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I was replace a 3 way switch and noticed when I touch the red ( common ) wire while it's connected to the switch I get a little "buzz" or shock.

I was curious if this is normal.

Obviously while replacing the switch I had the breaker off but when I turned it back on and touched the red wire connector/screw I got the buzz.

I really don't think it is incorrectly wired, it functions as it should and any other wiring pattern would/does make the switch not perform correctly (only turns on light if other switch is on, etc...).

Anyway, I was just curious if the red ( common ) wire should/can provide a little shock or I should be worried something is wrong.

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  • Even though the red was used for the 3-way common in this case it is still a hot and will carry voltage. I'm not sure why you are questioning getting a shock. Are you under the misconception that because it was on the "common" terminal it was not a hot wire?
    – Speedy Petey
    Jul 1, 2014 at 20:42
  • Yeah Petey, that's exactly what I thought. I wasn't quite sure how 3-way switches worked. I had my electrician friend come by and inspect everything I wired up to make sure it was all correct.
    – justinw
    Jul 11, 2014 at 0:02
  • "Common" is not "neutral".
    – Harper - Reinstate Monica
    Aug 7, 2017 at 0:42

2 Answers 2

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This is perfectly normal. One of the two travelers can be hot at all times if the switches are wired correctly. Which traveler is hot depends on the orientation of the switches.

That said, you shouldn't touch any wire in a circuit box when the branch is live. If you happened to have provided a better ground path, someone else very well could have been asking if it was normal for the red wire to have killed you when you touched it.

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  • good point, i shouldn't have touched anything!
    – justinw
    Jul 1, 2014 at 2:55
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Proper connection of a two-way circuit is (sorry about the ASCII sketch)

       sw1                 sw2    load
          _________________  
hot ____/                    ______()_____ neutral
          _________________ /

... two single-pole, double-throw switches back to back. When both are switched one way (up in this case), one of the wires between the switches (the travellers) carries current to the load. When both are switched the other way, the other wire between the switches carries current. When they disagree, as shown here, power is applied to one of the wires between the switches but the other switch is connected to the other wire and no power flows.

The details of how that's actually laid out in the house depends on the relative positions of switches and load. One approach is to bring three wires up to switch 1 (hot, neutral, safety ground), run four wires to switch 2 (top hot, bottom hot, neutral, and ground), then run three wires (output of switch 2, neutral, and ground) from there to the light. I've also seen variations where rather than running neutral between the boxes they ran the output of switch 2 back to switch 1's box and then wired to the load from there. I'm not sure whether both approaches meet code; I do think that either needs to be flagged to death so the next person to open the box is certain of what they're looking at.

One of the travellers, of course, will always be hot. If that's what you mean by "common", this isn't surprising and the answer is Don't Do That; touching any live circuit is a Bad Idea. If by "common" you mean neutral, there are other and larger problems...

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