Hoosierpopi wrote:
I was asked today about a motor stamped 240VAC. I kept saying 220
volts and my neighbor would interupt and remind me it said 240 VAC.

I told hm that I didn't think it mattered and that I'd never heard an
explanation of why we see stuff rated at 240 VAC when most of our
homes seem to come standard with 220 VAC and 115VAC.
....

In the US and Canada, national standards (NERC www.nerc.com) specify
that the nominal voltage at the source should be 120 V +/-5%.

Historically 110, 115 and 117 volts have been used at different times
and places in North America. Owing to the previous usage, main power is
still sometimes spoken of as 110; however, 120 is the present nominal
voltage (US).

BTW, the 110 V came from Edison; it was the compromise between the
voltage at which initial light bulb filaments could be made to last
sufficiently long (about 100 V) and the need for higher voltages for
distribution and lower current demands. Hence, initially generation was
at nominal 110V allowing for some 10 V distribution voltage drop to user.

As surmised, in the US the lower voltage is one side of the "hot" to
neutral and so is, indeed, precisely one-half of the greater.

--