Adding a pilot light to a 3-way switch

[John Smith]

I need a stack switch with one standard switch and one 3-way switch with
a pilot light. I called the electric supply warehouses around town and
found none. They do carry one without the pilot light. It looks like I
have to add the pilot light myself.

I believe what I need is a 120 V diode with a really small amperage,
less than 1 mA if possible. Is that correct? I haven't thought about how
to wire it. I have the impression that that part should not be too
difficult.

Thanks for any help.

 

[James Sweet]

I need a stack switch with one standard switch and one 3-way switch with
a pilot light. I called the electric supply warehouses around town and
found none. They do carry one without the pilot light. It looks like I
have to add the pilot light myself.

I believe what I need is a 120 V diode with a really small amperage,
less than 1 mA if possible. Is that correct? I haven't thought about how
to wire it. I have the impression that that part should not be too
difficult.

Thanks for any help.

I would use a small neon panel lamp mounted in the corner of the switch
plate. Keep in mind there may be code issues with anything of this
nature so check local codes and do not proceed unless you know what
you're doing. How to wire it depends on how the circuit is laid out, but
you need one side to the neutral, and one side to the hot wire out to
the light.

You can also get a pilot light which is designed to hold a standard C7
incandescent lamp and mounts in place of a wall switch, you could use an
LED retrofit lamp in one of those, but it would require an additional
gang in the junction box or a separate box. Again this isn't something
you should try yourself if you aren't sure.

 

[Jeff Strickland]

I would use a small neon panel lamp mounted in the corner of the switch
plate. Keep in mind there may be code issues with anything of this
nature so check local codes and do not proceed unless you know what
you're doing. How to wire it depends on how the circuit is laid out, but
you need one side to the neutral, and one side to the hot wire out to
the light.

You can also get a pilot light which is designed to hold a standard C7
incandescent lamp and mounts in place of a wall switch, you could use an
LED retrofit lamp in one of those, but it would require an additional
gang in the junction box or a separate box. Again this isn't something
you should try yourself if you aren't sure.

I don't think he can put a pilot light in a 3-way switch. The circuit will
become unstable because two hot leads have to be connected to the pilot
light. I suppose a couple of diodes could keep the circuit stability intact.

Having said that, I'm on board with the neon light too.

 

[James Sweet]

I don't think he can put a pilot light in a 3-way switch. The circuit
will become unstable because two hot leads have to be connected to the
pilot light. I suppose a couple of diodes could keep the circuit
stability intact.

Having said that, I'm on board with the neon light too.

Well like I said, it depends on how the circuit is laid out. In my house
power comes in and the wire goes out to the light from the same box,
then a 3 conductor cable runs from that box to the remote switch, so
adding a pilot to the master switch is easy, adding it to the remote
switch would require an additional wire. I've seen some 3 way
arrangements where power enters at one switch box and the light comes
off the other switch, as well as one that had power entering the light
fixture box and then a separate switch drop, that's the hardest to add a
pilot to.

I don't know where you're going with the stability and diodes thing,
none of that is necessary, you wire the pilot light up across the wires
going out to the light fixture. Perhaps you're thinking of an
illuminated switch? That's different than a pilot light, though it could
also be added if things are laid out favorably.

 

[Jeff Strickland]

Well like I said, it depends on how the circuit is laid out. In my house
power comes in and the wire goes out to the light from the same box, then
a 3 conductor cable runs from that box to the remote switch, so adding a
pilot to the master switch is easy, adding it to the remote switch would
require an additional wire. I've seen some 3 way arrangements where power
enters at one switch box and the light comes off the other switch, as well
as one that had power entering the light fixture box and then a separate
switch drop, that's the hardest to add a pilot to.

I don't know where you're going with the stability and diodes thing, none
of that is necessary, you wire the pilot light up across the wires going
out to the light fixture. Perhaps you're thinking of an illuminated
switch? That's different than a pilot light, though it could also be added
if things are laid out favorably.

Yes, I was thinking of an illuminated switch. Isn't that a pilot light?

What's a pilot light if not an illuminated switch?

