He forgot to mention that if you run a line to another building and
install a sub panel there that you ground the sub panel to an earth ground.
The ground connections in the sub panel are treated the same way as the
main disconnect ground is. Neutral and ground are tied together in that
sub panel.
The old way of using only 3 wires for large appliances (2 hot and a
ground) required that those be dedicated circuits. For a stove, only the
stove could be connected to that line directly from the breaker panel.
Same for the dryer. It must be the only thing connected to that line.
73
Gary K4FMX
Joe Isabella wrote:
Excellent explanation -- thanks!! I hope you don't mind me replying to the
reflector so we can
all absorb this. I remember hearing this from my brother, who as I mentioned
in an earlier post
is an electrician. This does make me think of another question: Since my amp
(and several others)
has only the 2 hots and a ground, does that now mean the ground is acting as the
"Neutral"? And
what are the ramifications of grounding it again via the station ground? BTW,
my shack is
literally right next to the breaker box and power entry, so my 240 outlet is ~3
feet from the
breaker. The power ground may actually be closer than the station ground I put
in...
Thanks again,
Joe,
N3JI
--- Gudguyham@aol.com wrote:
Hi Joe, coming into your house from the electrical company is a 3 wire system
ONLY. You have HOT-HOT- NUETRAL from them. They ground their transformer at
the pole to an earth ground. You ground your electrical system at your MAIN
DISCONNECT. (to an earth ground) Notice I said MAIN DISCONNECT not MAIN PANEL.
In most cases, the main disconnect is in the main panel, but in some special
cases, the main disconnect is NOT in the main panel. The NEC requires the
electrical system to be EARTH GROUNDED at the MAIN DISCONNECT. There are only 3
wires from the power company (on a single phase 240/120 system) to the main
disconnect point. After the main disconnect point (in most cases the main
panel) any further SUB PANEL and branch circuits are then 4 wire systems (for
240v). The ONLY place in a distribution system where the NUETRAL and the GROUND
(bond) are tied together is at the main disconnect point, after that point the
NUETRAL and GROUND (bond) MUST be seperated, hence separate wires. The NEC
says that the ONLY time that a GROUND (bond) should carry current is during a
fault situation, a fault situation would be when a metal compartment, chassis or
the like becomes energized by a HOT conductor, when this happens, current
flows on the bond back to the panel, and trips the circuit breaker. If you tie
the nuetral and ground together at any point then any current flowing on the
nuetral will be shared by the bonding system, in the case of BX it would be the
armour or in Romex the bare wire. You DONT want this as a rule!! It was
common practice in the old days with dryers and ranges to tie the ground and
nuetral together, but in the 1993 NEC code book they changed that, and now all
range and dryer plugs have 4 prongs instead of 3. The confusing thing is that
when you read the code book, they refer to the NUETRAL as the "grounded
conductor" and the earth ground (bond) as the 'gounding conductor". You wont really
see the term NUETRAL used in the codebook. Whats the moral of this story? If
you add ANY 240 line in your house be it, a sub panel or a branch circuit DO NOT
tie Nuetral and bond together. THEONLY TIME A NUETRAL AND BOND COME TOGETHER
IS IN THE MAIN DISCONNECT POINT, WHEREVER THAT MIGHT BE. 73 Lou W1QJ King
Conversions (electrician)
__________________________________
Do you Yahoo!?
Free Pop-Up Blocker - Get it now
http://companion.yahoo.com/
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|