<rbus...@es.com> wrote on 06/03/2003 08:56:53 AM:
> I have a customer that wants to remove the power plug (and IEC 309
> style) from our equipment and connect the wires to a power distribution
> system beneath the computer floor. This distribution system uses an IEC
> style "din rail" type of barrier strip where one inserts the bare wire
> into a hole and tightens two screws to affix the wire.
>
> My device is rated 200-240V single phase. When the plug is removed you
> have a blue, brown and green/yellow conductor. The power source is a
> 208V leg (two phase?) drop with two black wires. The electrician refuses
> to connect the blue (neutral) wire from the power cord to a black
> (phase) wire. How can I resolve this. Regardless of whether we are
> talking blue/brown or black/white, the white and blue are identified as
> neutral. Because we allow 200-240V single phase this does not preclude
> the use of 208V phase to phase input.
>
> Suggestions/Comments
>
> Thanks
>
> Rick Busche
> Evans & Sutherland
The power system you are dealing with is fairly common in commercial and
light industrial settings. It is Y connected 3-phase power. It is 120 volts
>from phase to neutral, and 208 volts from phase to phase. For 208 volts,
both conductors are hot with respect to ground.
If the power input circuitry of the product is symmetric with respect to
ground up to the diode bridge, then it is a matter of indifference which
connection is called hot and which is called neutral, or if both are hot
with respect to ground.
Now let me step out of my element, so take this with the appropriate grains
of salt. My suggestion would be to use power cable in which the colors are
black, red, and yellow/green. If I remember correctly, red stands for
something than can be either hot or neutral depending on circuit
conditions.
Don Borowski
Schweitzer Engineering Labs
Pullman, WA
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