Light faintly glowing

[HeelSpur]

Checked out a light today for a lady and she has a light on a 3 way switch that is faintly glowing with the switch turned off. I turned the breaker off undone the light, then turned breaker back on and my meter shows 30 volts on it.
What's the problem, thanks.

 

[theoldwizard1]

The 30V could be "ghost voltage". Check voltage with a load (the bulb) in the circuit.

 

[rburke65]

What the hell is a ghost voltage?

 

[PCustoms]

Induced current feom high voltage or high amperage wiring running in a parallel path.

How do you discern ghost voltage from a bigger issues, i.e. Dropped neutral or crossed wires?

 

[rlitman]

Sounds like a lighted switch. They'll have a mini neon bulb in them, and you're measuring the voltage across the bulb.

 

[theoldwizard1]

How do you discern ghost voltage from a bigger issues, i.e. Dropped neutral or crossed wires?

Ghost voltage will disappear if there is a load, even a small load.

Old analog meters (Simpson 260) actually had enough of a "load" (input impedance - about 10,000 Ω) as opposed to most DMM which are over 1M Ω.

 

[ctfjr]

Sounds like a lighted switch. They'll have a mini neon bulb in them, and you're measuring the voltage across the bulb.

This ^^^^

I have some small led candelabra bulbs in outdoor fixtures that never 'turn off'. The small current thru the lit 3 way switches is enough to energize the leds a little.

 

[HeelSpur]

Sounds like a lighted switch. They'll have a mini neon bulb in them, and you're measuring the voltage across the bulb.

Yes, there is a lighted switch. So, replacing that switch should take care of the problem I take it. Thanks.

 

[rlitman]

Yes, there is a lighted switch. So, replacing that switch should take care of the problem I take it. Thanks.

Yes. Lighted switches need at least one incandescent bulb under their control. If they only control LED bulbs, the bulbs may pulse or glow dimly when the switch is "off".

 

[zmaxmotorsports]

Sounds like a lighted switch. They'll have a mini neon bulb in them, and you're measuring the voltage across the bulb.

 

[HeelSpur]

Swapped out the switch and that fixed it, thanks again.

 

[rburke65]

Must have scared them ghosts away.......

 

[James-W]

Must have scared them ghosts away.......

Cute.

 

[shepherd]

Is there a mechanism other than adding an incandescent bulb to a circuit that will prevent "afterglow" from LED bulbs? Ceiling fixtures in both my kitchen and son's room never fully turn off...would it be sufficient to have a single incandescent bulb anywhere on the same breaker circuit (say, near the actual breaker in the basement) to "drain" the ghost voltage?

 

[rlitman]

The incandescent bulb needs to be controlled by the lighted switch. On the same circuit is not sufficient.

 

[ctfjr]

The incandescent bulb needs to be controlled by the lighted switch. On the same circuit is not sufficient.

^^^

right on, again!

 

[CJ7VFR]

This ^^^^

I have some small led candelabra bulbs in outdoor fixtures that never 'turn off'. The small current thru the lit 3 way switches is enough to energize the leds a little.

I had the same issue with some CFL candelabra bulbs I put in a light fixture on my basement stairwell that was controlled by a motion sensor switch. I put the motion sensor switch in there because for some reason everyone in my house "forgets" to turn that light out when they come up out of the basement.

At first I put in the CFL bulbs to save on electricity (at the time, 7 years ago, there were no LED's available) and then I put in the motion sensor switch. But the CFL bulbs would actually glow very dimly even with the switch off, so I put the old incandescent bulbs back in.

It was weird to see that dim glow. I thought I fried something....

Jim

 

[rlitman]

Yep, old motion sensing switches (that did not have a neutral wire), and certain types of dimmer switches have the same issue. New "LED compatible" switches require a neutral wire in the box, so they can power themselves through it, rather than through the bulb filament.

Again, if you wanted most of the power savings benefits, you could have left the CFL (or now LED) bulbs in all but one of the candelabra sockets, with just one incandescent bulb in the mix. That might look funny when lit though, unless you get power saving bulbs that closely match the light color and brightness of an incandescent.