[Amps] 4 wire 240VAC service? What to do now?

[James R Carr]

It should be treated as a seperate building. The panel would have it's own 
main breaker but the neutral would remain ungrouned and the panel enclosure 
and equipment ground would be grounded to the seperate ground rods. The 
neutral is normaly only  grounded at the service main. The neutral is coming 
from the center tap of the 240 volt winding on the pole pig and you need 
that to develope 120 volts. You can never use a ground as a current carrying 
conductor. You don't need the equipment ground from the house as you are 
establishing it at the tower. It's sole purpose is to trip the breaker in 
the event of a ground fault and keep all the metal enclosures etc at a 
ground potential.
Jim
N7FCF
----- Original Message ----- 
From: "Dick Green WC1M" <wc1m73 at gmail.com>
To: <jim at audiosystemsgroup.com>; <amps at contesting.com>
Sent: Monday, April 04, 2011 10:49 AM
Subject: Re: [Amps] 4 wire 240VAC service? What to do now?


> 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.
>
> 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, nor did he connect the subpanel to the tower ground. 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.
>
> 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.
> 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? 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?
>
> 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!
>
> 73, Dick WC1M
>
> -----Original Message-----
> From: Jim Brown [mailto:jim at audiosystemsgroup.com]
> Sent: Monday, April 04, 2011 12:35 PM
> To: amps at contesting.com
> Subject: Re: [Amps] 4 wire 240VAC service? What to do now?
>
> On 4/4/2011 8:26 AM, Commander John wrote:
>> I twisted the 2 grounds together and installed them in the center pin 
>> jack
> as it was that or cut one off.
>> Is there a better way?
>
> PLEASE go back and STUDY what I  and several others have written several
> times in this thread, and in the power and grounding  tutorial that's on
> my website.  http://audiosystemsgroup.com/publish.htm
>
> NEVER, EVER, connect NEUTRAL to GROUND at any point other than the point
> where it enters the building. The proper connections to your amplifier
> are the two 240V hot wires and the green wire. The neutral must NOT be
> connected.
>
> 73, Jim K9YC
>
>
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