3-way switches - Page 1
Forum section: electronics / beginners

author: Mpegger
author_rank: Contributor
timestamp: November 23, 2023, 06:02:27 am
content: I'm in the process of replacing some 3-way switches with some combo 3-way & outlet, and just came across a really weird wiring setup that has left me stumped. I should have taken pictures of the wiring before I took everything apart, but I wasn't expecting the wiring that I found after I removed the switch in the 2nd box. Hopefully my description is good enough.There is a light switch at the bottom of the stairs, and 2 light switches at the top of the stairs. The light switch at the bottom of the stairs is a 3-way, and one of the switches at the top of the stairs is a 3-way, which control the lights in the basement. The 2nd light switch is a regular light switch that controls a single light at the top of the stairs.The main 12/2 line from the breaker goes into the box at the bottom of the stairs. In that same outlet box there is a 12/3 line, and another 12/2 line. Seems normal enough, I figured the 2nd 12/2 was to get power to the box at the top of the stairs for the single light switch since its on the same breaker.The 2nd outlet box is a double size, as it has the 2nd 3-way switch and a separate regular switch (no combo switches). In this box, you have the 12/3 line coming into it, a 12/2 line going to the lone light at the top of the stairs, and then another 12/2 line coming in. I assumed that the 2nd 12/2 was the 12/2 from the first box bringing power to this box for the regular switch, and the 12/3 was wired with the lights between the two 3-way switches, so I'd have to break out the multi-meter and verify which wire should be which in the 3-way circuit as no wires were taped to designate Hot/Neutral/Red.Except the 12/3 wasn't feeding any of the lights in the circuit and was just a straight run from the first box, to the 2nd.And that 2nd 12/2 in each box? Turns out that 2nd 12/2 line in the first box is the same 12/2 line in the 2nd box as I assumed, but wired to the lights in the basement.And every light in the basement is wired properly like a normal circuit would be, Hot (Black) to the center pin in the light socket, Neutral (White) to the threads in the socket. This corresponds to the 12/2 in both boxes.Again, I know I should have taken pictures before just tearing everything apart as I wasn't expecting anything out of the norm (still kicking myself for that), but somehow with this wiring, they manged to not only control the lights in the basement with the 3-way switches, but also provide power to the lone light at the top of the stairs separate from the 3-way circuit, with the 12/3 wire run NOT going to the lights (as one would expect with lights BETWEEN two 3-ways). From what I recall, none of the wires were mixed (no Neutrals, Hots or Reds wire nutted together), none of the wires are wrapped with colored tape (which was done on other circuits in the house so the electrician would have done the same here), and every wire was connected to something, no wire was left hanging all alone.I thought this would be a simple job, but I can't figure this circuit out, and I'm at the point I'm just gonna wire everything straight to power and leave the 3-way switches out of the circuit and use smart lights instead, but I'd like to have the switches in play, even if I never actually use them cause of the smart lights (plus why have switches if they don't do anything). Anyone wanna take a crack at this puzzle?

author: donlisms
author_rank: Frequent Contributor
timestamp: November 23, 2023, 09:21:50 am
content: Word salad!Draw a diagram of everything you know, as correctly as you can, and let us see it.

author: Mpegger
author_rank: Contributor
timestamp: November 23, 2023, 05:55:30 pm
content: Very well. I shal bestow upon you the skills and artistry that have brought many a person to weep and bawl.

author: Zero999
author_rank: Super Contributor
timestamp: November 23, 2023, 06:23:40 pm
content: The first post didn't make much sense.Here's a schematic showing the internal switching in a 4-way circuit. You can play around with a battery and bulb, or LED and a suitable series resistor.Hopefully that's helpful.

author: Mpegger
author_rank: Contributor
timestamp: November 23, 2023, 06:44:16 pm
content: The wiring is as I show. It cannot be changed cause I'mnotabout to go making dozens of holes in the walls trying to trace where all the armor cable is running through and attached to pull it out and/or run new romex in its place.

