7 Oct
2005
7 Oct
'05
1:05 p.m.
I once worked in a hospital and repairing the TVs
was one of my
responsibilities. One day we had a call for a TV that won't work. When we
arrived it was working fine. A little latter we had a call for the same
thing from the adjacent room. This time we checked closer. We found that
the TVs were back to back on a common wall and both TVs used the same
electrical circuit. Somewhere there was an open circuit between the AC
outlets such that the two TVs were in series so neither one would work
unless both were turned on! That's why the patients TVs were dead, one
patient would turn their set off and it would turn both of them off. The
surprising thing was that both sets worked normal when in series. Very
surprising since each one was running off 1/2 the normal voltage!
Were they, though?
Obviously, I don't know the details, but the most obvious way this could
happen on the US mains wiring system would be if one live ('hot') side of
each socket outlet was wired to each side of the centre-tapped mains. The
neutral sides of the sockets were linked together, but for some reason
that connection was not connected back to the centre-tap of the mains
supply. That would put the 2 TVs in series across the 230V mains.
Assuming they were similar sets, each would see about 115V.
-tony