On Nov 13, 2005, at 3:36 PM, Mike McCarthy, W1NR wrote:
> You are not quite right on a couple of points.
>
> A standard 3 prong 220V plug has two hots and GROUND. There is no
> neutral.
> This creates a safety issue when wiring in 110V components using 1/2
> of the
> 220V outlet since you are now using the safety ground as a neutral.
>
> Most older service panels have neutral and ground bonded. Newer
> services
> have them separate. But all new services added to EITHER must run
> separate
> neutral and ground.
>
> The safest thing to do is to use 4 prong plugs with separate neutral
> and
> ground running back to the service panel. This is now NEC standard on
> all
> new electrical installations for nearly everything except heaters.
> All new
> dryer outlets are 4 prong. Electricians cannot put in a new 3 wire
> line in
> for them.
The result is that 2-wires carry current and two wires do not.
>
> If in doubt, consult a licensed electrician or the latest NEC and state
> electrical codes which can be found at your local library.
>
> 73 de Mike, W1NR
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
> On
> Behalf Of Keith Dutson
> Sent: Sunday, November 13, 2005 5:39 PM
> To: 'Bill Turner'; amps@contesting.com
> Subject: Re: [Amps] Question about safety ground connection
>
> Bill,
>
> As you have noted, the standard 240V plug does not bring the safety
> ground
> to your chassis. However, you can wire the 240V circuit with safety
> ground
> (4th wire) and run a separate ground wire from the outlet to your
> chassis.
> I have never seen this done, however.
>
> The neutral wire begins at the transformer outside (center tap) and is
> grounded there by the power company. The breaker panel has a ground
> rod
> just below and should connect to neutral. The safety ground is an
> independent ground. It SHOULD be at the same potential as neutral.
> The
> main difference is the safety ground wire has no relationship to the
> hot
> wires, so current cannot flow from the transformer. The neutral wire
> current should also be zero but could provide a path for current
> should the
> two 120V phases not draw equal amounts of current. This is an abnormal
> condition.
>
> 73 Keith NM5G
>
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
> On
> Behalf Of Bill Turner
> Sent: Sunday, November 13, 2005 12:35 PM
> To: amps@contesting.com
> Subject: [Amps] Question about safety ground connection
>
> I have a question about how to connect the safety ground from the AC
> mains.
>
> I'm building a 1500 watt amplifier with a separate power supply. The
> power
> supply will connect to a 120-0-120 wall socket. My question is whether
> the
> "0" pin is considered a safety ground pin or a neutral pin. If it's
> neutral,
> then do I have to run a separate safety ground wire back to the AC
> mains
> entrance? Conversely, if it's a safety ground pin, am I allowed to
> connect a
> 120 volt load (blower motor) from it to one of the 120 wires? I
> suspect not,
> so does this mean the 120 volt load will need its own separate 120v
> circuit
> (with its own ground), and is it ok to connect the two grounds
> together?
>
> Comments appreciated.
>
> 73, Bill W6WRT
>
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>
Richard L. Measures, AG6K, 805.386.3734. www.somis.org
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