 

[James Sweet]

Yes, I was thinking of an illuminated switch. Isn't that a pilot light?

What's a pilot light if not an illuminated switch?

A pilot light illuminates when the switch is on to let you know that a
remote light is on, an illuminated switch lights up when the light is
off so you can find the switch in the dark.

 

[Jeff Strickland]

A pilot light illuminates when the switch is on to let you know that a
remote light is on, an illuminated switch lights up when the light is off
so you can find the switch in the dark.

Okay, I get it.

I was thinking of an illuminated switch so one could find it in the dark.

 

[Tzortzakakis Dimitrios]

...which means that a standard 3-way lighting circuit cannot
have a pilot light on one of the switches without either
running additional wires or sensing current.

Consider the four possible states
of this standard 3-way circuit:

(Best viewed with a monospace font such as Courier)

We start with the lights on:

LINE A
O----------O
/ \
HOT-----O O-----(LIGHTS)--
LINE B |
O----------O LIGHTS |
STATE #1 ARE ON |
|
NEUTRAL--------------------------------

Someone switches the rightmost switch,
thus turning off the lights:

LINE A
O----------O
/
HOT-----O O-----(LIGHTS)--
LINE B / |
O----------O LIGHTS |
STATE #2 ARE OFF |
|
NEUTRAL--------------------------------

Someone switches the leftmost switch,
thus turning on the lights:

LINE A
O----------O

HOT-----O O-----(LIGHTS)--
\ LINE B / |
O----------O LIGHTS |
STATE #3 ARE ON |
|
NEUTRAL--------------------------------

Someone switches the rightmost switch,
thus turning off the lights:

LINE A
O----------O
\
HOT-----O O-----(LIGHTS)--
\ LINE B |
O----------O LIGHTS |
STATE #4 ARE OFF |
|
NEUTRAL--------------------------------

Someone switches the leftmost switch,
thus bringing us back to state #1.


The pilot light for the rightmost switch
is easy; just wire it in parallel with
the lights being controlled. The wire
between the rightmost switch and the lights
is hot when the lights are on.

The pilot light for the leftmost switch has
a problem: none of the three wires going to
the switch is hot only when the lights are on.
In fact, all the voltages on all three wires
going to the leftmost switch are the same in
state #1 and state #2. No clever arrangement
of diodes will allow the pilot light to tell
the difference between states #1 and #2.

So if you really need a pilot lamp on the
leftmost switch, you need to either run an
additional wire back from the rightmost
switch, or you need to sense current, not
voltage. A properly sized current sense
transformer would allow sensing the current.
It would also make the pilot light a detector
of a burned out or unscrewed bulb in the light
being controlled by the 3-way switch.

No idea about the OP's question, wonder why he used Chinese encoding in his
post. In Greece, we call 3-way switches aller-retour (French), and there's a
design with 3 switches, 2 3-way and 1 4-way.

 

[bud--]

I need a stack switch with one standard switch and one 3-way switch with
a pilot light. I called the electric supply warehouses around town and
found none. They do carry one without the pilot light. It looks like I
have to add the pilot light myself.

I believe what I need is a 120 V diode with a really small amperage,
less than 1 mA if possible. Is that correct? I haven't thought about how
to wire it. I have the impression that that part should not be too
difficult.

Sounds like an illuminated switch (lighted when off) might work. I
believe illuminated 3-ways connect a neon lamp between the travelers.

If a commercial combination is not available one way to do this in a
single opening is to use Despard devices, which are interchangeable
devices that mount on a strap with 3 openings. You could combine a
standard switch, a 3-way switch and a *neon* pilot light unit. Wire the
neon light across the 3-way travelers. You could have a light at each
end. The light will be on when the switched load is off. There needs to
be some load to light the neon light. Google for Despard.
If you are at the load-end 3-way, and a neutral is available, you can
connect the light across the load as a pilot light.

I would not recommend do-it-yourself. You might be able to find space
for a UL listed commercial pilot light unit with leads.

You could try the question at alt.home.repair. There are several good
electricians and some other sharp people. Someone might know of a
commercial device.

 

[Rich Grise]

Okay, I get it.

