An electrical puzzle: house mis-wiring - Page 1
Forum section: electronics / beginners

author: Analog Kid
author_rank: Super Contributor
timestamp: December 03, 2024, 12:44:26 am
content: Seeing that thread about 3-way switchesinspired this post.In my previous life as a handyman, I encountered many ... interesting electrical situations, including this one. Asked by my customer to fix their ceiling fan, I found the following situation in the wires sticking out of the ceiling (with black & white wires indicated):WTF??? It took a bit of head-scratching, but I finally figured out what was going on here. Good thing, too, as we here in the "states" aren't used to having 240 volts coming out of a box! (Keep in mind we live in 120-volt land here.)Can you solve the puzzle?Answer will be posted shortly.Why are they called "3-way" when there aretwoswitches controlling one device? And there arefourpossible switch positions. There's no "three" in there that I can see.

author: ejeffrey
author_rank: Super Contributor
timestamp: December 03, 2024, 01:09:12 am
content: It's a split phase setup. The lower left white wire is neutral. The upper left and lower right wires are the two hot phases. The upper right "black" line is disconnected, either deliberately due to a switch or a broken wire. The meter used did not have low-Z mode, so it saw a phantom voltage when measuring between the hot wires and the floating wire.QuoteIt's because the wall switches (at least for the simplest version) have 3 screw terminals instead of 2. It's a SPDT switch instead of a SPST switch.

author: Analog Kid
author_rank: Super Contributor
timestamp: December 03, 2024, 01:15:47 am
content: Dang, you weren't supposed to get it on the first try:OK, I guess I can buy that explanation of "3-way" (theswitchesare 3-way, sorta-kinda, not the circuit).

author: themadhippy
author_rank: Super Contributor
timestamp: December 03, 2024, 01:38:20 am
content: Quotebut the switch can only switch between 2 ways,3 wire switch yea i could get that ,and wot happens when you have a 2 way with 3 intermediate switches how many ways is that?

author: BradC
author_rank: Super Contributor
timestamp: December 03, 2024, 01:56:59 am
content: Quote from: Analog Kid on December 03, 2024, 12:44:26 amI think it's an Ughmerican thing. The rest of the world treats "three way" as having three (or more) switches. Your config would be a standard "two way" here and if you couldn't figure it out in 30 seconds you have no business breeding.

author: Analog Kid
author_rank: Super Contributor
timestamp: December 03, 2024, 01:58:35 am
content: Quote from: BradC on December 03, 2024, 01:56:59 am+1 for the rest of the world then.

author: BradC
author_rank: Super Contributor
timestamp: December 03, 2024, 02:01:30 am
content: Quote from: Analog Kid on December 03, 2024, 01:58:35 amLook, we're not perfect, but some of the stuff I see from over there leaves me scratching my head.

author: Analog Kid
author_rank: Super Contributor
timestamp: December 03, 2024, 02:02:16 am
content: Quote from: themadhippy on December 03, 2024, 01:38:20 amExcept that that's impossible (having more than two switches in a "3-way" circuit").Draw it out; no can work.

author: themadhippy
author_rank: Super Contributor
timestamp: December 03, 2024, 02:13:30 am
content: Quoteperfectly possible,cant be arsed drawing,

author: ejeffrey
author_rank: Super Contributor
timestamp: December 03, 2024, 02:37:43 am
content: Quote from: themadhippy on December 03, 2024, 01:38:20 amIt's like vacuum tube classification. Diode = two terminals, triode = three, tetrode = four and so on. A three way switch has three terminals, a four way (changeover) switch has 4. If you have a multi location switch you can use 2 three way switches, the rest need to be four way.

author: IanB
author_rank: Super Contributor
timestamp: December 03, 2024, 03:01:43 am
content: It's ultimately a problem of language and terminology.The "ways" are the terminals. Three terminals, three "ways" (ways = doorways, or ways in and out of the switch).But consider:1. Such a switch can have two latching positions: up/down, as is normal with wall switches.2. Or such a switch can have three latching positions: left/off/right, as might happen with a rotary switch.3. Or such a switch can be momentary, only switching when held down, as might happen with a microswitch.All are "three way switches" electrically, but all different in mechanical operation.So at the end of the day, you need to explain very carefully what is intended, and perhaps also draw a schematic, to make everything clear.