I agree with Gary about branch circuits - the ground and neutral must be
maintained separate & the neutral connection bar is isolated from the branch
circuit box chassis.
The discussion about 3-wire vs 4-wire triggered another code item I
discovered. I had planned to run a couple 240V feeds with 4-wire but not
use the neutral. Code says "no unused conductors". Rats, so much for
planning ahead.
Consult the codes, consult/hire an electrician if not comfortable. I'm
lucky that the town building inspector is a friend and neighbor, he's helped
out on my tower (a looong story) and electrical improvements. Helped keep
me out of trouble!
~~~~~~~~~~~~~~~~
Bill Coleman N2BC
http://home.stny.rr.com/n2bc
----- Original Message -----
From: "Gary Schafer" <garyschafer@attbi.com>
To: "Phil Clements" <philk5pc@tyler.net>
Cc: "Bill Coleman" <n2bc@stny.rr.com>; "Richard" <2@mail.vcnet.com>; "Steve
Katz" <stevek@jmr.com>; <RMead100@aol.com>; "AMPS" <amps@contesting.com>
Sent: Friday, March 08, 2002 1:20 PM
Subject: Re: [Amps] Source for 220V cords
>
>
> Phil Clements wrote:
>
> > > > 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.
>
> This is wrong. The neutral and ground are NEVER tied together except at
the MAIN
> breaker panel.
> This is even true when in some installations the main house breaker is
outside and
> the distribution panel with all the branch circuit breakers is mounted
inside. The
> ground and neutral are NOT connected together even in this panel. They are
only
> connected together at the outside main circuit breaker.
>
>
> >
> >
> > 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.
>
> This is wrong also. First you never hook a white wire to a hot 220
terminal. White
> ALWAYS goes to the neutral line. If you are running 220 you need a 4 wire
line. They
> have RED, Black, White and a bare ground wire. Again the only place the
neutral and
> bare ground wires are tied together is in the main breaker panel. The red
and black
> wires are the two hot lines from either side of the 220.
>
> The exception to this is sometimes window air conditioners have a 220 line
to them.
> Or a pool or well pump that is only 220 volts. In this case they have no
need for a
> neutral as they only operate on 220 volts. A three wire line can be used.
Sometimes
> a regular romex (black, white and ground wires) is used. The black goes to
one side
> of the 220 and the white goes to the other side of the 220. BUT it is
marked with
> RED tape at each end to identify it as a hot line. The bare wire is
connected to the
> ground buss in the panel and the outlet end of the line goes to the ground
pin.
> There is no neutral involved in this circuit.
>
> If a neutral is needed a 4 wire line and 4 wire outlet must be used.
>
>
>
> >
> >
> > 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
>
> 73
> Gary K4FMX
>
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