[Amps] NEC-think.

R.Measures r at somis.org
Fri Jan 6 00:15:09 EST 2006


On Jan 5, 2006, at 2:08 PM, John Popelish wrote:

> R.Measures wrote:
>
>> Without a ground/bond wire wouldn't connecting the Neutral wire to the
>> metal enclosure hold the enclosure to a safe potential until the
>> breaker trips?
>
> The neutral carries load current,

•   In a 240v appliance, why would it?

>  so it may have some voltage drop at
> the appliance end, compared to the end at the power panel.  And if it
> ever goes high resistance, then the moment any load is connected to
> it, it has full line voltage on it.  So a single failure (open
> neutral) would produce a shock hazard if the case were attached to it,
> the moment the appliance was turned on (a moment someone is likely to
> be touching the case, also).

•  For a shock hazard to exist, the person would also need to be 
grounded.  The Neutral wire on the 240v outlet in my radio room is 
#6-ga.  What would make the resistance of the Neutral go high and 
simultaneously connect one Line wire to the enclosure?
>
> The safety ground never carries current under normal conditions, so it
> take two failures (hot faulted to metal case and open ground
> conductor) to produce an unsafe condition.
>
>
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>

Richard L. Measures, AG6K, 805.386.3734.  www.somis.org



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