Few eletrical questions

[Sneezy]

I'm wanting to illuminate the area around my kitchen sink. There's a cupboard over it and when you stand at the sink the room light is behind you. I thought about getting a self-contained strip light that just plugs into the mains rather than wiring something into the lighting circuit(s). Screwfix sell them. I can screw the light to the underside of the cupboard. I'm a bit worried about the metal sink and all that water being a few feet from the light. There's no earthing - sink to pipe, pipe to pipe. There is an RCD though.

Is there anything about an energy saving bulb that might make it more likely for a fuse (5 amp) to blow in a table lamp?

Finally, I'm thinking of adding a second light to an existing light and switch, plus moving the existing light. I can't find instructions to do this anywhere on the web. Plenty of info on adding a new light /and switch/. I don't fully understand how it all works - I was a bit surprised to find that the mains and the switch both go to the light. I thought a switch came between the mains and the light - hence "switch". Must confess I'm not too sure what the neutral wire does either. I know, I know - if I don't know want I'm doing I should leave well alone but if the instructions are clear I should be fine :) The light's in the cellar and is on it's own fuse. All the cables are in sight.

TIA

[Christian McArdle]

As long as it is not in a position subject to splashing, it should be fine. Putting it on the RCD would be reasonable, as it isn't the only source of lighting. There is no need for supplementary bonding in the kitchen. Indeed, some regard it as increasing danger in a kitchen environment.

No. It is less likely to blow. Although it will draw additional energy during warm up phase, compared to an incandescent bulb, it will not have the huge spike that occurs when the bulb blows. If you are choosing a fuse for its plug/FCU find a smaller one. A 1A or 2A fuse would be better than a 5A, although 3A is easier to find.

You scaring me...

Christian.

[Sneezy]

"Christian McArdle" wrote in news:4034c77e$0$7072$ [e-mail]:

Good.

Exactly what I was thinking. The fuse has blown in a table lamp I have. In my life (27 yrs) I've only ever had 3 or 4 fuses blow, so it's rare. Hence me asking.

Why? :) Clear instructions and all should be fine. Not like open heart surgery where any number of things could go wrong. Just a case of putting the wires in the right place and hey presto. Am I violating the electrician's art? ;)

[Owain]

"Sneezy" wrote | Finally, I'm thinking of adding a second light to an existing | light and switch, plus moving the existing light. I can't find | instructions to do this anywhere on the web. Plenty of info | on adding a new light /and switch/. I don't fully understand | how it all works - I was a bit surprised to find that the mains | and the switch both go to the light. I thought a switch came | between the mains and the light - hence "switch".

The switch does come between the mains and the light *electrically* but the cable usually goes to the ceiling rose first *physically* because it usually makes wiring easier and cheaper.

But it doesn't have to. You can run the cable to the switch first if you want.

| Must confess I'm not too sure what the neutral wire does either.

It's the other half of the dual-carriageway that the electrikerons use to get home to the power station after they've had their day trip out through your lightbulb. Think of the earth wire in a T&E cable as the central reservation that keeps everything safe.

| I know, I know - if I don't know want I'm doing I should leave | well alone but if the instructions are clear I should be fine :)

You really should start with Reader's Digest Plugs and Wires 101 and work your way through to Lighting.

| The light's in the cellar and is on it's own | fuse. All the cables are in sight.

That makes things a lot easier as if it's the only thing on the fuse you don't have to worry about other lights Looping In And Out and Shaking All About.

Owain

[stefek.zaba]

As far as 'why is there a permanent live and a switched live in a ceiling rose' goes: look around the Web for the magick words "loop-in". You should find yourself able to work out why there are 4 separate terminals in a 'normal' ceiling rose, and how the switch is indeed 'electrically' inbetween the permanent live and the switched live.

If you're really 'not sure what the neutral wire does', I'm not sure we can explain - or that you ought to be fiddling with wiring. If I use words like 'it completes the circuit', or 'it provides the return path for the current flowing through the load', I'm referring to such basic concepts of electrickery that I don't feel I'm helping. Maybe you should spend some time with a battery, a bulb, and some bits of wire to get more on top of this mysterious force, and see if you can simulate say a two-way switching circuit using your bits of wire, before you tackle the wiring of your add-on lamp? Then you'll be in a much better position to work out what to do from the phrase 'it goes in parallel with the current lamp' than if someone spells out 'connect red wire here, bare copper wire which you must put sleeving over there, black wire there' which you try to follow with no mental model of what's going on...

HTH, Stefek

[nick smith]

Most decent switches come with a wiring diagram in the packet..... but as Stefek suggests, a bit of time spent getting the basics understood would be time well spent - don't forget touching a live mains wire gives you more than a little tickle, and may well kill you......

Nick

[Sneezy]

[e-mail] wrote in news:c12uue$crb$ [e-mail]:

It's sort of amusing (well it amuses me anyway). For some reason I didn't make the connection (no pun intended) between the battery, bulb and two bits of wire setup that I experimented with in science at school, and the live/neutral/earth of mains electric. I thought it was different - no idea why. Makes more sense now. Just a different nomenclature.

Parallel meaning that each lamp draws power from the same point rather than putting them in chain, which wouldn't work. I did think about wiring each new lamp into the existing lamp but that would mean too many wires unless I moved the whole lot to something suited to the task such as a junction box. Switch turns power on and off at the junction box, each light is powered from the box. Just guess work though. I'll do a Google on "loop-in".

Thanks.

[Sneezy]

"Owain" wrote in news: [e-mail]:

Understand. Like a Ethernet network is logically a bus but physically a star.

