[Amps] Safety grounding - was Mains Isolation Transformer

[R L Measures]

On Jul 3, 2006, at 2:43 PM, Jim Brown wrote:

>
>> 4-wire 240v circuits.
>
> A 4-wire 240V circuit requires a 4-contact appliance connector of
> some sort, not a conventional 3-contact 240V outlet, because the
> conventional 240V outlet bonds the third pin (the round pin) to the
> backbox, which grounds it (if the backbox is grounded, which it is
> required to be).
>
> In the 4-conductor connector, two contacts are the "hots" (that is,
> each is 120 either side of neutral), one is neutral, and the fourth
> must be a green equipment ground wire that bonds the equipment
> enclosure and backbox. That is the only way to legally (and safely)
> use a 4-wire 240/120 volt circuit.
>

Correct.  The 240v outlet on my Honda generator has 4 conductors, and  
two of them carry zero current.  How does this make it safe?
> 73,
>
> Jim K9YC
>
>
>
>
>
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