Re-wiring an EU 2 prong to a UK 3 prong plug - not sure which is live/neutral?

loz_the_guru

Well-known Member
Hi all,

My partner has a set of LED fairy light type things which came with a 2 pin EU style plug, which she used with an adapter. Unfortunately the plug got knocked, and the pin broke off inside (they're fairly cheap looking things). She's keen on them however and I'm keen not to re-pin them above the bed, so I thought I'd just whack a UK plug on.

However, i've come across a snag. The EU plug is presumably reversible, e.g. it doesn't matter which prong goes into which socket. The UK one isn't, and on top of this the wires into the original EU plug are the same colour - transparent!

Is there anyway of testing which one's which without trial and error? What's the worse case scenario if I do go for trial and error?

Thanks in advance!
 

Tempest

Distinguished Member
Perhaps I'm misunderstanding what you wrote here.
If the lights originally came with a plug that can be inserted into the socket in either orientation, then why would you think it matters which wire goes to live and to neutral now?
 

The Dreamer

Distinguished Member
I’m sure we have plenty of electricians on here that will give the definitive answer.

But as I understand it, it won’t matter which way round you wire it. As you’ve already said it doesn’t matter which way round the two pin plug goes, which would connect to Live and Neutral, so why should it matter which way round you wire it?

Live and Neutral are really bad names for each wire, as it’s AC, not DC - the only difference it makes to a circuit is where the protection (fuse or circuit breaker) goes - I’ve often thought they should be called something else.

edit: crossed with Tempest
 

John7

Well-known Member
If the wires are not colour coded, it will make no difference. Wires on an AC supply are usually given a colour so that the live wire is the one that is switched by the socket switch or the appliance switch. Also, if there is an earth connection to the appliance, you would need to identify and connect that to the correct terminal!
 

loz_the_guru

Well-known Member
Thanks all. I was assuming some fancy switching between live and earth may have been happening at socket level with the two prong plug? Do appliances on the other side of the channel not bother with the whole live/neutral thing?

No earth connection. Its all fairly cheap looking stuff, but I will wire up later today and see what happens...
 

noiseboy72

Distinguished Member
A couple of things...

Do check that what you are cutting off is just a plug and not a power supply of any sort. It may be that the cable coming out is actually low voltage not mains. Can you post picture to be sure?

Assuming it is mains voltage, fit a very low value fuse to protect the cable and fairy lights. 3A as a maximum.

In an AC supply, live and neutral can be interchanged and the device will still work. In the UK, we prevent live and neutral from being reversed if the appliance has an earth so that we always switch off the live side. Neutral is connected to earth at your fuse board, so if you had live and neutral swapped around and an appliance with an earth went faulty with an earth fault, if you only switched off the neutral, power would still flow through the live and earth. Without an earth connection, it doesn't matter which part of the supply you remove.

You will find that some TVs and other appliances only have a 2 prong connection into them, so the live and neutral can be swapped around going into them. It makes not difference to their operation whatsoever.
 

The Dreamer

Distinguished Member
@loz_the_guru

Oh sugar!

Do check that what you are cutting off is just a plug and not a power supply of any sort. It may be that the cable coming out is actually low voltage not mains. Can you post picture to be sure?


^^^THIS!!!

Running LEDs requires some sort of transformer/driver - as @noiseboy72 says, make sure that's not incorporated into the plug you've just removed, or you'll be putting 240v AC into something that only requires 12/24v DC.

Doing this will let the smoke out - which is bad!
 

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