> > Ground and Neutral are the same in the MAIN breaker box - not necessarily in
> > all breaker boxes... A branch circuit (probably quite common for
> > post-construction install of 240V in our shacks) must have the neutral and
> > ground separated. You should not wire up a device anywhere which requires
> > neutral (i.e. the neutral is carrying current) to the ground instead of
> > neutral.
Right on, Bill!
This subject comes up several times per year, so let me try to draw a mental
picture for those who are planning 240 volt service into the shack.
The location where the power lines come into the building and terminate in the
main breaker box is called the "service entrance" by those in the trade. As
close as possible to this breaker box, ground rod(s) are installed. The ground
rod should be 8 feet or longer. Do not try to save a few bucks by using cheap
rods; get a good one like the power companies use. As we will see later, this
rod plays an important part in the system. It is referred to in the trade as the
"service entrance ground." A good quality wire is run from the breaker box
ground bus bar ( a long bar with many holes and set screws for installing wires)
to the ground rod. As Bill stated, the difference between a main service panel
and a sub-panel is that on the main panel the ground bus bar and the neutral
bus bar (which is insulated from the box) are strapped together by a jumper
wire. When running romex throughout the building, the white wires go to the
neutral bus bar, and the bare wires go to the ground bus bar. When installing
a sub-panel down-line, the ground (un-insulated) bus bar in the sub panel
is unused. Both the white and bare romex wires are hooked to the neutral bus
bar.
To get 240 volts, a dual breaker is installed in the sub-panel. The black and
white wires on the romex go to the terminals on the dual breaker, and the
bare wire hooks to the neutral bus bar. The 240 volt plug and socket in the
shack are wired so that the black white and green wires coming from the
amp hook to the black white and bare wires coming from the sub-panel.
In an ideal installation, the power, phone, and TV antenna grounds should all
hook to the service entrance ground, and enter the building at the same place.
Another "RF Ground" rod(s) should be installed as close as possible to the
operating
position in the station, and solid strap, tubing, or wire run from the radio,
amp,
tuner and accessories to this rod. I also add several buried radials to this rod
to assist in keeping RF off all the equipment chassis.
(((73)))
Phil, K5PC
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