I have a water heater ( 220 VAC ) which is only connected to two phases ( each phase is 110 VAC ) with no heater. I have never came across such connection, how does the circuit work ? Are there any source material I can read or wTch to learn about it ? And why such connection exists ?

 

That is what the water heater uses: 230VAC. Does NOT need neutral nor two branches of 120VAC to work. So that is what is to be supplied. 230VAC, period.

----> http://waterheatertimer.org/How-to-install-electric-water-heater.html

 

Hello there, welcome to AAC!
I am in the United States.
Is it an on going argument is 240 single phase or two phase.
https://forum.allaboutcircuits.com/...volt-system-single-phase-or-two-phase.105861/

 

If you are in N.A. (USA), then a residential supply is not two phases , it is single-split phase. 120v-0-120v .
IOW it is fed from a single phase transformer.
The 0v is the neutral and is earth grounded at the transformer and the distribution panel.
No confusion.

 

I have a water heater ( 220 VAC ) which is only connected to two phases ( each phase is 110 VAC ) with no heater.

The 110Vac "phases" are the two hot sides from a single winding on the residential signal-phase transformer, which give 220Vac single-phase.
The 110Vac phases are simply each hot side to neutral, with neutral being the center-tap of the 220Vac winding.
This gives an apparent phase-shift of 180° between the two 180Vac lines.

Is it an on going argument is 240 single phase or two phase.

There should be no argument as the definitions are plain.
Two 120Vac phases that are 180° out-of-phase are split-phase.
True multiphase AC has phase-shift between phases that are other than 180°, such a 90° for 2-phase and 120° for 3-phase.

 

And to add, a 3ph transformer is made up of three 1ph cores, so for 2 phases, 2 cores would be required.
When in fact the residential 120-0-120 version is provided by one single phase core.

 

And to add, a 3ph transformer is made up of three 1ph cores, so for 2 phases, 2 cores would be required.
When in fact the residential 120-0-120 version is provided by one single core.

The 110Vac "phases" are the two hot sides from a single winding on the residential signal-phase transformer, which give 220Vac single-phase.
The 110Vac phases are simply each hot side to neutral, with neutral being the center-tap of the 220Vac winding.
This gives an apparent phase-shift of 180° between the two 180Vac lines.
There should be no argument as the definitions are plain.
Two 120Vac phases that are 180° out-of-phase are split-phase.
True multiphase AC has phase-shift between phases that are other than 180°, such a 90° for 2-phase and 120° for 3-phase.

Right Church, wrong pew.

 

And to add, a 3ph transformer is made up of three 1ph cores, so for 2 phases, 2 cores would be required.
When in fact the residential 120-0-120 version is provided by one single core.

I have 'real' 2-phase motors for cryogenic vacuum pump motors. A vendor installed the HE compressor drive system strapped for 3-phase motors. The 2-phase motor would run on two legs of 120 phase shifted power but was very noisy.

 

Thank you soooo much all. That solved the puzzle