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 10, 2024

westward10 said:
This is getting difficult for people from afar to give safe advice. You have now shot to pieces a bridge rectifier which you are considering replacing which is entirely your perogative but to give advice on what part you require is not sensible from our perspective.

I understand, @westward10 – didn't mean to create any issues I'm only really wanting to get these strings working and then I can rest easy. I won't be using the rewired strings permanently now... I'm just curious.

Richard Cook · Jun 10, 2024

1. Current per LED: 20mA (0.02A).
2. Current per Bulb: Since each bulb has 7 LEDs in parallel, the current for each bulb is:

0.02A \times 7 = 0.14A

3. Total Current for 10 Bulbs:

0.14A \times 10 = 1.4A

So a bridge rectifier of at least 400v with a current rating of at least 2A?

mainline · Jun 10, 2024

KungFuTurkeyLeg said:
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.

Using a bridge rectifier it wouldn’t matter if you reversed polarity either with ac or dc on its input.

Using ac on its input will create a rise in the dc voltage

Avo Mk8 · Jun 10, 2024

Richard Cook said:
1. Current per LED: 20mA (0.02A).
2. Current per Bulb: Since each bulb has 7 LEDs in parallel, the current for each bulb is:

0.02A \times 7 = 0.14A

3. Total Current for 10 Bulbs:

0.14A \times 10 = 1.4A

So a bridge rectifier of at least 400v with a current rating of at least 2A?

I believe it's established that the LED's are all in series. The fact that there are 7 in each bulb makes the bulbs 7x3.5=24.5V each, so the 10 bulbs in each string are using the 245V(!) mains directly from the bridge rectifier.
Each string is a series circuit using 20mA, you add these together to the give total current your rectifier will supply, your 5 strings 0.1A
However a rectifier rated at the magnitude of current you mention (1 or 2A) is more robust, and cheap enough.

mainline · Jun 10, 2024

The + and - from the rectifier will go directly to the socket for the next string.

Tagged onto the + will be the resistor and leds for that string, hence you get 3 wires but only 2 pins.

[ElectriciansForums.net] Identifying live, neutral and earth in outdoor festoon lighting

davesparks · Jun 10, 2024

Richard Cook said:
the starter lead tripped the RCD and presumingly knackered the bridge rectifier which is why I dismantled one of them.It tripped the RCD as I was changing the order of the cables and stupidly connected two wires together that stopped the bridge rectifier from working.

An RCD is a device designed to save your life should a potentially lethal fault occur. The fact the RCD has tripped multiple times during your experimentations is a clear warning sign.

I fully support your desire to learn about how LEDs work but please do it in a safer manner, you can get a breadboard, bench power supply, LEDs and all manner of electronic components cheaply online and experiment at a safe, low voltage. There are plenty of websites,you tube videos and books out there that you can learn from.

Richard Cook · Jun 10, 2024

mainline said:
The + and - from the rectifier will go directly to the socket for the next string.

Tagged onto the + will be the resistor and leds for that string, hence you get 3 wires but only 2 pins.

So what's the best way to determining which wires go together?

Avo Mk8 · Jun 10, 2024

mainline said:
The + and - from the rectifier will go directly to the socket for the next string.

Tagged onto the + will be the resistor and leds for that string, hence you get 3 wires but only 2 pins.View attachment 116843

Exactly that.
Except in the first string of lights there are 70 diodes and no resistor (and probably none needed)
And there is/was a CN0 between the bridge rectifier and R1 (two pins from the bridge rectifier, two mating pins but three wires to that connector on the right - as I understand, neither connectors now present)
Since the connectors have come apart, the OP wants to know, holding the ends of the two wires on the left, and the three wires on the right, which one goes where!
As above - What suggest you?

mainline · Jun 11, 2024

Avo Mk8 said:
Exactly that.
Except in the first string of lights there are 70 diodes and no resistor (and probably none needed)
And there is/was a CN0 between the bridge rectifier and R1 (two pins from the bridge rectifier, two mating pins but three wires to that connector on the right - as I understand, neither connectors now present)
Since the connectors have come apart, the OP wants to know, holding the ends of the two wires on the left, and the three wires on the right, which one goes where!
As above - What suggest you?

I suggest throwing it in the bin and get a decent low voltage transformer type.

Richard Cook · Jun 11, 2024

Hi folks... thanks again to everyone who has given advice – I'm almost there. Back to the original question.

I now have a set up of:

starter cable
first run of lights (end not plugged into starter cable has 2 pin female connector removed revealing the 3 wires)
second run of lights (2 pin male connector at one end removed revealing the 3 wires connecting to the 3 wires of the previous run)
third run (no connectors removed)
fourth run (no connectors removed)

The main focus is the first run of lights (3 exposed wires at one end) connecting to second run of lights (3 exposed wires at one end).

