[Amps] 220V wiring: Was Question about safety ground

[R.Measures]

On Nov 16, 2005, at 3:55 PM, John Finner wrote:

> To describe the 220v power wiring used in my shack.  I bought a Kenmore
> electric dryer in 1970.  Since it came without a line cord, I also 
> bought
> the Sears recommended cord.  The 10/3 cord came equipped with a NEMA 
> type
> 10-30P plug (3 pole 3 wire 2 hots a neutral and no ground).  I 
> realized the
> NEC has changed since then.  The dryer came with a ground wire, with
> instructions to connect to a suitable ground such as a copper water 
> pipe.
> The dryer heating element requires 220 and the timer and lamp require 
> 110
> making the neutral necessary.

Without a neutral on a 240v/120v circuit, the 120v circuit passes 
through terra firma.
>
> I ran 40 feet of 10/3 romex with ground from the mains panel to my 
> shack
> where the dryer is located.  I installed two wall receptacles, one a 
> NEMA
> type 10-30R for the dryer and the other a NEMA type 14-30R (3 pole 4 
> wire
> with ground) for the amp.  The amp is a SB221 is connect through a 15 
> foot
> extension cord made with 12/4 SJ cord.  One end with a NEMA type 
> 14-30P plug
> and the other end with a NEMA type 6-20R (2 pole 3 wire with ground)
> receptacle for the amp.  The amp is wired as per Heathkit with a 12/3 
> cord
> using 2 hots, a ground and a NEMA type 6-20P plug.  The neutral in the
> extension cord not being used.
>
> There is a bag of cloths pins on top of the dryer in case the XYL 
> needs to
> dry cloths while the amp is in use.
>
> John WA4EPI
>
> ----- Original Message -----
>> Date: Wed, 16 Nov 2005 10:27:37 -0600
>> From: Doug Renwick <ve5ra at sasktel.net>
>> Subject: Re: [Amps] 220V wiring: Was Question about safety ground
>> connection
>> To: amps at contesting.com
>> Message-ID: <MFBBJHMMGJLHBMKINBGLOEDCECAA.ve5ra at sasktel.net>
>> Content-Type: text/plain; charset=iso-8859-1
>>
>> The wiring manual I use states the following:
>>
>> A) A 120/240-volt, 30 amp receptacle (4 wires); connect the white
>> wire to the white receptacle terminal.  Connect the red and black
>> cable wires to receptacle terminal. Connect the bare ground
>> wire to the outlet box.  The bare ground wire does not attach
>> to the terminal.
>>
>> B) A 240-volt, 30 amp receptacle (3 wires); connect the white, black
>> cable wires to the receptacle terminal and recode the white
>> wire (red marker or tape).  Connect the bare wire to two green
>> jumpers, one screwed to the terminal box and the other attached
>> to the green receptacle terminal.  This terminal needs no neutral
>> wire.
>>
>> Doug/VA5DX
>>
>>
>>
>> On Wed, 16 Nov 2005 04:05:51 -0800, R.Measures wrote:
>>
>>> My 240V, 40A circuit is wired 2-hot and 1-neutral.  I assumed that no
>>> "safety" ground wire was needed because neutral is connected to
>> safety
>>> ground in the circuit breaker box.  Under normal operation, virtually
>>> zero current flows in the neutral wire.
>>
>> NO, NO, NO, NO, NO!
>>
>> Neutral is intended to carry current (although it is not used in the
>> 240 volt circuits in homes). Ground is a PROTECTIVE conductor that
>> should NOT carry current except in the case of a fault. (A fault is a
>> failure of some component or wiring that results in an equipment
>> enclosure being hot).
>>
>>
>> Jim Brown  K9YC
>>
>>
>>
>>
>>
>>
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>>
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>
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org