The case of the Glim lamp switch and LED lighting

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Customer:

We were pleased to receive the ordered products on Friday.
I immediately started replacing my traditional bulbs with modern LED bulbs. Most of the replacements went smoothly without any issues. Unfortunately, there are some problems.
When installing the E14 bulbs, I noticed that all of them, even when turned off, emit a faint light. I tried swapping them, but it didn’t help. One of the E27 bulbs has the same issue…

Response:

We certainly agree on one thing – something can only light up if it receives power because it can’t light up from nothing, though that would be really nice.
So, if the LEDs glow faintly even when turned off, there is likely stray current in your home.
This can happen if, for example, the wiring was done carelessly, and the switch interrupts the neutral wire instead of the phase wire.
Thus, the lamps remain powered even when switched off. The current flows through the lamp, continues along the neutral wire to the switch, and is interrupted there (since the switch is off).
However, the interrupted neutral wire next to the phase wire acts like a capacitor, generating a negative voltage in the wire piece when the phase is positive, and vice versa. Therefore, the bulb can receive induced power of up to 100-200 volts even when off. The current is weak, so it can’t fully power the LED, but it can make it glow faintly.
The solution is to properly wire the electricity, i.e., the phase wire should be interrupted by the switch, not the neutral wire, as this can be life-threatening.

Naturally, if you had stray current before, it was not visible with a traditional bulb because it requires more current. LED bulbs, being low-consumption, are more sensitive to stray current.

Not all LED lamps indicate stray current because some are designed to operate at 220-240 volts, while others operate at 85-265 volts. The brightness will vary depending on the voltage.

Customer:

Thank you for your comprehensive response. I was a bit worried when the LED bulbs I ordered for a considerable amount of money didn’t work as expected. I consulted with my electrician, whom I consider to be one of the best, and he provided a possible solution to the problem. He made all the connections according to regulations. Since I have several feedback (illuminated) switches (Prodax Archus), the issue was that the current required for feedback also passed through the bulbs, causing the faint light. I removed the feedback units from the switches, and the problem completely disappeared. No flickering or faint light can be observed.
Besides, thank you for your help, and I will place an order for the remaining bulbs in the house today.
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Response:
I also learned something new; I hadn’t thought of that.
So, your switch lights up when the light is off.
I have two Glim Lamp Prodaxes, but this can’t happen to me because my switch lights up when the light is on. To make it work that way, I had to route the neutral wire to the switch as well.
Your version is possible without the neutral wire, obviously, it wasn’t planned for LEDs back then. Thinking about it, the neutral wire wasn’t routed there, and a different switch module would have been needed to prevent the indicator light current from passing through the light source.

Tamás Tóth

THERE IS A SOLUTION!

István Székely’s proposed solution:
The problem can be solved by connecting a 220-330nF/400V non-electrolytic capacitor in parallel with the lamp at the ceiling terminal block of the chandelier or lamp fixture. This bypasses the LED lamps and provides ample current for the Glimm lamp as well.

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