What we have concluded is that one wire is +ve, one wire is -ve and then the third wire going to +ve also – let me know if this is incorrect.

See attached photos. I'm pretty sure I have the correct wires together on the first run (two wires connected together and one by itself). Now I connect the second run. I'm less positive about which wire is what on the second run but I manage to have the following setup:

1. First run and second run light up but third and fourth run do not
2. First run lights up, rest do not
2. First run lights up, second run does not, third and fourth do light up

I only have 3 wires so feel like I have exhausted all routes unless my first run is wrong?

1.

2.

3.

Richard Cook · Jun 11, 2024

If this helps...

Avo Mk8 · Jun 11, 2024

I think you want combination No. 3, but the third wire for the second string (on the right) should go to -ve.

Richard Cook · Jun 11, 2024

Avo Mk8 said:
I think you want combination No. 3, but the third wire for the second string (on the right) should go to -ve.

It works!!!

Can you explain what is happening? I kinda get it but just know if I was to do another run I’d get it wrong

+ve to +ve with the third wire
-ve to -ve with the third wire

Thanks so much for coming back and helping. Much appreciated.

Avo Mk8 · Jun 11, 2024

Just logic!
The straight through +ve and -ve must be consistent throughout.
You had first, third and fourth strings working, so that must be the correct wiring of the 'straight through' supplies.
So that just left the input to the second string to be on the wrong side.

Going back to my crude drawing in post #42, we now know the upper straight-through wire is -ve, and the lower wire +ve.
And the third wire starts on the -ve supply and ends on the +ve.
Good result!

littlespark · Jun 12, 2024

Very well done in working out what goes where…
I think AVO has gone above and beyond with this one where many of the rest of us just decided “bin it!”

Now you have a festoon string that’s held together with wagos…

Maybe some of these? But check the right size… this was just first one I found

https://www.amazon.co.uk/Waterproof-Connector-Extension-Electrical-Protector/dp/B09WDLB9CR/ref=asc_df_B09WDLB9CR?tag=bingshoppinga-21&linkCode=df0&hvadid=79920879569851&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=m&hvlocint=&hvlocphy=&hvtargid=pla-4583520400071921&psc=1

Richard Cook · Jun 12, 2024

littlespark said:
Now you have a festoon string that’s held together with wagos…

Maybe some of these? But check the right size… this was just first one I found

https://www.amazon.co.uk/Waterproof-Connector-Extension-Electrical-Protector/dp/B09WDLB9CR/ref=asc_df_B09WDLB9CR?tag=bingshoppinga-21&linkCode=df0&hvadid=79920879569851&hvnetw=o&hvqmt=e&hvbmt=be&hvdev=m&hvlocint=&hvlocphy=&hvtargid=pla-4583520400071921&psc=1

Yes! I had looked at these but with the three cables (wires) and not one single cable I didn't think they'd work as waterproof connectors as the seal would be round the single cable but with 3 wires there's room for water ingress?

I have heatshrink butt crimp connectors which would've been fine if each wire went to a single wire but as it's 2 to 1 on both sides I'm still not sure what would be best!

Richard Cook · Jun 12, 2024

Avo Mk8 said:
Just logic!
The straight through +ve and -ve must be consistent throughout.
You had first, third and fourth strings working, so that must be the correct wiring of the 'straight through' supplies.
So that just left the input to the second string to be on the wrong side.

Going back to my crude drawing in post #42, we now know the upper straight-through wire is -ve, and the lower wire +ve.
And the third wire starts on the -ve supply and ends on the +ve.
Good result!

Thanks again so much for all your help – it's been a really fun process but of course 240v is not fun

Avo Mk8 · Jun 12, 2024

If you'r happy to have a permanent joint (not a connector) there are epoxy or gel filled joint boxes that are waterproof, though a bit clunky! eg:

6A Gel Insulated Straight Through Joint - 3 Core Flex - IPx8 | Wiska (SH0325W)

mainline · Jun 12, 2024

One of those backlight Chinese testers may have helped that’s if the tester didn’t catch fire or electrocute you.

LED TV Backlight Tester 12W LED Strip LED Panel Single LED Bead COB Light Tester | eBay - https://www.ebay.co.uk/itm/294642898613?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=Yv_QNsB4RWO&sssrc=4429486&ssuid=urSTfeYDTiO&var=&widget_ver=artemis&media=EMAIL

UK Identifying live, neutral and earth in outdoor festoon lighting

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