[GingisK]

..but as far as I know you have 110/120 volts coming into the house, not 220/240...

No, 220/240 enters your house in two phases that are offset from each other by 180 degrees, with a common (neutral) between them. The voltage between the phases is 220/240 volts. The voltage between either to neutral is 110/220.

[ansel12]

Right, I guess I was mixing up the OP’s mentioning 220 as he did, as him thinking that his house outlets and light fixtures were 220, it is so rare for someone to talk about 220 coming into their house, we tend to talk about what it is at the outlets.

[fruser1]

two phases

Interesting topic.

It's actually only one phase. The wiring results in opposite polarity, which is not a different phase.

https://www.prosoundweb.com/phase-polarity-causes-and-effects-differences-consequences/

Note in the pics below, the input side of the transformer is only one line - i.e. one of the three phases available from the transmission lines. What you do not have are two different AC signals in that secondary coil.

Three phase is for transmission only. You only get one phase to a house. Three phase provides constant power (DC) even though Voltage and Current are AC. That's the mathematics of having three signals 60 degrees apart.

https://electronics.stackexchange.com/questions/763790/why-is-3-phase-power-the-standard-for-generation-and-transmission-instead-of-2-p

Here's a site with a lot of nice pole pics with varying connection types for 3 phase.

http://waterheatertimer.org/How-to-identify-transformer-wiring.html