On Wed, 03 Feb 2010 19:51:56 -1000, Ken Brown wrote:
>I believe the present NEC allows three wires for 240 VAC service. Two
>hot leads and one ground. There is not neutral run on a modern 240 VAC
>service feed, because it is no longer allowed to run any 120 VAC loads
>inside a 240 VAC operated device by using one hot lead and the neutral.
NO! It all comes down to how the 240V appliance uses power. Certainly
240V for the heating element, so that's two hots and a ground. It's easy
to make a motor that runs on 240V, so no neutral would be needed.
Remember -- most of the world outside of North America runs on 240V!
Now, if the appliance has a 120V motor, it DOES need a neutral (that is,
four wires), because is IS ILLEGAL to draw current between hot and
GROUND. AND -- any current drawn between hot and ground will set up a
magnetic field that will drive you nuts for hum and buzz, both in your
ham station and in your hi-futility rig.
Remember my drawing showing how Ten Tec properly uses a center tap on
the primary of the 240V power transformer to run the 120V fan in the
Titan 425? The Titan can run on 120V or 240V by changing the wiring of
the power transformer primary. That drawing is on my website.
http://audiosystemsgroup.com/publish.htm
73,
Jim K9YC
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