One thing I've always been slightly puzzled about. My back room has two sets of lights. There is a double switch by the door, one of the switches only works the set of lights near that switch. The other switch works the other lights which have their own switch on the other side of the room, obviously a two-way switch. If both switches on the double switch are switched off there's no problem. But if one of the the two-way switches on the double switch is switched on and it's switched off the other side of the room on the two-way switch, there is a very faint glow from the lights on the other side of the room.
I know that sounds absolutely confusing, but if anyone can understand it, I wonder whether it's dangerous if I forget and leave the two way switch the wrong way round which leaves the lights faintly on.

Lawrie

On 06/12/2019 16:19, Lawrie Davidson wrote:
One thing I've always been slightly puzzled about. My back room has
two sets of lights. There is a double switch by the door, one of the
switches only works the set of lights near that switch. The other
switch works the other lights which have their own switch on the
other side of the room, obviously a two-way switch. If both switches
on the double switch are switched off there's no problem. But if one
of the the two-way switches on the double switch is switched on and
it's switched off the other side of the room on the two-way switch,
there is a very faint glow from the lights on the other side of the
room. I know that sounds absolutely confusing, but if anyone can
understand it, I wonder whether it's dangerous if I forget and leave
the two way switch the wrong way round which leaves the lights
faintly on.

I am guessing that the lamps in question have LED or CFL lamps rather
than filament?

If so, this is a relatively common problem. It results from a
combination of low energy lighting which needs only a tiny current to
start to glow faintly (or sometimes to flash intermittently), coupled
with all the extra wire in a two way switching arrangement.

If you look at a typical wiring diagram for two way switching:

http://wiki.diyfaq.org.uk/index.php/...tching_circuit

You can see that you may end up with a long length of cable connected to
the live input of the lamp, but with the other end disconnected at one
of the switches. This wire is said to be electrically "floating". Since
it is running very close beside other live wires, it can pick up a
voltage induced by its closeness to the other wires. That voltage is
enough to cause the symptom you see.

Its not dangerous, since there is very little current involved - if you
put any significant load on the wire its voltage will fall away quickly.






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Cheers,

John.

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Thanks. Nice to know it's not dangerous, so I don't need to come downstairs from the bedroom just to make sure I've turned them off the right way,

Thanks again,

Lawrie

Thanks. Nice to know it's not dangerous, so I don't need to come downstairs from the bedroom just to make sure I've turned them off the right way,

Thanks again,

Lawrie

Try a different brand of lamp in the fitting. Some are more prone to
this than others.


--
Graham.

%Profound_observation%

I very much doubt it, its LED I assume and they are notorious for picking up
induced currents that makes them glow a bit.
Brian

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"Lawrie Davidson" wrote in message
...
One thing I've always been slightly puzzled about. My back room has two sets
of lights. There is a double switch by the door, one of the switches only
works the set of lights near that switch. The other switch works the other
lights which have their own switch on the other side of the room, obviously
a two-way switch. If both switches on the double switch are switched off
there's no problem. But if one of the the two-way switches on the double
switch is switched on and it's switched off the other side of the room on
the two-way switch, there is a very faint glow from the lights on the other
side of the room.
I know that sounds absolutely confusing, but if anyone can understand it, I
wonder whether it's dangerous if I forget and leave the two way switch the
wrong way round which leaves the lights faintly on.

Lawrie

If it annoys you I guess something like half meg resistor on the floating
end to neutral might fix it.

Of course it will use a tiny current.
Maybe a capacitor might work?
Brian

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"Lawrie Davidson" wrote in message
...
Thanks. Nice to know it's not dangerous, so I don't need to come
downstairs from the bedroom just to make sure I've turned them off the
right way,

Thanks again,

Lawrie

One might think that a good design of the unit might stop this from
happening.
Brian

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"Graham." wrote in message
...
Thanks. Nice to know it's not dangerous, so I don't need to come
downstairs from the bedroom just to make sure I've turned them off the
right way,

Thanks again,

Lawrie

Try a different brand of lamp in the fitting. Some are more prone to
this than others.


--
Graham.

%Profound_observation%

In article
,
says...

You can see that you may end up with a long length of cable connected to
the live input of the lamp, but with the other end disconnected at one
of the switches. This wire is said to be electrically "floating". Since
it is running very close beside other live wires, it can pick up a
voltage induced by its closeness to the other wires. That voltage is
enough to cause the symptom you see.

I wonder if that 'symtom' could not be very useful in some
cases. For example, my wife refuses to turn on a light at
night if she is on her way to the bathroom but there is some
light - an orange glow from the digital alarm clock and light
in the hall from the smart meter sitting on the ottoman and
some light in the bathroom from the streetlights on the main
road about 150m away, but there must be cases where everything
is in pitch darkness.

A suitable value of mains rated capacitor between live and the
switched side of a LED lamp could give just a gentle glow.

--

Terry

On Sat, 07 Dec 2019 11:10:02 +0000, Terry Casey wrote:

I wonder if that 'symtom' could not be very useful in some cases. For
example, my wife refuses to turn on a light at night if she is on her
way to the bathroom but there is some light - an orange glow from the
digital alarm clock and light in the hall from the smart meter sitting
on the ottoman and some light in the bathroom from the streetlights on
the main road about 150m away, but there must be cases where everything
is in pitch darkness.

We get enough light from the LEDs in the two smoke alarms on the landing,
and the 'pilot light' from the non-maintained emergency light on the
stairs. The bedroom is illuminated by the three LEDs on the phone!



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