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I have a strange problem with a domestic circuit.

I live in Belgium and in some old areas with old electrical installations the AC supply provided has a hot "live" and "neutral" wire (as opposed to neutral being held to ground). Both are at around half the standard voltate (240v). (I'll refer to them as "live" and "neutral" though, even though both are actually half-live).

Unfortunately, this allows a small current to flow in, for example, a lighting circuit even when switched off. I believe this is because the switch only breaks one of the wires and there is enough capacitance in the circuit to allow a small AC current to continue flowing through the non-broken wire. In addition, a small current may be induced as there are two parallel "live" wires due to there being two-sway switching.

The problem is that this small voltage is sufficient to illuminate an LED, so it is impossible to switch off.

My question is how it might be possible to easily dampen the small voltage? I can't install a switch that breaks both "live" and "neutral" as there is only one switched wire available and for that I believe I would need another.

So I am looking for some device that is commercially available (in Europe) that could be safely (and legally) attached to the cable somewhere and that would not in itself draw a lot of power.

I have heard that a Zener diode or a capacitor might be used, but I have no idea which might be best or what specification should be used.

Side note: The matter of the non-ground neutral wire generates a lot of interest but isn't that relevant to the question. For whatever reason, there is a voltage in the lighting circuit. A quote from the power company:

The 230 V network represents 88 % of the cable lengths. These cables have 3 wires for the 3 phases. You get 230 V single-phase power by connecting across two phases.

Additional information: I get the problem in two different rooms, a bedroom and a bathroom. The glow is only faint, so it must be a small voltage. Both rooms have standard manual switches (new ones). Both are LED lamps multi-bulb units with 6 and 3 bulbs of the G9 type. Only the bedroom is two-way. I actually have some G9 bulbs that don't glow and some that do, but the ones that don't are unbranded and don't really go with the lamp. I tried ordering various replacements, but they all glow.

I have other LED bulbs around the house (the standard-sized ones) and I don't get any glow.

rghome
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3 Answers3

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The center ground is a red herring

It has nothing to do with your lighting issue. The only other possible explanation is a combinatioj of two things: A) a seriously defective grounding electrode system/neutral-ground equipoetntial bond; and also a ground fault in some your equipment.

If your lights are screw-in or snap-in types, most likely they only have two terminals - such as the two pins on a GU connector, or the center and threads of a screw-in. If the bulb only has 2 terminals, it cannot interact with ground. So the odd ground is not causing the lighting issue.

It's your switch

99% of the time, the LEDs that won't extinguish, that's because your switch is not a switch. I bet incandescents work fine, or if it's a multi-lamp fixture, the problem goes away if one of the bulbs is incandescent.

The problem is that you have an "active switch" - it is a dimmer, lighted switch, motion sensor or smart switch that is a powered device and needs power to run its own stuff. A plain switch normally doesn't have access to ground, heck, doesn't even have access to neutral, which is the proper way for a device to power itself (between hot and neutral). So when these active switches are made for retrofit, they can't power themselves conventionally because neutral may not be present in the switch box.

Even if the switch gets ground for safety, it should not interact with it electrically.

So they use a trick of incandescent bulbs. An incandescent which is off is basically a dead short. That changes when the bulb warms up. ** Anyway, the trick is that the powered device leaks a tiny amount of current through the incandescent bulb - too little to light it, but enough to power the device. Effectively the device is "in series with" the bulb.

This falls apart with CFLs and LEDs. They have electronic switching power supplies, which Do Not Like weird mini-currents running through them, and they do unpredictable things. Some LEDs are able to simply allow the current through, and due to their efficiency it is enough to light them.

Change that obsolete switch out to either a plain switch or a modern one made for LED.

** When you read a relay spec and it has a much lower number for "tungsten", it is referring to that "inrush current" you get from that dead-short load as the incandescent is warming up. This differs from the "ballast" or "HID" number, which refers to the very-high-voltage inductive kick you get from a tranformer based ballast when you shut off the light. Generally, that’s what you use a snubber for, across the relay contacts to discharge that kick.

Harper - Reinstate Monica
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In most countries, the neutral is tied to earth at the supply end. It is often connected at the consumer end as well. But this is not something you should do yourself without consulting your local electrical installation codes and/or your electricity supplier. Connecting the two together in the wrong place, or in the wrong way, can be dangerous.

A a fix for LED lamps that flicker or glow when they should be off is to connect a suppressor or snubber between live and neutral, at the lamp, after the light switch. Make sure anything you use is designed to handle the full mains voltage.

Simon B
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My solution in the end was to install a wall lamp in parallel with the ceiling lamp. Luckily, the wiring was already in place as there had been an old wall pull switch, so there wasn't any re-wiring necessary.

A lamp with a standard E14 LED candle bulb was sufficient to mop up the excess voltage. No need for incandescant.

rghome
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