118 volts each outlet, combined 205 volts

[u666sa]

Trying to get 240 volts.

Code: [Select]

https://www.youtube.com/watch?v=64L4Pz4vuYc
Each outlet measures 118 volts. When I combine two hots I'm getting 205 volts. What's happening?

[bdunham7]

Each outlet measures 118 volts. When I combine two hots I'm getting 205 volts. What's happening?

Are you in a stand-alone house, commercial building or an apartment building?

[u666sa]

apartment building

I'm in appartment building in Florida

[Monkeh]

Each outlet measures 118 volts. When I combine two hots I'm getting 205 volts. What's happening?

apartment building

I'm in appartment building in Florida

You have two phases of a 120/208V 3-phase system, not two legs of a split single phase.

[themadhippy]

2 phase 120 degrees apart,instead of  a  split/center tapped 120/240 v supply

[fzabkar]

118 x sqrt(3) = 204

[TimFox]

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.

[calzap]

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

[floobydust]

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.

[coppercone2]

if you think thats confusing I found this
https://www.researchgate.net/profile/Resmi-Reghu/publication/335126905/figure/fig1/AS:857327460696064@1581414203101/Star-delta-star-connection-in-SPW-APW.png

just combine the two , and then add a tap

I wonder if we will see hexagons eventually

you wake up, go to the circuit panel and see a faded schematic on the side of the box with
https://encrypted-tbn0.gstatic.com/images?q=tbn:ANd9GcTw66lFJHA-MxxP2Pw25m_CbCIHkllMPoWh7A&s

it 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.

[bdunham7]

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.

I'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.