[AMRadio] 220 volt AC Power Question

Larry Will lhwill at verizon.net
Tue Oct 31 08:00:33 EST 2006


See NEC 250.134(B).  There is a discussion in my NEC handbook showing 
why the safety (ground) conductoe should be run with the neutral and 
hot conductors.  Its for making a low impedance for cancelling 
magnetic fields.  You can have a ground stake as you have but you 
should also have the ground going back to the panelboard right with 
the hot and neutral.

By the way NEC also has a complete section on amateur radio antennas 
and most of us do not meet code there as well.

All this is important when it comes to insurance.


PE in PA and NJ.

At 11:41 PM 10/30/2006, you wrote:
>         That is the way I am running mine Jim.  I have two power supplies
>(MOD/FINAL) 120 VOLT AC each and I run one from each leg of the 220 and a
>common line for the return. (Three Wire).  The plate relay/contactor is a
>three phase relay/switch but only 2 of the contactors are active of course.
>The earth/safety ground is a separate wire that is connected to a ground
>stake outside the shack.  I guess I could have run separate return along
>with each hot leg but I don't know why I should.  I use a clothes dryer plug
>and pigtail for mine.  The Filament XFMRS for the rectifiers, finals, and
>modulators all run from the same phase as the modulator plate supply. And
>the final plate supply is on the other phase.  There are breakers at the
>pole and a 3 phase breaker in the rig. Only two lines in use; Common stays
>connected at all times.
>         By the way I do not use a transformer for bias supply for either the
>final or for the modulator.  Bias supply comes from diodes that are
>connected through limit resistors from the 120V AC hot line.  Chassis is
>connected to common AC and earth ground at all times.
>John, WA5BXO
>-----Original Message-----
>From: amradio-bounces at mailman.qth.net
>[mailto:amradio-bounces at mailman.qth.net] On Behalf Of Jim candela
>Sent: Monday, October 30, 2006 7:10 PM
>To: Discussion of AM Radio in the Amateur Service
>Subject: [AMRadio] 220 volt AC Power Question
>Hi all,
>    I am building an amplifier that has a combination of 220 volt and 120
>volt transformers. The HV plate supply is 220V, and the rest is 120V. I will
>be keying the plate supply. My 220V outlet has phase, phase, and ground.
>There is NO neutral. The outlet is not a GFCI outlet so ground current will
>work, BUT.
>   The BUT here is whether this is legal with the National Electric Code?
>Before you say NO, consider the electric clothes dryer. These all run off
>220V, and have 3 prong power cords. I have heard that in some dryers there
>are 120 volt loads (lights, and timer) as well as 220V (heater and motor).
>If this is true, then my approach must be OK so long as my power switch uses
>a DPST switch and (double fuses)to insure everything is off when it is in
>the OFF position.
>Comments please...
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