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MystikIncarnate@lemmy.ca ⁨11⁩ ⁨hours⁩ ago

Oh this gets stranger.

It’s usually 120v, but I’m not going to split hairs over 10v.

So, 120v is not a voltage that is delivered from the grid… Technically speaking. Each home is given one circuit of 240v, which is usually part of one leg of a three phase, coming off of the Transformers… 120v is there because they center-tap the transformer. This halves the voltage by consequence. Inside the house the circuits are generally laid out to try to balance the load between each half of the 240v phase.

The idea is that two 120v loads, put in series, will total 240v. So power will ideally go from L1 to a 120v load, to “neutral”, then over to another 120v load, then finally back on L2.

More or Less.

120v is basically just half of what you should be loading the system with.

The center tap neutral from the transformer is to collect any load imbalance between L1 and L2 to allow for the two “sides” of the phase to be out of balance and still work.

The US “plug” ( aka receptacle ) is a NEMA 5-15R, or NEMA 5-20R (for 20A); these are designed for 120v operation using the half phase described above. Of course, you can mis-wire it and make all kinds of dangerous abominations if you so choose. There is, however, a less known NEMA 6-15R and NEMA 6-20R that is basically the same, but for 240v operation, replacing the neutral wire with L2 instead (and 15/20A respectively).

So it is entirely possible to have 240v outlets in a North American home, while still being compliant with code.

It’s actually really fascinating information when your dig into it.

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