On 9/6/2012 4:36 PM, GARY HUBER wrote:
Jim, just verifying my understanding of the following;
Green (Grounded) and White (Neutral) bond ONLY at the MDP (Main
Distribution Panel). Green wire must run with neutral to main or
supplemental panel and MAY also be grounded elsewhere but those
grounding points MUST be bonded to the system / site / premise ground
in accordance with the National Electrical Code.
Right.
The key here is that there MUST be ONE, AND ONLY ONE bond between
neutral and Ground (the Green Wire) in any System, and it MUST be where
the System is established. A "System" is established 1) at the Service
Entrance (where power comes into the building) and 2) at a transformer.
A typical residence or small building has only one System. Larger
buildings may have several systems.
One of the most common wiring errors made by electricians is to have
additional bonds between Neutral and Green. This most often happens two
ways. First, when you buy a breaker panel, there's a bonding screw that
automatically bonds the Neutral bus to the Ground bus (the Panel
chassis). That's fine if it's the Main Panel, but if it's a Sub-Panel
it MUST be removed, and sometimes that isn't done. The other way that
extra Neutral bonds happen is in older laundry equipment.
By contrast, the Green wire can be taken to earth as many times, and in
as many places, as you like.
BTW -- someone correctly observed that in many localities, most wiring
is three conductor cable with black, white, and bare copper for ground.
Yes, that bare copper is "the Green Wire." It's called the Green wire
partly because of history, partly because when wiring is in conduit or
other metal raceway the dedicated ground wire must be Green, and partly
because, in North America, the ground conductor in portable cables is
usually Green.
73, Jim K9YC
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