Neutral switch question

[Mikey]

Ok so I was asked this question recently, about a lighting circuit

Why is the switch in the live and not the neutral?

Ok, so a switch in the neutral side would still have the ability to turn the light on and off,

however, does this mean that there is still a voltage all the way round the circuit up to the light or is there a voltage all the way round the circuit up to the switch in the neutral, and this is dangerous for obvious reasons.

Does this mean you can have voltage without current?

Any feedback appreciated

 

[DurhamSparky]

does this mean that there is still a voltage all the way round the circuit up to the light or is there a voltage all the way round the circuit up to the switch in the neutral, and this is dangerous for obvious reasons.

Does this mean you can have voltage without current?


think you answered your own question

 

[Mikey]

so you can have voltage but no current?

is it uo to the switch or the light?

 

[jpmiff]

hi

there will be voltage upto the point were you break the nuetral with the switch.

 

[oldtimer]

Ok neutral switches works but here is the catch if you switch off a light in a room the light is electrically dead if you switch the live but if you switch the neutral then there is a perminant live at the light as fo current flow because no neutral no current BUT the majority of people who work on a light ie relamp/repair/replace do not isolate at the CU hey "just" switch it off at the switch. Now in a switched neutral situation you can switch the light off and when you go to work on it you can get current flow ie through your body or as we like to call it in the trade electricution.
Remember if Joe Bloggs does this it is an unfortunate accident if a spark did it he/she goes to jail.
The only thing I am confused about here is why people try to circumvent the regulations they are here for a reason and you could take it further and say why use fuses if you did not well thats another story

 

[Des 56]

One way of visualising the question

If a socket is wired wrong (reversed polarity) the washing machine is then plugged into the socket
Because the socket switch now switches the neutral
If the plug is left in the socket,"even with the switch in the off position",someone opening up and working on that socket will be working on a fully live machine

Because the plug fuse is always fitted at the live pin.it also means that there would be no local fuse protection to anyone having a whallop off that live machine

Reverse polarity or/and neutral switching is high up there on the most dangerous of bad wiring practice

 

[Mikey]

Thanks for the replies, yeh i just wanted to be sure, the idea of voltage but no current thing was confusing me a bit.

@ oldtimer, dont worry no one is putting a switch in the neutral, its was just a question from a bloke at work who tests me every now and then.

 

[Spudnik]

And its good to ask

 

[telectrix]

similar problem arises on some old installations where both L & N are fused at the board. if the neutral fuse fails for any reason, all the lights won't work but there is 240v all through the circuit.!!!

 

[EasT]

On a similar topic - I know that people decry the use of electrical screwdrivers with neon testers. I like them. Being cautious, if I cut a cable to make a connection with power of at CU and then pull the circuit fuse only to work I always test the cut wires to make sure I've pulled the correct fuse before jointing.

Well a few months ago an item plugged into a wall mounted trailing socket failed to work. I checked the fuse on the socket. No live thru it. Replaced the fuse and still no live. Suspicious I thought. I replaced fuse in appliance and all worked. I went back to the fused switch on the incoming to the garage and it had been wired the wrong way round meaning all neutrals were switched. I had been here for over 20 years and as a simple diy man would not have known without my neon screwdriver.

 

[High Tower]

Throw it away

Neons work on the principal that you become part of the circuit and provide the potential difference

The only thing between you and230v up your arm is a crappy 3p resistor in the handle, if this fails you get a wallop!!

Live testing is by far the most dangerous procedure we have to carry out so caution is a must. If you are going to do such tests then you need to spend the
Money and buy a GS38 approved voltage tester, I can highly recommend the Fluke T-5

Buy it as a deal with a volt stick as these are great for proving live and finding dropped neutrals, however only a approved voltage tester should be used for testing for dead

 

[EasT]

To be honest I have always believed that (provided one doesn't drop it in water (lol) a failure is unlikely to cause electrocution with the neon tube and resistor in circuit. Are there documented cases and if so I am suprised that they are sold in today's HSE environment.

I have always believed that the really significant danger was a false negative. I always test mine (in passing) before and after on a known live (plug socket for example).

 

[High Tower]

It's up to you at the end of the day but they are dangerous, inaccurate and more to the point look soo unprofessional if you want to be a spark then a approved tester is a must

 

[Darkwood]

Voltage without current.......

Think your visualising voltage the wrong way, the best way to look at voltage is by its dictionary meaning i.e. 'Potential Difference', the word potential in its self explains what it means, when you use your testers between 2 points in a circuit you create a high resistance connection between the two points which in effect allows a reading of the potential difference to be displayed, everything that isnt directly connected with each other has a potential difference but on a minute scale to large scale as in static electricity we experience daily, also the neutral as we call it is created by tapping off the star point in the step/down transformer in the sub station and this is also the same point we get the earth from hence their is no voltage difference between neutral and earth (normally), so taking a measurement between neutral and earth will show no voltage (provided all connection are correct), N/E are divided into seperate conductors either at the sub-station(tns) or the consumers cut-out (tncs).....

 

[telectrix]

agree with hightower, neons are inaccurate, but so are volt sticks. yesterday i was called out to a non working PIR Floodlight. volt stick said "dead". suspicious, i then checked at source, still "dead". out then comes the fluke approved tester. shows 230v at source. turned out to be a duff lamp. and its not a mickey mouse volt stick, either, its a fluke. just proves-- check and check again. test tester on known "live" first.

 

[oldtimer]

East in that situation why did you not do the standard procedure and test between L-N , L-E, N-E I was called out 2 weeks ago and the guy said there is no power in the garage and his father inlaw who knows a little about electrics said there was no supply. So I did the above and found there was no neutral

 

[High Tower]

agree with hightower, neons are inaccurate, but so are volt sticks. yesterday i was called out to a non working PIR Floodlight. volt stick said "dead". suspicious, i then checked at source, still "dead". out then comes the fluke approved tester. shows 230v at source. turned out to be a duff lamp. and its not a mickey mouse volt stick, either, its a fluke. just proves-- check and check again. test tester on known "live" first.

That's it mate, that's why it's always said that volt sticks should never be used to test for dead, if used right they do have their place but only if used right! I do the same and only use mine for fault finding but I do the same I double check everything with my T5.

 

[EasT]

I don't think I would trust any equipment (other than my fingers ) to not give me a false negative. As before: are there any reports of neon drivers leading to electrocution, other than when they have been immersed in water etc.?

 

[Rikki Barrett]

Neon drivers light up on alot of things that are NOT live, thats why they cannot be trusted and should not be used for dead testing. Why rest ur life on a cheap and unreliable product? I agree with everyone else...............bin it. If you dont want to spend to much money, buy a steinel combi-check.

 

[Mikey]

@ darkwood - thanks for your reply,

also the neutral as we call it is created by tapping off the star point in the step/down transformer in the sub station and this is also the same point we get the earth from hence their is no voltage difference between neutral and earth

this is an area im trying hard to get my head around ^ im finding it a bit confusing.

There is 240v between live and neutral, but there is 0v between earth and neutral because they are connected together, and are sort of the same thing???

Also if neutral is 0 volts how does current flow through it, or is it that there is 240volts potential difference between the live and neutral that causes the current to flow in the first place??

I find it confusing because the neutral is described as the return of current but really we know that the electrons are just sort of moving back and forth????

Generally confused by the almighty neutral...

Again, any feedback greatly appreciated, this is driving me a bit bonkers.......