Jim,
Your method #1:
This method was allowed several years ago but NEC no longer allows this. You
must now run 4 wires to building #2 and NOT bond neutral and ground in
building #2. that panel is treated as a sub panel and it also requires a
ground rod in addition to the ground wire from the main panel.
Under the old method as you describe neutral and ground would be bonded at
the sub panel.
Your Method #2:
You say to run two hots and neutral. You didn't mention a ground wire. Did
you mean to say that 4 wires would be run?
If so then ok. However a local ground rod is STILL required at the panel in
the 2nd building. The only time a ground rod is not required at a sub panel
is when the sub panel is located in the same building as the main panel.
73
Gary K4FMX
> -----Original Message-----
> From: amps-bounces@contesting.com [mailto:amps-bounces@contesting.com]
> On Behalf Of Jim Brown
> Sent: Monday, April 04, 2011 5:08 PM
> To: Dick Green WC1M
> Cc: amps@contesting.com
> Subject: Re: [Amps] 4 wire 240VAC service? What to do now?
>
> On 4/4/2011 10:49 AM, Dick Green WC1M wrote:
> > Yes, and the neutral and ground must be isolated in any subpanels as
> well.
> > However, there's one exception: if the subpanel is more than a certain
> > distance from the main panel (not sure how far), such that the code
> requires
> > a separate ground rod at the subpanel, the neutral and separate ground
> rod
> > are connected together in the subpanel. This could be the case for a
> > subpanel in a separate outbuilding.
>
> The issue is NOT distance, but rather creating a separate SYSTEM. A
> separate system is created by a TRANSFORMER, or by feeding another
> building. A power system MUST have its neutral bonded to ground where it
> is created, but ONLY at that point. The service entrance creates a
> system, and is the ONLY permitted neutral-to-ground bond in most homes
> and small buildings.
>
> The GROUND that we're talking about here is the system of green wires,
> and ALL grounds associated with the building must be connected to it.
> The BOND we're talking about is the connection of NEUTRAL to that system
> of grounds, which may occur at ONLY at the service entrance..
>
> If power enters one building and is fed to another one (like a shack or
> garage or workshop), there are two legal ways to do it. I used Method #1
> to feed my shack, which is in the second building. In both methods,
> power enters building #1, neutral is bonded to the steel enclosure at
> the entry panel, one or more ground rods are bonded to that steel
> enclosure, and all grounds associated with building #1 (CATV, telco,
> structural steel, satellite dish, roof antennas, etc. coax entry panel
> for your shack) must be bonded to that steel enclosure. In both methods,
> you can have as many ground rods as you like, but they must all be
> bonded together and to that system of green wires, and the best place to
> make the connection is at a common point where they connect to the steel
> enclosure.
>
> In Method #1, power is fed from Building #1 to Building #2 with the two
> 240V phase (hot) conductors and the neutral. There must be NO GROUND
> connection between the two buildings. In Building #2, there must be one
> or more driven rods bonded to the steel enclosure of the entry panel,
> all of the grounds associated with Building #2 must be bonded to that
> steel enclosure, AND there must be a bond between neutral and ground in
> that panel.
>
> In Method #2, power is fed from Building #1 to Building #2 with the two
> 240V phase (hot) conductors, the neutral, AND there must be NO bond
> between neutral and ground in Building #2. All of the grounds associated
> with Building #2 must be bonded together, and to that steel enclosure.
> Additional driven rods are certainly a very good idea adjacent to the
> point where ham antennas enter the building and are bonded to ground.
>
> With Method #1, you MUST also provide transformer isolation for any coax
> lines running between buildings, and with Method #2 this is also a good
> thing. I use isolators made by Jensen Transformers for my CATV feed
> between buildings. Google to find them.
>
> > I have this situation at my station, though not for an outbuilding. I
> have a
> > motorized crankup tower with a 120VAC motor about 270 feet from the
> house.
> > Four #10 wires buried in a 4' deep conduit (separate from the radio
> cables,
> > of course) carry 240VAC from the main panel in the house to an
> outdoor-rated
> > subpanel mounted next to the tower. The wiring and subpanel were
> installed
> > by a licensed electrician.
> >
> > As I recall, the electrician did not bond neutral and ground together
> at the
> > subpanel,
>
> That's good.
>
>
> > nor did he connect the subpanel to the tower ground.
>
> That's bad.
>
> > I'm sure that
> > I had not built the tower ground system when he installed the
> subpanel, and
> > he didn't bother to install a separate ground rod for the panel.
> > Essentially, the installed it like a subpanel inside a house would be
> > installed.
>
> There is no requirement for a separate rod for that panel.
>
> > After the subpanel went in, I built an extensive ground rod system for
> the
> > tower: 12 rods spaced 16' apart in a radial pattern from the base,
> cadwelded
> > with 1/0 wire. Several years ago, I read up on the code, and changed
> the
> > wiring at the subpanel. I don't recall exactly what I did, but I do
> know
> > that I connected the subpanel to the tower ground and bonded the local
> 120
> > VAC neutral to the tower ground in the subpanel. I believe this is
> correct.
>
> No, the neutral to ground bond is WRONG.
>
> > What I don't remember is whether I disconnected the neutral and ground
> wires
> > coming from the house. It seems to me that they should be disconnected
> in
> > this case. In other words, ground and neutral for the 120VAC branches
> from
> > the subpanel should use the local neutral and ground, not the ones
> coming
> > from the house. Anyone care to comment on that?
>
> See my summary above.
> > What would be the specific
> > hazard if the house ground and neutral wires are connected to the
> subpanel
> > ground and neutral, and thus to each other?
>
> It violates safety codes, can cause hum, buzz, and RFI, and is unsafe
> for the reasons several have already cited.
> > As soon as the snow melts, I'm going to take a walk to that subpanel
> and
> > refresh my memory on how it's wired!
>
> That would be a VERY good idea. If it's wired the way you think it is,
> it's WRONG. :) The home I bought in California was wired by licensed
> electricians. It is was WRONG, and I had to fix it.
>
> All of this boils down to three fundamental principles.
>
> 1) Neutral and ground must be bonded (connected) at ONE, AND ONLY ONE
> POINT, at the point where the system is created.
>
> 2) You can have as many ground rods as you want, more is better, but all
> the rods (and other grounds) associated with a building MUST be bonded
> together and to the power system ground (the service entrance steel
> panel and the green wires).
>
> 3) The power system ground must extend to every outlet, to every piece
> of equipment fed by the power system.
>
> 73, Jim Brown K9YC
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