[Amps] Question about safety ground connection

[Mike McCarthy, W1NR]

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.

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 at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Keith Dutson
Sent: Sunday, November 13, 2005 5:39 PM
To: 'Bill Turner'; amps at 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 at contesting.com [mailto:amps-bounces at contesting.com] On
Behalf Of Bill Turner
Sent: Sunday, November 13, 2005 12:35 PM
To: amps at 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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