[BC] Electrical Code

[Davis, Jack L. KTXL]

<Message: 12
<Date: Thu, 20 Oct 2005 21:56:29 -0400
<From: "Milton R. Holladay Jr." <miltron at mindspring.com>
<Subject: Re: [BC] Re: Saving Your Own Life
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<One of the most hazardous, stupid xmtrs that most of us have encountered is
<the FM-20 and its smaller brothers which have not only the 3 phase circuit,
<but a separate 120 volt circuit, waiting to bite you. Any that I have had
my
<hands in now have the 120V tied to one of the 120V legs of the 3 phase, so
>that when it's off, it's ALL OFF !
<M

This does not meet code, but for reasons other than previously discussed.
The three phase Wye connected power is actually 208 volts leg to leg and 120
volts to neutral.  So it is perfectly legitimate to use any leg to neutral
for a single phase load.  The code problem gets to be one of fusing, the
three phase is most likely fused (or circuit breaker) at a high value and
the wiring on the single phase load is not capeable of that kind of current.
If you fuse the single phase load at a proper value there should not be a
problem.  If the three phase is Delta connected (Not common anymore) then
the voltage is 240 volts leg to leg and one of the leg to leg connections is
normally center tapped to form the neutral and 120-0-120 for single phase
load.  Either end of the center tapped transformer winding to neutral is 120
volts and is usable the third leg (often reffered as the "wild leg") can not
be used to neutral as it varys wildly depending on the load and current
unbalance.

Is the FM-20 the one with the ceramic fuse holder on the floor of the
cabinet?  The one that attracts every dropped tool in a 5 foot radius?


Jack Davis
K6YC