On Nov 16, 2005, at 9:15 PM, Gary Schafer wrote:
>
>
>> -----Original Message-----
>> From: amps-bounces@contesting.com
>> [mailto:amps-bounces@contesting.com] On
>> Behalf Of Bill Turner
>> Sent: Wednesday, November 16, 2005 9:27 AM
>> To: amps@contesting.com
>> Subject: Re: [Amps] 220V wiring: Was Question about safety ground
>> connection
>>
>> At 05:20 PM 11/15/2005, Gudguyham@aol.com wrote:
>>
>>> Your safest bet is to run 4 conductor wire and outlets. All new
>>> ranges
>> and
>>> dryer circuits must be 4 wire. As far as I am concerned, all new
>> amplifier
>>> circuits should be too.
>>>
>>> Mike, W1NR
>>
>> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>>
>> I'm not sure that is the "safest" approach, event though it is
>> allowed by
>> NEC.
>>
>> IMO, the safest system is to use two hots and a safety ground, and no
>> neutral at all. This requires having NO 120 volt circuits in the
>> equipment, something which may require a bit of redesign, but is
>> quite doable. This eliminates the rare but real possibility of
>> problems due to an open neutral. As one other poster has observed,
>> open neutrals have been caused on more than one occasion by lightning
>> strikes.
>>
>> I believe NEC's position on allowing four-wire circuits is an attempt
>> to placate all parties involved rather than create a more safe but
>> awkward to implement (no-neutral) standard. Am I wrong?
>>
>> 73, Bill W6WRT
>
>
> You are trying to make it complicated when it is not.
Good point. Letting those in the business decide the national code
virtually assures that more business will result. I would not be
surprised that - in the next 50-yrs - it will be determined by the
"experts" that 4-wire 240v outlets are really and truly not safe
enough, so 5-wire 240v receptacles will become the new national
standard, and we will have 3 wires carrying zero current in a 240v
circuit instead of only 2.
>
> Suppose your neutral does open with a four wire circuit, your 120 volt
> fan
> just stops running.
Putting a R in series with the fan to drop 120v and running it from
240v would prevent this possibility.
>
> Same thing happens to your 240 volt power supply if one side of the
> 240 line
> opens. Your amp stops working.
>
> The reason the NEC allows four wire circuits is to bring the part of
> the
> code that previously allowed neutral and ground circuits to be run on
> the
> same wire (electric stoves) up to same standard as the rest of the
> code.
> That is, "no safety ground shall carry current".
> This has been the standard for all but a few exceptions in the past,
> stoves
> and dryers. The code has been updated to not allow those exceptions any
> longer.
>
> 73
> Gary K4FMX
>
>
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>
>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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