Re: 3-way switch illuminated when off??


"Bob Monsen" <rcsurname@xxxxxxxxxx> wrote in message
news:pan.2005.04.17.17.50.29.922471@xxxxxxxxxxxxx
> On Sun, 17 Apr 2005 10:14:38 -0700, js5895 wrote:
>
> > 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.
>
> ----
> Regards,
> Bob Monsen
>

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


.

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