DIY Doctor

3 questions on switched live

Postby Gilbo777 » Sun Dec 13, 2020 11:13 am

Please bear with me. I had an electrician put in spotlights and a dimmer in my bedroom about a year ago. On a whim a bought a smart switch dimmer, naively believing a recent installation would have a neutral.

However opening the switch I have a brown live , terminated earth (as all plastic), and a blue. So I’m assuming the blue is a switched live, but he didn’t mark it up. And therefore I don’t have a neutral. Please correct me if this sounds wrong. I’m sticking with the old dimmer as I’d rather be ocd than rip

So my 3 questions
Should the spark have marked up the switched live, or is it best practice rather than regs?
If someone mistook the switched live for neutral would it blow the smart switch or worse?
The smart switch instructions mentioned a Load(light) line, which I assume is a switched live. Should they have used uk terminology of switched live, or again is that optional, or not official terminology?
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Postby chriscba » Sun Dec 13, 2020 1:46 pm

If it is connected to the switch it is not a neutral.

Yes you are correct in saying he should have marked the switch live, it is done with a brown sleeve or tape.

Usually if there is a neutral in a switch it is in a connector block doing nothing, just a loop to the light
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Postby Mr White » Sun Dec 13, 2020 2:50 pm

Gilbo777 wrote:If someone mistook the switched live for neutral would it blow the smart switch or worse?


No, because where would they connect it to? Only 2 wires and 3 terminals.

Gilbo777 wrote:The smart switch instructions mentioned a Load(light) line, which I assume is a switched live. Should they have used uk terminology of switched live, or again is that optional, or not official terminology?


"Load" is UK terminology. (In plain English) It is the device to be connected to. Lamp in this case.

You may be able to buy "smart lamps" depending on what the actual fittings you have are.
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Postby Gilbo777 » Tue Dec 15, 2020 4:32 pm

Thanks for clarifying
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Postby ericmark » Tue Dec 15, 2020 10:26 pm

Live is the word used for line and neutral, with a TN system we are permitted to just isolate the line, but with TT systems but lives need switching before working on the system.

Yes line wires when blue should be over sleeved, but until the spot lamp became popular, it was rare to take a neutral to the switch, so was common not to over sleeve.

With no neutral at the switch unlikely to do damage, just will not work.

Until the LED you could get away without a neutral, but although some smart switches will work without them flicker and flashing is a problem.
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Postby Gilbo777 » Wed Dec 16, 2020 12:23 pm

Thanks for the clarification. Is TN the more common one in the UK then ?

I think I will stick with the manual dimmer, I don’t want to risk the issues you mentioned
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