Tunnel Switching

[Caesium]

Hi all,

I have read some things on here referring to tunnel switching or traveling three way. And was wondering how it worked?
I have searched a bit and couldn't find any thing. And google hasn't been too good theses days.

Thank you much,
Nathan

 

[hurk27]

Hi all,

I have read some things on here referring to tunnel switching or traveling three way. And was wondering how it worked?
I have searched a bit and couldn't find any thing. And google hasn't been too good theses days.

Thank you much,
Nathan

A tunnel switching system was used on the old mining tunnels, and is not code compliant.

first you always have one more three-way then loads (lights) or groups of lights, each three-way has the circuit hot and neutral connected to the traveler terminals, the common terminal terminals are connected to each load between any two three-way.

so if you draw three, three-ways in a row with common up, you will have the hots going to one of the traveler terminal of each three-way, and the neutral going to the other traveler terminal of each three-way, lets number them 1, 2, 3. Now put a lamp above and between three-way 1&2, and another above and between 2&3, label them L1, L2 from L1 draw a line to the common of switch 1, and another from L1 to SW2 common, again draw a line from L2 to the same common on SW2 and another from L2 to SW 3, as you can see as the first switch is turned on, the first light is lit, as the second switch is turned on, the first light goes out and the second light is lit, as you exit the tunnel and hit the last switch the last light goes out, this can be added to for as many lights can be supplied by the circuit.

But as stated in other post, this reverses the polarity of the lamp sockets and can be a shock hazard where screw shell lamps are used, as far as bi-pin lamps go I don't see this problem?

 

[Caesium]

Hmmm, Thats really neat. I wonder if there's a way to do it thats code complaint. I'll have to think about that. I'll see if I can whip up a diagram when I get a chance.

Nathan.

 

[hurk27]

Hmmm, Thats really neat. I wonder if there's a way to do it thats code complaint. I'll have to think about that. I'll see if I can whip up a diagram when I get a chance.

Nathan.

Here is a rude and crude diagram I did in paint, not too good but it gets the message across:grin:

 

[Caesium]

Oh neat, Thanks you. That just what I had in my mind from reading your post.
Still pondering a way to do it to code without using relays.

Nathan.