I was thinking of an illuminated switch so one could find it in the dark.

Then go back to the light switch store and tell the guy that that's
what you were looking for in the first place. Tell him, "Oops!".

Cheers!
Rich

 

[Tim Shoppa]

I need a stack switch with one standard switch and one 3-way switch with
apilot light. I called the electric supply warehouses around town and
found none. They do carry one without thepilot light. It looks like I
have to add thepilot lightmyself.

Look in the catalogs... e.g. Hubbell HB1203PL. Stock item at Grainger
and probably at the big electrical suppliers if you give them the part
number .

Tim.

 

[Jeff Strickland]

Then go back to the light switch store and tell the guy that that's
what you were looking for in the first place. Tell him, "Oops!".

I'm not the one that was asking for it, I'm one of the people that attempted
to give an answer based on my false assumption/misunderstanidng of the
device being sought.

 

[John Smith]

Thanks to all of you who replied to my question.

I think I'll settle with a neon lamp since it's easy to find 120v neon
lamps while 120v LED is hard to find.

I'm replacing an existing standard switch with two 3-way switches so I
can control the attic fan from 2nd floor also. That means I can decide
which is the rightmost and leftmost switch in Guy's drawing (BTW, thanks
for taking time to draw the diagram).

So, the hot of the rightmost switch goes to, in addition to the attic
fan, a 47K Ohm resistor, a neon lamp then to the neutral of the other
switch (the standard switch in the stack switch) because the 3-way
switch doesn't have a neutral.

Thanks again to everyone.

 

[James Sweet]

Thanks to all of you who replied to my question.

I think I'll settle with a neon lamp since it's easy to find 120v neon
lamps while 120v LED is hard to find.

I'm replacing an existing standard switch with two 3-way switches so I
can control the attic fan from 2nd floor also. That means I can decide
which is the rightmost and leftmost switch in Guy's drawing (BTW, thanks
for taking time to draw the diagram).

So, the hot of the rightmost switch goes to, in addition to the attic
fan, a 47K Ohm resistor, a neon lamp then to the neutral of the other
switch (the standard switch in the stack switch) because the 3-way
switch doesn't have a neutral.

Thanks again to everyone.

Just get a neon lamp which is already a finished assembly with a
resistor and all, you can pick them up at Radio Shack among other
places, then just drill a hole and mount it. If you're adding the second
switch yourself, you can run an additional wire to put the pilot light
in either or both locations.

You can also get thermostats designed specifically to run attic fans
automatically.

 

[bud--]

That won't work on one of the ends. Neon lamps are voltage devices,
and all the voltages at the switch closest to the main stay exactly
the same as the switch closest to the load is toggled. See my post
with wiring diagrams.

If there is a load (like a light bulb or fan), and the switches are in
an off combination, there will always be 120V between the travelers (the
2 wires connecting the switches). A neon light connected between the
travelers will light up. That works at both ends. It works when 4-way
switches are added. It works when wired with the with the less common
"California 3-way" setup.

I wouldn't advise that. It will be hard to find replacements.
Better to redo the box to allow standard devices.

Despard devices *are* "standard devices" available from several
manufacturers. They have been around for a real long time. Even Roy can
find them.

 

[[email protected]]

| Years ago I added a pilot light to a similar situation at my parent's
| house. See thus:
|
| O----------O O----------O
| / | / \
| HOT-----O | / O-----(LIGHTS)--
| | / |
| O----------O O----------O | 3-WAY
| | | |
| R R |
| | | |
| +___+ |
| | |
| NEON |
| | |
| NEUTRAL---------+-------------------------------------
|
| Resistors "R" were around 100k, and the neon light an NE-2 equivalent.
| When the lights are off, the neon light sees 1/2 the line voltage,
| divided by the resistors. When the lights are on, then one of the
| resistors floats (except for capacitance of the wiring), and the other
| drives the neon light. This depends on the non-linearity of the neon
| light: at 1/2 line voltage it either fails to light, or just barely comes
| on.

Why not just wire the neon light directly between the two wires you have
the resistors on, with the appropriate ballast resistor, and not connected
to the neutral at all?