Two sets of wires for a wall light

tkhawkey · Post by **tkhawkey** » Sat Jun 29, 2024 11:20 am

I'm replacing a wall light in a house I've moved into, and there are two sets of wires coming from the wall rather than 1.

The light is on a staircase. There is another light on the opposite wall. Both lights are controlled by the same two switches, one at the top of the stairs and one at the bottom. The other light is wired with only one set of wires.

Then there is a second issue that the new wall light does not indicate which side is for the live wire and which is for the neutral.

1) do I wire both sets of wires to the light?

2) if yes, is there a way to know which side is L/N?

Someone-Else · Post by **Someone-Else** » Sat Jun 29, 2024 11:54 am

One cable may be supply in, and the other is supply out,
Or it could be one cable is supply in and the other goes to the switch
Without any means of testing it is not possible to give a definitive answer. (Which often results with a BANG)

As for which way round Live and Neutral should be connected, with that lamp holder it does not matter.

Sorry it is not the answer you wanted, next time, take pictures first.

wine~o · Post by **wine~o** » Sat Jun 29, 2024 1:11 pm

A clear in focus photo ofthe wiring at the switch MAY help us to work out how your lights should be wired.

tkhawkey · Post by **tkhawkey** » Sat Jun 29, 2024 1:18 pm

Thank you for the reply!

With the electricity on, the other light no longer turns on or off. Does that narrow it down at all?

And if not, is there a way to test the wires to find out, perhaps a multimeter?

tkhawkey · Post by **tkhawkey** » Sat Jun 29, 2024 1:28 pm

It's quite a tangle in there! There are two switches here, the one on the left in is the switch for these lights. The one in the right controls a different set of lights running up the stairs.

aeromech3 · Post by **aeromech3** » Sat Jun 29, 2024 1:29 pm

Someone-Else wrote: ↑Sat Jun 29, 2024 11:54 am As for which way round Live and Neutral should be connected, with that lamp holder it does not matter.

Beg to differ, this is a screw in lamp fitting, the centre pin should be positive and the screw thread negative.
My experience with non UK fittings, for years my hall light was this, worked fine, then it did not, my Son went to screw the lamp out and got a nasty shock, it is quite easy to touch the screw thread of the lamp (bulb) when doing this and if it is the positive and in the frame of my fitting brass

shock! Son did not remember the wall switch was in on position, did not isolate mains.
Centre pin to connecting stud better the +tve.
The surround of the Ops fitting is metal even if the lamp holder is ceramic, it also has an earth terminal and metal bracket.

Someone-Else · Post by **Someone-Else** » Sat Jun 29, 2024 1:56 pm

aeromech3 wrote: ↑Sat Jun 29, 2024 1:29 pmBeg to differ,

What you said used to be true with old plastic and metal lamp holders (Oh and it's live and neutral, where a.c. is concerned, +ve & -Ve is for d.c.) But ceramic lamp holders have a shorter connection to the outer part of the lamp and are deeper in height, the idea is as you screw the lamp (in or out) the outer (screw part) disconnects as the lamp is unscrewed. (Also the deeper height shields the thread until it is disconnected.)

Also you should never assume that cable colours are what they appear to be, hence the need for testing.

Someone-Else · Post by **Someone-Else** » Sat Jun 29, 2024 2:07 pm

tkhawkey wrote: ↑Sat Jun 29, 2024 1:18 pmThank you for the reply!

can but try

tkhawkey wrote: ↑Sat Jun 29, 2024 1:18 pmWith the electricity on, the other light no longer turns on or off. Does that narrow it down at all?

You would have thought so, but it still doesn't identify what the two cables are

tkhawkey wrote: ↑Sat Jun 29, 2024 1:18 pmAnd if not, is there a way to test the wires to find out, perhaps a multimeter?

For safety you should NOT use a multimeter, you need a proper mains tester, now I wonder where you could get one of those from (see my signature)

ericmark · Post by **ericmark** » Sun Jun 30, 2024 7:50 pm

aeromech3 wrote: ↑Sat Jun 29, 2024 1:29 pm Beg to differ, this is a screw in lamp fitting, the centre pin should be positive and the screw thread negative.

Yep you are correct, centre pin line, screw is neutral, although the outer connection is in the base of the fitting, the bulb itself will connect it to the screw thread, so it does matter.

As to wiring, not a clue what I am looking at, if I was doing it, with power off test blue to brown and see if the switch connects or disconnects the two wires, failing that with all wires in a connector block so unlikely to touch any, test for line using the earth as a reference.

ericmark · Post by **ericmark** » Sun Jun 30, 2024 8:27 pm

Someone-Else wrote: ↑Sat Jun 29, 2024 2:07 pm For safety you should NOT use a multimeter, you need a proper mains tester, now I wonder where you could get one of those from (see my signature)

I would say you will need a multimeter, one of these,

: Clamp-meter-small.jpg (55.86 KiB) Viewed 955 times

is what I would use, they have no wired amp range, so unlikely to do you any harm if wrong range selected. The red one also have a non-contact volts range.

Yes, in theory to test for dead, the tester should not need batteries, and have no range change switch, and you should use a proving unit to test the tester, which must test at 50 volt or less AC as part of the test, it will normally ramp to 400 volts to show all indicators work, but the 50 volt indicator could be faulty and only work with 400 volts, so it must be also tested at extra low voltage 50 volts to show it will work with lower voltages.

When I have used the proving units, most did not test at 50 volts, so all the hype was to no avail as the proving unit was not fit for purpose.

Since you may need to live test with earth as a reference point, the tester needs to draw very little current, or it will trip the RCD/RCBO so the old bulb proving units are not any good any more.

And to test if there is current in the neutral or not, to test for borrowed neutrals, one needs either a clamp on meter, so you can test without disconnecting, or a neon screwdriver, which may light as you disconnect a borrowed neutral, although not always, however anyone who says put neon screwdrivers in the bin, is being a bit silly, they are not what should be used to test with, but they are a good second string to ones bow.

The tester in the link is not suitable to test for dead, as it uses batteries. Even these

: Tester and proving unit.jpg (19.18 KiB) Viewed 955 times

are no good, although better, as the proving unit does not ramp test, however at least testing at 240 volts not 400 volts, but since the testers are not foolproof, what one needs is common sense, realise the tester may not work A1 and allow for it by using more care and maybe a second tester like a neon screwdriver.

I love my clamp meter, it will measure AC, DC, amps and volts, also a continuity test, and non-contact volt test with the red one, it does need some care as can select wrong range, but would I knock a nail in with a handy shoe or rock to make it safe, yes I would, clearly better if one has a hammer to hand, but to claim I could not make the nail safe as only had a shoe to knock it in with, don't think that would be accepted.