Installing Smart Switch That Requires Neutral?


Postby TheVOID » Tue Jul 03, 2018 4:16 pm

So I had a 3 way switch setup in my bedroom. Light switch by the door and a light pull by the bed. The cable that runs between the door switch and the pull is a 4 core.

So I've bypassed the the pull switch and tested with a standard light switch and this works perfectly fine.

Now I've come to install the smart switch, I've used a spare wire in the 4 core to act as a neutral but once it's all connected up the light constantly flickers regardless of it being on or off

I've attached a diagram of how the wire is setup and two pictures of the switch and my 'neutral' line I created.

I've either completely misunderstood how the neutral works or I've got a faulty switch. Any help or advice would be great thank you
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IMG_2316(1).JPG
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Postby Mr White » Tue Jul 03, 2018 6:15 pm

Even your drawing shows that you have no neutral at the switch.
Your drawing actually shows where the neutral is. (It is the black one at the ceiling rose)

You could save yourself a lot of grief by putting the old switch back and buying a Philips HUE lamp. (You can control it from your phone, and if you have an Amazon echo, you can tell it to turn the light on or off or to dim it. )
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Postby TheVOID » Thu Jul 05, 2018 5:24 pm

If I have no neutral how is power flowing through the blue cable?

If I follow the black cable the power goes through the light, out the brown, connects to the red, goes to the old switch which sends the power down the blue and the red at the same time. The black circle in the middle isn't a switch anymore, I'm using the metal connectors in it to hold the wires together.

L1 and N are connected to the same wire and both provide power to the device as my light is constantly on.

I'd rather figure out what's wrong and resolve it than purchase another item as a quick fix.
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Postby Mr White » Thu Jul 05, 2018 9:37 pm

There is no neutral at the switch. Your own drawing shows where the neutral is.

As you said

TheVoid wrote:I've either completely misunderstood how the neutral works


When most 2 way switching systems are installed, a "twin and earth" is run from the ceiling rose to the first switch. From the first switch to the second switch a 3 core and earth is run. (The 3 core and earth used to be coloured as you have, red, yellow and blue)

So unless you can get the other end of the cable (with Red, Blue and Yellow) up to the ceiling rose, your switch will never work.

If it is of any consolation, a lot of people buy "smart switches" and find out (as you have done) that at most switches there is no neutral.
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Postby TheVOID » Thu Jul 05, 2018 9:48 pm

What difference does it make if I run the neutral from the rose rather than the middle part, the old switch that’s just a connector now

I know these come off as dumb questions but I’d rather learn why I’m wrong than give up
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Postby Mr White » Fri Jul 06, 2018 8:38 am

Your switch has no neutral, that is why it does not work.

As I have said before your drawing clearly shows you have no neutral. Just because you connect a wire to something does not mean it is neutral.

Your drawing clearly shows you have connected the blue wire to the switched live.

Its not where the neutral comes from (In this case) it's the fact the only neutral you have is (where it should be) at the ceiling rose.

If I am wrong then your new light switch would work, but it doesn't.
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Postby TheVOID » Fri Jul 06, 2018 9:23 am

Right now we’re getting somewhere, my understanding was the live and neutral are the same type of wire so feeding off it would be okay.

If this isn’t the case I’ll try and find a neutral at the ceiling rose and connect that up but at the moment I only see a red and a black cable going from the power source to the ceiling rose
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Postby Mr White » Fri Jul 06, 2018 6:14 pm

In your case red is supposed to be live and black is neutral (That does seem to be the case) But you can not use one in place of the other, which is what you have so far done.

The Neutral is at the ceiling rose (where you would expect it) and you have connected your new switch to the blue (which is connected to red)

I admire your determination, but if it is wired conventionally (Which is seems to be) there is no easy way to get a neutral to your switch.

A clear in focus picture of your ceiling rose would help
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Postby TheVOID » Tue Jul 10, 2018 4:57 pm

Just trying to find a way to light it up so I can get a clear picture but maybe this diagram will help as it's clearer than the photos I'm taking

So the black wire is the neutral coming from the power source and the red wire is the live, should there be a 3rd wire coming from the power source for this to work our can you split the neutral at the ceiling rose?

When this is setup the Smart Switch shows as off but the light is actually on, then when you turn it on the light goes bright for a second and the switch reboots.
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Postby TheVOID » Wed Jul 11, 2018 3:42 pm

I've finally sorted it. So I was getting confused by the way the switch instructions are worded. You need TWO lives going into the switch and one neutral out, so I ran the second live to the switch and hey presto it's all working.

Thank you for your patience and for taking the time to help me Mr White
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Postby Mr White » Wed Jul 11, 2018 6:16 pm

Please do not tell me that drawing is how you have wired it.
You can not under ANY circumstances use the earth as a normal conductor.
To do so is not only dangerous it has the potential to KILL ! electricity has no prejudices, it kills anyone

Your error is that you do not understand how electricity works, your switch does not need two lives, it needs a live and a switched live and a NEUTRAL as I said all along, most switches do not have a neutral and what you have done is in ignorance which will end up in some poor soul being electrocuted. Just because it works does not mean it is right or safe.
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