light switch terminals 'live' when off

[Raybuild]

With the light switch in 'off mode' the live wire lights my neon screwdriver and the 'return' wire doesn't - OK. If I take the light bulb out and with the switch still 'off' the 'live' wire still lights the neon but now so does the 'retun' wire. All the upstaire lights are like this. The downstairs lights are normal and OK .
I'm not an electrical idiot- I've always rewired my own houses and my sons' and daughters - this house I've never touched . The wireing must be over twenty years old - some of it more.
I wll appreciate your oppinions -RAY

 

[kai]

Is this a spoof post? - I hope not.

You state that you have rewired houses in the past?

The input terminals of a lightswitch, or indeed any switch will remain live when switched off, because the incoming supply is still available at the switch inputs - that is the reason you have to be careful when looking inside your consumer unit - even when the main switch is OFF, the main input terminals remain live.

 

[EFLImpudence]

If I take the light bulb out and with the switch still 'off' the 'live' wire still lights the neon but now so does the 'retun' wire.

Do you mean the terminals in the lampholder?

All the upstaire lights are like this. The downstairs lights are normal and OK .

Please explain the meaning of 'normal' and use the proper term instead of 'return'.

 

[PrenticeBoyofDerry]

my neon screwdriver

then

I'm not an electrical idiot- I've always rewired my own houses and my sons' and daughters -

and

I wll appreciate your oppinions -RAY

Ray, my opinion would be to use the correct electrical test equipment, I have no doubt you have some with the comments made regarding DIY and family re-wires. This will then offer some credible results.
Do you have pictures of what you are testing?

 

[RF Lighting]

Take your neno screwdriver to your local police station and place it in their neon screwdriver amnesty bin. All polices stations have them.

Then go back and try testing your circuit with a proper tester, not some piece of junk which may end up killing you.

 

[Taylortwocities]

 

[ebee]

Like said I think we need a bit more info with a proper tester.

However I think we are wondering if the L & N supplies to this circuit have been transposed. The circuit would appear to work normally although it is not unknown for bog standard fluorescent fittings to strobe dull (only visible when dark) too

 

[bernardgreen]

With the light switch in 'off mode' the live wire lights my neon screwdriver and the 'return' wire doesn't - OK.

Because the switched live ( you call it return ) is connected to neutral via the lamp

If I take the light bulb out and with the switch still 'off' the 'live' wire still lights the neon but now so does the 'retun' wire.

because the switched live is capacitively coupled to live and with out the connection to neutral via the lamp this capacitive coupling passes enough energy to light the neon. Also in the circuit is the capacitive coupling of your body to earth upon which these dangerously inaccurate neon screw drivers depend.

.I'm not an electrical idiot- I've always rewired my own houses and my sons' and daughters

Maybe not an idiot but you do appear to be ignorant, as in not knowing some of the essential basic knowledge required for carrying out safe electrical work.

 

[ebee]

Bernard,
with a simple (one way) switch.

the T & E or usually singles of old were known as "Feed & Return" ie L & SwL

 

[Raybuild]

Is this a spoof post? - I hope not.

You state that you have rewired houses in the past?

The input terminals of a lightswitch, or indeed any switch will remain live when switched off, because the incoming supply is still available at the switch inputs - that is the reason you have to be careful when looking inside your consumer unit - even when the main switch is OFF, the main input terminals remain live.

Kai - No this is not a'spoof post'. I know what you are saying - the feed to the switch is always live beacause this is coming from the Main Lighting Feed. The return from the switch goes to the light bulb vier the cieling rose. It is this return that is indicating 'Live' when the switch is 'Off' and the light bulb removed. ( I know it would indicate 'Live' if the switch was 'On'

 

[Raybuild]

Do you mean the terminals in the lampholder?

Please explain the meaning of 'normal' and use the proper term instead of 'return'.

EFL - 'sorry I'm not familiar with current terms (excuse the pun) - I'm 'old school' -also this 'Forum chat' process is new to me and I'm not too sure how to use it.
'Normal' - the down stairs light switches are indicating the live wire (from the main lighting feed) 'Live' and the return wire ( to the light bulb via the ceiling rose) 'dead' (with the switch 'Off' and with or without the light bulb)
Upstairs lighting - at the light switch (with the light switch 'Off') the Live feed is indicating 'Live' (correct) but the 'return' (sorry) which goes to the bulb via the ceiling rose is indicating 'Live' (incorrect) - (this is with the light bulb removed). If I put the bulb back the 'return' is indicating 'dead' (correct). At the ceiling rose the the switch 'return' and lamp terminal and thus the lamp holder are showing the same results ( ie. with light switch 'off' and bulb in or removed.

 

[Raybuild]

Bernard,
with a simple (one way) switch.

the T & E or usually singles of old were known as "Feed & Return" ie L & SwL

Ebee - you have taken the time and trouble to try and tell me something in order to help me - I'm not quite sure what you are saying. Could you elaborate - I'm always keen to learn what I don't know or am unsure of.

 

[londonboy]

I hope I dont live in one of these houses youve 'rewired'.

 

[Raybuild]

]Because the switched live ( you call it return ) is connected to neutral via the lamp

Yes I know this (I'm sorry that you think I am that ignorant to have to point this out).


because the switched live is capacitively coupled to live and with out the connection to neutral via the lamp this capacitive coupling passes enough energy to light the neon. Also in the circuit is the capacitive coupling of your body to earth upon which these dangerously inaccurate neon screw drivers depend.

How is this 'switched live' 'capacitively coupled' to live (everything is insulated) and if so why does this 'capacitive coupling' NOT happen in the down stairs lighting where this scenario is NOT happening

Maybe not an idiot but you do appear to be ignorant, as in not knowing some of the essential basic knowledge required for carrying out safe electrical work.[/quote]

The use of 'The Neon Screw Driver' was only used as a quick tool and observation and the fact that I had it in my hand. I would not dream of assuming that with a Neon Screwdriver in my hand I am now equipped to tackle all kinds of electrical testing and fault finding. But I have to come clean and admit that the only other equipment I have is a couple of Voltmeters (one analogue and the other digital) - I know that these are NOT to be used with Mains Voltage but I can test for continuity.

 

[bernardgreen]

How is this 'switched live' 'capacitively coupled' to live (everything is insulated)

Any two conductive items separated by an insulator form a capacitor. A change of voltage on one will affect the voltage on the other. sheets of tin foil separated by very thin paper or other insulator make capacitors for use in electronics ( there are many other types of capacitor ). Two insulated wires running side by side form an un-intentional capacitor ( stray capacitance )

and if so why does this 'capacitive coupling' NOT happen in the down stairs lighting where this scenario is NOT happening

Probably due to a shorter lengths of live to switched live stray capacitance and/or longer lengths of switched live to neutral stray capacitance which will leak away energy that crossed the live to switched live.

the only other equipment I have is a couple of Voltmeters (one analogue and the other digital) - I know that these are NOT to be used with Mains Voltage but I can test for continuity.

[/quote]If the meter has a range 0 to 250 AC then with care they can be used to measure voltages up to mains voltage.