I have a 2 gang box with a light and a duplex in it. The light is 277 and the duplex is, of course, 120. (Yes I know it's illegal but it's been there since '62). Here's the question: When I take a reading between the switch feed and the duplex I get 310 volt. Why? Is it always this? Is this just a coincidence? Will this vary in other locations?
The 277/480 that feeds the light also feeds the xfmr that feeds the 120/208.
Any long detailed explinations will be appreciated.
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