Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!brutus.cs.uiuc.edu!apple!xanadu!michael
From: michael@xanadu.COM (Michael McClary)
Newsgroups: sci.electronics
Subject: Re: grounding by pipe (was ... true ground?)
Keywords: ground, pipe, electrocution
Message-ID: 
Date: 12 Aug 89 12:40:23 GMT
References: <741@encad.wichita.ncr.com> <4474@merlin.usc.edu>
Reply-To: michael@xanadu.UUCP (Michael McClary)
Organization: Xanadu Operating Company, Palo Alto, CA
Lines: 36

In article <4474@merlin.usc.edu> guncer@nunki.usc.edu (Selim Guncer) writes:
>how about using the "ground" as ground (:-)).  back home (in Turkey),
>as new ee majors, we were operating our electric heaters by connecting
>one end to the live terminal, and the other end buried in the front
>garden. since the return path was not provided, we weren't charged for
>the electricity! ofcourse, whoever did happen to jump over the fence
>and step in the garden may have been electrocuted.

If they provided service and meters of the same sort as you find in
the U.S., you paid for the energy you used in the heater, plus the
energy lost heating the ground.

The typical watthour meter has two current windings (one for each of
the hot sides of a 220 center-tapped feed), and one voltage winding
(connected between the two hot lines).

When you draw power between the two hot lines, the current is counted
twice (once for each winding).  When you draw power from one side and
return it through neutral, it only gets counted once.  If the neutral's
voltage is exactly halfway between the two hot feeds, you got exactly
half the power, so it comes out right.

If the neutral is a little off, say because of voltage drop from a
crummy connection, you get to pay for the power lost in the voltage
drop as well.  (If it's off to one side because you're placing a
light load on one side and your neighbor is placing a heavy load
on the other, he gets to pay a smidgeon of your bill.)

In a 110 feed (rather than a center-tapped 220 feed), you may find
the meter wired so both the neutral and the hot side go through
current windings.  In this case, you save half your bill by
bypassing the neutral current winding.  (If it's wired with just
one current winding, though, you're back to the same case as the
220 feed.)

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