this post was submitted on 15 Mar 2025
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You're correct, phase-to-phase is 173.2% of the phase-to-neutral voltage in 3-phase "Wye" service.
But that's not what consumers (typically) use in North America. We don't bring three phase to the home.
Our single-phase final distribution transformers have a center tap on the secondary coil, bonded to neutral. So, one side of the coil provides a 120v leg with respect to that neutral, and the other side provides an opposing leg, 180° from the first, and 120v with respect to that same neutral. Most of our appliances use leg-to-neutral, 120v. But leg-to-leg is 240v.
(Commercial and industrial facilities can get a wide variety of voltages in single or three phase, and we do have some actual, 2-phase generators and customers: the phases are 90° apart rather than 120° or 180°)
The technology connections video talking about 240v power mentioned some apartment buildings having 208v because they're bringing in two phases instead of center tapping or whatever. So their comment could be right in the correct locations i think.
I'm clearly no sparky.
Correct. It's not typical, but it does exist. 208v is usually close enough for 240v appliances.
And lots of things meant to run on 240 are dual labeled 208/240. If it's a motor it will end up running a little hotter, if it's a heater it will end up a little colder.