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As I begin to add a 240VAC power drop to my radio shack at the new QTH, =
I began to consider cable sizing, connectorization and grounding issues. =
At my previous home, I used #10/3 CU cabling for a total distance of =
60-feet to my Alpha 77Dx (single tube). I then terminated the drop into =
a Hubbell 30-amp Twist-Lock receptacle. I then began thinking about =
various 240VAC distribution possibilities:
1) Some 240VAC circuits employ two phases and a ground, but no neutral. =
2) Some 240VAC circuits employ two phases and a neutral, but no ground.
3) I have not encountered a "4-pole" circuit which provides for two =
phases, a neutral AND a ground. =20
Although the ground and neutral are tied to a common buss within the =
home's central load center, why is it that a safety ground is not =
carried out in addition to circuits which employ a neutral? The neutral =
is allowed to carry AC current, a ground is not. The ground is present =
only to establish a non-current reference back to the load center. It =
would seem then that in configuration #2, the chassis of the amp is =
referenced to a current carrying neutral potential, thereby negating the =
safety potential to the chassis as would be provided for by a separate =
ground. =20
I'm no NEC expert, and perhaps there may exist an electrical contractor =
on this reflector who can better explain the thought process behind =
240VAC distribution in a home.=20
Interestingly, the Alpha amplifiers (and perhaps others) allow for the =
use of either configuration #1 OR #2 as referenced above. The manual =
takes the owner through steps which change various AC input taps to =
match the wiring distribution. =20
If I were to take a poll, how many of you run your amps with the =
configurations as stated above? If NEC allows it, have any of you =
successfully tried configuration #3, also assuming there may exist a =
4-pole 240VAC plug/receptacle?
-Paul, W9AC
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<DIV><FONT face=3DArial size=3D2>As I begin to add a 240VAC power drop =
to=20
my radio shack at the new QTH, I began to consider cable sizing,=20
connectorization and grounding issues. At my previous home, I used =
#10/3=20
CU cabling for a total distance of 60-feet to my Alpha 77Dx (single =
tube). I then terminated the drop into a Hubbell 30-amp=20
Twist-Lock receptacle. I then began thinking about =
various=20
240VAC distribution possibilities:</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>1) Some 240VAC circuits employ two =
phases and=20
a ground, but no neutral. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>2) Some 240VAC circuits employ two =
phases and a=20
neutral, but no ground.</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>3) I have not encountered a "4-pole" =
circuit which=20
provides for two phases, a neutral AND a ground. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Although the ground and neutral are =
tied to a=20
common buss within the home's central load center, =
</FONT> <FONT=20
face=3DArial size=3D2>why is it that a safety ground is not carried out =
in addition=20
to circuits which employ a neutral? The neutral is allowed to =
carry AC=20
current, a ground is not. The ground is present only to establish =
a=20
non-current reference back to the load center. It would seem then =
that in=20
configuration #2, the chassis of the amp is referenced to a current=20
carrying neutral potential, thereby negating the safety potential =
to the=20
chassis as would be provided for by a separate ground. =
</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>I'm no NEC expert, and perhaps there =
may exist an=20
electrical contractor on this reflector who can better explain the =
thought=20
process behind 240VA</FONT><FONT face=3DArial size=3D2>C distribution in =
a=20
home. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>Interestingly, the Alpha amplifiers =
(and perhaps=20
others) allow for the use of either configuration #1 OR #2 as =
referenced=20
above. The manual takes the owner through steps which change =
various AC=20
input taps to match the wiring distribution. </FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>If I were to take a poll, how many of =
you run your=20
amps with the configurations as stated above? If NEC allows it, =
have any=20
of you successfully tried configuration #3, also assuming there may =
exist a=20
4-pole 240VAC plug/receptacle?</FONT></DIV>
<DIV> </DIV>
<DIV><FONT face=3DArial size=3D2>-Paul, W9AC</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV></BODY></HTML>
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