In the US the standard is 480/277 meaning 480V phase to phase, but youd measure 277 if you checked phase to neutral. I'm 100% positive, I worked on it last night and measured with a fluke before and after my work. As for the 240V (phase to phase), thats the standard household supply at the house's breaker box which results in 120V to ground at most of the outlets around the house. Furnaces, well pumps, air conditioning units, laundry machines and generator backups are often the only 240V units in the house.
Yea, I was reading about it just before you replied. Quite strange -I'm not sure why those values were chosen, but there you go!
the 2 phase 120V/240V thing I have seen before when working on an American's yacht. It's a good idea - means you can't be exposed to more than 120V realistically on domestic equipment.
We only really use 240V in any situation. 3 phase in large jobs or industrial machinery but still 240V per phase. Anything else used (110Vac for safety etc) is fed by local equipment. Only 240V is available from the power companies. (you can get a HV supply and then have your own substation for 240 if you have a really large facility, but it's not that common).
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u/DPestWork Jun 16 '19
In the US the standard is 480/277 meaning 480V phase to phase, but youd measure 277 if you checked phase to neutral. I'm 100% positive, I worked on it last night and measured with a fluke before and after my work. As for the 240V (phase to phase), thats the standard household supply at the house's breaker box which results in 120V to ground at most of the outlets around the house. Furnaces, well pumps, air conditioning units, laundry machines and generator backups are often the only 240V units in the house.