I replaced some existing incandescent bulbs by LED bulbs, then noticed
that they do not switch off completely but still glow dimly.
Checking the voltage at the lamp socket with a high-resistance
electronic multimeter, I get a reading of 48v!! A few volts might be OK
-- induction, stray voltages, etc., but 48V!!!
This occurs in two different rooms, but I think the various lighting
circuits are all connected to one breaker.
What could cause this?
its the meter, take a walk around high sensitivity meters will show 60
volts under the neighborhood power line........
connect a 100 watt light bulb with the meter voltage will go away.
relax yours must be one of the most frequent questions asked.
(1) there are no overhead power lines within a mile. Walking around the
house with that meter and a lead trailing like an antenna I see not even
a 1 volt reading.
(2) It's a pain that the LED lights don't switch off completely. The
voltage with the switch off is sufficient to keep them glowing dimly.
Perhaps replacing one of the bulbs by a low-wattage incandescent would
hold the voltage down, but that offsets the power saving benefit of the
On Mon, 06 Apr 2009 17:05:08 -0400, "Percival P. Cassidy"
Cover the bulb - make it completely dark - the voltage will likely go
away. You are LIKELY getting a DC voltage FROM the light because an
LED is ALSO a photocell. An LED will produce a DC voltage when exposed
Green ones are Gallium Phosphide and make 1.65 to 1.74 volts each.
Not sure what the white ones are and what voltage they produce but I
think they are Indium Gallium Nitride - so likely around the same
On Sun, 05 Apr 2009 16:20:03 -0400, "Percival P. Cassidy"
LED? You don't mean complact fluorescent? I havent' seen LEDs that
fit wthout changes.
But in the kitchen with a timer in place of the wall switch, I
couldn't get my CFL to turn off. Do you have a timer in the circuit.
A timer in each room, and on lamps, seems unlikely.
I'm going to guess here that you have
some kind of electronic switch, i.e. a
dimmer or something similar. As long as
there is enough voltage to turn on the
LEDs, a small leakage current from an
electronic switch could make them glow
That's it. I bet your timer was designed to not require a neutral.
As such, it has to draw a little current through the lamps to power
itself even when off. x-10 switches are notorious for that, but any
electronic device that gets wired in place of a switch and does not
require a neutral connection will do it. Usually placing a small
incondescent bulb (like a 7 watt night light bulb) or a resister in
parallel with the LED's will solve the issue. Or, get a different
timer that requires a neutral (if the box in question has a neutral
wire in it, Or, get rid of the timer if you don't really need it.
On Apr 6, 5:38 am, email@example.com wrote:
Yes, agree that the electronic timer is what's causing the bulbs to
light dimly. Most of those type devices are designed to work without
a neutral, so they rely on some very small current always flowing.
In the case of incandescent bulbs, it's not a problem. But CFLs,
LEDs take so little current, it's enought o start to light them. If
you look at the data sheet for that electronic timer/switch it most
likely says it's for incandescent use only.
I hadn't measured the voltage in the second room, but I assumed that the
glowing LEDs after switching off had the same cause. In fact this was
simply a brief "decay time," probably as a capacitor discharged.
It turns out that it was a lighted switch after all -- but no light had
been visible in the switch with the CFL bulbs that I replaced by LED.
And even when I had the switch hanging out of the wall. the "Lighted"
label was on the side away from me.
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