118 volts each outlet, combined 205 volts - Page 1
Forum section: electronics / beginners

author: u666sa
author_rank: Frequent Contributor
timestamp: March 09, 2025, 04:53:42 pm
content: Trying to get 240 volts.Code:https://www.youtube.com/watch?v=64L4Pz4vuYcEach outlet measures 118 volts. When I combine two hots I'm getting 205 volts. What's happening?

author: bdunham7
author_rank: Super Contributor
timestamp: March 09, 2025, 04:58:01 pm
content: Quote from: u666sa on March 09, 2025, 04:53:42 pmAre you in a stand-alone house, commercial building or an apartment building?

author: u666sa
author_rank: Frequent Contributor
timestamp: March 09, 2025, 05:00:08 pm
content: Quote from: bdunham7 on March 09, 2025, 04:58:01 pmI'm in appartment building in Florida

author: Monkeh
author_rank: Super Contributor
timestamp: March 09, 2025, 05:02:04 pm
content: Quote from: u666sa on March 09, 2025, 05:00:08 pmYou have two phases of a 120/208V 3-phase system, not two legs of a split single phase.

author: themadhippy
author_rank: Super Contributor
timestamp: March 09, 2025, 05:04:04 pm
content: 2 phase 120 degrees apart,instead of a split/center tapped 120/240 v supply

author: fzabkar
author_rank: Super Contributor
timestamp: March 09, 2025, 05:12:37 pm
content: 118 x sqrt(3) = 204

author: TimFox
author_rank: Super Contributor
timestamp: March 09, 2025, 05:54:19 pm
content: As a visualization of three-phase power distribution, I consider three identical light bulbs, each connected from one line to neutral. Since there is no current in the neutral lead, it can be open-circuit with no change. This facilitates calculating the relationship between line current and power. The root-three results follow.

author: calzap
author_rank: Frequent Contributor
timestamp: March 09, 2025, 07:18:00 pm
content: If you want 240 VAC, you’ll need a transformer unless there is an alternate source in the building. Even if there is, getting it to a specific apartment would probably take some persuading and expense.Mike

author: floobydust
author_rank: Super Contributor
timestamp: March 09, 2025, 08:19:00 pm
content: I've encountered this only in commercial buildings and know it as a "high leg delta" connection. It's a bit confusing until you see how the distribution transformer is wired up.Usually the 208V is for bay lighting but here it must be air conditioning as a 3-phase load balanced somewhat in the overall building.

author: coppercone2
author_rank: Super Contributor
timestamp: March 09, 2025, 08:23:11 pm
content: if you think thats confusing I found thishttps://www.researchgate.net/profile/Resmi-Reghu/publication/335126905/figure/fig1/AS:857327460696064@1581414203101/Star-delta-star-connection-in-SPW-APW.pngjust combine the two , and then add a tapI wonder if we will see hexagons eventuallyyou wake up, go to the circuit panel and see a faded schematic on the side of the box withhttps://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTw66lFJHA-MxxP2Pw25m_CbCIHkllMPoWh7A&sit means you are in the year 50000 A.D. . Your home also has a old rusty dedicated gas pipe for helium/oxygen/sulfur hexaflouride tri-mix.

author: bdunham7
author_rank: Super Contributor
timestamp: March 09, 2025, 08:27:42 pm
content: Quote from: floobydust on March 09, 2025, 08:19:00 pmI've had that high-leg arrangement in a commercial building and it was that way because of 240VAC 3-phase loads (machinery) that wouldn't tolerate 208V. It could get really weird. The OP's situation is different. He is in an apartment building and in the 1960s-80s (IIRC--perhaps more) they would run 208VAC 3-phase WYE connections and provide 120V L-N connections off of that for individual units. 240VAC loads such as ovens would operate OK with 208VAC. There weren't necessarily any real 3-phase loads involved, this just reduced initial costs. Phase balancing was by random usage patterns. Neutral current issues were managed by less than capacity loads most of the time and I'm sure they hadn't even thought about them at that time since the big loads were light bulbs, electric ovens and wall air conditioners.