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3-way switch illuminated when off??

J

js5895

Jan 1, 1970
0
Hi,

I have a 3-way wall switch that lights when the load is off.
It somehow seems to work with one wire or in series with the load.
how does that work? I understand basic electrical but, this is weird.

Thank you.
 
C

Chris

Jan 1, 1970
0
js5895 said:
Hi,

I have a 3-way wall switch that lights when the load is off.
It somehow seems to work with one wire or in series with the load.
how does that work? I understand basic electrical but, this is weird.

Thank you.

It's most likely a neon in series with the line/active/hot and the load and
neutral to complete the circuit. When the switch is in the on position it
shorts this out.
If it isn't lit, it means the globe is blown.

Cheers.
 
J

js5895

Jan 1, 1970
0
a single AC phase by it's self can't power anything, may it be an AC or
DC circuit, right?
 
J

John G

Jan 1, 1970
0
js5895 said:
a single AC phase by it's self can't power anything, may it be an AC or
DC circuit, right?

Chris's reply was correct . There is a neon (and resisitor) across the
switch contact.
When the switch is OFF the neon is fed from the hot side thru the load
to neutral.
When the switch is ON the neon is shorted and the load works.
 
J

js5895

Jan 1, 1970
0
I find that strange, because, won't the load's resistance dim or
brighten the switches neon lamp. Or would if the load was a receptacle.
 
J

John G

Jan 1, 1970
0
js5895 said:
I find that strange, because, won't the load's resistance dim or
brighten the switches neon lamp. Or would if the load was a
receptacle.
In the case of a lamp the current used by a neon is so small as to be
insignificant compared to the lamp so will not be dimmed by a change in
lamp power.

If there was no lamp or no load on a receptical then this approach would
not work correctly and it would be better to have the neon on the load
side of the switch withits other end conected to neutral thereby
lighting when the switch is on, not off, regardless of the load.

Having it light when the lamp is off allows you to find the switch in
the dark.
 
L

Lord Garth

Jan 1, 1970
0
js5895 said:
I find that strange, because, won't the load's resistance dim or
brighten the switches neon lamp. Or would if the load was a receptacle.

Neon lamps need a series resistance and the draw extremely little power.

O---------------------------traveler------o--------------------O
| |
(NE2 shorted) |
Hot O---^^^^---neon--- ---neon---^^^^---O---O
incandescent lamp O---O neutral
(NE2 open) |
On
O--------------------o------traveler------o--------------------O

OR

O---------------------------traveler------o--------------------O
|
(NE2 open)
Hot O---^^^^---neon--- ---neon---^^^^---O---O
incandescent lamp O---O neutral
| (NE2 shorted) |
| On
O--------------------o------traveler------o-------------------O





O---------------------------traveler------o--------------------O
| |
Hot O---^^^^---neon--- ---neon---^^^^---O---O
incandescent lamp O---O neutral
|
| Off
O--------------------o------traveler------o--------------------O

OR

O---------------------------traveler------o--------------------O
|
|
Hot O---^^^^---neon--- ---neon---^^^^---O---O
incandescent lamp O---O neutral
| |
Off
O--------------------o------traveler------o-------------------O
 
L

Lord Garth

Jan 1, 1970
0
Neon lamps need a series resistance and the draw extremely little power.




O--o-----------------traveler------------------o---O
| | (NE2 on) |
Hot O --^^^^---neon-- --neon---^^^^--o O---O incandescent lamp O---O neutral
(NE2 on) | | | Off
O----------------o---traveler---o------------------O

OR

O--o-----------------traveler------------------o---O
| (NE2 on) | |
Hot O --^^^^---neon-- --neon---^^^^--o O---O incandescent lamp O---O neutral
| (NE2 on) | | Off
O----------------o---traveler---o------------------O





O--o-----------------traveler------------------o---O
| | (NE2 off) | |
Hot O --^^^^---neon-- --neon---^^^^--o O---O incandescent lamp O---O neutral
(NE2 off) | | On
O----------------o---traveler---o------------------O

OR

O--o-----------------traveler------------------o---O
| (NE2 off) |
Hot O --^^^^---neon-- --neon---^^^^--o O---O incandescent lamp O---O neutral
| (NE2 off) | | | On
O----------------o---traveler---o------------------O


Looks better in Courier
 
B

Bob Monsen

Jan 1, 1970
0
I tried connecting a meter, in voltage mode, and it acted weird see:
http://home.nycap.rr.com/joshs/threewaywire.bmp
I also connected the meter to the line, and just one screw and it
lit!!, but very dimly.

Thanks.

Are you saying that the switch itself is illuminated, or that the lamp
plugged into the switch is illuminated? I have a wall switch that is
lighted, in which the light is on when the switch is off.

