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I wonder if someone can put me straight on a self-caused problem please.

The other day I noticed that the fluorescent light fitting in the kitchen was very close to falling off the ceiling, so I decided to fix it but also decided to give it a good clean. I fixed it securely and then reconnected the wires. I turned back on the power and to my horror the light wouldn't switch off.

Ok, here's the problem: old house = old wiring.

In the ceiling are two red wires - live twisted together go into the connector block marked L.

There are also two black wires, which I guess should be neutral tho I believe one of them to be earth as this is what I connected to the earth point on the connecter within the fluorescent light housing. I realise that these do need to be earthed.

The fact that the light switch controlling the light won't function now suggests that I've made a mistake somewhere up on the light fitting bypassing the switch altogether.

I would like to get this working as switching the kitchen light off now means I have to turn off the downstairs lighting circuit from the main fusebox. Can anyone give me a good ticking off and redirect me please in the right direction?
Many thanks.

Tekman (or perhaps in this case not so)

personal email welcome

tek @ icw24. net

This is quite scary Tekman, there is a good possibility that you will liven the body of the fluoro as with most older places lighting circuits where not earthed. I would think one cable is the supply RED is ACTIVE and BLACK is NEUTRAL, the other pair may be the switch wire.

I guess the two red cores were joined initially, so the active loops to the switch, the black neutral goes to the neutral of the fluoro, and the black from the switch goes to the active or line of the fluoro. As the light stays on it sounds like the L is the fluoro Line/Active.

My recommendation is get an electrician as this is not a thing inexperienced, unqualified, and unlicensed (depending on where you are from) person should be doing.

Re reading my last post I made a bit of an error yet again. (not my week)

Country United Kingdom

House built 1922

Ceiling wiring 2 red twisted together and 2 individual black.

Light switch end 1 red and 1 black.

Judging from Trevors post I believe the mist is beginning to clear though it does seem rather odd to me that there isn't and earth wire in any of the light switches throughout the house. Mind you the main boxes under the stairs all have an individual bare copper earth connected.
think this must be the original house wiring which is a bit scary I guess but it all works and I've inspected the cable runs and all seems in perfectly good order.

I would guess that the fuse boxes were probably replaced at some point when either the size of the service was upgraded or it became difficult to get the original style of fuses. There may be no earth grounds anywhere in the original wiring. It's not unusual to find a mix of old and new wiring in a house, but ceiling fixtures would be the most likely to be the oldest wiring as electric lights would have been the original reason for having electricity (much nicer and safer than gas lamps).

I have heard of people finding water pipes being used as grounds, and even as neutrals. People find hot and neutral reversed on some circuits even on newer houses. Don't take for granted anything you see. Check it with a multimeter first. Electrical codes first came about because of lobbying by the fire insurance industry who were upset over all the buildings burning down because of bad wiring.

Before you kill yourself or someone else, or burn down your house, call a professional electrician to fix things up. First of all, black is not neutral. It is hot. I know, black is usually the standard for ground in radios and such, but in house wiring, black is hot. Treat it with respect. Don't guess. Either study the situation until you are sure what goes where, or call a professional to help you.

Robert Scott

Mr Scott,
Before you make such categorical statements, please realise that large parts of the world do not comply with the North America way of doing things. In older installations in Australasia and the UK, red was active/live and black was neutral.

Bruce.

What country are you in?
What are the colors of the wires coming from the ceiling fixture?
What are the colors of the wires from the light fixture?

my apologies for some reason I made typo in my email address. I would prefer if people who may kindly respond to this to contact me directly rather than post on the forum as I don't have a high speed connection.

Incidentally I failed to mention this is in a house in London England built in the 1920's.
The odd thing is from what I've read pre 1971 the colour coding for wires in English houses were red for live, Black for neutral and Green for earth. However as stated I have at each light switch 1 red and 1 red. from the ceiling 2 red and two red.

tek @ ic24. net

If this is the original wiring, I wouldn't want to even guess at what the "correct" connection would be. In a lot of houses in Canada from that era, the wiring was installed by people who didn't really know what they were doing and then modified over the years by home owners who knew even less. People would add or change circuits by just making connections to whatever wires seemed to work without worrying about where those wires went.

I wouldn't put much faith in the wire colours if the wiring is old. The wiring methods installed today are completely different from how things were done in the past. I imagine that things in the UK are not much different.

There is no reason to believe that the original circuit was ever "right" to begin with, other than that the light went on and off. I have heard of people who have had similar problems, and ended up having to replace their wiring.

I think you would at the least need a volt meter to trace out the wiring to find out where it goes. As others have suggested, if you don't have experience in this area, then getting an electrician to have a look at it would be a good idea.

AC is hot both on load and neutral. By connecting one of the neutral wires to ground, you have completed a backfeed circuit.

Seems quite simple to me.

I am an electrician from New Zealand and I know that the wiring in UK is similar, 240V 50Hz right?
There is one cable Red/Black (Line/Neutral) that is powered from the switchboard, one cable Red/Black from the light switch.

The two Reds are connected together but not to the light, this provides a hot at the switch. The black wire from switchboard is the neutral for the light. The black wire from the switch is the hot for light.

Jumpering the hot in the light fitting is quite common but not so in NA. Also not having a ground at the switch is OK because you probably don't have a metal box there either.

If you aren't sure, do get an electrician, 240V can give a nasty jolt.

Roy