----- Original Message -----
From: "R.Measures" <r@somis.org>
To: "John Popelish" <jpopelish@rica.net>
Cc: <Amps@contesting.com>
Sent: Friday, January 06, 2006 12:15 AM
Subject: Re: [Amps] NEC-think.
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?
Rodents? knaw. Lightning? Maybe. But you're toast anyway.
How about a tree on the service drop ripping the neutral open right
through the wall and twistin the legs to bare metal in the box?
Hey. It could happen.
Mike k1ern
>
> 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.
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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