Problems with Three way switch wiring

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• posted on May 17, 2004, 12:31 pm
But it is the current flow that kills, not voltage. I agree current is proportional to voltage assuming a fixed resistance and a low impedance source. However, if voltage alone killed, then an electric fence or static electricity from walking across a carpet would be lethal. These voltages are many times higher than the 3000 volts or so used for executions but are not usually injurious because they are high impedance sources with very low current flow. When 120 Volts comes in contact with a person, it sees an initial fixed resistance which is dependent on several factors such as salt content and moisture on the skin, grounding and the body's internal resistance. With continued contact, the body chemistry begins to change and resistance lowers resulting in increased current. Aside from electrocution, other injuries have resulted from body reflexes causing a hand to smash into anything that is close by. Never work on a live circuit if you can diagnose the problem with power off. Keep your work area free of clutter and don't have anything on the floor that you can trip over. Also, never work on a live circuit when you are alone.
Bob

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• posted on May 18, 2004, 1:05 am
HI all,
Thanks for all the responses. Well I got it working yesterday evening. I will post the secret here.
First, some terminology:
Hot: The wire with the electricity source. Typically black, but not necessarily in a three way.
Neutral: The white wire. Opposite of black.
Ground: The green wire. Grounds the circuit.
Traveller: A wire that runs between two three way switches. It might be any color. In my case, it was red.
Note that color might be anything in a three way depending on the style or laziness of the original installer.
Common: This the single point on the three way switch that the switch pivots on. Electricity will always have to flow through this point for the circuit to work. It is marked on the back of the switch. Be sure to check the back, not just the color.
Most all the sources I read failed to define these things. But then just mentioned them. Duh.
So, what I finally had to do, was to: - find the travellers. - find the power source - connect everything.
First, shut down your computer, in case it is on the same circuit, as mine was.
Find the travellers:
Find ohm meter. Replace burnt out batteries. Touch two leads together to make sure that the meter is working. Meter will respond positively. Find extension cord.
Turn off power to the circuit with the three ways. Disconnect both three ways completely from the wires.
Attach extension cord, and ohm meter to one wire at one switch. At the other switch, check each wire, until you figure out which one is the same wire. Label: T1.
Do this with the other wires. Label T2, and T3.
(Note: I used T1 - T3. Industry standard may be different. Obviously, one wire will not be a traveller, and so t? could be strange. )
Find the power:
(This is what I did. There may be much safer ways. Be very careful. )
Put on rubber gloves.
Turn off power to the circuit (again, just in case you skipped above).
Separate the wires so that they will not touch each other, or anything else.
Turn on power to circuit. At one switch, touch one side of your tester to ground. Touch each other wire (with the tester) until you find the wire with the power. Mark this wire. It will now be marked with both T?, and power.
Interestingly, I only found power in one box, not the other.
Connect:
Disconnect the power.
Connect the wire with the power to the common.
Connect the other end of the same wire to the other common.
At each end, connect the two travellers to the two remaining available terminals. The order does not matter.
Turn on the power to the circuit.
Test. Be sure to switch a, switch b, switch a, switch b. Each time you switch, the light should change from on to off, or vice versa.
This is what worked for me.
In retrospect, I messed up when I changed the first three way. To work, it required both switches to be turned on.
Since I changed the wires at one end, to all six possibilities, and still nothing worked, it was obvious that I made a mistake. I'm surprised that no one noticed.
Good luck to anyone who is struggling. It only took me two days of struggle.