Neon Indicator in Lighting circuit

[Hysteresis]

I have a cloakroom with no windows. The internal light is switched from the outside of the room. The door of this room has spring return hinges so as to keep the door closed. The internal light is regularly left on for hours sometimes days without knowing.
I intend to replace the light switch with a 10A double pole isolation switch with Neon indicator. As we all know, the Neon indicator is connected across the output terminals of the Double pole isolator and as such the neon would not work in a lighting switch replacement situation using one pole of the Isolator as the light switch.
What I intend to do is use the one pole of the switch as the on/off switch for the internal light and connect the other terminal of the neon to earth. As the Neon is not a current device and senses voltage only then this arrangement would not compromise any earth leakage device. The RCD device in the house is only on the power circuit so there is no safety issue to consider.
There is another solution to the problem and that would be to redesignate the light switch earth wire as a neutral return for the neon indicator as an earth is not required at the light switch as far as I can recall. The new isolator switch is all plastic and not a metal plate switch.
Is the former arrangement of using the earth as the return for the neon indicator Legal, and has anyone any comments, positive or negative , with respect to my intentions.

 

[JohnW2]

Neither of the approaches you suggest are really acceptable; you would need to get a 'proper' neutral (with an insulated conductor, not a bare 'earth' one) to the switch. I would also question whether you would necessarily notice that the neon was alight.

In an almost identical situation, I installed a small light fitting outside of (above) the door, connected in parallel with the existing light. That provides an unmissable indication than the interior light is on. An alternative to consider might be some sort of door-operated switch, such that the light only came on if the door was open.

Kind Regards, John.

 

[holmslaw]

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[Hysteresis]

Thanks for your thoughts JohnW. The earth return form the light switch is in fact a fully insulated wire as the instalation used a three core cable and not twin and earth , so may be redesignating the earth as a neutral return is the best solution.
Incidentally using the earth as a return for the neon works perfectly well. I wired it up as a test. I really can't see that there is anything wrong with the circuit as the neon indicator is a very high impedance device. They are used in power test screwdrivers for that very reason. But to have a neon conected to the earth as a permanant feature is may be not recommended.

 

[Hysteresis]

Thanks for the suggestion Holmlaw.
I was not aware of that particular device and looks to be a good solution.
My only comment on the switch is that it is rather counter intuitive. ie the neon ondicator is ON when the internal light is OFF.

 

[sparkwright]

Are you saying you have an old three core cable without the bare earth wire - colours red, yellow and blue? You need permanent live, switched live and neutral - and earth is strongly recommended too.

You could use a 20 amp double pole switch with neon, the neutral would go in N load, N feed would be unused. However, the screws and the earth bar would be unearthed so you should think about replacing the cable for a 3 core and earth cable.

You keep going on about using the earth as the neutral for the neon - very bad practice in my opinion.

 

[holmslaw]

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[AndyPRK]

I was going to suggest the same as Holmlaw.

You connect a neon across the switch.

It lights when the room light is off. It's the simple solution.

Other options could be a PIR in the room to turn light on automatically.
or a Timer switch (not good if it's a bath/shower room)

 

[Hysteresis]

You keep going on about using the earth as the neutral for the neon - very bad practice in my opinion.

I agree that using the earth as a neutral is very bad practice, but a Neon is of such High impedance, it is no different from using a neon screwdriver as a 'Live' test, and on the face of it, touching a live wire with a screwdriver is very bad practice.
My suggestion seems OK to me, but is it Legal?. If it isn't Legal then I would suggest that Neon Screwdrivers would also illegal.

 

[JohnW2]

I agree that using the earth as a neutral is very bad practice, but a Neon is of such High impedance, it is no different from using a neon screwdriver as a 'Live' test, and on the face of it, touching a live wire with a screwdriver is very bad practice.
My suggestion seems OK to me, but is it Legal?. If it isn't Legal then I would suggest that Neon Screwdrivers would also illegal.

Firstly, just to be a little pedantic about the technicalities, a neon 'tube', per se, has a relatively low impedance once it 'strikes' (lights) - the high impedance of 'a neon' being due to the presence of a resistor; if you look inside the neon test screwdriver, you'll find a high value resistor (usually 1 or 1.5 M&#937 between your finger and the neon itself.

The concept of 'deliberately' introducing a leakage path, no matter how small (and I agree that the neon+resistor does represent a very small leak) between live and earth is somewhat of an anathema to electricians. As for 'legal', I can't off the top of my head think of any explicit way why it would be contrary to the Wiring Regulations (which, by the way, are not 'law'), but it doesn't feel nice - and it could produce hassle and heartache if an electrician carrying out insulation resistance tests on your wiring did not notice that it was there.

If there is an easy route from the switch to the light, the 'best' solution would be run a proper three core and earth cable between them, thereby getting neutral to the neon without the 'bad practice' of using an earth-designated conductor for that purpose.

I've just realised that I missed out an important bit of the story about theh situation in my house. I did initially try using a neon indicator, but we found that we overlooked that almost as much as we had been overlooking the fact that the light had been left on - hence the alternative approach we ended up taking.

Kind Regards, John

 

[RF Lighting]

Would it not be easier to fit an occupancy sensor in or near the light so it can't get left on?

 

[Hysteresis]

Thanks JohnW. I really appreciate your comments.
I think you are dead right. I have as a result discarded my thoughts as very Bad Parctice.
It was also very interesting to learn of your initial discarded solution. I think I would also fall into the same category there.
If I have a fully insulated Earth core going to the switch, I think I will disconect the earth and use that core as a proper neutral and not have the light switch earthed.
All of these solutions are only to avoid having to install new wiring into walls and cielings with the attendant Plastering and rececoration.
I think I may have to just bite the bullet and do it 'Properly'.
Thanks again for your thoughts.

 

[RF Lighting]

No no no.

Leave the light switch earthed.

Either do it properly and safely, or don't do it at all.

 

[JohnW2]

All of these solutions are only to avoid having to install new wiring into walls and cielings with the attendant Plastering and rececoration.
I think I may have to just bite the bullet and do it 'Properly'.

Do you have a particularly 'plush' cloakroom? We don't, and all I had to do was to drill a hole straight through the wall above the door to take a cable through from the external 'indicator light' and then run that cable on the surface of the cloakroom to the light - so no making good was needed, and nothing was visible outside the cloakroom other than the indicator light itself. I also did the same with our large cellar, since the (many!) lights were frequently being left on down there!

Anyway, you clearly understand the issues and the 'proper' and 'bad' practices, so it's up to you to decide what approach you are comfortable with.

Kind Regards, John.

 

[Hysteresis]

Would it not be easier to fit an occupancy sensor in or near the light so it can't get left on?

Hi RF Lighting.
Have you a type and part number/supplier of such a sensor?
It sounds like a good solution provided I can wire it directly into the Light circuit and avoid the installation of extra wiring with the attendant plastering and redecoration. Presumably these sensors can be ceiling mounted adjacent to the room light.
Thanks for the suggestion.