I have 2 strings of LED lights on my patio wired to a switch/outlet combo. This is controlled by an interior switch that also controls my exterior door light. I can either just have the door light on or switch on the LEDs at the combo box. All was working well.

However, I just recently tapped into the end of the strings with a 16/3 exterior extension cord, cut off the female end and hardwired it into another switch/outlet to control some LED rope lights in a screened porch. When the rope lights are switched off, they continue to glow very dimmly - visible only after dark.

How do I stop them from glowing when they're turned off?

  • Are those “switch-outlet combos” some sort of smart device? Are they web-bought-mail-order items? What plugs into that farthest outlet? – Harper - Reinstate Monica Aug 1 '20 at 13:52
  • Thank you for the quick reply, Jasen! Would the phantom current, hence the glow, do any damage to the lights? I plan on checking on/off voltage at the outlet today. – nome Aug 1 '20 at 14:25
  • Harper - the switch/outlet combos are store bought; readily available, and not a smart device. The rope lights are plugged into the farthest outlet and controlled by the switch. – nome Aug 1 '20 at 14:28

This is caused by phantom current, it's does not indicate a problem and need not be remedied unless the glow bothers you.

  • yes, fancy dimmer switches and smart outlets actually pass a small amount of current 24/7. (surprise- turning them off doesn't cut the flow of electricty completely). – Jaime Guerrero Aug 31 '20 at 18:29

yes, to Jasen.

fancy dimmer switches and smart outlets actually pass a small amount of "phantom" current 24/7 -- this energy is needed to 'power' them, i.e. the smart device has a radio listening on wifi for commands. (surprise- turning them off doesn't cut the flow of electricty completely!).

modern LEDs are so efficient that they will glow with even this tiny amount of current.

Solution: don't use fancy dimmers or smart devices for your switch; use devices with a separate actual on/off switch (many dimmers have a mechanical on/off switch independent of the dial/slider). Or put a traditional mechanical switch in series with the dimmer (but then the 'smart' behaviors won't work when it is off).

Some rare expensive dimmers, sold for commercial settings where safety codes are stricter, need a separate neutral lead in their box for their power, are are thus independent of the controlled lamp circuit; these don't use the phantom power trick and won't send any current to the lamp circuit when dimming level is set to 0%.

  • I would not call Lutron residential dimmers rare and expensive, many of them require a neutral wire and have 0 phantom current through the switched load – Richie Frame Oct 2 '20 at 0:32

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.