2 way switching with neon & no neutral.

[jondiy]

I have been asked to replace a lightswitch - and its in a non-notifiable location!!!

Problem is, the new switch that is to replace the old, MUST have a neon indicator on it - or be illuminated in some way at the switch!! Here is the slight dilemma.

The switch is currentlly wired as 2 way, and the other switch on that circuit must be kept as it is. SO , I would like to know if ther is available, a neon switch, that somehow illumiates , without a neutral connected. The cable runs are in plaster , and the boxes are sunk in, so running a new neutral is out of the question. At this switch I have the usual 3 core and earth , as per 2 and 3 way lighting , all 3 wires are obviously used for the switching , and the earth is terminated into the backbox.

Has anybody come across 2 way lightswitches that have neons (or illuminated faceplates) that don't require a permanent neutral ?? If so can anyone point me in the right direction.

 

[Adam_151]

Depending on how the two way switching is wired, it might be possible to put the neon in parallel with the switch drop (like those illuminated switch surrounds), and then providing the switched load is a filament lamp then the neon will light when the light is off.

The naughty option would be to wire the neon between phase and earth (though we baulk at the idea, yet we regulaly plug in electronic equipment that has switched mode power suppies that contain capacititors between phase and earth)

 

[jondiy]

Thanks Adam , Just for the record.

The live, switch return live and earth from the ceiling rose are fed to the first switch (Which does'nt need the neon) , The live goes into the L1, the switch return live to the L2 , then the 3 core and earth are connected like for like ie com 1st to com 2nd ,Ll1 1st to L1 2nd and L2 1st to L2 2nd and earths linked via backboxes , pretty common stuff.

Also, the lamp is a filament lamp, so no problems there , however , if using the illuminated faceplate option you spoke of , does it always remain illuminated, or will it stop glowing when the actual lamp is on?? Reason for asking is that the switch is not in the vicinity of the actual lamp, hence the need for an 'indicator' , and it must be neon , as the person has bad vision.

If the illuminated faceplates do toggle (ie indicator on/off) , then they would be ideal.

Don't really want to go the 'Naughty' option!!

 

[Jaymack]

For indication of a remote lamp in the On position, you need a neutral connection, I've drawn in another cable in the past; when wiring up for a loft light, as an example where the switch is on the landing.
The alternative is Specsavers for the handicapped person.

Jaymack

Say No to morons with monotonous, repeating signatures.

 

[Spark123]

If the neon was connected across L1 and L2 at the remote end it will form a circuit from permanent live through the neon to switched live (in effect @ 0v) and then through the lamp to neutral. The current involved to light the neon is so small it doesn't illuminate the lamp. When the switch is closed it forms a short across the neon and it will extinguish. The neon should also extinguish if the lamp fails.

 

[jimbox]

^ ingenious! but I don't quite understand the science behind it. Is it because the neon is a high impedence?

 

[Adam_151]

Yes, its just wired in series with the lamp, and because the current that flows (limited by the high impedance of the neon) the lamp will not light

@OP just connect it between L1 and L2 on the switch, unfortunatly the neon will go out when the light is on, because you are shorting it out with the switch, the illuminated surrounds are available from the likes of B+Q and just slip under the edge of the switch plate, or you can make up a panel with a two way switch and neon using grid modules, if you want the neon on all the time, then I'm afraid there is no way to do that without a neutral, save for using the earth as a return (ignoring any heath robinson ideas of putting extra impedance in series with the switch and parralleling the neon across that...)