However is there is a short through the switch, you should replace it.
Sadly, I had trouble interpreting your picture.

For a three way switch, you have this situation:
{view with fixed-point font)

S1
line --[lamp]--o o---------------------oo
\ \
\ \
oo---------------------o o---- neutral
S2

Thus, either of the switches can light the lamp.

If one of the switches has failed such that it is closed on both paths,
or if the wiring is broken in this way, it'll light in either
position. So, for example, if S2 has a path like this:

S1
line --[lamp]--o o---------------------oo
\ \
\ \
oo---------------------oxxxxxxo---- neutral
S2

Then even if the xxxxx path is fairly high resistance, the lamp may
act like you are describing. You can test this by disconnecting
neutral from S2, and line from S1 and testing the resistance between
the two throws of S1. If it is less than 10MEG, you have trouble.

Note that the lamp may be in a different place; thus, I wouldn't trust
that pulling the lamp will disconnect you from line.
 
L

Lord Garth

Jan 1, 1970
0
Bob Monsen said:
I tried connecting a meter, in voltage mode, and it acted weird see:
http://home.nycap.rr.com/joshs/threewaywire.bmp
I also connected the meter to the line, and just one screw and it
lit!!, but very dimly.

Thanks.

Are you saying that the switch itself is illuminated, or that the lamp
plugged into the switch is illuminated? I have a wall switch that is
lighted, in which the light is on when the switch is off.

However is there is a short through the switch, you should replace it.
Sadly, I had trouble interpreting your picture.

For a three way switch, you have this situation:
{view with fixed-point font)

S1
line --[lamp]--o o---------------------oo
\ \
\ \
oo---------------------o o---- neutral
S2

Thus, either of the switches can light the lamp.

If one of the switches has failed such that it is closed on both paths,
or if the wiring is broken in this way, it'll light in either
position. So, for example, if S2 has a path like this:

S1
line --[lamp]--o o---------------------oo
\ \
\ \
oo---------------------oxxxxxxo---- neutral
S2

Then even if the xxxxx path is fairly high resistance, the lamp may
act like you are describing. You can test this by disconnecting
neutral from S2, and line from S1 and testing the resistance between
the two throws of S1. If it is less than 10MEG, you have trouble.

Note that the lamp may be in a different place; thus, I wouldn't trust
that pulling the lamp will disconnect you from line.

I learned to never switch the neutral line, only the hot (black) wire.
Be careful, you set up a situation where you are the ground link.

Use courier font to view the diagram, it is a fixed width font.
I drew all four possible switch positions. The three O at each end
are the three terminals on the SPDT switches, center is the toggle.
The resistor and series neon are within the switch & connected across
the throws...that's the top and bottom O at the ends. The lines labeled
'traveler' is the interconnect between the switch throws at each end
of the room.

The neons in the switches should go out when the bulb is removed
from the socket. This is because they loose their connection to neutral
through the incandescent bulb.



O--o-----------------traveler------------------o---O
| | (NE2 on) |
Hot O --^^^^---neon-- --neon---^^^^--o O---O incandescent
lamp O---O neutral
(NE2 on) | | | Off
O----------------o---traveler---o------------------O

OR

O--o-----------------traveler------------------o---O
| (NE2 on) | |
Hot O --^^^^---neon-- --neon---^^^^--o O---O incandescent
lamp O---O neutral
| (NE2 on) | | Off
O----------------o---traveler---o------------------O





O--o-----------------traveler------------------o---O
| | (NE2 off) | |
Hot O --^^^^---neon-- --neon---^^^^--o O---O incandescent
lamp O---O neutral
(NE2 off) | | On
O----------------o---traveler---o------------------O

OR

O--o-----------------traveler------------------o---O
| (NE2 off) |
Hot O --^^^^---neon-- --neon---^^^^--o O---O incandescent
lamp O---O neutral
| (NE2 off) | | | On
O----------------o---traveler---o------------------O
 
J

js5895

Jan 1, 1970
0
There is no bulb, the switch isn't wired up, it's in my hand right now.
I did a test on my desk with a digital clock, by wiring it normally,
hooked up the travelers and tested it with the load connected to
the common, then the line conected to the common and then the
neon stayed lit, when the switch was off, BTW, I'm setting it up
with one neon switch in my dark hall way, and one non-neon, 3-way
switch in the house. I just wanted to know how a switch can light
up inside, with no neutral connection, because it's a switch, and light
up and be off at the same time, FYI, I changed the picture:
http://home.nycap.rr.com/joshs­/threewaywire.bmp

Thanks.
 
