Three-way switch with on/off indicator

[bud--]

As RBM wrote "Pilot light switches are lit when the circuit is on, and illuminated switches are lit when the circuit is off." Both of these have the light in the handle of the switch (not a separate pilot light).

"Illuminated switches" are easy - as I said before you connect a neon lamp between the traveler terminals If you work out the circuit, this is the same as connecting a neon lamp across a single-pole switch.

"Pilot light switches" from Leviton require a neutral connection - I believe that is true for all of them. They don't use a ground connection. The circuit for one that I saw had resistors from each traveler terminal to a common point. A neon lamp connected from that point to a neutral.

Both of these use current through the load to light the neon lamp. If a light bulb is burned out they will not work. They may or may not work with fluorescents (CFLs).

------------------------- All switch straps that are metal these days have a ground screw. If the switch is not installed in a metal box you have to ground the strap. The strap is grounded so any metal plate - present or future - will be grounded.

[J Burns]

As quoted above, Michael says his switch box is not grounded and has only two wires. He says the indicator light is on when the outdoor light is on. With only a hot wire and a load wire, how would you connect your neon indicator light to come on when the outdoor light came on?

[krw]

YEs, but Claire was talking about a pilot light (on when the circuit was on). This does require some sort of return.

Yes, I mentioned the same thing, up there a while. I'm not seeing how this works for 4-way, though. I remember having illuminated 4-ways in my parent's house.

That's the discussion. ISTR, and maybe it's changed now (GFCIs throw a wrench in here), that some "leakage" current to ground was allowed for this purpose.

Good point. They do work with the old-style inductive ballast fluorescents, however. We had a house full of them. Another reason to shun CFLs. ;-)

Assuming there is a ground in the box, of course.

[bud--]

Maybe someone can find a 'pilot light' switch without a neutral connection. The only ones I saw had a neutral (and I believe they all do).

A 4-way has the 2 travelers traveling through the switch and swaps them, or not, as they go through. Both kinds of 3 way switch handle light also work on a 4-way if you connect to either of the traveler terminals.

Find a pilot light switch that does not have a neutral connection. The ones I found did (so there is no ground leakage). (Manufacturers don't seem to want to tell you if there is a neutral connection or not - important piece of information if you are going to be using one of these.)

If not the NEC says what to do.

[J Burns]

In the Leviton system you describe, suppose R is the resistance of each resistor in the voltage divider (between travelers). Suppose I is the current of the neon indicator.

If the load bulb is burned out, the voltage divider will be between hot and open regardless of switch positions. Voltage across the indicator should be 120-IR. I would expect the indicator to glow.

If the bulb is burning, the voltage divider will also be between hot and open. The indicator should glow as above.

If the bulb works but is switched off, the voltage divider will be between hot and neutral (ignoring the bulb's small resistance). The voltage across the indicator should be 60-(IR/2). I suppose the indicator wouldn't light.

So it appears to me that load current is required not to turn the indicator on but to turn it off.

[krw]

You may be correct. Because of GFCIs, these may no longer be kosher.

I don't understand your second sentence, but looking at it again, it's clear to me that there is a neon "drop" on each traveler from the voltage at the "off" end. A neon between travelers at each 4-way will illuminate it and there will never be more than two neon drops in the chain (always two - or zero, with at least one 4-way).

Certainly, in jurisdictions where the NEC applies. ;-)

[The Daring Dufas]

Perhaps I'm suffering from premature postification again? 8-)

TDD

[bud--]

Apologies for over-explaining.

The travelers are the 2 wires that connect between the 3-way switches.

A 4-way switch has terminals A-B that connect to one 3-way switch and terminals X-Y that connect to the other 3-way switch. In one position the connections are A-X and B-Y. In the other switch position the connections are A-Y and B-X. If you add 10 more 4-way switches, each one just connects the travelers 'straight' through or 'swaps' them.

If either 3-way scheme is connected to terminals A-B (or terminals X-Y) inside a 4-way switch it is the same as connecting to the traveler terminals on the 3-way switches. If you understand how pilot/illuminated

3-ways work you understand pilot/illuminated 4-ways.

The handles on both 3-way snitches, and all 11 4-way switches, will glow or not glow the same. All the neon lamps are connected in parallel.

[bud--]

Neon lamps are not like incandescents in that the voltage across the lamp is essentially constant after the lamp has 'fired' (ionized the gas and started conducting). And if the voltage is not high enough the neon lamp will not fire on every half cycle.

60V may not be enough to 'fire' the neon lamp. Or, because the neon lamp is at constant voltage, the drop across the resistors is much lower than you expect and the current is relatively low - dim neon lamp

Sounds eminently reasonable. I was 1/2 wrong.

If the bulb is burned out, (or maybe fluorescent), or switched receptacle with nothing plugged in the switch won't indicate right.

[krw]

Yes...

Yes...

Um...

Ah! Yes, I see, the 3-way neon isn't across the switch, as it is with a SPST switch, rather across the travelers like the 4-way neon connection.

[jsnc9099]

This topic came up again, and a Search on this topic brought up this old th read. I could not find a 3-way switch (current sensing) that did not require a pi lot light wire for installation at the feed/hot (master) switch. Easy enoug h at the load/slave switch, but the extra wire for a pilot light is not sta ndardly run, so if you are doing a retrofit, the standard lit when on switc hes (eg Leviton 56-38-2W) won't work. I found a solution that requires a bi t of tinkering, CR Magnetics (model CR 2250) uses a current sensing transfo rmer with self powered LED. For the trigger current based on your load, jus t add wraps of the hot through the hole and around the transformer. drill a 1/4" hole in your cover plate, and snap in the LED. Add conductor as neede d for the wraps, and wire nut to the feed. Note that the LED saturates at t he trigger current, and will take up to 20 amps AC being read, so there is no problem if you set for LED current, and incandescents are later put in. This solution will work with any switch configuration (3-Way, 4-Way). For s ingle pole, standard pilot light switches are the easy solution (eg Leviton 5628-(color)). The CR 2258 is .32" thick, and so can be fitted in the J-Bo x behind the switch.