Subject:  Bonding screws (fwd)
Date:     Wed, 26 Aug 1998 085848 -0500 (CDT)
From:     "Roy L. Beavers" <rbeavers@llion.org>
To:       emfguru@hotmail.com
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---------- Forwarded message ----------
Date: Wed, 26 Aug 1998 08:43:29 -0500
From: Edward Maxey 
To: "Roy L. Beavers" 
Subject: Bonding screws

Hi Roy,

Your several recent blurbs on using water line
dielectric couplings to halt magnetic fields from
stray return currents were great.

Another common source of such currents is the
bonding screw.  It is a bolt in electric panels 
which metallically bonds the neutral bus to the
panel box.  Until recently some city inspectors
here in Arkansas required this installation, not
realizing that it was a violation of the 
electric code.

Here's the code [NEC 250-23(a)],
"The main rule is that a grounding connection
shall not be made to any grounded circuit
conductor on the load side of the service
disconnecting means."

The service disconnecting means is a series of
circuit breakers or switches which firemen use
to disconnect electric power from a building. 
They are usually on the outside of a building
close to the electric meter.

Bonding screws in outside electric panels usually 
do not set up significant stray currents.  

The rub comes in apartment houses and condominiums
where each unit has its own electric panel.  Here
the presence of bonding screws often causes large 
magnetic fields whenever 120-130 volt appliances are
used in individual units.  The fields accompanying
power usage in a single apartment may often be 
measured throughout the entire complex.

The municipal government here has been apprised of
its former error.  It has not alerted its citizens
the the dangers emanating from that error.

Felicitations,

Ed



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Reprinted with permission of Roy Beavers, http://www.feb.se/EMF-L/EMF-L.html