[Heathkit] Gadzooks, when is a ground a ground?

[Bob McGraw - K4TAX]

Current NEC code requires L1, L2, Neutral, and ground for 240 volt 
residential service.  That's 4 wires.  Neutral and Ground are to be 
connected to a common buss bar only at the main circuit breaker.  To the 
best of my knowledge all local codes do accept a driven ground with less 
than 20 ohms resistance located at or below the service entrance.  Most 
residential electric services no longer recognize connection to the water 
line as adequate ground due to the use of plastic pipe or "current breakers" 
being and insulated section of line to prevent currents flowing and 
subsequent electrolysis of the water lines or water mains.  Further, NEC 
code requires that all driven grounds for equipment served by a common 
electric service must be bonded together.

Now for hams this likely gets to be a sticky wicket.  Yes, your driven 
ground for your station or your tower or your antenna system must be bonded 
{i.e. connected} via a hard conductor back to the service entrance ground in 
order to comply with NEC code.  Now what happens if it is not done that way. 
Well in the event of a fire, thus loss of the structure, and the insurance 
fire investigator finds such installation exists, it is likely that your 
insurance company will simply thank you for your business.  Otherwise, we'll 
see you in court and you, the homeowner, should expect to loose.

The 240 volt service is split thus providing two 120 volt sources with the 
phase between the two being 180 degrees.  Thus the neutral will carry any 
difference in current identified by the two lines, L1 and L2.  Thus if L1 
has a 10 amp load and L2 has a 12 amp load the neutral will have 2 amps of 
current, power factor not withstanding.  At the same time, a 240 volt load 
connected between L1 and L2 will not have any effect on neutral current, 
again power factor not withstanding.

At the same time, NEC does acknowledge the "grandfather clause" {I forget 
the date}  in that older residences are considered safe with L1, L2 and 
Neutral with neutral being the common ground point.

73
Bob, K4TAX



----- Original Message ----- 
From: "Rick Brashear" <rickbras at airmail.net>
To: <heathkit at mailman.qth.net>
Sent: Thursday, December 06, 2007 4:21 PM
Subject: RE: [Heathkit] Gadzooks, when is a ground a ground?


That's the way I understand it too, Larry.  You should never use the neutral
for the ground wire either in a 120 vac setup or a 220 vac setup.  Like you
said, it defeats the entire concept of the ground.

Rick/K5IAR



While all of this seems correct, my input is that these grounds do not take
the place of the neutral wire.
If the 220V is used to derive two separate 110 volt lines, the neutral needs
to be carried with the 220 volt line.
The Ground is separate.  The grounds will be connected to a common point,
usually at the service entrance panel,
it would scare me to wire a house without the neutral being carried in
addition to the ground.  If the integrity
of the neutral is compromised, the 110 volt lines can measure a lot
different than what is expected.

Just my opinion.  Thanks
Larry N7LB

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