So how come if I grab hold of the live wire I get fried - how are the "electrikerons" getting home?? Lightening doesn't go back to the cloud neither. Science was never my strong point, sorry. Computers I do understand, he says desperately trying to redeem himself :)

Will see if I can get my paws on the book.

The guy that did the wiring clearly had a thing for separate fuses. There are single plug sockets that have their own fuse. All I can think of is that he lost his chisel and couldn't dig out the walls :)

[Martin]

Unless its token ring.

Thats because home is anywhere that is a lower potential than the source and you are a path to home (ground) unless your standing on a rubber mat. In terms of the carriage way example above there are many ways home.

[Andy Hall]

Yebbut that ain't Ethernet.

There is 10base2 thin ethernet I suppose, but that is not used very much any more.

.andy

To email, substitute .nospam with .gl

[Martin]

Good point :)

[Sneezy]

Andy Hall wrote in news: [e-mail]:

Yep. Ain't Ethernet if the topology isn't a bus/star - requires CSMA/CA whereas ring uses a token, hence token ring. Ancient anyway. The 10base2 and similar designations just refer to the cable medium, connectors and distancing AFAIK. Networking isn't my thing.

[Sneezy]

Sneezy wrote in news:Xns9494854C5199mapspartntlworldcom@62.253.162.201:

Making progress on this :) Thanks to Stefek "loop-in" clue I found this:

which initially confused me because the picture of loop-in and explanation look/read more like serial than parallel. However, I now see that the lights are physically in serial but electrically in parallel - the destinction Owen explained. The live/neutral wires are carried on from light to light rather than having one live wire in the first light and a neutral coming out the last light in the chain. It would be the fairy light nightmare writ large :) I'm now guessing that the difference between light/switch|light/switch and light/light/switch is the location of the live wire that feeds the second light. A bit more searching on the Web should give me the answer. It's looking much more simple than I first imagined.

Look on the bright side - I could be wanting to fit a gas fire :D

[John Rumm]

CSMA/CD actually ;-)

[stefek.zaba]

Yes, you've got it: the 'permanent live' and neutrals are a buss which feeds each lighting point and runs from each one on to the next; while at each lighting point there's also an 'outgoing' wire to the switch from the permanent live, and a 'switch return' from that switch (second wire, carried in same cable, wire sheath typically black and should have little bit of red sleeving or tape on it to say 'I'm Live Too!' but often doesn't) which feeds the live side of the bulb. The conventional arrangement is that the neutral and switched-live terminals are at the outer edge of the rose, while the permanent-live and earth terminals are towards the middle.

I wouldn't put it like that: simply, you run the 2-core+earth cable to the second light by connecting at the existing rose as follows (speaking cable-to-terminal): earth-to-earth, neutral-to-neutral, live-to-switched-live. The second light just 'parasites in parallel' :-) off the first one.

HTH - Stefek

[Sneezy]

John Rumm wrote in news:kKbZb.8037$Y% [e-mail]:

Yeah - the A comes after the D :)

[Sneezy]

[e-mail] wrote in news:c13hqm$t87$ [e-mail]:

So it's the live that's switched. If black is used to carry live back to the light/rose, then neutral is doubling as a live wire, in addition to black being live to carry power to the switch. That explains a lot. Given all the regulations governing electrical installations, it seems a bit naff to rely on a bit of tape to spare some poor electrician from being fried. Should be special wire for the purpose??

So if I wanted to have a second switch rather than run 2 lights from the same switch I would do live-to-live rather than live-to-switched-live to supply the second light, and then wire in a second switch at that light.

I have a bit of cable that some electricians kindly left behind when fixing a fault in the lighting at my previous address. Handy :) Just need a rose and I'm sorted.

A big help - thanks!

[John Rumm]

A tad O/T this (well alright, completely then ;-)

Bizarre lightening factoid: The strike often does go back to the cloud!

Normally you get the first stage of the strike as an almost invisible "stepped leader", as the high electrical field strength causes the air between cloud and ground to break down and ionise. This trail of ionised particles is highly conductive, so when this leader reaches the ground it completes a circuit which then allows a massive current to flow between cloud and ground. This is the "return stroke", and it is this that you can normally see, because, you get the massive current flow causing rapid heating of the air creating the flash and the bang. Since this may not actually fully discharge the cloud before the ionised particles disperse, you can get a number of follow on "dart leaders" that re-establish the ionised pathway and allow successive strikes in rapid succession.

[John Rumm]

The convention is to use the red to carry power to the switch and the black (suitably marked) as the return to the bulb.

Well if you work on the principle that if there are only two wires to the switch then they must both be live when the switch is closed.

There is - you can get twin red T&E - e.g. :-

So if I wanted to have a second switch rather than run 2 lights from the

Yup. There are some diagrams here:-

[Owain]

"Sneezy" wrote | "Owain" wrote | >| Must confess I'm not too sure what the neutral wire does either. | > It's the other half of the dual-carriageway that the electrikerons | > use to get home to the power station after they've had their day | > trip out through your lightbulb. Think of the earth wire in a T&E | > cable as the central reservation that keeps everything safe. | So how come if I grab hold of the live wire I get fried - how are the | "electrikerons" getting home??

They're running down your legs and scampering across the wet grass to home. I know they've got legs because there's a picture of an elektrikeron with little legs scampering about in Every Boys Book Of Home Bell-Hanging and Gas-fitting.

| > You really should start with Reader's Digest Plugs and Wires 101 and | > work your way through to Lighting. | Will see if I can get my paws on the book.

Or something similar of that nature.

Owain