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I have overhead ceiling LED light fixtures.

When I turn on Main Switch of the house, I see the LED starts emitting very dim light ( have to look for a 3-4 second to perceive) even when LED's switch is off!

Is that normal or I need to check it out by an electrician ?

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    \$\begingroup\$ For more details please check this out. \$\endgroup\$
    – Virange
    Jun 22, 2016 at 16:53
  • \$\begingroup\$ Is the light switch a normal on-off type or is there any kind of electronic switching such as a remote or dimmer? \$\endgroup\$
    – Transistor
    Jun 22, 2016 at 17:22
  • \$\begingroup\$ @transistor Normal On/off \$\endgroup\$ Jun 22, 2016 at 17:40

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There are two typical reasons for this:

  1. The Phosphorous used in the led is experiencing chemiluminescence, a cold chemical reaction that produces light. The Phosphor is normally used to be give leds their white color through photo luminescent reaction, reacting to photons of a different wavelength, but it can glow in the dark without that.

  2. The light bulb is on a circuit with a switched neutral wire, instead of a switched hot wire. This means that the AC voltage on the hot wire can still slightly power the leds and/or the capacitors in the light bulb, leading to a few milli or micro amps of current to flow through ultra efficient leds, lighting them up.

You could test this by putting the bulb in a switched lamp with a non-polarized power connector plugged in one way, and then flip the connector around the other way. One way should result in completely off leds.

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  • \$\begingroup\$ I am not able to understand the term - switched hot / neutral wire. What I know is there are two wires Live and Neutral connected with any appliance. But I didn't understand - switched to neutral. \$\endgroup\$ Jun 22, 2016 at 18:10
  • \$\begingroup\$ @mit the switched wire is the wire that is being disconnected when the switch is turned off. So a Switched Neutral cuts the neutral side of the circuit, leaving the hot or live side connected. You normally want to switch the hot side. \$\endgroup\$
    – Passerby
    Jun 22, 2016 at 18:16
  • \$\begingroup\$ So in my case the probability of the lights switched to neutral, and this leads to hot connected even after switching off . And to rectify this i need to reverse the Line and neutral from my current setup. Right? \$\endgroup\$ Jun 22, 2016 at 18:19
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Some switches have a neon illumination to help find it in the dark; if so it will be connected ACROSS the open switch forming the leakage path mentioned above. No problem as long as the load is much higher than the neon needs, but can cause a CFL or LED to flicker or light dimly.

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