as to if this will work now

 

[ZuPoint]

You have only 2 options :-

1. Get a sparky in or trace the old cables yourself ( hopefully to find/add a neutral )

2. Forget the WiFi switch and go for a WiFi bulb.

Good luck.

 

[John Bennett]

It seems a bit flawed to need a neutral, seeing as lighting circuits normally just pass live down to the switch and then return the switched live up to the bulb. People will have to carve up their walls to bring the neutral down from the lighting ring main.

It would be rather alarming if someone had taped over a wires from live circuit - as said, they're probably from a second light that's long gone.

 

[dj_yt]

I started looking into my homes wiring recently and found it positively horrifying. Just removing a single light switch revealed all kinds of horrors. My arcade cabs are completed to a far superior standard!

 

[Brettster]

I think it's due to it being always powered so you can voice control or app control it from your phone

 

[bonehead]

I would probably get a sparky it to sort it. If it’s a simple job probably only looking at £50.

 

[Jon-A-Tron]

Why smart switches need a neutral

This link gives some good info on this problem which is common in UK houses. You may be lucky and that disconnected cores go somewhere that can be used to pull through a new neutral.

 

[John Bennett]

I think the cost/effort might be in the redecorating required, if the cable is embedded in the wall/ceiling.

 

[andrewsm]

The only way this could be made to work is have a small battery charging when the switch is off. Then whe it is turned on, the live is shorted to the switched live to illuminate the bulb. At this point no power would be available to the switch electronics, hence battery backup. Im guessing this is not available but would be a much better solution than the current setup. No extra wires would be needed.
andrewsm2017-12-16 19:32:39

 

[John Bennett]

Why smart switches need a neutral

This link gives some good info on this problem which is common in UK houses. You may be lucky and that disconnected cores go somewhere that can be used to pull through a new neutral.

I think some can do it without a neutral - I'm presuming they do it via a trickle of current (enough to power the switch but not illuminate the bulb). That would explain why they only work with incandescent bulbs (you can't put a trickle through an energy saving bulb as they've got inverter circuits in them).

 

[SUPERSPRINT]

The switch needs a neutral for its relay circuit. You can’t use a 5v dc signal to switch the 240v ac without a relay and as the relay needs a neutral for the electromagnetic coil to operate. If you can trace the spare cable to a pendant or Junction box you may well be able to get yourself a neutral at the switch. If I had that job I would be looking for the other end of the spare cable to see if I could connect it to a neutral. If it’s taped up though I would be very careful as it’s probably still live. Like it has been suggested the spare was probably for another light as another switch and will be 240v in and 240v out on the black. Colours don’t mean a thing with switches as all colours can be live. If in doubt get an electrician, you could end up in the dark. SUPERSPRINT2017-12-16 19:58:17

 

[Brettster]

The switch needs a neutral for its relay circuit. You can’t use a 5v dc signal to switch the 240v ac without a relay and as the relay needs a neutral for the electromagnetic coil to operate. If you can trace the spare cable to a pendant or Junction box you may well be able to get yourself a neutral at the switch. If I had that job I would be looking for the other end of the spare cable to see if I could connect it to a neutral. If it’s taped up though I would be very careful as it’s probably still live.

I'll have a look in the ceiling rose tomorrow and see whats up there!

strange that I was able to put my multimeter onto the black taped wire and one of the ones from the switch and get a reading.

I've since tested the switch using a desklamp, and the switch is working fine, so just that pesky Neutral wire in the wall now to go

 

[SUPERSPRINT]

Unless your getting 230v plus between known live and that black, assume it’s not a neutral. Check the 2 spare wires to earth. You should have a Earth there. SUPERSPRINT2017-12-16 20:08:49

 

[Jon-A-Tron]

If the switch was on then the 230v would have been at the switch cable and not the taped black. If the switch was off then you could have been at the live end of the switch supply. If you were at the switched side of the switch and the switch was off and you got 230v at the black taped cable, then that cable is live.

 

[SUPERSPRINT]

Here’s what you may be able to do. If you can prove one of your spares is a permanent live, probably the red, then you can replace that with the existing red on the used switch. Then with a bit of luck you will find at the Pendant or light fitting the switch cable, which is the other end of the cable at the switch. The red will be usually connected to the other reds and the black will be the switched live. You can then use the switch live wire to connect to the blacks as a neutral and use the red (connected to the reds) as your switched live. That would work.

If you only have a red and a black at the pendant, then there is defiantly a junction box somewhere and you will need to find it.SUPERSPRINT2017-12-16 20:38:56