no neutral line in light switch... recommended practice to add

[gamb00ler]

Despite asking our home builder to provide a neutral line in all circuits .... we only have a neutral at power outlets... none at light switches.

 

I'm sure my lack of understanding of even the basics of residential wiring will be obvious from my questions.

 

I only need the neutral to make home automation simpler.  The "brains" and wireless hardware in the smart switches need a little power to operate wether the switch is open or closed.  Many smart switches require the neutral to make a circuit to supply that power.

 

I know there are smart switches that do not require a neutral.  At this time I prefer to restrict my switch selection to those that support Matter and Thread protocols.  If that doesn't turn out to be reasonable I can change my plans easily.

 

If I understand correctly I can provide continuous power to the smart switch by adding wiring and a resistor to allow a trickle of power to flow to the load even when the switch is open.  The flow won't be enough to light the bulb.... just enough to keep the smart switch functioning.

 

The obvious alternative is to run a neutral line from the switch box(es) to the consumer unit.  That isn't an easy job with our wiring embedded below the render on the walls.  Possibly there may be room in the embedded conduit to make the job easier.

 

Or... if there's a nearby power outlet can I just use the neutral line available there?  I have read comments that sharing a neutral like that is not a good idea.  Can I share a neutral between several lighting only circuits in the same wall box?  Also one of the switches I want to replace is a momentary switch to open/stop/close the driveway gate.

 

Fortunately there are only 3 or 4 switch boxes where I hope to install smart switches.

 

 

[bluejets]

9 hours ago, gamb00ler said:

If I understand correctly I can provide continuous power to the smart switch by adding wiring and a resistor to allow a trickle of power to flow to the load even when the switch is open. 

Definitely NOT.

 

9 hours ago, gamb00ler said:

The obvious alternative is to run a neutral line from the switch box(es) to the consumer unit. 

The ONLY alternative AND it must be the associated circuit neutral.

9 hours ago, gamb00ler said:

Or... if there's a nearby power outlet can I just use the neutral line available there?

Again...definitely NOT.

 

There is basically nothing "wrong" with your install as you seem to imply, simply "loop at the light" wiring arrangement which is normal.

There is also loop at the switch system but many cables must pass down the wall and be terminated in the switch box which is why the former is sometimes preferred especially when solid block wall and conduit is in use.

 

Many "smart" switches do NOT require a neutral and it might be your best shot to look for those instead.

 

Instructions to provide a neutral at certain switches have gone unheeded, obviously you were not there at the time to make sure it was done, so bad move on your part.

First rule of any work being done in LOS, be there, make sure yourself.

[thaibeachlovers]

10 hours ago, gamb00ler said:

If I understand correctly I can provide continuous power to the smart switch by adding wiring and a resistor to allow a trickle of power to flow to the load even when the switch is open.  The flow won't be enough to light the bulb.... just enough to keep the smart switch functioning.

Sounds like you need an expert ( obviously not Somchai the village electrician, and not advice on here ). Good luck finding one.

 

 

[ElwoodP]

10 hours ago, gamb00ler said:

If I understand correctly I can provide continuous power to the smart switch by adding wiring and a resistor to allow a trickle of power to flow to the load even when the switch is open.  The flow won't be enough to light the bulb.... just enough to keep the smart switch functioning.

Nope, most smart switches can be powered by a capacitor connected between live and neutral at the light.

My home is full of them as I run 'Google Home' voice commands to control almost everything.

No need to think, the switches come with the capacitor.

https://www.lazada.co.th/products/smatrul-wifi-tuya-app-alexa-google-home-123-gang-i3783968316-s14384376219.html 

[gamb00ler]

3 hours ago, ElwoodP said:

Nope, most smart switches can be powered by a capacitor connected between live and neutral at the light.

With your switch you had to access the light and add the capacitor at that point ?

 

I have a string of lights on the perimeter fence using one switch so I just need to add one capacitor for that circuit?

 

Update:  I found a YTube video that has answered these questions

[gamb00ler]

Here's a YTube video that uses the exact Sonoff module that I bought to test. 

 

This video shows in detail the wiring required to eliminate the need for a neutral line.

 

 

[CecilM]

Apart from not doing as instructed, the electrician did nothing wrong. A neutral to the light is not required.

Obvious answer would be to pull new wires, but whether that is worth the effort??? (I rewired a few switches and outlets in our house.)

PS: "Most electricians here are idiots." and I'm quoting our interior designer and head contractor. Having seen some of the work and their disregard for requests, I'm open to believing that. 

[gamb00ler]

The circuit I need to use at the light socket looks fairly simple to make.  It requires 2 diodes, 1 fusible resistor, 1 regular resistor and a capacitor.  I've never done any soldering so I would like to hire someone to make 3 or 4 of these circuits.

 

What kind of shop should I look for in CM to fabricate these simple circuits?

 

I'm attaching a schematic and a picture of a completed circuit.

[jojothai]

26 minutes ago, CecilM said:

Apart from not doing as instructed, the electrician did nothing wrong. A neutral to the light is not required.

Just to clarify this.

A neutral to the light switch is not normally required. 

Neutral is required to the light.

Smart switches may be different, but check the installation instructions.

Some may, some may not. You will get to know from the instructions for the product.

[OneMoreFarang]

On 6/19/2024 at 7:25 PM, gamb00ler said:

Or... if there's a nearby power outlet can I just use the neutral line available there?  I have read comments that sharing a neutral like that is not a good idea

Yes, it is not a good idea.

And no, you shouldn't do it.

But, it still might "work". But not the way it was intended.

 

So, just in case you have someone who proves to you that it "works", by adding such a wire, don't do it!

 

 

In general, I think ordinary electricians can't be blamed for not adding a neutral to light switches. Because in normal installations, >99%, a neutral would never be used.

 

I use plastic pipes behind the walls for all my electrical boxes. And I use 100% home automation. I like it.

I use mostly Shelly devices and WLAN and LED lights.

Easy Smart Home Automation (shelly.com)

They offer many different devices including units which don't need neutral. 

 

[nickycakes]

On 6/22/2024 at 12:30 PM, gamb00ler said:

The circuit I need to use at the light socket looks fairly simple to make.

 

 

 

I have the parts on order to build the rectifiers myself so I'll let you know how it goes.  The other options are to get an electrician to pull a neutral all the way back to the switch for each light (as mentioned earlier, not recommended to grab one from the nearest wall socket), or use the zigbee version of the relays because they use way less power and can let enough through for communication but not for the lights.  I don't want to set up zigbee and ive already got 10 of these rather expensive relays.  I really dont want to tear my ceiling apart just for some light switch automation.   

 

Will let you know how it goes and maybe can ship a few up there if you still need.

[sometimewoodworker]

23 hours ago, nickycakes said:

as mentioned earlier, not recommended to grab one from the nearest wall socket

The reason for not using a random circuit neutral is that the recommended practice is to use an RCBO for each circuit and grabbing a neutral from a wall socket will virtually guarantee that at least 2 of  your RCBO’s will instantly trip.

 

That Thailand is just getting round to a single house RCBO doesn’t change the recommendation for multiple RCBOs just that few do it

[gamb00ler]

On 1/24/2025 at 5:19 PM, nickycakes said:

The other options are to get an electrician to pull a neutral all the way back to the switch for each light

I did have neutrals run to two locations each with 6 separate lighting circuits.  The two locations I chose will likely be the only places requiring automation.  My house has decent access to the wiring above the ceiling in most areas and the in-wall conduit had room for one more wire.

 

The neutral line at the switches is just to supply power to the WiFi transceivers to control the lighting relays. 

The power draw will be extremely low.