Paul Christensen wrote:
>
>Now, if the neutral is lost for any reason, the chassis will not be hot
>through the blower winding. If allowed to continue in this condition, I
>suspect that the blower would continue to run by finding its neutral return
>through the BNC, SO-239, or RCA jacks and potentially complete the path back
>to neutral via the ground lead on another piece of equipment.
There are two sides to separating neutral from ground. One is in the
mains supply and cable, but the other is in the equipment. The rule is
that "neutral is only for power", and "ground is only for grounding".
Therefore all 115V power supplies - including the blower and everything
- must return through neutral.
To check, you should be able to find no continuity and good insulation
between neutral and chassis at the power input to the equipment.
However, because of the historical confusion between these two different
conductors in the USA, there have been published examples of 4-conductor
circuits where they get it wrong.
It's easier to understand this in Europe where there is only one 230V
phase to think about. Here, "neutral is only for power", and "ground is
only for grounding" has been SOP for generations. Most home
installations have a circuit breaker which will trip if all the line
current doesn't return through neutral. As little as 30mA not returning
through neutral (maybe because it's flowing through a person to ground)
will trip the breaker.
73 from Ian G3SEK Editor, 'The VHF/UHF DX Book'
'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.com/g3sek
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