Bloody electricians!

[havoc]

Which bright spark(y) decided that, when talking about light switches, they'd have two lots of interchangable terms:-

Common = live
Live = switched live (which also happens to be neutral, but nowhere on the switch or the attached instructions does the word "neutral" appear).

So, you're at home, changing a light switch (removing a dead dimmer switch and putting a normal one in its place). You're faced with a black and a red wire. Great, neutral and live - I recognise them! You then look at the new switch, which has marked on it C and LI (L1?!?) LI = live, surely, and so by elimination C = neutral, right? But then the instruction leaflet doesn't mention C or LI, but Live and Switched Live. So C must be the same as Switched Live, of course.


NOPE...depending on the set of terms you're referring to, "Live" could be either one of the two terminals. Are these guys bloody suicidal, or is this a deliberate attempt to keep themselves in business by turning a simple DIY operation into a game of Russian Roulette?!?


Anyway, after a couple of phone-calls to ensure I don't plunge the whole house into darkness or send myself into orbit, it's now done. Didn't enjoy one second of it though...

[netherfield]

Simple answer: don't touch what you don't understand.

[Gareth79]

There shouldn't be any risk because none of the wires will be live if you have switched off the circuit (and used a meter to test that).

Anyway, switches can be connected in various ways, so the terminal labeling won't look straightforward if you are only expecting to connect it as on/off.

[tank slapper]

There is no neutral connection at a light switch. C is common, which is the live feed from the lighting circuit. L1, is the switched output and goes to the lamp. If you had a 2 way switch, it would be marked C, L1 and L2.

If you are only installing a simple one way (on/off) switch, chances are that the red wire is the live feed and the black one is the switched live. You can check by looking at the light fitting. Since it is a simple loop circuit with only one output, there is no functional difference whichever way you connect it.

If there are more than two wires, and you aren't sure what you are doing then please get someone who knows to do it for you.

Edited by tank slapper on Sunday 16th October 20:23

[miniman]

As above, in a simple one way switch it makes 2/3 of fk all difference which way round you connect it.

[driverrob]

tank slapper said:

.... You can check by looking at the light fitting.

Really? Any light fitting (aka ceiling rose) I've had to work on makes the switch itself look child's play. A neon mains testing screwdriver is my friend.
e.g.

[tank slapper]

Well for one fitting with one switch, there will normally be two ends of ring main and one end that leads to the switch. The lives, neutrals and earth connections of the ring main will be connected to each other somehow, and the wire leading to the switch will have one end connected to the lives and the other connected to the lamp holder - it will be the odd one out. The other wire from the lamp holder will connect to the neutrals. If you have more than one fitting off the same switch or more than one switch then it can get a bit more complicated.

As with anything mains electrical, if you aren't sure, leave it alone. It has the potential to kill you or cause a fire if you get it wrong.

[PoleDriver]

The lettering on the switch/dimmer/light fitting is very obvious if you know what you are doing. If you don't understand them find someone who does!

{Or at least make sure that you are insured against fire and self-inflicted injury!)

[VEX]

Pah, 230v only tickles after a while.

Did it twice to myself on circuits my electrician was supposed to leave dead or safe.

Time to find a new electrician!

V.

[Brite spark]

tank slapper said:

Well for one fitting with one switch, there will normally be two ends of ring main and one end that leads to the switch. The lives, neutrals and earth connections of the ring main will be connected to each other somehow, and the wire leading to the switch will have one end connected to the lives and the other connected to the lamp holder - it will be the odd one out. The other wire from the lamp holder will connect to the neutrals. If you have more than one fitting off the same switch or more than one switch then it can get a bit more complicated.

As with anything mains electrical, if you aren't sure, leave it alone. It has the potential to kill you or cause a fire if you get it wrong.

lighting circuit as a ring main? its a radial circuit usually
Live conductors also includes the neutral, line conductors wouldn't

I've also seen lighting circuits wired in weird and wonderful ways over the years, so would be very reluctant to suggest that something will be wired a certain way, it may well not be.

Brite spark said:

tank slapper said:

There is no neutral connection at a light switch.

I wouldn't guarantee that to be the case.

havoc said:

stuff

Your lack of electrical knowledge isn't really an electricians fault is it! The light switch you struggled with isn't part of some grand conspiracy, although the wearing of a tinfoil hat could of had some interesting consequences when added with electricity.
Every profession has elements that would be unfamiliar to people not involved with it.

Edited by Brite spark on Monday 17th October 01:20

[jas xjr]

My way of doing it would be to replace like for like

[King Herald]

Gareth79 said:

There shouldn't be any risk because none of the wires will be live if you have switched off the circuit (and used a meter to test that). and flicked your finger across the wire to test that.

Anyway, switches can be connected in various ways, so the terminal labeling won't look straightforward if you are only expecting to connect it as on/off.

It will either work or not work, or make a great huge bang.

[havoc]

You guys are getting more like The Lounge - "lets have a go at the OP!"

- I sought advice
- I got it right
- ...and of course the Circuit Breaker was off!


