I just moved into my house and replacing switches and receptacles when I come across a 3 way circuit not working correctly. I pulled the 2 switches to find someone had replaced one with a single pole switch. Unfortunately they did a sloppy job and didnt pigtail their hot wires properly, so wondering if someone can tell me how to properly rewire this to my 3 way switch. Thanks in advance.
Multiway Switch – How to Fix a 3-Way Switch Mess
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That screw looks like it's for the wire clamp that secures wiring going through the back of the junction box. Instead, you should connect the green wire with a wire nut to the exposed copper wires that I believe are visible in the bottom of the picture. Make sure to use the proper size wire nut, which is based on the wire size and number of wires being joined together.
It looks like it is a three way switch, but I am not sure
It isn't. What I see is
That seems fairly straightforward to me
- The black wires are permanent line (live/hot/phase)
- The red wires are switched line (live/hot/phase)
- The white wires are neutral
- The green wire is a ground (earth) bond between switch housing and metal wall-box
So, I don't see a three-way arrangement (two switches controlling one light)
Whether the use of colours is compliant with local code (regulations) depends on where this is located and when it was installed.
Sorry for the horrible diagram, I must find a better tool than MS-Windows-Paint!
As bib pointed out in a comment, my diagram omits one black wire from the left switch to the bottom left (room light) cable. I conjecture that this may have been to provide power to something like a ceiling fan with a separate pull-switch built into the hub - but that's just a guess on my part.
how can I tell if the box is actually grounded?
It probably isn't, unless there is a connection to the back-box we can't see (perhaps to the outer metal sheath of an amoured cable.
You can test this with a multimeter and, with all power to the building turned off and verified off, measure resistance between metal-back box and the white wires. If the resistance is low there is a ground connection between back-box and the neutral-ground bond near the main incomer or main panel.
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Best Answer
OK. A 3-way switch complex acts exactly like a plain switch. Meaning if you take the two 3-ways and the /3 cable between them, and pretend they're not there, you see what else is going on.
In this case, if you ignore the 3-ways and /3, all that's left is a /2 cable to the top box. That makes this a switch loop.
Normally, in a switch loop, the white wire carries always-hot * and the black wire carries switched-hot. Code has two things to say about this:
It appears the last guy wired the 3-way loop with the white wire being always-hot. That is fine, but again you need to mark the white wires at each of their ends with black tape.
The remaining wires in the /3 (red and black) are travelers. I recommend you mark both travelers with yellow tape (readily available as part of 5-packs of colored tape). Travelers don't need to be distinguished from each other.
Then it's easy: On the 3-way switches, the travelers go on the brass screws, and the remaining wire (whatever it is) goes on the remaining black screw.
*The white wire is used for always-hot so a voltage tester will always show it as hot; that means it won't be confused for a neutral. The switched-hot wire will test as "at neutral" when the switch is off, because it's connected to neutral via the light bulb.