At 09:15 PM 11/16/2005, Gary Schafer wrote:
>You are trying to make it complicated when it is not.
>
>Suppose your neutral does open with a four wire circuit, your 120 volt fan
>just stops running.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I'm afraid it actually is more complicated than you think.
First of all, if your fan stops running that itself is a safety
hazard, but the complications go beyond that.
Consider the case of a 120 volt blower connected from neutral to one
hot, and a 120 volt relay connected from neutral to the other hot.
Perfectly legal, right? What happens if the neutral opens? You then
have 240 volts across the series string of blower and relay. The
blower is almost certainly a lower impedance than the relay, so it
will most likely slow way down or stop completely, while the relay
will become seriously overheated. Both are a safety hazard. It would
be far better to have both items be 240 volt to begin with, and
connected from hot to hot.
I still maintain the existing NEC code allowing use of a neutral is
an attempt to placate some powerful special interests in the
electrical industry. It is NOT the safest approach to the issue.
73, Bill W6WRT
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