LED ghosting - LEDs remain dimly lit when lighting circuit switch is OFF

Question

I have just had my house rewired. Unfortunately a couple of lighting circuits exhibit LED ghosting - LEDs remain dimly lit when lighting circuit switch is OFF. I am considering adding a capacitor and resistor to form an RC circuit across the switch which hopefully will allow these small currents to dissipate. Does anyone have any other suggestions? What values of resistor and capacitor should I consider?

broadgage · Accepted Answer

This is almost certainly caused by capacitive leakage currents between an "always live" wire to the switch and the switched live from the switch to the lamps. With incandescent lamps, these minute currents have no effect, but LED lamps can glow dimly. 
 To prevent this, connect a small capacitor across the lamps. No need for a resistor, and the value of the capacitor is not important. It must however be suited for continued connection to mains voltage. Any small MAINS RATED capacitor intended for interference suppression or power factor correction should work. 
 Leave notes explaining what has been done, inside the light switch and the consumer unit, in order to avoid later confusion.

mapj1 · Answer

Not sure you have quite got it, the C1 C2 is not an alternative - rather it is the circuit view explanation for what is happening and how adding the suppressor in parallel with the lamps will help. 
 The suppressor once fitted will be an increased "C2" right now its just the capacitance of the wiring to the lights after the switch, while the "C1"represents the wiring in parallel with the switch in the off state,and is giving you the problem as it allows a modest current to 'sneak round' the switch when it is off. Increasing C2 lowers the voltage at the mid point... 
 Trivially in the "on" state C1 is bypassed by the light switch, and then the lamps see full mains voltage and come on. 
 M

Former Community Member · Answer

Thanks for taking the time to explain.

LED ghosting - LEDs remain dimly lit when lighting circuit switch is OFF

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