L

Lord Garth

Jan 1, 1970
0
There is no bulb, the switch isn't wired up, it's in my hand right now.
I did a test on my desk with a digital clock, by wiring it normally,
hooked up the travelers and tested it with the load connected to
the common, then the line conected to the common and then the
neon stayed lit, when the switch was off, BTW, I'm setting it up
with one neon switch in my dark hall way, and one non-neon, 3-way
switch in the house. I just wanted to know how a switch can light
up inside, with no neutral connection, because it's a switch, and light
up and be off at the same time, FYI, I changed the picture:
http://home.nycap.rr.com/joshs­/threewaywire.bmp

Thanks.
 
L

Lord Garth

Jan 1, 1970
0
There is no bulb, the switch isn't wired up, it's in my hand right now.
I did a test on my desk with a digital clock, by wiring it normally,
hooked up the travelers and tested it with the load connected to
the common, then the line conected to the common and then the
neon stayed lit, when the switch was off, BTW, I'm setting it up
with one neon switch in my dark hall way, and one non-neon, 3-way
switch in the house. I just wanted to know how a switch can light
up inside, with no neutral connection, because it's a switch, and light
up and be off at the same time, FYI, I changed the picture:
http://home.nycap.rr.com/joshs­/threewaywire.bmp

Thanks.


Yes, it should have a resistive load connected, like an incandescent lamp.
I suspect a fluorescent lamp wouldn't be right either but since the
neon is all that's affected, no big deal. I wonder about folded fluorescent
screw-in replacement lamps.

Were you able to see my diagram using courier font?

Your AOL / RoadRunner link isn't working here. :-|
 
L

Lord Garth

Jan 1, 1970
0
js5895 said:

Hmm, You know, you're going to make me go buy a switch just to cut it
open! The setup should have been equivalent with the line & neutral
either way though it needs an incandescent load. I hope you weren't
reading voltage since you have your meter is in series. Reading current
can lead to some bright flashes that you won't want to see when the
source is the mains, usually current is read with a clamp on current probe
for your own safety and the life of your meter.

Your picture makes it hard to tell what is the pole and which are the
throws. I'm going with top being the pole and the bottom two being
the throws. If so, then I don't know how the neon lit at all. My though
was that the neon was across the throws.
 
J

js5895

Jan 1, 1970
0
I have the meter in voltage reading mode, not current mode, ouch!, lol.
I was testing it the night I got it, and forgot the load, and it was
lights out. When I have it in voltage mode it's in a complete circuit.
I had it in current mode, line to each screw on the switch but,
making sure it's wasn't a complete circuit, that's when it dimly lit,
which was weird, since it wasn't a complete circuit, but it only did
this once, I tried it again and nothing happened, it could of been
some anomaly from the no load incident or, because it's new.
I updated the image to show the common point, and where the switch
is sending power, here:
http://home.nycap.rr.com/joshs/threewaywire.bmp

Thanks.
 
L

Lord Garth

Jan 1, 1970
0
js5895 said:
I have the meter in voltage reading mode, not current mode, ouch!, lol.
I was testing it the night I got it, and forgot the load, and it was
lights out. When I have it in voltage mode it's in a complete circuit.
I had it in current mode, line to each screw on the switch but,
making sure it's wasn't a complete circuit, that's when it dimly lit,
which was weird, since it wasn't a complete circuit, but it only did
this once, I tried it again and nothing happened, it could of been
some anomaly from the no load incident or, because it's new.
I updated the image to show the common point, and where the switch
is sending power, here:
http://home.nycap.rr.com/joshs/threewaywire.bmp

Thanks.

Hey thanks, that little arrow help a bunch. No, I can't tell you why it
lit the neon at all, I'll just have to waste one! Have Dremel, will travel.
Remember that voltage is read across a circuit or device, not in series.
Please don't read current when your testing mains unless you get a clamp
on probe. I'm glad you and the meter are okay!

I have accidentally probed an outlet with my meter set to Ohms.
Fortunately,
I have a (generation one 1982) Fluke DMM. It shrugs off this sort of abuse.

Once, while using a friends cheap DMM, I didn't see that his probes were in
common and 10A. When he activated the light switch, the resulting bang
blew me off the ladder! My friend caught me and I was uninjured but I was
seeing spots for a while. Get this, the meter fuse was INTACT after
that!!!!
The rotary switch was welded though.
 
S

spudnuty

Jan 1, 1970
0
3 way switches have 3 terminals: a common and two non common. The
common is wired to the load or to the hot. The two non commons are
wired between the 2 switches via two wires, usually black and red. When
the load is activated there is no potential between the common and non
common 1 (shorted) or non common 2 (no connection), nor between the two
non commons 1&2 (one is active the other no connection) When the load
is off a potential appears between the two non commons 1&2 since one
will carry the hot and the other will be connected to neutral through
the load.
The neon and series resistor will be connected between non common 1&2.
Typically they draw .5 to 3 ma so when you connected your meter it
caused the neon to light but dimly. The resistor is usually 19k to
220k.
Richard
 
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