author: Zero999
author_rank: Super Contributor
timestamp: November 23, 2023, 07:01:39 pm
content: Quote from: Mpegger on November 23, 2023, 06:44:16 pmI was not suggesting changing any of the wiring. The schematic was posted, with the intention of you studying, so you can understand how it works.How it was wired is anyone's guess.

author: themadhippy
author_rank: Super Contributor
timestamp: November 23, 2023, 07:37:31 pm
content: Quotewhilst thats the often seen example of a 2 way and intermediate lighting circuit in real life its often impracticable to have your feed in at one end of the circuit and the switched live at the other,often you'll find it wired like this,both the feed in and switched live are at the same switch.

author: soldar
author_rank: Super Contributor
timestamp: November 23, 2023, 07:59:55 pm
content: Have a look at this. One wire is not needed and is not connected.

author: themadhippy
author_rank: Super Contributor
timestamp: November 23, 2023, 08:27:41 pm
content: Quotewhilst it will work it wouldnt be acceptable in the uk,and depending on the local regs else were as your switching the neutral

author: soldar
author_rank: Super Contributor
timestamp: November 23, 2023, 09:16:21 pm
content: Sigh.

author: Mpegger
author_rank: Contributor
timestamp: November 23, 2023, 09:43:09 pm
content: I thought of something similar, but tossed the idea aside because I clearly remember that every wire in both boxes was in use, and most of the neutrals were all tied together in each box. There was no wire left floating in either box, which is why I couldn't think of any way to complete such a circuit with every wire in use. I'll go ahead with your setup though as I dont want to waste more time with the wires hanging out of the boxes, nor no lights available in the basement other then what I plug into the receptacles around the room.

author: Zero999
author_rank: Super Contributor
timestamp: November 23, 2023, 09:52:51 pm
content: The circuit posted by soldar is a two way, not a three way switch. Is that what the original poster meant? Correct terminology is very important.

author: soldar
author_rank: Super Contributor
timestamp: November 23, 2023, 09:57:56 pm
content: Quote from: Mpegger on November 23, 2023, 09:43:09 pmDouble sigh.

author: themadhippy
author_rank: Super Contributor
timestamp: November 23, 2023, 10:11:05 pm
content: Quotesame thing different language,and a 2 way with intermediate is a 4 way switch

author: MarkF
author_rank: Super Contributor
timestamp: November 24, 2023, 03:58:37 am
content: This is the about the only way I can figure that doesn't have two colors tied together and all the wires are used. Although a couple wires should have their color taped as black. I can't figure any way with the wire runs you have that will meet code.

author: WimWalther
author_rank: Regular Contributor
timestamp: November 24, 2023, 04:22:06 am
content: My only advice - Make no assumption so foolish as to think the original circuits met code. You may be forced to work with existing runs that simply cannot be made to meet current codes without sacrificing functionality.

author: MarkF
author_rank: Super Contributor
timestamp: November 24, 2023, 04:51:10 am
content: Or it could have been something like this.

author: Mpegger
author_rank: Contributor
timestamp: November 24, 2023, 06:08:30 am
content: Nice job leaving no line disconnected.Unfortunetly its all moot as I noticed half-way wiring up the downstairs box, that the extension box I was using to run a new armored 12/2 over the exterior of the wall to the breaker panel, is too narrow to house anything other then those super skinny single-pole toggle switches because of the cable clamp and 12/2 cable protruding too far into the box.So for now I just wired the downstairs box to feed power straight to the basement lights with no switch (they are all "smart" lights anyway), and straight upstairs where I swapped the 3-way switch there for a double outlet, and the single-pole switch for a combo single-pole + single outlet (this combo I had originally planned to switch). I don't need 3 outlets at the top of the stairs, but I might as well wire something up instead of leaving a dead 3-way switch in place.Looks like I'm going to need to cut into the drywall anyway and swap that single gang box for a double if I want to place a outlet there, which I do cause theres no outlet near the main panel, nor anywhere around that corner of the basement.