UK Identifying live, neutral and earth in outdoor festoon lighting

Richard Cook · Jun 4, 2024

I bought some outdoor festoon lighting a few years ago and the 2 pin connectors (male and female) have corroded so I’m going to splice the connectors together using heat shrink butt connectors. Each run is 5m with a male and female 2 pin connector at each end. My first thought was that this would be a 2 min job but it turns out none of the wires are labeled so it’s tricky to work out which wires are live, neutral and earth once the connectors have been cut off.

See a few photos attached.

I can connect one end (thankfully the one end that isn’t damaged) to the “starter plug” which has a transformer (31v) so can voltage check each cable and plug it in.

At the other end, with the now exposed wires, what’s the best way to find the live, neutral and earth? I’ll then need to Wago, for testing, this to the other run but how do I work out which is live, neutral and earth on that run? Trial and error? What am I looking for? Would it trip the RCD until right? What about the transformer? Any way I can avoid breaking it with testing?

Richard Cook · Jun 5, 2024

I've carried out a continuity test on the three wires at one end of a 5m length and the other end (with either a male 2 pin connector or a female connector accepting 2 pins) and have identified which wire (out of the three) isn't "connected" to the pins. I'm assuming this is then an earth?

The next test will be to find out which wire is neutral and which is live, I'm guessing. I'll need to plug it in to test this. I'm guessing one wire should be returning 240v and the other ~0v? Do I just use the positive prob for this or do I need both?

westward10 · Jun 5, 2024

There is a remote possibility the other wire is nothing more than support like a catenary wire although making it from copper seems a needless expense. Is there continuity between the wires?

Richard Cook · Jun 5, 2024

Good point.

Yep so I get a continuity reading between a wire and a pin/hole in the other end so I know which two wires are connected to the pins/holes I just don’t know which is live or neutral, yet.

westward10 · Jun 5, 2024

Is the unknown wire not connected to the pins?

Richard Cook · Jun 5, 2024

westward10 said:
Is the unknown wire not connected to the pins?

Doesn’t seem so. No continuity reading between either pin…

Richard Cook · Jun 5, 2024

I think if I get a continuity reading between two pins and two (out of the three) wires I'm going to assume the wire without a reading is the earth and the other two wires are live and neutral. I'll then do a voltage test between the assumed earth and the other two wires. The one with a voltage would be the live and the one without would be the neutral.

I'm guessing this, on a basic level, makes sense?

westward10 · Jun 5, 2024

It isn't earth the plug is only two pin. Can you show a pic inside of the plug where the pinscare.

Richard Cook · Jun 5, 2024

westward10 said:
It isn't earth the plug is only two pin. Can you show a pic inside of the plug where the pinscare.

It's all moulded closed. To get access to the wires on the corroded end I broke it up but it's quite soft plastic so didn't smash open but I'll send you a couple more of the inside.

Richard Cook · Jun 5, 2024

westward10 said:
It isn't earth the plug is only two pin. Can you show a pic inside of the plug where the pinscare.

Some further photos. Is it unusual for three wires but only 2 pins? If that’s the case what could be the purpose of the wire not showing continuity. Maybe inside the moulded plug it was connected to one of the pins? But if so when I did my continuity test on the length with the 2 pins and then the three wires (female end cut off to reveal 3 wires) one of the pins should have continuity twice, right?

westward10 · Jun 5, 2024

You can try it.

Richard Cook · Jun 5, 2024

westward10 said:
You can try it.

Thanks for the help, by the way.

What’s strange though is when I connect an end to the power supply the lights don’t come on. But technically they should as they come in 5m lengths. I’m wondering if the unknown wire was connected to a pin to complete a circuit within each length? If so would you reckon that wire would’ve been connected to neutral or live? I’m worried about connecting them wrong to even test.

littlespark · Jun 5, 2024

its looking like the two strings of lights come from two different sets.... the pattern of pins are completely different.

what does the other gold label say?

Richard Cook · Jun 5, 2024

littlespark said:
its looking like the two strings of lights come from two different sets.... the pattern of pins are completely different.

what does the other gold label say?

No it’s all from the same set and they’re all the same. Three rubber wires going into either a male or female 2 pin connector.

KungFuTurkeyLeg · Jun 5, 2024

You really shouldn't plug them in to measure voltage if it's kicking out 230v. With the plug pins facing you, the bottom right pin is live and the bottom left is neutral. Tap out as before and you will know what is live and neutral at the other end using resistance again. No need to risk a shock.

Is the the top pin made of plastic or metal? This is the earth pin. If it's plastic there is no earth wire down that cable.

KungFuTurkeyLeg · Jun 5, 2024

Those LEDs will have a bridge rectifier in them if they are 230v. If you reverse the polarity they won't turn on. And depending on how much chineseium was used in the manufacturing, they could already be cooked.

UK Identifying live, neutral and earth in outdoor festoon lighting

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