Does anyone here have a Quality Control / Health & Safety / Process Analysis / Process Improvement background? I must assume not. My point, which everyone has soundly missed, is that it's frankly stupid/dangerous to have two CONFLICTING frames of reference for something like electrical circuits.

Just saying "if you don't understand it don't touch it" is avoiding the problem in the most facile way - this SHOULDN'T be difficult. If you were designing this from scratch no-one in their right mind would set these frames of reference up, yet you've all carried on as if it's perfectly normal/logical.

Do you disagree?

[Bill]

But you might DIE or cause a FIRE.

I too love the irony of people telling you not to mess with things if you don't understand them, when you've only asked so you can understand.

[Brite spark]

havoc said:

Does anyone here have a Quality Control / Health & Safety / Process Analysis / Process Improvement background? I must assume not. My point, which everyone has soundly missed, is that it's frankly stupid/dangerous to have two CONFLICTING frames of reference for something like electrical circuits.

Do you disagree?

There isn't " two conflicting frames of reference" as you put it, com and L1 when marked on a switch are a well known commonly used standard.

Common (com) is the feed to the switch, this may link to more than one point. (Hence common feed)
L1 (switch wire) is the return live from the switch to the light, this has power through it when the switch is on and is dead when the switch is in the off position. How is that dangerous?

I assume you have a background in process improvement/analysis and quality control?
If I had a go at any of those there would be bits that may not be logical to me and may even seem daft, but someone who understood it at a better level would know the reasoning behind it.

Edited by Brite spark on Monday 17th October 11:11

[havoc]

I think you're arguing out of defensiveness, not through logic. Read my first post again - 'live' was used in opposite contexts in the two different naming structures - one on the switch, one in the attached leaflet.

For you to say there's no issue there is ridiculous - there isn't to you because you're an expert in the area. But to an objective observer it's patently absurd.

My background - I have a little training in process review, but this is surely common sense?!?

[rsv gone!]

havoc said:

For you to say there's no issue there is ridiculous - there isn't to you because you're an expert in the area. But to an objective observer it's patently absurd.

Are you approaching that as somebody who has no knowledge of electrics? Would you tackle a boiler in the same way?

When you understand that a switch only closes the circuit, you realise that it makes no odds which way you wire it. There is no live marked on a switch as they are both live (when the switch is closed). The red (or brown) is 'most live' black/blue is switched live. (You could also get cable specifically for switch drops which had two red cores.)

Edited by rsv gone! on Monday 17th October 14:09

[King Herald]

havoc said:

You guys are getting more like The Lounge - "lets have a go at the OP!"

- I sought advice
- I got it right
- ...and of course the Circuit Breaker was off!


Does anyone here have a Quality Control / Health & Safety / Process Analysis / Process Improvement background? I must assume not. My point, which everyone has soundly missed, is that it's frankly stupid/dangerous to have two CONFLICTING frames of reference for something like electrical circuits.

Just saying "if you don't understand it don't touch it" is avoiding the problem in the most facile way - this SHOULDN'T be difficult. If you were designing this from scratch no-one in their right mind would set these frames of reference up, yet you've all carried on as if it's perfectly normal/logical.

Do you disagree?

How can you criticise something that you obviously know nothing about??? What you are referring to is probably easy peasy to a proper electrician, and just because you don't understand it doesn't mean it is dangerous.

[no eye deer]

havoc said:

................So, you're at home, changing a light switch (removing a dead dimmer switch and putting a normal one in its place). You're faced with a black and a red wire. Great, neutral and live - I recognise them!

Herein lies a large part of the issue. Faced with these two wires at a switch you could be forgiven for assuming that Red (now brown)= live and black (now blue) = neutral especially considering as this is how the cables in a ring final (eg for sockets) would present themselves.

However, with respect, what that assumption displays is a lack of understanding of how lighting circuits are configured. You would not usually expect to find a neutral at the switch (although you may do so in certain configurations e.g. loop in at the switch or where a neutral has been deliberately introduced in addition to the usual Live and switched live to perhaps feed a neon indicator).

It seems as if the cable at the switch that you found was not correctly marked. The red would indicate the live and the black should have been sleeved with red tape or sleeving to denote it as being switched live (or vice versa depending on how the switch cable was connected). Sleeving the cable in this way is designed to aid in identification. Switch cable can also contain 2 cores of the same colour for this very purpose but as its about x2 the price of standard t&e it's seldom seen in practice.

Had the cable been so marked would that have caused you to think again as far as your assumption that red was live and black neutral? What I'm getting at is that faced with such a cable at the switch, experience would suggest that it's either not been sleeved or that possibly somethings afoot. A quick check at the rose/junction box would clear that up.

havoc said:

I think you're arguing out of defensiveness,

Again, with respect, the defensiveness would seem to be on your part. There need be no reason for you to be so though. That you found the markings confusing is in no way a sleight against you. That does not mean that the marking system is wrong either. Simply put it is not aimed at the diyer it's aimed at the experienced installer. Please don't be offended if you are the former and not the latter.

regards

jeff

[netherfield]

If OP had asked for help and used a different title for the thread, I have no doubt help would have flooded in.

A bit like saying ' Bloody Accountants make tax forms difficult to fill in'.