I would like to understand the reason for a light that keeps glowing in low even when it is turned off in the night.

When it is actually on:

When it is actually off:


Some may say it may be due to leakage current, but I have tested the power supply by removing the bulb and testing it with AC tester on the holder and there is no supply at all. Then I was wondering how it glows?

 

Does the switch have a little indicator lamp that turns on when the light is off? If so, that works by passing a small amount of current through the lamp. Historically, that amount of current was too low to see any light. But those were the days of incandescent bulbs. With modern bulbs, all bets are off.

 

I am assuming this is LED?
Some phosphorus of the lamp interior coating?
Persistent phosphorescence?
https://en.wikipedia.org/wiki/Phosphorescence#Persistent_phosphorescence

 

The very tiny capacitance by proximity between conductors in the wiring does the faint effect. More noticeable in two-way switched circuits as there is longer-more wiring involved.

 

Y

The very tiny capacitance by proximity between conductors in the wiring does the faint effect. More noticeable in two-way switched circuits as there is longer-more wiring involved.

FYI... Yes it's a two-way switched circuit.

 

Does it glow if you remove it from the bulb holder?

 

You could put a resistor in parallel with the LED lamp to reduce the voltage caused by the capacitance between the conductors. The problem with this is that the resistor would disipate power and heat up when the LED was switched on. To get round the heating problem I have used a capacitor instead of a resistor. I find the most convenient way is to use a contact suppressor (Which is a capacitor in series with a low value resistor.) Many of these have flexible wire connections so they can be connected straight across the LED lamp.
The current in the capacitor is out of phase with the voltage so no power is disipated so no heat is generated.
This is one example of a contact suppressor.

Les.

 

Does it glow if you remove it from the bulb holder?

After removing it from the holder it glows for couple of seconds and goes off fully.

 

After removing it from the holder it glows for couple of seconds and goes off fully.

Okay so if you then put it back in the holder ( no power applied) does it start to glow ?

It may be the cables acting as a capacitor as said earlier...

 

If this is a low power LED bulb, and IF it is a "3-way " switch arrangement where there are two different switches that can switch the light on or off, then it might be capacitive coupling between the two wires that connect the two switches.
Next question: What part of the world is this located in? and what is the mains voltage?

 

We had a problem after the supply cables to the house were replaced.
The fluorescent strip lights would flicker even when switched off. This turned out to be because the supply wires had been swapped so the switch was now in the neutral wire to the light but the live wire was permanently connected.

 

We had a problem after the supply cables to the house were replaced.
The fluorescent strip lights would flicker even when switched off. This turned out to be because the supply wires had been swapped so the switch was now in the neutral wire to the light but the live wire was permanently connected.

The problem of the reversed switching connection indicates a lack of competence on the individual who replaced the wires. Either careless or unknowing.

 

Maybe this light bulb is like those birthday candles you can't blow out.

 

The problem of the reversed switching connection indicates a lack of competence on the individual who replaced the wires. Either careless or unknowing.

It was the electric company "responsible" for our electricity supply.

 

Use a different LED bulb.

And as MrBill mentions, it's a 3-way wire configuration, not a "2-way".

There's more than one way to wire a switched 3-way ckt (bad ways, and the right way), but it should be noted, the hot side of the wiring on fixture should always be interrupted by a switch toggle.

I would turn off the light, pop the bulb out, and then use a contactless volt probe to see if that socket dings hot.

 

And as MrBill mentions, it's a 3-way wire configuration, not a "2-way".

US 3-way is the same as UK 2-way.

 

3 way in UK also known as Intermediate switching.
i.e. 3 or more switches.

 

There are two arrangements with the "3-way" that function correctly, all the others are incorrect. AND it is possible that the common side is switched and it is either capacitance to common of the two conductors or leakage or funny lights. I did get a case of LED bulbes that include a battery and they do switch on and off when the mains power fails.
So the first step is to check by installing a NON-LED bulb an see what happens. No great skill or equipment required.

 

So the first step is to check by installing a NON-LED bulb an see what happens. No great skill or equipment required.

If it is some kind of high impedance leakage, there will not be enough current to support a filament lamp anyway!
So does not really prove anything!

 

Hi
the problem is well known for me. And was solved several times- just put capacitor 0.2-1 uF 250VAC or 630VDC in parallel to the lamp. Small current will pass the capacitor. Resistor, in general, can also be applied, but it is not recommended as it consumes power and dissipates heat