On 9/13/2014 10:53 PM, Gary Schafer wrote:
"I would think the farther apart the buildings, the more likely the
differential in time and magnitude of induced voltages would be more of
a problem than conducted voltages. Conducted voltages would lose much
of the higher frequency component due to inductance than lower while
induced would not, leaving more of a voltage difference at the high
frequency ones. It would also smooth out the rise and fall times.
Conducted would also loose magnitude due to capacitive coupling to earth.
Whether green wire (earth) or neutral, running from panel to panel they
are essentially ground.from the main panel. I have 2 main panels and
unfortunately the station grounds provide a common, low impedance ground
between systems.
Both systems "in my case" require green (earth ground) and neutral tie
together in the panels. There is no power wiring running directly
between buildings and they have their own feeds from the pole
transformer. However, both my feeds and my neighbors feed are all off
the same winding and that puts them in parallel. So essentially, my
shop and house have the same hot 120-0-120 (240) feeds in parallel, The
pole and both panels are tied to ground rods. Essentially a very leaky,
high resistance ground back to the transformer.
With this arrangement, I see no real problem with green and neutral
(white) tying together in both main panels even with the low resistance
system ground between buildings...IF they coded the phases correctly.
IE, blue in the house and shop tie to the same connection at the pole
transformer. The same for red. Of course, if one is correct the other
has to be correct.
Neutral is usually the steel messenger cable in above ground feeds.
Under ground uses the copper wires for all three. At least it was here
before going underground. There are many places where the drops are
much less than 12 feet. The concrete delivery truck took out our old
feed which was only a pair of #6s and the steel messenger cable.
The highest voltage on each phase has been 120 and the lowest has been
117.but is rare to see anything other than 120.
I have a 3KVA line conditioner for the equipment in the den with true
sin wave out. So it maintains a 120 VAC sin wave out whether in the
line conditioning mode or as a UPS. Now all I have to do is get it
hooked up!
73
Roger (K8RI)
.
I don't know if you are including me as one who is "railing against you" but
this is exactly what I have said from the start.
From my very first post on the subject:
On Fri,9/12/2014 5:27 PM, Gary Schafer wrote:
You only think that there is no ground between your house and
shack/garage.
That neutral wire is serving both as ground and neutral between the
two buildings.
73
Gary K4FMX
I disagree with your analysis, and as I noted, the system I described >>
is specifically listed as acceptable in the last code I bought, about >>
2003.
Neutral and ground are two separate conductors.
You are also ignoring inductance between these points you want to bond.
73, Jim K9YC
-----Original Message-----
From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
Jim Brown
Sent: Saturday, September 13, 2014 6:22 PM
To: towertalk reflector
Subject: [TowerTalk] Grounding Multiple Buildings
/ExceptionNo. 1:For installations made in compliance with previous
editions of this Code that permitted such connection, the grounded
conductor run with the supply to the building or structure shall be
permitted to serve as the ground-fault return path if all of the
following requirements continue to be met:/
/If the grounded conductor is used for grounding in accordance with the
provision of this exception, the size of the grounded conductor shall
not be smaller than the larger of either of the following:/
Bottom line -- what I did in my buildings was according to Code in 2010
when I did it, and the installation is "grandfathered" by the 2011 and
2014 Codes. But it is not permitted now.
73, Jim K9YC
73
Gary K4FMX
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73
Roger (K8RI)
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